Shorter Contributions to 

Paleontology and Stratigraphy 

U.S. GEOLOGICAL SURVEY BULLETIN 1837 

Shorter Contributions to 

Paleontology and Stratigraphy 

Edited by WILLIAM J. SANDO 

U.S. GEOLOGICAL SURVEY BULLETIN 1837 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1988 

For sale by the 

Books and Open-File Reports Section 

U.S. Geological Survey 

Federal Center, Box 25425 

Denver, CO 80225 

Ubrary of Congress Cataloging-in-Publication Data 

Shorter contributions to paleontology and stratigraphy. 

(U.S. Geological Survey bulletin ; 1837) 

Includes bibliographies. 

Supt. of Docs. no.: 119.3:1837A-E 

1. Paleontology. 2. Geology, Stratigraphic. I. Sando, 

William jasper. II. Series. 

QE75.B9 no. 1837 557.3 s[551.7] 88-600006 

(QE723] 
CONTENTS 

CHAPTER A 

Latest Cambrian and Earliest Ordovician Conodonts from the 

Conococheague and Stonehenge Limestones of Northwestern Virginia A 1 

Randall C. Orndorff 

CHAPTER B 

Conodont-Based Determination of the Silurian-Devonian Boundary in the 

Valley and Ridge Province, Northern and Central Appalachians 81 

Kirk E. Denkler and Anita G. Harris 

CHAPTER C 

Homeognathodus peniculus (Conodonta), a New Earliest Pridolian Index 

Species, and the Ludlovian-Pridolian Boundary in the Central 

Appalachian Basin C1 

Kirk E. Denkler and Anita G. Harris 

CHAPTER D 

Occurrence of the Early Cretaceous Ammonite Venezoliceras 

in Puerto Rico 

William A. Cobban and Glenn R. Scott 

CHAPTER E 

Ammonites in Clasts of the Juana Lopez Member of the Carlile Shale 

01 

(Upper Cretaceous) near Pueblo, Colorado E1 

William A. Cobban 

Contents Ill 

CHAPTER A 

Latest Cambrian and Earliest Ordovician Conodonts 

from the Conococheague and Stonehenge Limestones 

of Northwestern Virginia 

By RANDALL C. ORNDORFF 

Conodonts from two sections place the 

base of the Ordovician System within 

the upper Conococheague Limestone 

U.S. GEOLOGICAL SURVEY BULLETIN 1837 

SHORTER CONTRIBUTIONS TO PALEONTOLOGY AND STRATIGRAPHY 

CONTENTS 

Abstract Al 

Introduction Al 

Acknowledgments Al 

Lithostratigraphy A3 

Faunal evaluation A3 

Proconodontus Zone AS 

Cordylodus proavus Zone AS 

Conodont Fauna B AS 

Conodont Fauna C AS 

Discussion AS 

Systematic paleontology AS 

References cited A17 

PLATES 

[Plates follow References Cited] 

1. Acodus, Acontiodus, Cambrooistodus, Clavohamulus, Cordylodus, 

Drepanodus, Drepanoistodus, Eoconodontus, Eucharodus, Fryxellodontus, 

Hirsutodontus, Loxodus 

2. "Oistodus," Paltodus, Proconodontus, Prooneotodus, Rossodus, Scandodus, 

Scolopodus, Semiacontiodus, Teridontus, Utahconus 

FIGURES 

1. Generalized geologic map of part of northwestern Virginia showing locations 

of sampled sections A2 

2-5. Stratigraphic charts showing: 

2. Cambrian and Ordovician formations in northwestern Virginia A3 

3. Conodont and trilobite zones and faunal intervals for the Upper 

Cambrian and Lower Ordovician A4 

4. Distributions of selected conodont species in the Narrow Passage 

Creek section A6 

5. Distribution of selected conodont species in the Timberville 

section A7 

Contents Ill 

Latest Cambrian and Earliest Ordovician Conodonts 

from the Conococheague and Stonehenge Limestones 

of Northwestern Virginia 

By Randall C. Orndorff 

Abstract 

Conodonts from two sections in northwestern Virginia 

demonstrate that zonations and faunal intervals for uppermost 

Cambrian and lowest Ordovician strata established elsewhere 

in North America can be recognized in the central Appalachians. 

Several North American Midcontinent Province cratonic and 

miogeoclinal faunal units are present in the Conococheague 

Limestone and the overlying Stonehenge Limestone, including 

the Proconodontus and Cordylodus proavus Zones, and Conodont Faunas B and C. At present the Cambrian-Ordovician 

boundary in North America is based on trilobites and is placed 

at the base of the Missisquoia Zone. This systemic boundary can 

be approximated, using conodonts, as the lowest subzone of 

the Cordylodus proavus Zone. A horizon 43 m below the base 

of the Stonehenge Limestone yielded the lowest Cordylodus proavus Zone conodonts, demonstrating that in northwestern 

Virginia the Cambrian-Ordovician boundary, as now recognized, 

lies within the upper part of the Conococheague Limestone. The 

boundary between the Proconodontus and Cordylodus proavus 

Zones in many sections around the world is thought to be a 

eustatic event. This event may be represented in the rocks of 

northwestern Virginia as an unconformity above a Conococheague Limestone cycle in which the two lowest subzones of 

the Cordylodus proavus Zone either are missing or are represented by only 2 m of strata. 

INTRODUCTION 

The Shenandoah Valley of northwestern Virginia is 

along the eastern margin of the Valley and Ridge province; 

the valley is underlain by folded and thrust-faulted, chiefly 

carbonate strata of Cambrian through Middle Ordovician age 

(fig. 1). Although fossils from these rocks have been reported 

in previous geologic studies, the Cambrian-Ordovician 

interval has not been documented paleontologically in northwestern Virginia. Sando (1957, 1958) established the stratigraphic position of the Cambrian-Ordovician boundary in the 

Great Valley of Pennsylvania and western Maryland by utilizing various fossil groups, including brachiopods, mollusks, 

and trilobites. In these earlier studies, Hass (in Sando, 1958) 

first illustrated conodonts from Cambrian-Ordovician boundary strata in the central Appalachians. Since then, little has 

been added to the conodont biostratigraphic data base for the 

region. The objective of this investigation was to use 

conodonts to locate the Cambrian-Ordovician boundary in 

northwestern Virginia. 

The sections sampled for conodonts in this study are 

west of the Massanutten synclinorium and east of the North 

Mountain fault, a structure that places Cambrian carbonate 

rocks of the Elbrook Formation above Devonian clastic rocks 

(fig. 1). These sections are 32.5 km apart and are along 

Narrow Passage Creek, 3 km southwest of Woodstock, 

Shenandoah County; and along Honey Run, 4 km northwest 

of Timberville, Rockingham County. Sampled strata include 

the upper part of the Conococheague Limestone and the lower 

part of the Stonehenge Limestone. Although the limestone 

unit above the Conococheague Limestone is mapped as 

Stonehenge by many Virginia mappers, it is apparent that 

this interval differs considerably from rocks in Pennsylvania 

and Maryland where the Stonehenge was first described. 

Acknowledgments 

This paper is part of a master's thesis completed at Old 

Dominion University, Norfolk, Va., under the supervision 

of J.E. Repetski (U.S. Geological Survey, Washington, 

D.C.), S.J. Culver, and C.F. Koch. Among others I wish 

to thank J. F. Miller, Southwest Missouri State University, 

for critical review of the manuscript. I also thank J. F. Taylor, 

E.K. Rader, and W.J. Sando for insight and discussion of 

the lithostratigraphic problems of this interval in northwestern 

Virginia. 

Cambrian and Ordovician Conodonts from the Conococheague and Stonehenge limestones A 1 
78°30' 

I --r ,., I.Jt:- :- :- :-

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9 ? 19 KILOMETERS '-------'---~ 

I 

Figure 1. Generalized geologic map of part of northwestern Virginia showing locations of sampled sections (modified from Hack, 

1965). 

A2 Shorter Contributions to Paleontology and Stratigraphy 
LITHOSTRATIGRAPHY 

The Conococheague Limestone is 750 m thick in northwestern Virginia and is composed of limestone, dolostone, 

sandstone, and siltstone. These lithologies occur in 5- to 

12-m-thick shallowing-upward cycles that consist of subtidal 

oolitic lime grainstone, intraclastic lime grainstone, and 

thrombolitic and stromatolitic lime boundstone in the lower 

part, and supratidal laminated dolostone and sandstone in the 

upper part. The boundary between the cycles is sharp where 

the peritidal carbonate cap is overlain by subtidal carbonates 

of the following cycle. 

Overlying the Conococheague Limestone in northwestern Virginia is the Stonehenge Limestone (fig. 2), which 

was first described by Stose (1908) as the lowest member 

of the Beekmantown Formation in Franklin County, Pennsylvania, and later raised to formational rank by Sando 

(1956). Several typical Conococheague lithologies (mainly 

lime grains tones) occur within the Stonehenge Limestone. 

The 150 m of Stonehenge strata in northwestern Virginia 

includes a thick-bedded to very thick bedded gray to darkgray limestone with crinkly siliceous laminations, minor algal 

bioherms, and intraclastic lime grainstone. In this study the 

Conococheague-Stonehenge contact is placed at the base of 

the lowest thick-bedded limestone with crinkly siliceous 

laminations, a characteristic Stonehenge lithology. The lower 

part of the Stonehenge in northwestern Virginia is not consistent with the lower member of the Stonehenge described 

by Sando (1958) for sections in Maryland. Sando (oral 

commun., 1986) noted a change in the lithofacies of the lower 

part of the unit in Virginia and believed the formation could 

not be mapped as Stonehenge. The major difference in the 

Stonehenge of Virginia from that of Maryland is that the 

distinctive algal unit at the base of the Stonehenge and the 

lower member are not recognized in northwestern Virginia. 

Others, however, have found it possible to map the Stonehenge in Virginia as far south as Roanoke (Henika, 1981). 

Young and Rader (1974) and Rader and Biggs (1976) also 

used the name Stonehenge for the limestone above the 

Conococheague Limestone in northwestern Virginia. 

FAUNAL EVALUATION 

Conodont biostratigraphic units recognized for the 

uppermost Cambrian and lowest Ordovician of northwestern 

Virginia are correlated with trilobite-based biostratigraphic 

units in figure 3. At this time the Cambrian-Ordovician 

boundary in North America is placed at the base of the 

Missisquoia Zone (Winston and Nicholls, 1967). However, 

it should be noted that the International Working Group on 

the Cambrian-Ordovician Boundary, part of the International 

Subcommission on Stratigraphy, International Union of 

Geological Sciences, is in the process of selecting an international standard for this systemic boundary. It may be a 

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Conococheague Limestone 

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Elbrook Formation 

150 m 

~~--------------~ 

Figure 2. Cambrian and Ordovician formations, with thicknesses, in northwestern Virginia (from Young and Rader, 1974). 

Cambrian and Ordovician Conodonts from the Conococheague and Stonehenge Limestones A3 
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A4 Shorter Contributions to Paleontology and Stratigraphy 
horizon above the Missisquoia Zone, possibly at the base 

of the conodont Hirsutodontus simplex Subzone of the Cordylodus proavus Zone (Derby, 1986). The base of the Missisquoia Zone falls within the lowest conodont subzone 

(Hirsutodontus hirsutus Subzone) of the Cordylodus proavus 

Zone as developed by Miller (1978, 1980). The base of this 

subzone serves as an approximation of the CambrianOrdovician boundary in this study, and it is another horizon 

being considered for the international standard. Ethington 

and Clark (1971) established five conodont faunal intervals 

for the Early Ordovician (Faunas A to E). Miller (1978, 

1980) reevaluated the latest Cambrian and earliest Ordovician 

faunas and erected the Proconodontus Zone and the Cordylodus proavus Zone, the latter equivalent in part to Fauna 

A of Ethington and Clark. 

Conodont faunas recovered from northwestern Virginia 

represent several North American Midcontinent Province 

cratonic and miogeoclinal faunal units. The Narrow Passage 

Creek section yielded conodonts indicative of the Proconodontus and Cordylodus proavus Zones and Conodont Faunas 

B and C. The Timberville section yielded conodonts from 

the Cordylodus proavus Zone and Conodont Faunas Band C. 

Proconodontus Zone 

The lowest productive sample from the Narrow Passage 

Creek section was from the upper part of the Conococheague 

Limestone, 5 m above the base of the sampled section, and 

yielded Eoconodontus notchpeakensis (Miller), Proconodontus serratus Miller, Prooneotodus rotundatus (Druce and 

Jones), and Teridontus nakamurai (Nogami). Specimens of 

Cambrooistodus minutus (Miller) were first recovered 

53.5 m higher (fig. 4). Because Cambrooistodus minutus and 

Proconodontus serratus are not known to range into the 

overlying Cordylodus proavus Zone, the lower 64 m of the 

Narrow Passage Creek section is within the Proconodontus 

Zone. 

No conodonts indicative of the Proconodontus Zone 

were recovered from the Timberville section. 

Cordylodus proavus Zone 

The lowest Cordylodus proavus Zone conodonts from 

the Narrow Passage Creek section occur 65 m above the base 

of the section. This horizon yielded Clavohamulus elongatus? 

Miller, Cordylodus proavus Muller, Eoconodontus notchpeakensis (Miller), Fryxellodontus inomatus Miller, F. 

lineatus Miller, Hirsutodontus hirsutus Miller, Semiacontiodus nogamii (Miller), and Teridontus nakamurai. The 

association of Fryxellodontus inomatus and F. lineatus with 

Clavohamulus elongatus? and Semiacontiodus nogamii suggests that this horizon lies within the Clavohamulus elongatus 

Subzone. Clavohamulus elongatus and Semiacontiodus 

nogamii are not known to occur below the C. elongatus Subzone, and both Fryxellodontus inomatus and F. lineatus may 

extend to the top of the C. elongatus Subzone. The remainder 

of the Cordylodus proavus Zone interval yielded few conodonts. However, Utahconus utahensis (Miller) first occurs 

108 m above the base of the section, marking the base of 

the Hirsutodontus simplex Subzone. 

Cordylodus proavus Zone conodonts occur at the base 

of the Timberville section (for example, Hirsutodontus hirsutus; fig. 5). Because conodonts are sparse in this interval, 

subzones could not be recognized. The Cordylodus proavus 

Zone extends at least to 67 m above the base of the section, 

and specimens of Eoconodontus notchpeakensis, Teridontus 

nakamurai, and Utahconus utahensis were recovered from 

this zone. 

Conodont Fauna B 

Fauna B of Ethington and Clark (1971) is characterized by an association of conodonts, the lower limit of which 

is defined by the lowest occurrence of Cordylodus lindstromi 

Druce and Jones. Miller and others (1982) divided this faunal 

interval into a lower part with Cordylodus lindstromi and an 

upper part with Cordylodus angulatus. In both the Narrow 

Passage Creek and Timberville sections, Cordylodus lindstromi was first recovered with species characteristic of 

Fauna C and therefore is not useful as a local approximation of Fauna B. Other conodonts characteristic of Fauna B 

were used to identify this interval. At Narrow Passage Creek, 

the lowest occurrence of ''Oistodus '' triangularis Furnish 

s.f. at 142m above the base of the section was used to approximate the lower limit of Fauna B because this species 

is not known from the Cordylodus proavus Zone. The lowest 

occurrence of ''Oistodus ''triangularis s.f. at the Timberville section is at 90 m above the base of the section. 

However, Cordylodus angulatus Pander was recovered 3 m 

higher, indicating that the horizon 93 m above the base is 

within the upper part of Fauna Borin Fauna C. Therefore, 

it is difficult to recognize Fauna B in the Timberville section. Fauna B may be present in this section, but larger 

samples would be required to document this possibility. 

Conodont Fauna C 

Loxodus bransoni Furnish is a distinctive species 

occurring within Fauna C (Ethington and Clark, 1971); however, in this investigation as in others, it was not abundant. 

Repetski and Ethington (1983) suggested that Rossodus 

manitouensis Repetski and Ethington is characteristic of 

Fauna C. By using the lowest occurrence of this species as 

an approximation of the faunal interval, Fauna C can be 

delineated at both sections. Rossodus manitouensis first 

occurs at 169m above the base of the Narrow Passage Creek 

Cambrian and Ordovician Conodonts from the Conococheague and Stonehenge Limestones A5 
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Figure 4. Distributions of selected conodont species in the Narrow Passage Creek section, along Narrow Passage Creek, 

3 km southwest of Woodstock, Shenandoah County, along State Road 605, lat 38° 51.8' N., long 78° 30.0' W., Edinburg 

7.5-minute quadrangle. Numerals next to dots represent number of specimens. 

A6 Shorter Contributions to Paleontology and Stratigraphy 
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Figure 5. Distributions of selected conodont species in the Timberville section, along Honey Run, 4 km northwest of Timberville, Rockingham County, along State Road 881, lat 38° 40.3' N., long 78° 48.5' W., Timberville 7.5-minute quadrangle. Numerals next to dots represent number of specimens. 

Cambrian and Ordovician Conodonts from the Conococheague and Stonehenge Limestones A7 
section and 104 m above the base of the section at Timberville. A greater diversity of conodonts appears in the interval of Fauna C; these taxa are listed in the systematics section 

and selected species are shown in figures 4 and 5. The 

uppermost beds of both sections are within the interval of 

Fauna C. 

DISCUSSION 

Conodont data from northwestern Virginia demonstrate 

that conodont zonal units and faunal intervals recognized 

elsewhere in North America are present in the central 

Appalachians. The faunal succession from the upper part of 

the Proconodontus Zone through the Cordylodus proavus 

Zone is similar to that described by Miller (1978, 1980) for 

sections in the Western United States. Although these zonal 

units are recognized in northwestern Virginia, conodont 

yields were too low to document subzonal units precisely. 

Faunal intervals Band C of Ethington and Clark (1971) are 

also present, at least in part, in the study area. 

Pending a decision by the International Working Group 

on the Cambrian-Ordovician Boundary, the CambrianOrdovician boundary for North America is now placed at 

the base of the trilobite Missisquoia Zone, within the conodont Hirsutodontus hirsutus Subzone of the Cordylodus 

proavus Zone. Using this definition, the CambrianOrdovician boundary lies within the uppermost 50 m of the 

Conococheague Limestone in northwestern Virginia. The 

possible establishment of a stratigraphically higher horizon 

for the international standard may raise the systemic boundary close to the Conococheague-Stonehenge formational 

contact. 

Carbonate depositional environments through the 

Cambrian-Ordovician boundary interval in northwestern 

Virginia show a progression from subtidal-to-peritidal cyclic 

deposition in the Conococheague Limestone through a persistent subtidal environment in the Stonehenge Limestone. 

Cyclic carbonate deposits of intraformational lime grainstone 

through laminated dolostone gradually gives way to completely subtidal lime grainstone deposits with sparse 

stromatolite bioherms near the Conococheague-Stonehenge 

boundary. Therefore, a rise in sea level may have occurred 

through this interval. Although the paleoenvironmental 

change is not drastic, the peritidal dolostone deposits become 

less prominent in the lower part of the strata within the 

Cordylodus proavus Zone. 

Preliminary data in this investigation and by Orndorff 

and others (1988) for northwestern Virginia, and by Taylor 

(1986) for sections in western Maryland and central Pennsylvania, suggest that the paleoenvironmental changes near 

the Conococheague-Stonehenge contact may occur at 

different biostratigraphic levels along strike in the central 

Appalachians. Additional study throughout the central 

Appalachians is needed to substantiate this hypothesis. 

A8 Shorter Contributions to Paleontology and Stratigraphy 

The biostratigraphic data from the Narrow Passage 

Creek section show a 2-m separation between conodonts of 

the Cambrooistodus minutus Subzone and Clavohamulus 

elongatus Subzone. Therefore, the two lower subzones of 

the Cordylodus proavus Zone are either missing or are 

represented by only 2 m of strata. Samples from this interval were barren of conodonts. Elsewhere in North America 

and on other continents, these two lower subzones are 

represented in an interval considerably thicker than that at 

the Narrow Passage Creek section. In the House Range of 

Utah, the Hirsutodontus hirsutus and Fryxellodontus inornatus Subzones are contained in a 30-m interval while in central Texas, this same interval is 6 m (Miller and others, 

1982). Miller (1984) explained the smaller interval in Texas 

by means of an unconformity, with part of the Hirsutodontus hirsutus and Fryxellodontus inornatus Subzones missing. 

Because of physical evidence of unconformities, other 

lithologic data (shallow-water and high-energy sediments), 

and paleontologic changes (disappearance of many Proconodontus Zone conodonts and Saukia Zone trilobites), 

Miller suggested the occurrence of a eustatic event near the 

Cambrian-Ordovician boundary. He named this event the 

Lange Ranch Eustatic Event (LREE) for the well documented 

Lange Ranch section in central Texas. Miller considered this 

event eustatic because many sections throughout the world 

show evidence of a sea level change near the CambrianOrdovician boundary. The top of the Proconodontus Zone 

in central Texas is an unconformity thought to be caused by 

a rapid drop in sea level. A subsequent slow rise in sea level 

is thought to have occurred at the beginning of Cordylodus 

proavus Zone time, as evidenced by shallow-water deposits 

in many parts of the world. 

Even though the Proconodontus Zone-Cordylodus proavus Zone boundary occurs within the cyclic carbonates of 

the Conococheague Limestone in northwestern Virginia, the 

postulated LREE may be represented in the 2-m interval 

between the Cambrooistodus minutus Subzone and the 

Clavohamulus elongatus Subzone. The top of each carbonate 

cycle is an unconformity, and it is difficult to establish how 

much time is missing; however, the unconformity above the 

Cambrooistodus minutus Subzone at the Narrow Passage 

Creek section may have a considerable amount missing compared to sections in Utah and Nevada discussed by Miller 

and others (1982) and Miller (1984). If the LREE is 

represented by the top of the cycle above the last sample 

yielding Cambrooistodus minutus Subzone conodonts, then 

the drop in sea level is represented by the unconformity, and 

the subsequent transgression may be recognized by the 

initiation of the following cycle. 

SYSTEMATIC PALEONTOLOGY 

Multielement taxonomy is used for taxa that have 

apparatuses previously established. Species whose appara-
tuses are uncertain or poorly known are reported in form 

taxonomy (sensu formo; s.f.). Generally, only the rare 

species of the latest Cambrian and earliest Ordovician are 

described here; descriptions of the more common species can 

be found in the original diagnoses or in the cited references. 

Notable variations or similarities of the specimens in this 

study to previously described taxa are noted under remarks. 

Sample numbers are coded abbreviations of the sampled 

section followed by meters above the base of the section. 

Illustrated specimens are reposited in the collections of the 

U.S. National Museum (USNM), Washington, D.C. 

Acodus oneotensis Furnish s.f. 

Plate 1, figures 1, 2 

Acodus oneotensis Furnish, 1938, p. 325, pl. 42, figs. 26-29, text-fig. IN; 

Ethington and Clark, 1971, p. 72. pl. 1, figs. 3, 6, 8; Ethington and Clark, 

1981, p. 20, pl. 1, fig. 16; Repetski, 1982, p. 12, pl. 2, figs. 7, 8, textfig. 4C. 

Description.-The elements of Acodus oneotensis s.f. 

are erect cones with three prominent costae. These costae 

are arranged asymmetrically, occurring at anterolateral and 

posterolateral positions and extending to slightly above the 

basal margin. The basal cavity is moderately deep to deep. 

In lateral view, the basal margin is straight; the basal cross 

section is circular. 

Remarks.-Previous workers have discussed possible 

multielement relationships between Acodus oneotensis s.f. 

and other form species (Sweet and Bergstrom, 1972; Repetski, 1982). However, these multielement relationships are 

uncertain. Sweet and Bergstrom (1972) suggested that Acodus 

oneotensis s.f. is part of an apparatus containing Paltodus 

bassleri Furnish s.f., Paltodus variabilis Furnish s.f., and 

"Oistodus" triangularis Furnish s.f. Ethington and Clark 

( 1981) rejected this multielement reconstruction due to a 

difference in robustness between elements of Acodus oneotensis s.f. and "Oistodus" triangularis s.f. Nowlan (1985) 

included Acodus oneotensis s.f. in a taxonomic grouping 

"Paltodus bassleri" which included P. bassleri s. f., 

P. variabilis s.f., and A. oneotensis s.f. The "Paltodus 

bassleri '' group was based on the co-occurrence of these 

form species in Canadian Arctic Island collections. Repetski (1982) suggested a relationship between Acodus oneotensis s. f., Scolopodus sulcatus Furnish s. f., and Scolopodus 

sexplicatus Jones s.f. However, these relationships cannot 

be determined from my material because of few specimens, 

and thus they are considered as form taxa. 

Occurrence.-Narrow Passage Creek samples 

NPC-178, NPC-181, NPC-188, NPC-194, NPC-197; 

Timberville samples T -134, T -148, T -153, T -157, T -175. 

Number of specimens.-34. 

Figured specimens.-NPC-178, NPC-197. 

Acontiodus iowensis Furnish s.f. 

Plate 1 , figure 3 

Acontiodus iowensis Furnish, 1938, p. 325-326, pl. 42, figs. 16, 17, textfig. lL; Ethington and Clark. 1981, p. 23, pl. 1, fig. 15; Repetski, 1982, 

p. 14, pl. 4, figs. 1, 3. text-fig. 4G; Nowlan, 1985, p. 105, fig. 4.12. 

Scolopodus iowensis (Furnish). Druce and Jones, 1971, p. 93, pl. 16, figs. 

la-7e; Jones, 1971, p. 64, pl. 6, figs. 3a-4c, pl. 9, figs. 5a-c; Landing 

and Barnes, 1981, p. 1614, pl. 4, figs. 7, 11-14, 16, 18-21. 

Semiacontiodus iowensis (Furnish). Landing and others, 1986, p. 1942, 1943, 

pl. 1, figs. 4, 6, 10, text-figs. 3B, C, H. 

Remarks. -Specimens from this study assigned to 

Acontiodus iowensis Furnish s.f. conform to the description 

of Furnish (1938). These elements contain a well-rounded 

and broad anterior keel and lateral keels. The posterior face 

of the cusp has a central carina with a large groove to either 

side. The base is elliptical with the long axis in the lateral 

direction. Rapid tapering of the cusp is characteristic of the 

genus. A multielement apparatus for this species was suggested by Landing and others ( 1986) as Semiacontiodus 

iowensis. These authors included Acontiodus staufferi Furnish s. f. and Oistodus mehli Furnish s. f. with Acontiodus 

iowensis s.f. Specimens of Acontiodus staufferi s.f. and 

Oistodus mehli s.f. were not recovered from Faunas B or 

C in northwestern Virginia, thus the form sense is maintained 

in this study. 

Occurrence.-Narrow Passage Creek samples NPC169, NPC-181, NPC-188. 

Number of specimens. -6. 

Figured specimen.-NPC-181. 

Acontiodus propinquus Furnish s.f. 

Plate 1, figure 4 

Acontiodus propinquus Furnish, 1938, p. 326, pl. 42, figs. 13-15, textfig. 1M; Ethington and Clark, 1971, p. 72, pl. 1, fig. 5; Repetski and 

Ethington, 1977, p. 95, pl. 1, fig. 8; Ethington and Clark, 1981, p. 24, 

pl. 1, fig. 26; Repetski, 1982, p. 14, pl. 2, fig. 13, text-fig. 4J; Nowlan, 

1985, p. 107, fig. 4.11. 

Remarks.-The specimen of Acontiodus propinquus 

Furnish s. f. recovered from the Timberville section is 

bilaterally symmetrical with a rounded anterior and a dishshaped posterior, and conforms to the diagnosis of Furnish 

(1938). The basic form of this species is similar to Acontiodus iowensis s.f., but A. iowensis s.f. contains a posterior 

carina that is not present in A. propinquus s.f. 

Occurrence.-Timberville sample T -116. 

Number of specimens.-!. 

Figured specimen.-T -116. 

Cambrooistodus minutus (Miller) 

Plate 1 , figure 5 

Oistodus minutus Miller, 1969, p. 433, pl. 66. figs. 1-4, non 5-7, text-fig. 

5B. 

Cambrooistodus minutus (Miller), 1980, p. 11, pl. 1, fig. 8, text-fig. 4F; 

Chen and others, 1985, p. 84, 85, pl. 26, figs. 8, 9, text-fig. 13(4). 

Remarks.-Two specimens of Cambrooistodus minutus 

were recovered from the Narrow Passage Creek section. 

These specimens conform to Miller's ( 1980) description of 

the compressed, asymmetrical element of the genus, and are 

identified to the species level by the shallow basal cavity. 

Elements of Cambrooistodus contain white matter and have 

Cambrian and Ordovician Conodonts from the Conococheague and Stonehenge Limestones A9 
anterior and posterior keels along with a carina on the inner 

side of the base. Miller (1969, 1980) described two species, 

Cambrooistodus cambricus and C. minutus, that he separated 

by the greater depth of the basal cavity and the robustness 

of C. cambricus. 

Occurrence.-Narrow Passage Creek samples NPC58.5, NPC-63. 

Number of specimens.-2. 

Figured specimen.-NPC-63. 

Clavohamulus densus Furnish 

Plate 1, figure 6 

Clavohamulus densus Furnish, 1938, p. 327, pl. 42, figs. 18-21; Ethington 

andClark, 1971,p. 72,pl.l,fig.I3;EthingtonandClark, 198I,p. 30, 

pl. 2, fig. 26; Repetski, 1982, p. 15, pl. 4, fig. 6. 

Remarks.-The diagnosis of this species by Furnish 

(1938) agrees well with specimens recovered from the 

Narrow Passage Creek and Timberville sections. Most of 

the specimens in this study have a shallow pit or an attachment surface. The specimen described by Furnish (1938) 

possessed a bladelike cusp; however, specimens from this 

study have a cylindrical cusp. 

Occurrence.-Narrow Passage Creek samples NPC181, NPC-194, NPC-197; Timberville samples T-139, 

T-157. 

Number of specimens.-15. 

Figured specimen.-NPC-197. 

Clavohamulus elongatus? Miller 

Plate I, figure 7 

?Clavohamulus elongatus Miller, 1969, p. 442, pl. 64, figs. 13-18; Ethington 

and Clark, 1981, p. 30, pl. 2, fig. 23. 

?Clavohamulus primitus Miller, 1969, p. 423, pl. 64, figs. 7-12; Ethington 

and Clark, 1981, p. 30, pl. 2, fig. 20. 

Description.-The specimen from Narrow Passage 

Creek tentatively assigned to Clavohamulus elongatus? is 

a bulbous, bilaterally symmetrical element that is elongated 

antero-posteriorly and has a short cusp on the posterior. 

Nodes are present on the upper surface, and only a small 

basal depression exists. 

Remarks.-This element resembles the oldest Clavohamulus species, C. elongatus. Lindstrom (1973) discussed 

the synonymy of Clavohamulus primitus s. f. Miller with C. 

elongatus s.f. and concluded that C. primitus may approach 

radial symmetry and therefore could be a synonym of C. 

elongatus. This synonymy was later accepted by Miller 

(1980). 

Occurrence.-Narrow Passage Creek sample NPC-65. 

Number of specimens. -1. 

Figured specimen.-NPC-65. 

Cordylodus angulatus Pander 

Plate 1 , figures 8, 9 

Cordylodus angulatus Pander, 1856, p. 33, pl. 2, figs. 27-31, pl. 3, fig. 

10; Muller, 1973, p. 27, pl. 11, figs. 1-5, ?6, 7, text-figs. 2G, 3; Miller, 

1980, p. 13-16, pl. I, figs. 22, 23, text-figs. 4Q, ?R; Landing and Barnes, 

1981, p. 1614, pl. 3, fig. 11, text-fig. 3(4); Repetski, 1982, p. 16, pl. 

A 1 0 Shorter Contributions to Paleontology and Stratigraphy 

4, fig. 9, text-fig. 4L; Nowlan, 1985, p. 108-109, fig. 4.10; Landing 

and others, 1986, pl. I, fig. 18. 

Cordylodus prion Lindstrom, 1955, p. 522, pl. 5, figs. 14-16; Druce and 

Jones, 1971, p. 70, pl. 2, figs. 1-7, text-figs. 23i, k, o; Muller, 1973, 

p. 33, pl. 10, fig. 4, text-figs. 2E, 8. 

Cyrtoniodus prion (Lindstrom). Ethington and Clark, 1971, pl. 1, fig. 21; 

Miller, 1971, (in part) p. 79, pl. I, figs. 14-16. 

Cordylodus sp. A Druce and Jones, 1971, p. 72, pl. 8, fig. 10, text-fig. 23U. 

Remarks.-Miller (1980) reassigned many species of 

Cordylodus from previous investigations to Cordylodus 

angulatus mainly based on the shape of the basal cavity. He 

recognized the basal cavity as the distinctive feature in 

designating species of Cordylodus. All Cordylodus specimens 

in this study are identified to species level by their basal cavity 

following Miller's (1980) descriptions. He noted a possible 

evolution from Cordylodus intermedius Furnish, which has 

an anteriorly concave or straight anterior edge of the basal 

cavity of the rounded element, to Cordylodus angulatus 

whose basal cavity profile is strongly concave anteriorly. 

Also, he noted possible transitional elements between the two 

species. The apparatus is interpreted to contain a compressed 

element (the form species Cordylodus prion Lindstrom). This 

form species has also been associated with other Cordylodus 

apparatuses such as Cordylodus rotundatus Pander, C. intermedius, and C. drucei. Miller suggested that elements conforming to this morphotype of the form species C. prion were 

part of all of these apparatuses. 

Occurrence.-Narrow Passage Creek samples NPC169, NPC-178, NPC-181, NPC-188, NPC-194, NPC-197; 

Timberville samples T-93, T-104, T-116, T-144. 

Number of specimens. -46. 

Figured specimens.-NPC-169, NPC-181. 

Cordylodus intermedius Furnish 

Plate 1 , figure 10 

Cordylodus intermedius Furnish, 1938, p. 338, pl. 42, fig. 31, text-fig. 

2C; Druce and Jones, 1971, p. 68, pl. 3, figs. 1-3, text-figs. 23f, g; 

Muller, 1973, p. 30, pl. 10, figs. 1-3, text-figs. 2C, 4; Miller, 1980, 

p. 17-18, pl. 1, figs. 16, ?17, text-figs. 4L, ?M; Landing and others, 

1980, p. 19-20, figs. 5E, 6A, B; Fortey and others 1982, text-figs. 8D, 

K; Repetski, 1982, p. 17, pl. 5, fig. 2, text-fig. 4M; Nowlan, 1985, p. 

109, figs. 4.1, 4.2; Landing and others, 1986, pl. 1, fig. 13, text-fig. 3F. 

Cordylodus cf. C. angulatus Pander. Druce and Jones, 1971, p. 67, textfig. 23c. 

Cordylodus caseyi Druce and Jones, 1971, p. 67, pl. 2, figs. 9-12, textfigs. 23d, e. 

Cordylodus Ienzi Muller, 1973, p. 31, pl. 10, figs. 5-9, text-figs. 2F, 5. 

Cordylodus oklahomensis Muller. Druce and Jones, 1971, p. 69, pl. 5, figs. 

6, 7, text-fig. 23j. 

Cordylodus proavus Muller. Druce and Jones, 1971, p. 70, pl. 1, fig. 1, 

text-fig. 23p. 

Remarks.-Druce and Jones (1971) interpreted Cordylodus intermedius as the evolutionary intermediate between 

Cordylodus proavus, which has a basal cavity whose tip 

extends well into the main cusp, and Cordylodus angulatus, 

whose basal cavity extends only as deep as the height of the 

posterior process. These observations were based mainly on 

the rounded elements. Miller (1980) included a compressed 

element in the apparatus, the form species of Cordylodus 
previously assigned to C. oklahomensis Muller and C. prion 

Lindstrom. These compressed elements also show, in some 

cases, the distinctively shaped basal cavity. 

Occurrence.-Narrow Passage Creek samples NPC169, NPC-178, NPC-181, NPC-188, NPC-197; Timberville 

sample T -93. 

Number of specimens.-23. 

Figured specimen.-NPC-181. 

Cordylodus lindstromi Druce and Jones 

Plate 1 , figure 11 

Cordylodus lindstromi Druce and Jones, 1971, p. 68, pl. 1, figs. 7-9, pl. 

2, fig. 8, text-fig. 23h; Muller, 1973, p. 32, pl. 9, figs. 10, 11, text-figs. 

2D, 6; Miller, 1980, p. 18-19, pl. 1, figs. 18, 19, text-figs. 41, J; Repetski, 1982, p. 17-18, pl. 5, figs. 4, 5, text-fig. 40; Landing and others, 

1986, pl. 1, figs. 9, 14, text-figs. 31, Q. 

Cordylodus angulatus Pander. Lindstrom, 1955, p. 551, text-fig. 3E. 

Cyrtoniodus prion (Lindstrom). Miller, 1971, (in part) p. 79, pl. 1, figs. 

14-16, non 17. 

Remarks.-Elements of Cordylodus lindstromi in this 

study are similar to Cordylodus intermedius. However, the 

basal cavity of Cordylodus lindstromi contains a secondary 

apex that extends into the first and in some cases the second 

denticle posterior to the cusp. Also, elements of Cordylodus 

lindstromi do not have lateral bulges on the posterior process, 

as do elements of C. intermedius. 

Occurrence.-Narrow Passage Creek samples NPC169, NPC-178, NPC-194. 

Number of specimens. -13. 

Figured specimen.-NPC-178. 

Cordylodus proavus Muller 

Plate 1 , figures 12, 13 

Cordylodus proavus Muller, 1959, p. 448, pl. 15, figs. 11, 12, 18, textfig. 3B; Miller, 1969, p. 424, pl. 65, figs. 37-45, text-fig. 3D; Ethington 

and Clark, 1971, pl. 1, fig. 19; Druce and Jones, 1971, p. 70, pl. 1, 

figs. 2-6; Muller, 1973, p. 35, pl. 9, figs. 1-9, text-figs. 2A, 9; Fahraeus 

and Nowlan, 1978, p. 453, pl. 1, figs. 8, 9; Miller, 1980, p. 19-20, pl. 

1, figs. 14, 15, text-figs. 4G, H; Fortey and others, 1982, text-figs. 8F, 

J; Nowlan, 1985, p. 111, figs. 5.12, 5.13, 5.17-5.19; Landing and others, 

1986, pl. 1, fig. 5, text-fig. 3E. 

Cordylodus cf. C. proavus Muller. Druce and Jones, 1971. p. 71, pl. 1, 

figs. 10-12, text-fig. 23s. 

Cordylodus oklahomensis Muller, 1959, p. 447, pl. 15, figs. 15, 16, textfig. 3A; Miller, 1969, p. 423, pl. 65, figs. 46-53, text-fig. 31; Ethington 

and Clark, 1971, pl. 1, fig. 24; Muller, 1973, p. 33, pl. 9, figs. 12, 13, 

text-figs. 2B, 7; Landing and others, 1980, p. 21-24, figs. 5A, D, 6C-E; 

Fortey and others, 1982, text-figs. 8G, 0. 

Remarks.-Both rounded and compressed elements are 

present in the Narrow Passage Creek section. The distinguishing characteristic of Cordylodus proavus from other 

species of Cordylodus is the convex anterior edge of the basal 

cavity that parallels the edge of the element. Also, the basal 

cavity extends well into the main cusp, above the level of 

the posterior process. This study follows Miller ( 1980) in 

which the compressed element, formerly Cordylodus oklahomensis s.f., is included in the Cordylodus proavus 

apparatus. 

Occurrence.-Narrow Passage Creek samples NPC65, NPC-108. 

Number of specimens.-59. 

Figured specimens.-NPC-65. 

Cordylodus rotundatus Pander 

Plate 1, figure 14 

Cordylodus rotundatus Pander, 1856, p. 33, pl. 2, figs. 32, 33; Lindstrom, 

1955, p. 533, pl. 5, figs. 17-20, text-fig. 3F; Druce and Jones, 1971, 

p. 71, pl. 3, figs. 8-10, text-fig. 23f; Ethington and Clark, 1971, pl. 1, 

fig. 17, text-fig. 2; Muller, 1973, p. 36, pl. 11, figs. 8-10, text-figs. 

2H, 10; Miller, 1980, p. 20-21, pl. 1, fig. 24, text-fig. 4P; Repetski, 

1982, p. 18, pl. 5, fig. 3, text-fig. 4N; Nowlan, 1985, p. 111-112, fig. 4.3. 

Cordylodus subangulatus Furnish, 1938, p. 337, pl. 42, fig. 32, text-fig. 2D. 

Cyrtoniodus prion (Lindstrom). Ethington and Clark, 1971, pl. 1, fig. 21. 

Remarks.-Miller ( 1980) discussed the Cordylodus 

rotundatus apparatus as containing the form species C. rotundatus as the rounded element and C. prion s. f. as the compressed element. The distinctive basal cavity of the rounded 

element is recognized by the strongly concave anterior edge 

and recurved tip. Also, the anterobasal margin is well 

rounded. 

Occurrence.-Narrow Passage Creek samples NPC181, NPC 188; Timberville samples T-116, T-134. 

Number of specimens.-?. 

Figured specimen.-NPC-181. 

Drepanodus cf. D. arcuatus Pander 

Plate 1 , figure 15 

cf. Drepanodus arcuatus Pander, 1856, p. 20, pl. 1, figs. 2, 4, 5; Lindstrom, 1955, p. 558-560, pl. 2, figs. 30-33; Lindstrom, 1973, p. 67-68, 

pl. 1, figs. 1, 2; Fahraeus and Nowlan, 1978, p. 458, pl. 2, figs. 1?, 

2, 8; Ethington and Clark, 1981, p. 36, 37, pl. 3, figs. 4-6, 12; Repetski, 1982, p. 19, pl. 6, fig. 1; Landing and others, 1986, pl. 2, fig. 2. 

cf. Drepanodus jlexuosus Pander, 1856, p. 20, pl. 1, figs. 6-8. 

cf. Drepanodus cf. arcuatus Pander. Lindstrom, 1955, p. 560-561, pl. 2, 

figs. 45, 46, text-fig. 4C. 

cf. Drepanodus sculponea Lindstrom, 1955, p. 567, pl. 2, fig. 40, textfig. 3L. 

cf. Scandodus pipa Lindstrom, 1955, p. 593, pl. 4, figs. 38-42, text-fig. 

3P; Ethington and Clark, 1964, p. 698, pl. 114, fig. 8. 

cf. ?Drepanodus arcuatus Pander. Ethington and Clark, 1981, p. 36-37, 

pl. 3, figs. 4-6, 12. 

Remarks.-This multielement apparatus was diagnosed 

by Lindstrom (1973) to include the form species Drepanodus 

arcuatus Pander s. f., Drepanodus sculponea Lindstrom s. f., 

and Scandodus pipa Lindstrom s.f. The specimen recovered 

from Narrow Passage Creek identified as Drepanodus cf. 

D. arcuatus resembles the arcuatiform element as illustrated 

by Ethington and Clark (1981). 

197. 

Occurrence.-Narrow Passage Creek sample NPCNumber of specimens. -1. 

Figured specimen.-NPC-197. 

Drepanoistodus pervetus Nowlan 

Plate 1, figures 16-18 

Drepanoistodus? pervetus Nowlan, 1985, p. 112, figs. 5.53-5.55, 6.1-6.3. 

Oistodus suberectus Branson and Mehl, 1933, p. 111, pl. 9, fig. 7. 

Cambrian and Ordovician Conodonts from the Conococheague and Stonehenge Limestones A 11 
Drepanoistodus? n. sp. Landing and Barnes, 1981, p. 1615-1616, pl. 2, 

figs. 1, 2, 5, 7, 8. 

Drepanoistodus suberectus subsp. A, n. sp. (Branson and Mehl), Repetski, 

1982, p. 25, pl. 7, fig. 13, pl. 8, fig. 5. 

Remarks.-Nowlan (1985) recognized the multielement 

apparatus Drepanoistodus? pervetus that included a nongeniculate oistodontiform element, a suberectiform element, 

and a homocurvatiform element. Characteristic of this species 

are the variability of the curvature between the cusp and the 

base, and the lack of costae. Only the suberectiform and 

homocurvatiform elements were recovered from Narrow 

Passage Creek and Timberville. 

Occurrence. -Narrow Passage Creek samples NPC169, NPC-181, NPC-206; Timberville samples T-153, 

T-162. 

Number of specimens. -Suberectiform-6, homocurvatiform-4. 

Figured specimens.-NPC-181, NPC-206, T-153. 

Eoconodontus notchpeakensis (Miller) 

Plate 1, figures 19, 20 

Proconodontus notchpeakensis Miller, 1969, p. 438, pl. 66, figs. 21-29, 

text-fig. 5G; Lindstrom, 1973, p. 43, pl. 4, fig. 6. 

Oneotodus nakamurai Nogami, 1966, (in part) p. 216, pl. 1, figs. 10, 11, 

text-figs. 30, E. 

Proconodontus carinatus Miller, 1969, p. 437, pl. 66, figs. 13-20, textfig. 51; Landing and others, 1980, p. 31-33, figs. 5C, F, 80-H. 

Eoconodontus notchpeakensis (Miller), 1980, p. 22, 23, pl. 1, figs. 10-12 

[synonymy to 1980]; Landing 1983, p. 1177, text-figs. llP, Q; Chen 

and others, 1985, p. 89, pl. 25, figs. 12-14, text-fig. 13(3). 

Remarks.-Miller (1980) erected the genus Eoconodontus to include coniform elements with both oval and compressed cross sections. The compressed element of this 

apparatus possesses anterior and posterior keels and formerly 

was assigned to the form species Proconodontus carinatus 

(Miller, 1969). The rounded element is Proconodontus notchpeakensis s.f. The characteristic that separates Eoconodontus elements from those of Proconodontus is the occurrence 

of white matter in the cusp of elements of Eoconodontus. 

Occurrence.-Narrow Passage Creek samples NPC-5, 

NPC-37, NPC-43, NPC-48, NPC-52, NPC-58, NPC-59, 

NPC-62, NPC-64, NPC-65 NPC-136; Timberville sample 

T-67. 

Number of specimens. -183. 

Figured specimens. -NPC-59. 

Eucharodus cf. E. parallelus (Branson and Mehl) 

Plate 1 , figure 21 

cf. Drepanodus parallelus Branson and Mehl, 1933, p. 59, pl. 4, fig. 17; 

Jones, 1971, p. 52-53, pl. 8, figs. 5a-c; Lee, 1975, p. 86, pl. 1, fig. 

16, text-fig. 3M; Repetski, 1982, p. 21, pl. 6, figs. 9, 10. 

cf. Drepanodus simplex Branson and Mehl, 1933, p. 58, pl. 4, fig. 2; Barnes 

and Tuke, 1970, p. 86, pl. 19, fig. 8, 12, 13; Muller, 1973, p. 37, pl. 

5, fig. 5; Fdhraeus and Nowlan, 1978, p. 450-451, 457, pl. 2, fig. 14. 

cf. Drepanodus arcuatus Pander. Branson and Mehl, 1933, p. 58, pl. 4, 

figs. 7, 8, 13. 

cf. Drepanodus subarcuatus Furnish, 1938, p. 320, 328, pl. 41, figs. 25-30, 

pl. 42, figs. 2, 3; Ethington and Clark, 1971, p. 72-74, pl. 2, fig. 1, 

text-fig. 2. 

A 12 Shorter Contributions to Paleontology and Stratigraphy 

cf. Drepanodus tortus Furnish, 1938, p. 329, pl. 42, fig. 6. 

cf. Eucharodus parallelus (Branson and Mehl). Kennedy, 1980, p. 58-60, 

pl. 1, figs. 35-38 [synonymy]. 

Remarks.-Various workers have concluded that 

several form species, including Drepanodus parallelus Branson and Mehl s.f., D. arcuatus Pander s.f. (sensu Branson 

and Mehl, non Pander), D. simplex Branson and Mehl s.f., 

and D. subarcuatus Furnish s.f. are conspecific and that the 

species is variable (Kennedy, 1980; Repetski, 1982). Kennedy (1980), in his reexamination of Branson and Mehl's 

(1933) fauna from the Jefferson City Formation, assigned 

the apparatus to Eucharodus parallelus (Branson and Mehl). 

Eucharodus parallelus is a common species of Early Ordovician Faunas D and E. However, the ancestry is unclear 

and possibly occurs in the Fauna C interval. Noting the long 

range of this species and its wide variability in morphology, 

one hyaline and finely striated cone recovered from Narrow 

Passage Creek is assigned as being comparable to 

Eucharodus parallelus. 

169. 

Occurrence.-Narrow Passage Creek sample NPCNumber of specimens. -1. 

Figured specimen.-NPC-169. 

Fryxellodontus inornatus Miller 

Plate 1, figures 22, 23 

Fryxellodontus inornatus Miller, 1969, p. 426, pl. 65, figs. 1-10, 12-16, 

23-24, text-figs. 4A, C-E; Miller, 1980, p. 23, text-fig. 5; Landing and 

others, 1980, p. 24-25, fig. 7C-G; Chen and others, 1985, p. 89, 90, 

pl. 25, figs. 15, 16. 

Genus et sp. indet. B, Druce and Jones, 1971, p. 102, pl. 12, fig. 9, textfig. 33. 

Description.-This species consists of laterally compressed, bilaterally symmetrical and asymmetrical coniform 

elements with a strongly developed posterior costa extending from the tip of the cusp to the basal margin. The anterior 

is rounded and the basal cavity is very deep. The anteroposterior width of one element in the material at hand is only 

slightly less than the height; however, the other specimen 

is quite elongated (pl. 1, fig. 23). 

Remarks. -Miller (1969) described four element types 

for this species, including planar, serrate, symmetrical, and 

intermediate elements. Both specimens from Narrow Passage 

Creek are of the planar type. 

Occurrence.-Narrow Passage Creek sample NPC-65. 

Number of specimens.-2. 

Figured specimens.-NPC-65. 

Fryxellodontus lineatus Miller 

Plate 1 , figure 24 

Fryxellodontus lineatus Miller, 1969, p. 429, pl. 65, figs. 17-22, 26-29, 

text-figs. 4B, F. 

Fryxellodontus inomatus Miller, (part) 1969, p. 426, pl. 65, fig. 11. 

Description.-The specimen assigned to Fryxellodontus lineatus is an asymmetrical simple cone that is slightly 

compressed antero-posteriorly and possesses a posterior costa 

that extends from the tip of the cusp to the basal margin. 
Also, this specimen contains linear ridges on the rounded 

anterior side and the basal cavity is very deep. 

Remarks.-Three morphotypes were described by 

Miller (1969): a planar element, a symmetrical element, and 

an intermediate element. One intermediate element was 

recovered from Narrow Passage Creek. 

Occurrence.-Narrow Passage Creek sample NPC-65. 

Number of specimens. -1. 

Figured specimen.-NPC-65. 

Hirsutodontus hirsutus Miller 

Plate 1, figure 25 

Hirsutodontus hirsutus Miller, 1969, p. 431. pl. 64, figs. 25, 26, 29-31, 

text-fig. 41; Lindstrom, 1973, p. 119.2, 123; Miller, 1980, p. 25, pl. 

2, fig. 14; Fortey and others, 1982, text-fig. 8S. 

Remarks. -Specimens of Hirsutodontus hirsutus recovered in this study resemble those of Miller (1969). Some 

specimens have only anterior nodes whereas others have 

nodes that extend around one side. Miller (1980) discussed 

the differences in the species of Hirsutodontus, noting a well 

developed cusp consisting of nodes for H. hirsutus, large 

spines on the later species H. simplex (Druce and Jones), 

and small spines with a poorly developed cusp in H. rarus 

Miller. 

Occurrence.-Narrow Passage Creek samples NPC65, NPC-108, NPC-130, NPC-136; Timberville sample T-0. 

Number of specimens.-31. 

Figured specimen.-NPC-65. 

Loxodus bransoni Furnish 

Plate 1 , figure 26 

Loxodus bransoni Furnish, 1938, p. 339, pl. 42, figs. 33, 34, text-fig. 2A; 

Ethington and Clark, 1971, p. 72-73, pl. 1, fig. 11; Abaimova, 1975, 

p. 112, 114, pl. 10, figs. 12, 13, 15, text-figs. 8(35, 40, 43); Ethington 

and Clark, 1981, p. 52-53, pl. 5, fig. 15; Repetski, 1982, p. 27-28, pl. 

9, fig. 7, text-fig. 5P; Nowlan, 1985, fig. 4.29. 

Description. -Specimens of this species consist of a 

denticulate bar with the denticles erect at the anterior and 

progressively reclined posteriorly. Denticles decrease in size 

toward the posterior. The basal cavity is narrow and 

moderately deep. 

Remarks. -Specimens of Loxodus bransoni recovered 

from the Timberville section conform well with Furnish's 

(1938) description. Repetski (1982) noted an inward deflection of the basal margin in specimens of Loxodus bransoni 

from the El Paso Group of west Texas and southern New 

Mexico, found also in specimens from the Stonehenge 

Formation from south-central Pennsylvania by Sando (1958). 

This deflection was not shown in Furnish's specimens from 

the Prairie du Chien beds of the upper Mississippi Valley 

(Repetski, 1982), but it is present in the specimens recovered 

from the Timberville section. 

157. 

Occurrence.-Timberville samples T -121 , T -148, TNumber of specimens.-3. 

Figured specimen.-T -157. 

''Oistodus" triangularis Furnish s.f. 

Plate 2, figure 1 

Oistodus? triangularis Furnish, 1938, p. 330-331, pl. 42, fig. 22, textfig. lP; Ethington and Clark, 1971, p. 72, pl. 1, figs. 18, 22, 23. 

"Oistodus" triangularis Furnish. Repetski and Ethington, 1977, p. 95. 

Acodus triangularis Furnish. Repetski, 1982, p. 13, pl. 2, figs. 9-12. 

"Drepanodus" triangularis Furnish. Nowlan, 1985, p. 112, figs. 4. 7, 4.8. 

Description. -Specimens of '' Oistodus '' triangularis 

s.f. are erect to reclined coniform elements with a posterior 

keel that terminates at the lower margin. The cusp is compressed laterally and the cross section is triangular to ovate. 

One anterolateral corner of the base is keeled, but the keel 

does not continue to the cusp. The basal cavity is moderately deep. 

Remarks.-The multielement relationship of this conodont is uncertain. It was assigned tentatively to the genus 

Oistodus; however, it lacks the diagnostic characteristics of 

that genus in the form and multielement sense (Nowlan, 

1985). Repetski (1982) placed elements of "Oistodus" 

triangularis in an uncertain multielement apparatus that he 

called Acodus triangularis which may contain an oistodontiform element. Later, Repetski and Ethington (1983) rejected 

the idea of an oistodontiform element because that element 

was assigned to Rossodus manitouensis. Nowlan (1985) noted 

a relationship to the form genus Drepanodus. 

Occurrence.-Narrow Passage Creek samples NPC142, NPC-175, NPC-178, NPC-181, NPC-188, NPC-194, 

NPC-197; Timberville samples T-93, T-104, T-116, T-139, 

T-153. 

Number of specimens. -32. 

Figured specimen. -NPC-194. 

Paltodus bassleri Furnish 

Plate 2, figures 2, 3, 14 

Paltodus bass/eri Furnish, 1938, p. 331, pl. 42, fig. 1; Ethington and Clark, 

1971, p. 72, pl. 2, figs. 2, 4, 6; Repetski and Ethington, 1977, p. 95-96, 

pl. 1, fig. 1; Repetski and Perry, 1980, pl. 1, fig. 9, pl. 2, figs. 3, 17; 

Repetski, 1982, p. 37, pl. 14, fig. 12, text-fig. 6Q; Nowlan, 1985, p. 

118-120, figs. 10.1-10.4, 10.8-10.14, non 10.5-10.7. 

Paltodus variabilis Furnish, 1938, p. 331, pl. 42, figs. 9, 10, text-fig. IE; 

Ethington and Clark, 1965, p. 197-198. 

Variabiloconus bassleri (Furnish). Landing and others, 1986, p. 1946, 1947, 

pl. 3, figs. 1?, 2-7, 9. 

Remarks.-Elements from the Narrow Passage Creek 

and Timberville sections assigned to Paltodus bassleri conform to the description of Furnish (1938). Both symmetrical 

and asymmetrical elements were recovered. Furnish (1938) 

reported a relationship between the form species Paltodus 

bassleri and P. variabilis. This relationship was discussed 

by Repetski (1982), who suggested that both taxa are 

members of a symmetry-transition series within a single 

species. This symmetry-transition is recognized here and 

Paltodus bassleri is treated in the multielement sense. 

Landing and others (1986) referred specimens of Paltodus 

bassleri to a new genus Variabiloconus to emphasize the morphologic variation of elements within the apparatus; however, 

Cambrian and Ordovician Conodonts from the Conococheague and Stonehenge Limestones A 13 
specimens other than those previously referred to as Paltodus 

bassleri were included in their apparatus construction. 

Occurrence.-Narrow Passage Creek samples NPC157, NPC-166, NPC-169, NPC-175, NPC-178, NPC-181, 

NPC-188, NPC-194, NPC-197, NPC-206; Timberville 

samples T-104, T-116, T-130, T-139, T-148, T-153, T-157, 

T-167, T-175. 

Number of specimens.-??. 

Figured specimens.-NPC-157, NPC-181. 

Paltodus aff. P. spurius Ethington and Clark s.f. 

Plate 2, figure 4 

aff. Paltodus spurius Ethington and Clark, 1964, p. 695, pl. 114, figs. 3, 

10, text-fig. 2B; Ethington and Clark, 1971, p. 72, pl. 1, fig. 12. 

aff. "Paltodus" spurius Ethington and Clark, 1981, p. 76, pl. 8, figs. 9, 13. 

Description.-This specimen is a robust coniform 

element with a large base that expands posteriorly and 

anterolaterally. A lateral· groove extends from the basal 

margin to part way along the cusp. The basal cavity is 

moderately deep. 

Remarks.-This specimen resembles Paltodus spurius 

s.f. of Ethington and Clark (1964). Paltodus spurius s.f. was 

reported to have a lateral groove that becomes less prominent during growth (Ethington and Clark, 1981). The 

specimen identified as Paltodus aff. P. spurius s. f. from 

Narrow Passage Creek has a lateral groove at the basal 

margin that extends toward the cusp. The disappearance of 

the groove below the cusp may be an example of the larger 

elements mentioned by Ethington and Clark (1981) that have 

a less prominent groove. The single specimen reported here 

occurs in the interval of Fauna C and is consistent with 

published reports of Paltodus spurius s.f. 

197. 

Occurrence.-Narrow Passage Creek sample NPCNumber of specimens. -1. 

Figured specimen.-NPC-197. 

Proconodontus muelleri Miller 

Plate 2, figure 5 

Proconodontus mulleri mulleri Miller, 1969, p. 437, pl. 66, figs. 30-40, 

text-fig. 5H. 

Proconodontus muelleri muelleri Miller, 1971, pl. 2, fig. 18; Nowlan, 1985, 

p. 114, fig. 5.1. 

Proconodontus muelleri Miller, 1980, p. 29-30, pl. 1, fig. 7, text-fig. 4C; 

An, 1982, p. 141-142, pl. 12, figs. 8, 9, 11-13, pl. 16, figs. 10, 12; 

Landing, 1983, p. 1180, figs. llG, H; Chen and others, 1985, p. 95, 

pl. 26, figs. 10-13, text-figs. 13(1). 

Remarks. -Specimens assigned to this species conform 

to the description of Miller ( 1980). All of the specimens contain both anterior and posterior keels that extend to the basal 

margin in some specimens and terminate half-way down the 

cusp in others. 

Occurrence.-Narrow Passage Creek samples NPC58.5, NPC-62, NPC-63. 

Number of specimens.-10. 

Figured specimen.-NPC-63. 

A 14 Shorter Contributions to Paleontology and Stratigraphy 

Proconodontus serratus Miller 

Plate 2, figures 6, 7 

Proconodontus muelleri serratus Miller, 1969, p. 438, pl. 66, figs. 41-44; 

Lindstrom, 1973, p. 402, 403, 409. 

Coelocerodontus burkei Druce and Jones, 1971, p. 61, pl. 11, fig. 12. 

Proconodontus serratus Miller. Muller, 1973, p. 44, pl. 4, figs. 1, 2; Miller, 

1980, p. 31, pl. 1, fig. 13, text-fig. 4D; Landing and others, 1980, p. 

33, figs. 81-L. 

Description. -Proconodontus serratus consists of prodined, laterally compressed, coniform elements possessing 

an anterior keel that extends from the tip of the cusp to the 

basal margin. The posterior edge is partly serrated proximally 

and in some specimens may be entirely serrated. The basal 

cavity is very deep and extends to the tip of the cusp. 

Remarks.-This species is very similar to Proconodontus muelleri except that P. serratus has a serrate posterior 

edge. Miller (1980) suggested that Proconodontus serratus 

evolved from P. muelleri because of the similarities between 

the two species. Specimens from Narrow Passage Creek 

show variation in position of the serrations on the cusp. 

Generally, the serrations occur close to the tip of the cusp. 

However, one specimen has the serrations extending to about 

half-way down the cusp. 

Occurrence.-Narrow Passage Creek samples NPC-5, 

NPC-59. 

Number of specimens.-3. 

Figured specimens.-NPC-5, NPC-59. 

Prooneotodus rotundatus (Druce and Jones) 

Plate 2, figure 8 

Coelocerodontus rotundatus Druce and Jones, 1971, p. 66, pl. 9, figs. 

10a-13b, text-figs. 22c, d. 

Prooneotodus? rotundatus? (Druce and Jones). Landing, 1983, p. 1180, 

figs. 10D, E. 

Prooneotodus rotundatus (Druce and Jones). Chen and others, 1985, p. 96, 

pl. 26, figs. 1-3, text-fig. 14(1). 

Remarks.-Druce and Jones (1971) described simple 

hollow cone shaped conodonts with circular cross sections 

and minute cusps as Coelocerodontus rotundatus. Muller 

(1973) placed these elements within the genus Proconodontus. However, Landing (1983) rejected this placement 

because Prooneotodus rotundatus has a protoconodont or 

paraconodont histology as opposed to Proconodontus which 

has a euconodont histology. 

Occurrence.-Narrow Passage Creek samples NPC-5, 

NPC-37, NPC-43. 

Number of specimens.-3. 

Figured specimen.-NPC-37. 

Rossodus manitouensis Repetski and Ethington 

Plate 2, figures 9-11 

Rossodus manitouensis Repetski and Ethington, 1983, p. 293, figs. 1A-V, 

2A-T, 3A-R, 4A-D [synonymy to 1982]; Landing and others, 1986, p. 

1940, pl. 2, figs. 10, 11, 14, non 18. 

New Genus A, n. sp. A, Repetski and Perry, 1980, pl. 1, figs. 4, 6, pl. 

2, figs. 11, 12, 15; Repetski, 1982, p. 56, pl. 28, figs. 1-4. 

New Genus 3, Ethington and Clark, 1981, p. 118-119, pl. 13, figs. 21-23, 

25, 27. 
Remarks.-Repetski and Ethington (1983) described the 

apparatus of Rossodus manitouensis as including oistodontiform elements and bladelike coniform elements that show 

symmetry transition. The cusps of all the elements are albid. 

The symmetry-transition series of costate to bladelike coniform elements shows a change from nearly symmetrical 

through asymmetrical to bilaterally symmetrical elements. 

Repetski and Ethington noted a similarity of the coniform 

element symmetry-transition series to elements of Juanognathus. The major difference between these two apparatuses is the absence of oistodontiform elements in the 

Juanognathus apparatus. A similarity between the apparatuses of Rossodus and Utahconus also was recognized by 

Repetski and Ethington ( 1983) and with the presence of an 

oistodontiform element in U. tenuis (Miller), they reassigned 

U. tenuis to the genus Rossodus. Rossodus tenuis is present 

in rocks older than rocks with R. manitouensis, and is preceded by Utahconus utahensis (Miller). This sequence of 

species led these authors to suggest an evolutionary lineage 

from Utahconus utahensis through Rossodus tenuis to R. 

manitouensis. No specimens assignable to Rossodus tenuis 

were recovered from the Narrow Passage Creek and Timberville sections. Thus, the evolutionary lineage put forth by 

Repetski and Ethington (1983) was not observed in the study. 

Occurrence.-Narrow Passage Creek samples NPC166, NPC-169, NPC-172, NPC-175, NPC-178, NPC-181, 

NPC-188, NPC-194, NPC-197, NPC-206; Timberville 

samples T-104, T-134, T-153. 

Number of specimens. -Coniform elements-65, 

oistodontiform elements-14. 

Figured specimens.-NPC-169, NPC-181. 

Rossodus sp. 

Plate 2, figure 12 

Remarks. -Several specimens resemble elements of 

Rossodus but do not conform to R. manitouensis. These 

elements are more robust than Rossodus manitouensis and 

have sharp costae situated posterolaterally and anterolaterally. Other Rossodus species have been reported high in 

Fauna C and into Fauna D (Repetski and Perry, 1980). The 

specimens recovered in this study are coniform elements 

possibly belonging to a new species of Rossodus. 

Occurrence.-Narrow Passage Creek samples NPC188, NPC-197. 

Number of specimens.-5. 

Figured specimen.-NPC-188. 

Scandodus sp. s.f. 

Plate 2, figure 13 

Description. -One specimen of a lanceolate, reclined 

cone with a slightly expanded base recovered from the 

Narrow Passage Creek section is assigned to the genus Scandodus in the form sense. The base expands posteriorly and 

laterally, and the basal margin is slightly concave downward 

in lateral view. 

169. 

Occurrence. -Narrow Passage Creek sample NPCNumber of specimens. -1. 

Figured specimen.-NPC-169. 

Scolopodus sulcatus Furnish s.f. 

Plate 2, figure 15 

Scolopodus sulcatus Furnish. 1938, p. 334, pl. 41, figs. 14, 15, text-fig. 

11; Ethington and Clark. 1971, p. 105, pl. 12, figs. 7, 8, text-fig. 26; 

Repetski, 1982, p. 51, pl. 24, figs. 6, 8, text-fig. 7Y. 

Remarks.-Specimens from the Narrow Passage Creek 

and Timberville sections identified as Scolopodus sulcatus 

Furnish s.f. conform to the diagnosis of the species by Furnish (1938). Repetski (1982) suggested that Scolopodus 

sulcatus s.f. is a member of a symmetry-transition series that 

includes Acodus oneotensis s.f., and Scolopodus sexplicatus 

s.f. This multielement relationship will remain uncertain until 

large collections containing these conodonts have been 

evaluated. The material at hand is not suitable for such an 

evaluation. 

Occurrence.-Narrow Passage Creek samples NPC157, NPC-181; Timberville samples T-139, T -175. 

Number of specimens.-8. 

Figured specimen.-NPC-139. 

Scolopodus sp. s.f. 

Plate 2, figure 16 

Remarks. -Several coniform specimens recovered 

from the Narrow Passage Creek and Timberville sections 

have cusps or cusp fragments that contain lateral and 

posterior grooves or costae and a rounded anterior and 

posterior. These specimens conform to the diagnosis of the 

genus by Pander (1856) and later workers (Furnish, 1938; 

Ethington and Clark, 1981; Repetski, 1982). 

Occurrence. -Narrow Passage Creek samples NPC181, NPC-197; Timberville sample T-139. 

Number of specimens.-12. 

Figured specimen.-NPC-181. 

Semiacontiodus nogamii (Miller) 

Plate 2, figures 17, 18 

Acontiodus (Semiacontiodus) nogamii Miller, 1969, p. 421, pl. 63, figs. 

41-50, text-fig. 3G. 

Semiacontiodus nogamii Miller. Lindstrom, 1973, p. 441-443; Miller, 1980, 

p. 32, pl. 2, figs. 10-12, text-figs. 4V. W; Fortey and others, 1982, textfigs. 6J, T. 8V. X; Chen and others, 1985, p. 97, 98, pl. 23, figs. 12-16, 

text-figs.14(13, 14). 

Acodus housensis Miller, 1969, p. 418, pl. 63, figs. 11-20, text-fig. 3A. 

Oneotodus datsonensis Druce and Jones, 1971, p. 80, pl. 14, fig. 4. 

Oneotodus erectus Druce and Jones, 1971, p. 80, pl. 15, figs. 2-9, textfig. 26d. 

Remarks. -Specimens of this species resemble those 

illustrated by Miller (1969; 1980). Several asymmetrical 

elements possess the distinctive lateral costa and groove 

( = ''Acodus housensis '' morphotype). Symmetrical elements 

have a rounded posterior costa and are flanked by two 

posterolateral grooves. Miller (1980) suggested that Teridontus nakamurai is the ancestor of Semiacontiodus nogamii. 

Cambrian and Ordovician Conodonts from the Conococheague and Stonehenge Limestones A 15 
The specimens from this study that lack pronounced lateral 

costae are similar to those of Teridontus nakamurai and are 

distinguished from them by the posterior grooves. 

Occurrence.-Narrow Passage Creek samples NPC65, NPC-136. 

Number of specimens.-14. 

Figured specimens.-NPC-65. 

Teridontus nakamurai (Nogami) 

Plate 2, figure 19 

Oneotodus nakamurai Nogami, 1967, p. 216, pl. 1, figs. 9, 12, text-figs. 

3A, B; Miller, 1969, p. 43S, pl. 63, figs. 1-10, text-fig. SE; Druce and 

Jones, 1971, p. 82, pl. 10, figs. 3, 4, 7, 8, text-fig. 26i; Muller, 1973, 

p. 41, pl. S, fig. 4; Landing and others, 1986, pl. 1, figs. 1, 2. 

Oneotodus datsonensis Druce and Jones, 1971, p. 80, pl. 14, figs. 1-3, 

text-fig. 26c. 

"Oneotodus " nakamurai N ogami. Landing and others, 1980, p. 28-31, 

figs. 8A-C. 

Teridontus nakamurai (Nogami). Miller, 1980, p. 34, pl. 2, figs. 1S, 16; 

Fortey and others, 1982, text-fig. 9N, Q, R; Chen and others, 198S, p. 

99, pl. 21, figs. 4-6, text-fig. 14(S); Nowlan, 198S, p. 116, figs. 

S.26-S.32. 

Teridontus huanghuachangensis (Ni). Chen and others, 198S, p. 98, pl. 

21, figs. 12, 13, text-fig. 14(10). 

Remarks. -Miller (1980) reassigned the coniform 

elements previously assigned to Oneotodus nakamurai to 

Teridontus. Elements from this study having a narrow or 

posteriorly expanded basal margin, circular cross section, 

simple morphology, fine striations, and abundant white 

matter in the cusp are assigned to Teridontus nakamurai. 

Previously, the rounded element of Eoconodontus notchpeakensis was considered a paratype of Oneotodus nakamurai, but it was reassigned by Miller ( 1980). Chen and 

others (1985) illustrated specimens of Teridontus huanghuachangensis which has a cusp with the white matter ending 

in a sharp boundary oblique to the cusp as opposed to 

specimens of T. nakamurai with the white matter boundary 

transverse to the cusp. Other than the difference in the white 

matter boundary, there seems to be no other morphologic 

difference between Teridontus huanghuachangensis and T. 

nakamurai. The range of Teridontus huanghuachangensis is 

reported from sections in China by Chen and others (1985) 

and Chen and Gong (1986) as within the range of T. 

nakamurai, and I believe these two species are actually both 

T. nakamurai. 

Occurrence.-Narrow Passage Creek samples NPC-5, 

NPC-65, NPC-108, NPC 123, NPC-136; Timberville 

samples T-0, T-45, T-64, T-93. 

Number of specimens.-668. 

Figured specimen.-NPC-65. 

Teridontus aff. T. nakamurai (Nogami) 

Plate 2, figures 20, 21 

aff. Teridontus nakamurai (Nogami). Miller, 1980, p. 34, pl. 2, figs. 1S, 

16, [synonymy]. 

Remarks.-Some elements in the interval of Fauna C 

show affinities with Teridontus nakamurai but are more 

robust than specimens from older strata. These specimens 

A 16 Shorter Contributions to Paleontology and Stratigraphy 

are symmetrical or nearly symmetrical coniform elements 

with circular cross section, a narrow base, and abundant 

white matter in the cusp. They differ from Oneotodus gracilis 

(Furnish) in that they do not have a flattened posterior. 

Teridontus aff. T. nakamurai occurs in the range of Fauna 

C in this study, thus possibly extending the range of T. 

nakamurai into Fauna C. Nowlan (1985) also reported aff. 

T. nakamurai in Fauna C in the Arctic. Landing and others 

(1986) suggested that Oneotodus-like elements of this interval may belong to the Variabiloconus bassleri (previously 

Paltodus bassleri) apparatus. It is difficult to test the relationship between Teridontus aff. T. nakamurai and Variabiloconus bassleri with the collections from northwestern 

Virginia. Thus, Teridontus aff. T. nakamurai is recognized 

for its affinities to T. nakamurai. 

Occurrence. -Narrow Passage Creek samples NPC166, NPC-169, NPC-178, NPC-181, NPC-188, NPC-197; 

Timberville samples T-104, T-121, T-134, T-148, T-153, 

T-162. 

Number of specimens. -68. 

Figured specimens.-NPC-169, NPC-181. 

Utahconus utahensis (Miller) 

Plate 2, figures 22, 23 

Paltodus utahensis Miller, 1969, p. 463, pl. 63, figs. 33-40, text-fig. SF. 

Acontiodus (Semiacontiodus) unicostatus Miller, 1969 (in part), p. 421, pl. 

64, figs. 46-48, text-fig. SF. 

Acodus sevierensis Miller, 1969 (in part), p. 418, pl. 63, figs. 21-24, textfig. 3H. 

Scandodusfumishi Lindstrom. Druce and Jones, 1971, p. 88, pl. 13, figs. 

6-8, text-fig. 29. 

Semiacontiodus utahensis (Miller). Lindstrom, 1973, p. 442, 443, 449. 

Utahconus utahensis (Miller). Miller, 1980, p. 3S, 36, pl. 2, figs. 1, 2, 

text-figs. 3B, C, F, G; Chen and others, 198S, p. 99, 100, pl. 23, figs. 

1-8, text-fig. 14(6). 

Description.-The apparatus consists of two coniform 

elements. Bicostate elements are erect to reclined, asymmetrical to nearly symmetrical simple cones that are compressed 

antero-posteriorly. They possess lateral or posterolateral 

keels that extend from the tip of the cusp to the basal margin. 

The basal cavity is shallow to moderately deep. Unicostate 

elements are erect to reclined simple cones that possess a 

posterior keel that extends from the tip of the cusp to the 

base or basal margin. 

Remarks.-This apparatus was named by Miller (1980) 

to include one bicostate element (' 'Paltodus utahensis '') and 

two unicostate elements (Acontiodus (Semiacontiodus) 

unicostatus in part; Acodus sevierensis in part) from a 

previous study (Miller, 1969). The majority of specimens 

recovered in this study were bicostate elements; this is the 

reverse of Miller's (1980) observation that the unicostate 

element usually is the more abundant. 

Occurrence. -Narrow Passage Creek samples NPC108, NPC-136; Timberville sample T-45. 

Number of specimens. -Unicostate element-8, bicostate element -16. 

Figured specimens. -NPC-108, T -45. 
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L.F., and Taylor, J.F., 1982, Potential Cambrian-Ordovician 

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M.G., and Dean, W.T. eds., The Cambrian-Ordovician boundary: Sections, fossil distributions, and correlations: National 

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Miiller, K.J., 1959, Kambrische conodonten: Deutsches 

Geologische Gesellschaft Zeitung, V. 111, p. 434-485. 

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from northern Iran: Geological Survey of Iran, Report 30, 77 p. 

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Conodonten aus den oberkambrischen Kushan-Schichten: Kyoto 

University, College Science Memoir Series B, v. 32, p. 

331-367. 

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University, College Science Memoir Series B, v. 33, p. 96-122. 

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islands: Journal of Paleontology, v. 59, no. 1, p. 96-122. 

Orndorff, R.C., Taylor, J.F., and Traut, R.W., 1988, Uppermost 

Cambrian and lowest Ordovician conodont and trilobite 

biostratigraphy in northwestern Virginia: Virginia Division of 

Mineral Resources, Contributions to Virginia Geology, in 

press. 

Pander, C.H., 1856, Monographie der fossilen Fische des 

Silurischen Systems der Russisch-Baltischen Gouvernements: 

St. Petersburg, Konigliche Akademie de Wissenschaften, 91 p. 

Rader, E.K., and Biggs, T.H., 1976, Geology ofthe Strasburg and 

Toms Brook quadrangles, Virginia: Virginia Division of 

Mineral Resources Report of Investigation 45, 104 p. 

Repetski, J.E., 1982, Conodonts from El Paso Group (Lower 

Ordovician) of western Texas and southern New Mexico: New 

Mexico Bureau of Mines and Mineral Resources Memoir 40, 

121 p. 

Repetski, J .E., and Ethington, R.L., 1977, Conodonts from graptolite facies in the Ouachita Mountains, Arkansas and 

Oklahoma, in Stone, C.G., ed., Symposium on the geology 

of the Ouachita Mountains: Arkansas Geologic Commission, 

A 18 Shorter Contributions to Paleontology and Stratigraphy 

p. 92-106. 

1983, Rossodus manitouensis (Conodonta), a new early 

Ordovician index fossil: Journal of Paleontology, v. 57, no. 

2, p. 289-301. 

Repetski, J .E., and Perry, W .J., Jr., 1980, Conodonts from structural windows through the Bane Dome, Giles County, Virginia, 

in Contributions to Virginia Geology-IV: Virginia Division of 

Mineral Resources Publication 27, p. 12-22. 

Sando, W.J., 1956, Nomenclature of Lower Ordovician rocks of 

Washington County, Maryland: Geological Society of America 

Bulletin, v. 67, p. 935-938. 

1957, Beekmantown Group (Lower Ordovician) of 

Maryland: Geological Society of America Memoir 68, 161 p. 

1958, Lower Ordovician section near Chambersburg, 

Pennsylvania: Geological Society of America Bulletin, v. 69, 

p. 837-854. 

Stose, G. W. , 1908, The Cambrian-Ordovician limestones of the 

Appalachian Valley in southern Pennsylvania: Journal of 

Geology, v. 16, p. 698-706. 

Sweet, W.C., and Bergstrom, S.M., 1972, Multielement taxonomy 

and Ordovician conodonts: Geologica et Palaeontologica, v. 1, 

p. 29-42. 

Taylor, J.F., 1986, Variations in lithofacies and trilobite faunas 

in the Stonehenge and Grove Formations (CambrianOrdovician) across the central Appalachian shelf, PennsylvaniaMaryland-Virginia: Geological Society of America Abstracts 

with Programs, v. 18, no. 6, p. 770. 

Winston, Don, and Nicholls, Harry, 1967, Late Cambrian and Early 

Ordovician faunas from the Wilberns Formation of central 

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Wolf Gap, Conicville, and Edinburg quadrangles, Virginia: 

Virginia Division of Mineral Resources Report of Investigations 35, 69 p. 
PLATES 1 AND 2 

Contact photographs of the plates in this report are available, at cost, from U.S. Geological 

Survey Library, Federal Center, Denver, Colorado 80225 
PLATE 1 

FIGURES 1, 2. Acodus oneotensis Furnish s.f.; inner lateral views, NPC-197 {X 140), USNM 

417972, NPC-178 {X90), USNM 417973, respectively. 

3. Acontiodus iowensis Furnish s.f.; posterior view, NPC-181 {X 105), USNM 417974. 

4. Acontiodus propinquus Furnish s. f.; oblique posterior view, T -116 (X 160), USNM 

417975. 

5. Cambrooistodus minutus (Miller); inner lateral view, NPC-63 {X 120), USNM 

417976. 

6. Clavohamulus densus Furnish; oblique upper view, NPC-197 {X 160), USNM 417977. 

7. Clavohamulus elongatus? Miller; inner lateral view, NPC-65 {X 110), USNM 413598. 

8, 9. Cordylodus angulatus Pander; lateral views; rounded element, NPC-181 (x75), 

USNM 417978; and compressed element, NPC-169 {X 150), USNM 417979. 

10. Cordylodus intermedius Furnish; lateral view of rounded element, NPC-181 {X 125), 

USNM 417980. 

11. Cordylodus lindstromi Druce and Jones; lateral view of rounded element, NPC-178 

{X 100), USNM 417981. 

12, 13. Cordylodus proavus Miiller; lateral view of rounded element, NPC-65 {X90), USNM 

413591; and inner lateral view of compressed element, NPC-65 ( x 70), USNM 

417982. 

14. Cordylodus rotundatus Pander; lateral view of rounded element, NPC-181 {X65), 

USNM 417983. 

15. Drepanodus cf. D. arcuatus Pander; inner lateral view, NPC-197 {X 130), USNM 

417984. 

16-18. Drepanoistodus pervetus Nowlan, 

16. Inner lateral view of suberectiform element, NPC-206 {X 175), USNM 

417985. 

17. Lateral view of homocurvatiform element, T-153 {X80), USNM 417986. 

18. Outer lateral view of suberectiform element, NPC-181 {X 140), USNM 

417987. 

19, 20. Eoconodontus notchpeakensis (Miller); lateral views of rounded elements, NPC-59 

{X140), USNM 417988, NPC-59 {X120), USNM 417989, respectively. 

21. Eucharodus cf. E. parallelus (Branson and Mehl); lateral view, NPC-169 {X 140), 

USNM 417990. 

22, 23. Fryxellodontus inomatus Miller; inner lateral views, NPC-65 {X 100), USNM 413595, 

NPC-65 {X 125) USNM 417991. 

24. Fryxellodontus lineatus Miller; outer lateral view, NPC-65 {X 125), USNM 413593. 

25. Hirsutodontus hirsutus Miller; lateral view, NPC-65 {X 100), USNM 413592. 

26. Loxodus bransoni Furnish; lateral view, T-157 {X80), USNM 413594. 
U.S. GEOtOGICAL SURVEY BULLETIN 1837-A PLATE 1 

ACODUS, ACONTIODUS, CAMBROO/STODUS, CLAVOHAMULUS, CORDYLODUS, DREPANODUS, DREPANOISTODUS, 

EOCONODONTUS,EUCHARODUS,FRYXELLODONTUS, H/RSUTIJDONTUS,LOXODUS 
PLATE 2 

FIGURE 1. "Oistodus" triangularis Furnish s.f.; outer lateral view, NPC-194 (X 100), USNM 

417992. 

2, 3. Paltodus bassleri Furnish; lateral view of symmetrical element, NPC-157 (X 120), USNM 

417993; and inner lateral view of asymmetrical element, NPC-157 (x85), USNM 417994. 

4. Paltodus aff. P. spurius Ethington and Clark s.f.; oblique lateral view, NPC-197 (X90), 

USNM 417995. 

5. Proconodontus muelleri Miller; lateral view, NPC-63 (X 80), USNM 417996. 

6, 7. Proconodontus serratus Miller; inner lateral views, NPC-59 (X 100), USNM 413589, 

NPC-5 (X 85), USNM 413590 respectively. 

8. Prooneotodus rotundatus (Druce and Jones) s. f.; lateral view, NPC-37 ( x 190), USNM 

417997. 

9-11. Rossodus manitouensis Repetski and Ethington, 

9. Inner lateral view of coniform element, NPC-169 (X 190), USNM 417998. 

10. Outer lateral view of coniform element, NPC-181 (x 140), USNM 417999. 

11. Outer lateral view of oistodontiform element, NPC-181 ( X200), USNM 418000. 

12. Rossodus sp.; lateral view, NPC-188 (X70), USNM 418001. 

13. Scandodus sp. s.f.; inner lateral view, NPC-169 (x75), USNM 418002. 

14. Paltodus bassleri Furnish s. f.; lateral view, NPC-181 (X 85), USNM 418003. 

15. Scolopodus sulcatus Furnish s. f. ; lateral view, T -139 (X 1 00), USNM 418004. 

16. Scolopodus sp. s.f.; lateral view, NPC-181 (X 100), USNM 418005. 

17, 18. Semiacontiodus nogamii (Miller); inner lateral views, NPC-65 (x95), USNM 418006, 

NPC-65 (X75), USNM 418007, respectively. 

19. Teridontus nakamurai (Nogami); lateral view, NPC-65 (X 175), USNM 418008. 

20, 21. Teridontus aff. T. nakamurai (Nogami); lateral views, NPC-169 (X100), USNM 418009, 

NPC-181 ( x 130), USNM 418010, respectively. 

22, 23. Utahconus utahensis (Miller); lateral view of bicostate element, T-45 (X 180), USNM 

413597; and oblique posterior view of bicostate element, NPC-1 08 (X 215), USNM 

413596. 
U.S. GEOlOGICAL SURVEY BULLETIN 1837-A PLATE 2 

"0/STODUS," P ALTODUS, PROCONODONTUS, PROONEOTODUS, ROSSODUS, SCANDODUS, 

SCOLOPODUS, SEM/ACONT/ODUS, TERIDONTUS, UTAHCONUS 

CHAPTER B 

Conodont-Based Determination of the 

Silurian-Devonian Boundary in the 

Valley and Ridge Province, 

Northern and Central Appalachians 

By KIRK E. DENKLER and ANITA G. HARRIS 

U.S. GEOLOGICAL SURVEY BULLETIN 1837 

SHORTER CONTRIBUTIONS TO PALEONTOLOGY AND STRATIGRAPHY 

CONTENTS 

Abstract Bl 

Introduction Bl 

Acknowledgments Bl 

Lithostratigraphy B2 

Southern and north-central areas (Virginia to central Pennsylvania) B2 

Northeastern area (northeastern Pennsylvania, New Jersey, and easternmost 

New York B4 

Silurian-Devonian boundary BS 

Previous work BS 

Conodont biostratigraphy B6 

Stratigraphic position of the base of the Devonian System B7 

Southern and north-central areas B8 

Northeastern area B8 

Systematic paleontology B8 

Genus Icriodus Branson and Mehl, 1938 B8 

Genus Oulodus Branson and Mehl, 1933 B9 

Locality register Bll 

References cited Bll 

PLATE 

[Plate follows References Cited] 

1. Conodont indices to the Silurian-Devonian boundary interval, Valley and Ridge 

province, Appalachians. 

FIGURES 

1. Index map of study area in the Appalachian basin showing location of sampled 

measured sections B2 

2. Correlation chart of uppermost Silurian and lowermost Devonian stratigraphic units 

in the Valley and Ridge province, west-central Virginia to eastern New York B3 

TABLE 

1. Stratigraphic position of important conodont biohorizons for the placement of the 

Silurian-Devonian boundary in the Valley and Ridge province of the central and 

northern Appalachian basin B7 

Contents Ill 

Conodont-Based Determination of the 

Silurian-Devon ian· Boundary in the Vall"ey and Ridge Province, 

Northern and Central Appalachians 

By Kirk E. Denkler and Anita G. Harris 

Abstract 

The first appearance of the principal auxiliary index species 

to the base of the Devonian System, Icriodus woschmidti, is 

documented in 21 sections in the Valley and Ridge province 

of the central and northern Appalachian basin. The absence of 

graptolites and the endemism of the shelly fauna in this region 

necessitate using the first appearance of I. woschmidti for determination of the Silurian-Devon ian boundary in the Appalachian 

basin, thus permitting relatively precise intrabasinal and extrabasinal correlation. In addition to I. woschmidti, two other 

species are useful accessory indices for boundary approximation: Oulodus e/egans and 0. cristagalli. Thus far there are four 

conodont-based biostratigraphic criteria that can be used to identify uppermost Silurian or lowermost Devonian strata and to 

approximate the base of the Devonian in the Valley and Ridge 

province: (1) the presence of 0. elegans indicates a late 

Ludlovian-Pridolian age; (2) the co-occurrence of 0. e/egans 

and 0. cristagalli indicates a very latest Pridolian age; (3) the 

presence of 0. cristagal/i indicates a very latest Pridolian to 

middle Lochkovian age; and (4) the occurrence of I. woschmidti 

indicates an earliest Devonian age. The conodont data, along 

with extrapolation from regional lithofacies relationships, indicate 

that the Silurian-Devonian boundary lies within the uppermost 

Keyser Limestone in the southern part of the study area and 

within the Whiteport Dolomite Member of the Rondout Formation in the north. The apparatuses of all three index species are 

briefly discussed. 

INTRODUCTION 

The international agreement establishing the SilurianDevonian boundary stratotype has greatly facilitated intercontinental correlation of this chronostratigraphic horizon. 

The decision, however, to fix this boundary using the first 

occurrence of Monograptus uniformis at Klonk, Czechoslovakia, (Chlupac and others, 1972; Martinsson, 1977) 

requires that in terranes lacking graptolite-bearing facies, the 

boundary can only be approximated by using other cosmopolitan taxa. Because conodonts are well documented in 

graptolite-bearing sequences worldwide, they are the principal auxiliary biostratigraphic indices for approximating the 

Silurian-Devonian boundary. The most utilized cosmopolitan 

conodont for diagnosing the base of the Devonian System 

is Icriodus woschmidti. Globally, I. woschmidti first appears 

2 m below to 2 m above the first occurrence of M. uniformis 

(Jaeger, 1968; Chlupac and others, 1972; Klapper and 

Murphy, 1975). 

The absence of graptolites and the pronounced endemism of the shelly fauna in Upper Silurian-Lower Devonian 

rocks of the Appalachian basin (Boucot and others, 1969; 

Oliver, 1976; Copeland and Berdan, 1977) necessitates that 

conodonts be used to approximate the Silurian-Devonian 

boundary in this region. As part of a continuing investigation of the conodont biostratigraphy of the Silurian-Devonian 

carbonate sequence in the Appalachian basin, we have 

recovered representatives of Icriodus woschmidti from many 

measured sections of the Keyser and New Creek Limestones 

and the Manlius and Coeymans formations that span the 

Silurian-Devonian boundary along the eastern limit of the 

Appalachian basin. In addition to I. woschmidti, Oulodus 

elegans and 0. cristagalli are supplemental indices of the 

boundary interval. Our conodont data together with data from 

other reports (Helfrich, 1978; Cook, 1981) now permit an 

approximation of the boundary in a large part of the Appalachian basin and a refined correlation with the international 

boundary stratotype. 

Acknowledgments 

We are grateful to J.M. Berdan and W.A. Oliver, Jr., 

U.S. Geological Survey, for sharing with us their expertise 

on the stratigraphy and paleontology of the Upper Silurian 

and Lower Devonian of the Appalachian basin. 

Conodont-Based Determination of the Silurian-Devonian Boundary, Valley and Ridge Province Bl 
LITHOSTRATIGRAPHY 

Southern and North-Central Areas (Virginia to 

Central Pennsylvania) 

In the Valley and Ridge province of west -central 

Virginia to central Pennsylvania, the Silurian-Devonian 

boundary is within the Keyser Limestone (figs. 1, 2). In part 

of this area (northeastern West Virginia through central PennAREA 

OF FIGURE 1 

sylvania), Head (1972) formally subdivided the Keyser 

Limestone into three members; in ascending order, these are 

the Byers Island Member, Jersey Shore Member, and La 

Vale Member, which are herein accepted for use by the U.S. 

Geological Survey. The Keyser Limestone reaches a maximum thickness of approximately 85 m at its type locality 

near Keyser, W. Va., and thins to 30 m or less near its 

southern limit of exposure and to 60 m near its northern limit 

in Pennsylvania. The absence of the Keyser Limestone south 

OHARRISBURG 

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from King and Beikman, 1974) and location of sampled measured sections (numbers keyed to locality register). 

82 Shorter Contributions to Paleontology and Stratigraphy 
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;:, Section locations shown in figure 1 and described in locality register. Latest Silurian conodont zonation from Denkler and Harris (1988). 

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of west -central Virginia and in the easternmost outcrop belts 

of the Valley and Ridge province from Virginia to southeastern Pennsylvania is due to subsequent erosion or to 

nondeposition (Dennison and Boucot, 1974). Fossiliferous 

wackestones to grainstones of the basal Keyser contrast 

sharply with the laminated carbonate mudstones of the 

underlying Tonoloway Limestone. The Keyser grades into 

the overlying arenaceous, crinoidal packstones and 

grainstones of the New Creek Limestone through a 1-m 

interval. 

The Keyser consists of a diverse suite of carbonate and 

lesser siliciclastic lithofacies deposited in shallow subtidal 

to peritidal environments in a restricted foreland basin. Facies 

patterns were controlled by eustatic sea-level changes, differential basin subsidence, and rate of influx of clastic 

sediments (Dorobek and Read, 1986). Additional factors 

include proximity to a southwestern seaway through which 

normal marine waters entered the basin and to an eastern 

clastic source area, particularly to the southeast. 

Two transgressive-regressive sequences characterize 

deposition of the Keyser Limestone. A basal transgression 

produced basinwide open-marine lithofacies consisting 

primarily of thin, nodular-bedded fossiliferous wackestone 

along the basin axis and massive crinoidal packstone and 

grainstone in the south and east of the basin axis (=Byers 

Island Member or lower limestone member, fig. 2). A subsequent minor regression accompanied by a northwestward 

progradation of clastic sediments resulted in the deposition 

of more restricted lagoonal and shelf deposits represented 

by calcareous shale (=Big Mountain Shale Member) and 

calcareous protoquartzite (=Clifton Forge Sandstone 

Member) in the southern part of the study area (fig. 2). The 

lower part of the upper limestone member or Jersey Shore 

Member marks a second, less extensive transgression and 

a return of more normal marine lithofacies. These units consist chiefly of massive encrinite and lesser shaly wackestone 

and packstone in the south to lagoonal and biohermal deposits 

in the north and locally along the southern basin margin. The 

succeeding uppermost part of the Keyser, in the north, consists chiefly of peritidal laminated dolomitic carbonate 

mudrock deposited during a basinwide regression (=La Vale 

Member or upper part of the upper limestone member). 

Similar lithologies predominate in the south except for a 

limited area in east-central West Virginia and west-central 

Virginia where more subtidal, normal marine conditions 

persisted. This area lay near the basin axis, close to the 

incursion of normal marine waters from the southwestern 

seaway and sufficiently distant from the effects of terrigenous 

sediments prograding northwestward. It is only in this area 

that conditions favorable for more normal marine faunas 

persisted across the Silurian-Devonian boundary. Consequently, collections from within this interval have yielded 

the stratigraphically lowest representatives of index species. 

The overlying New Creek Limestone ranges in thickness from a maximum of approximately 20m in west-central 

84 Shorter Contributions to Paleontology and Stratigraphy 

Virginia to a few meters in central Pennsylvania. It consists 

chiefly of thick- to massive-bedded and locally crossbedded, 

quartzose, crinoidal packstone to grainstone. Bedforms, rock 

type, and fossil content indicate deposition in high-energy, 

shallow subtidal environments. The New Creek represents 

the onset of a long continuous interval of normal marine 

deposition that persisted through the overlying Helderberg 

Group and into the Oriskany Group. 

Northeastern Area (Northeastern Pennsylvania, 

New Jersey, and Easternmost New York) 

From near Albany to Catskill, N.Y., a distance of about 

50 km, the Rondout Formation, Manlius Limestone, and 

Coeymans Formation range from 20 to 30m in thickness, 

combined, and rest with angular unconformity on Ordovician 

rocks (the Taconic unconformity). These units consist of a 

variety of carbonate lithofacies deposited in shallow subtidal 

to peritidal environments. Southwest of Catskill, increasingly 

older units intervene along this unconformity. Beds included 

in the Rondout Formation increase from a few meters in 

thickness to nearly 30m, 15 km northeast of the New YorkNew Jersey-Pennsylvania border (Epstein and others, 1967); 

more significantly, about 1,000 m of dominantly clastic strata 

of Silurian age are interposed between the Rondout and the 

Taconic unconformity. From this area southwestward, the 

Rondout thins to 13m at the Nearpass quarries (fig. 1, section 18) and then gradually to 9 m near the Delaware Water 

Gap (fig. 1, section 11). The Rondout is underlain by the 

Decker Formation, a fossiliferous, slightly quartzose grainstone to wackestone (in southeastern New York and northern 

New Jersey) that becomes increasingly quartzose southwestward. Near Delaware Water Gap (fig. 1, section 11), 

this unit is chiefly fossiliferous, calcareous, conglomeratic 

sandstone. The Decker has been interpreted as a biostromal 

bank (carbonate lithofacies) to barrier bar (clastic lithofacies) 

deposit. From southeastern New York into northeastemmost 

Pennsylvania, the Rondout is subdivided into three members 

(Epstein and others, 1967); in ascending order, the Duttonville, Whiteport Dolomite, and Mashipacong Members. The 

Duttonville Member consists chiefly of laminated, generally fissile and mud-cracked, argillaceous carbonate mudstone 

with a few layers of scattered to abundant ostracodes and 

corals. The Whiteport Dolomite Member is a slightly 

argillaceous, quartzitic and pyritic, laminated, generally mudcracked dolomudstone. The Mashipacong Member consists 

of chiefly mud-cracked, laminated to thin-bedded, calcareous 

shale and argillaceous carbonate mudstone. The contact of 

the Rondout with the overlying Thacher Member of the 

Manlius Limestone or Depue Limestone Member of the 

Coeymans Formation ranges from abrupt to gradational. The 

Rondout has been interpreted as a chiefly carbonate mudflat 

deposit; the Whiteport Dolomite Member represents the most 

supratidal conditions during deposition of the formation as 
well as the culmination of the regression near the SilurianDevonian boundary in the Appalachian basin (Epstein and 

Epstein, 1969). The onset ofMashipacong deposition marks 

the beginning of a transgression that correlates with the onset 

of New Creek deposition in the southern and north-central 

study areas. 

In southeastern New York and northern New Jersey, 

the Rondout Formation is overlain by the Thacher Member 

of the Manlius Limestone. The Thacher ranges from 11 to 

16 min thickness in this area and consists of platy argillaceous and dolomitic carbonate mudrock succeeded by 

stromatoporoid biostromes and argillaceous limestone. It 

becomes increasingly quartzose and less biostromal in New 

Jersey where it grades laterally into the Depue Limestone 

Member of the Coeymans Formation. The contact of the 

Thacher with the overlying Ravena Member or Shawnee 

Island Member of the Coeymans Formation varies from 

abrupt to gradational. The Thacher is inferred to have been 

deposited in a shallow, relatively open lagoon with scattered 

patch reefs. 

The Coeymans Formation is about 7 m thick near the 

northern limit of the study area, where it consists only of 

fossiliferous, irregularly bedded to crossbedded grainstone 

to wackestone of the Ravena Member. Quartzose silt, sand, 

and conglomerate as well as coral-stromatoporoid bioherms 

characterize the Coeymans in New Jersey and northeasternmost Pennsylvania. The Coeymans reaches a maximum 

thickness of23 m near the Delaware Water Gap (fig. 1, sections 12 and 13) as a result ofbiohermal development in the 

Shawnee Island Member of the Coeymans and by the inclusion of suprajacent (Kalkberg equivalent) and subjacent 

(Manlius equivalent) beds within the Coeymans. Southwest 

of Delaware Water Gap the Coeymans becomes dominantly 

calcareous quartzose sandstone and conglomerate and thins 

to a feather edge (Epstein and Epstein, 1969). The contact 

between the Coeymans and overlying Kalkberg Limestone 

in New York and part of New Jersey is marked by the first 

appearance of relatively abundant blue-black chert nodules 

and an increase in clay-sized to fme sand-sized quartz. Across 

New Jersey, the Kalkberg becomes increasingly coarse 

grained and quartzose and grades into the Stormville Member 

of the Coeymans Formation (Epstein and others, 1967). The 

Stormville is abruptly overlain by argillaceous calcisiltite of 

the New Scotland Formation. The Coeymans was deposited 

in a mosaic of relatively high-energy, shallow subtidal 

environments that include dominantly clastic to dominantly 

carbonate barrier and barrier apron deposits. 

SILURIAN-DEVONIAN BOUNDARY 

Previous Work 

The position of the Silurian-Devonian boundary in relation to the Keyser Limestone has long been controversial. 

The Keyser contains a predominantly endemic shelly fauna 

with affinities to underlying Silurian and overlying Devonian 

strata. Endemism coupled with relatively long species ranges 

has inhibited high-resolution interregional and intercontinental correlation. 

Affinities between the Keyser shelly fauna and that of 

the overlying Helderberg led some early workers to assign 

the entire Keyser Limestone to the Devonian (Ulrich, 1911; 

Swartz, 1913; Reeside, 1917). Other investigators have also 

placed the Keyser in the Devonian because of its lithostratigraphic affinities with the rest of the overlying Helderberg 

Group of established Devonian age (Swartz, 1929; Woodward, 1943). The entire Keyser was placed in the Silurian 

by Swartz and others (1942) and excluded from the Devonian 

by Cooper and others (1942). 

Early investigators recognized two successive faunas 

in the Keyser, a lower Eccentricosta jerseyensis Zone and 

an upper Favosites helderbergiae praecedens Zone (Swartz, 

1913; Reeside, 1917; Swartz, 1929). Bowen (1967), in a 

study of the brachiopods of the Keyser Limestone, proposed 

the Meristella praenuntia Zone as an approximate replacement of the praecedens Zone. He considered this zone to 

be Early Devonian based on the presence of representatives 

of the brachiopods Cyrtina and the terebratulid Nanothyris. 

The strong Silurian affinities of the brachiopods in the lower 

Keyser as well as the presence of Cystihalysites supported 

a Late Silurian age for the jerseyensis Zone. The SilurianDevonian boundary was thus placed within the middle of the 

Keyser Limestone. Some subsequent studies (Head, 1969; 

Berry and Boucot, 1970; Dennison and Head, 1975; Stock 

and Holmes, 1986) followed Bowen and placed the base of 

the Devonian at the base of the praenuntia Zone. In Pennsylvania and western Maryland, this corresponds to the base 

of the Jersey Shore Member and, further south, to the base 

of the upper limestone member. The most recent correlation charts for Silurian and Devonian rocks in Pennsylvania 

and Maryland (Berg and others, 1983; American Association of Petroleum Geologists, 1985) have placed the base of 

the Devonian within the uppermost beds of the Keyser 

Limestone based on extrapolations, we assume, from published (Helfrich, 1978) and unpublished conodont data 

(Cook, 1981). 

In the northeastern area, the Silurian-Devonian boundary has been placed historically at the contact between the 

Manlius Limestone and Coeymans Formation because at 

most localities a stromatoporoid-coral biostrome at the top 

of the Manlius is abruptly succeeded by crinoidal packstone 

to grainstone of the Coeymans. This contact is sharp and 

undulose and has been interpreted as a disconformity at the 

Silurian-Devonian boundary. In addition, similar to the 

Keyser-New Creek relationship in the southern and northcentral parts of the study area, the fauna of the Coeymans 

Formation is defmitively Devonian whereas the Manlius contains a fauna of mixed Silurian-Devonian aspect. More recent 

studies (Rickard, 1962; Laporte, 1969) have shown that the 

Conodont-Based Determination of the Silurian-Devonian Boundary, Valley and Ridge Province B5 
contact between the Manlius and Coeymans is not an unconformity but at most a diastem and possibly merely a sharp, 

conformable lithofacies change. Rickard (1962) included the 

Thacher Member of the Manlius Limestone in the Helderberg 

Group and placed the Silurian-Devonian boundary at the base 

of the Thacher in eastern New York. The Silurian-Devonian 

boundary has also been placed at the base of the Rondout 

Formation in the Becraft Mountain and Mount Ida outliers, 

New York (fig. 1, section 21) and Green Pond-Schunemunk 

Mountain outlier, New York-New Jersey (Rickard, 1975) 

and in the main outcrop belt of southeastern New York 

(American Association of Petroleum Geologists, 1985). In 

addition, the boundary has been placed within the Rondout 

Formation in the easternmost outcrop belt of the Valley and 

Ridge province in Pennsylvania and New Jersey (Epstein and 

Epstein, 1969; Oliver and others, 1967) and southeastern 

New York (Rickard, 1975). Although until now, beds of the 

Rondout Formation have not produced index fossils, 

definitive Silurian megafossils and conodonts have been 

recovered from the underlying Decker Formation and 

definitive Devonian conodonts have been recovered from the 

upper part of the overlying Manlius Limestone. Thus, by 

default and somewhat arbitrarily, the boundary has been 

placed within the Rondout Formation. 

Studies based on shelly faunas from the Keyser Limestone (Head, 1969; Makurath, 1975) and Manlius Limestone 

and Coeymans Formation (Laporte, 1969; Anderson, 1967) 

have contributed significantly to the interpretation of the 

depositional environments of these units. Brachiopods, 

ostracodes, and corals form the basis for the regional 

biostratigraphic framework of these rocks (Swartz and Whitmore, 1956; Bowen, 1967; Berdan, 1972; Oliver and Pedder, 

1979; Sorauf and Oliver, 1983, among others). These faunal 

elements, however, have proven limitations for intercontinental and even intracontinental correlation because of endemism 

and facies dependence. Although conodonts, in general, 

exhibit some facies restrictions and various degrees of 

provinciality, they are more cosmopolitan and thus more 

biostratigraphically useful than the shelly benthos. In this 

study, we document the distribution of the most biostratigraphically diagnostic conodont species in uppermost Silurian 

and lowermost Devonian rocks in the Valley and Ridge 

province of the Appalachian basin and use these data for 

intercontinental correlation and determination of the base of 

the Devonian System. 

Conodont Biostratigraphy 

Since established by Walliser (1964), the Icriodus 

woschmidti Zone has been used to delineate lowermost 

Devonian strata worldwide. Prior to formal acceptance of 

the Silurian-Devonian boundary stratotype in 1972, the base 

of the woschmidti Zone was considered by some to mark the 

base of the Devonian (Walliser, 1971). Detailed analysis of 

86 Shorter Contributions to Paleontology and Stratigraphy 

the distribution of graptolites and conodonts as well as other 

fossil groups in the Barrandian of Czechoslovakia (Chlupac 

and others, 1972) indicated that in the Certovy schody section, I. woschmidti occurs with Monograptus transgrediens 

and first appears 1. 5 m below the base of the M. uniformis 

Zone. In the Carnic Alps (Jaeger, 1968) and in the Roberts 

Mountains, Nevada (Klapper and Murphy, 1975), the base 

of the woschmidti Zone is approximately 2 m below the base 

of the uniformis Zone. At the international boundary stratotype at Klonk, Czechoslovakia, however, I. woschmidti first 

appears approximately 2 m above the base of the uniformis 

Zone (Chlupac and others, 1980). The same biostratigraphic 

relationship occurs at three other sections in the Barrandian 

area, including the auxiliary stratotype section. Even though 

the relative first appearance of these two index species is 

apparently not coincident, their stratigraphic separation is 

known to be within 2 m, thus making I. woschmidti an 

acceptable alternative index for recognition of the base of 

the Devonian. 

The shallow-water carbonate rocks of the Keyser 

Limestone consistently yield low-diversity conodont faunas 

of generally low abundance. Like those of the underlying 

Tonoloway Limestone, the conodont faunas are dominated 

by morphotypes of Ozarkodina remscheidensis (Ziegler). 

Aside from locally abundant representatives of Oulodus 

elegans (Walliser), all other conodont species known to occur 

in this interval elsewhere in the world are either absent or 

present in less than 5 percent of the approximately 170 

samples collected. 

Denkler and Harris ( 1988) used the first appearance 

and stratigraphic range of a new endemic species from the 

middle member of the Tonoloway Limestone to define the 

Ludlovian-Pridolian boundary and delineate lower Pridolian 

strata in the central Appalachian basin. Attempts to further 

subdivide Pridolian strata in this area based on morphometric 

studies or subspecies distribution of Ozarkodina remscheidensis proposed by Barnett (1971, 1972) or Walliser (1964, 

1971) and Klapper and Murphy (1975), among others, have 

been unsuccessful. Denkler and Harris (1985) noted that 

0. remscheidensis morphotypes are long-ranging (late 

Ludlovian-early Lochkovian), coeval, intergradational 

ecophenotypes that cannot be used for biostratigraphic subdivision in the central Appalachian basin. In addition, some 

cosmopolitan long-ranging Silurian species that do not extend 

into the latest Pridolian, such as 0. conjluens (Branson and 

Mehl), have not been found above the middle member of 

the Tonoloway Limestone (lower Pridolian). Thus far, 

Oulodus elegans (Walliser) appears to be the only species 

possibly restricted to the Silurian that extends into the Keyser 

Limestone. Its highest occurrences in nine sections (table 1) 

that include the upper half of the Keyser Limestone and its 

contact with the overlying New Creek Limestone range from 

as high as 1. 8 m below the top of the Keyser Limestone in 

the southern study area to at least 20.1 m below the top in 

the north-central study area. Thus, the presence of this 
Table 1. Stratigraphic position of important conodont biohorizons for the placement of the Silurian-Devon ian boundary 

in the Valley and Ridge province of the central and northern 

Appalachian basin 

[Location of sections shown in fig. 1 and described in locality register; sections 1 and 4 from Cook (1981); sections 5 and 7 from Helfrich (1978)] 

Measured 

sections 

Virginia 

1 

2 

3 

4 

West Virginia 

5 

6 

7 

Central Pennsylvania 

8 

9 

10 

Northeast Pennsylvania 

11 

12 

13 

New Jersey 

14 

15 

16 

17 

18 

New York 

19 

20 

3

21 

1

Last occurrence. 2

First appearance. 

First appearance or last occurrence of species in 

meters above ( +) or below (-) contact of 

Keyser-New Creek Limestones (sections 1-1 0) or 

Manlius Limestone and correlatives8Coeymans Formation (sections 11-21) 

Oulodus Oulodus Icriodus 

e/egans 1 cristagal/i 2 woschmidti 2 

-4.5 -4.5 +2.7 

-1.8 +0.8 

-17.0 -2.7 -1.7 

-9.0 -13.5 -3.3 

-9.5 to -12.5 -2.5 to -5.5 

-34.8 -3.6 +1.2 

-7.0to -11.0 +1.0 

-26.0 +0.3 +0.3 

+1.2 

-20.1 +0.1 +0.1 

+1.0 

-2.3 +2.3 

-2.7 + 1.3 

-0.3 + 1.5 

-1.5 +0.3 

-0.3 +0.3 

-1.6 +0.3 

-2.6 -2.6 

-3.0 +0.3 

-22.0 -13.4 

-7.5 -5.0 

3

A collection (USGS colin. 10649-SD) from at least 2m below the top of the 

Manlius Limestone at Becraft Mountain outlier, about 5 km southwest of section 21, 

also produced representatives of Oulodus cristagalli and Icriodus woschmidti. 

species can be used to identify Silurian strata in sections that 

straddle the Silurian-Devonian boundary in the Appalachian 

basin. 

0. cristagalli is a common associate of the basal Devonian index species I. woschmidti. This species is known only 

from shallow-water facies in eastern North America, part 

of Europe, Turkey, and eastern Australia, but unfortunately has not been reported from the boundary stratotype. The 

Pb 1 element of the species has been reported, however, from 

one section, near the base of the Lochkovian in the Barrandian area (Walmsley and others, 1974, table 2). In the central 

Appalachian basin there is a small overlap in the ranges of 

0. elegans and 0. cristagalli within the uppermost Keyser 

Limestone (table 1) that is below the first appearance of I. 

woschmidti. Thus 0. cristagalli apparently ranges into the 

very latest Pridolian. In the northern part of the basin, inappropriate lithofacies (La Vale Member of the Keyser 

Limestone or Rondout Formation-lower Manlius Limestone) 

within this interval of overlap separate the occurrences of 

0. elegans and 0. cristagalli. In central Pennsylvania, 0. 

cristagalli first appears within the basal meter of the New 

Creek Limestone coincident with the first occurrence of I. 

woschmidti. In the northeastern study area, however, 0. 

cristagalli typically first occurs within the upper 3 m of the 

Thacher Member of the Manlius Limestone (table 1) and 

generally below the first occurrence of I. woschmidti in the 

base of the overlying Ravena or Shawnee Island Member 

of the Coeymans Formation. 

Icriodus woschmidti is a significant component of the 

conodont fauna of the New Creek Limestone and Ravena 

and Shawnee Island Members of the Coeymans Formation. 

In most measured sections it first appears within the basal 

few meters (table 1) of these stratigraphic units. Exceptions 

include the Mohonk Lake section in New York (fig. 1, section 20) where I. woschmidti occurs as low as 1 m above 

the base of the Manlius Limestone, 3 m below the top of 

the Manlius Limestone in the Nearpass quarries section in 

New Jersey, and in three sections in east-central Virginia 

and west -central West Virginia where it occurs within the 

Keyser Limestone, 3m below the base of the New Creek 

Limestone. Other species commonly associated with /. 

woschmidti are Oulodus cristagalli, morphotypes of Ozarkodina remscheidensis, and simple-cone species. This species 

association is generally indicative of high-energy, relatively shallow-water, normal marine depositional environments. 

Stratigraphic Position of the Base 

of the Devonian System 

As indicated above, there are four biostratigraphic 

criteria based on conodonts that can be used to identify uppermost Silurian or lowermost Devonian strata and to approximate the base of the Devonian in the central and northern 

Valley and Ridge province: (1) the presence of Oulodus 

elegans indicates a late Ludlovian-Pridolian age; (2) the cooccurrence of 0. elegans and 0. cristagalli indicates a very 

latest Pridolian age; (3) the presence of 0. cristagalli 

indicates a very latest Pridolian to middle Lochkovian age; 

and (4) the occurrence of Icriodus woschmidti indicates the 

woschmidti Zone and an earliest Lochkovian age. We are 

well aware that I. woschmidti has been reported from the 

uppermost Monograptus transgrediens Zone (Chlupac and 

others, 1972) at a single locality in the Barrandian. We also 

recognize that the first occurrence of I. woschmidti in any 

section does not necessarily correspond to the base of the 

Conodont-Based Determination of the Silurian-Devonian Boundary, Valley and Ridge Province 87 
woschmidti Zone. Nevertheless, we choose to follow the 

recommendation of Chlupac and others (1972) by using the 

first occurrence of I. woschmidti as an auxiliary index to the 

base of the Devonian System. 

Southern and North-Central Areas 

Icriodus woschmidti occurs as low as 3 m below the 

top of the Keyser Limestone in three sections in Virginia and 

West Virginia (table 1). Of these, the Silurian-Devonian 

boundary can be most precisely placed at Strait Creek, near 

Monterey, Va. Cook ( 1981) reported the highest occurrence 

of 0. elegans together with 0. cristagalli 6 m below the first 

appearance of I. woschmidti. Thus the Silurian-Devonian 

boundary is between 9 and 3. 3 m below the top of the Keyser 

Limestone. Even though in all other sections sampled thus 

far I. woschmidti is restricted to beds above the Keyser 

Limestone, its presence in uppermost Keyser strata near the 

southern basin axis strongly suggests that elsewhere in this 

area uppermost Keyser beds are also of Devonian age. 

Because the Silurian-Devonian boundary occurs within strata 

that were deposited during a basinwide regression (uppermost Keyser Limestone), appropriate environments for the 

occurrence of index conodonts persisted only in a limited 

part of the southern study area (fig. 1, sections 3-5). We 

suspect that a greater thickness of the upper Keyser is of 

Devonian age in the north-central part of the study area than 

in the south, because the New Creek transgression proceeded 

northward and therefore Keyser lithofacies persisted longer 

in the north. At Tyrone, Pa. (fig. 1, section 10), the SilurianDevonian boundary lies within the upper 20 m of the Keyser 

in an interval that contains no biostratigraphically diagnostic 

conodonts (table 1). In general, basinwide regression during 

uppermost Keyser deposition and the subsequent transgression that initiated New Creek deposition resulted in a northward lowering of the lithostratigraphic position of the 

Silurian-Devonian boundary and a younging of the first 

occurrence of I. woschmidti. 

Northeastern Area 

Icriodus woschmidti first appears within the basal 2 m 

of the Ravena and Shawnee Island Members of the Coeymans 

Formation in all sections sampled except at the Nearpass 

quarries, New Jersey, in the Mohonk Lake quadrangle, New 

York, and at Mount Ida, New York (fig. 1, sections 18, 20, 

21). At the Nearpass quarries, I. woschmidti occurs in the 

Thacher Member of the Manlius Limestone, 2.6 m below 

the base of the Coeymans. The lowest occurrence of Oulodus 

cristagalli in this area is 2.6 m below the top of the Manlius 

in this section. Out of nearly 100 samples processed for 

conodonts from the Bossard ville, Decker, Rondout, and 

lower Manlius formations in the area that includes sections 

11 to 19 (fig. 1), 0. elegans has been recovered from only 

one sample (USGS colln. 10657-SD) collected 5 m above 

88 Shorter Contributions to Paleontology and Stratigraphy 

the base of the Decker Formation at Bossardsville, Pa., approximately 10 km southwest of section 11 (fig. 1). All other 

samples only produced variable abundances of morphotypes 

of Ozarkodina remscheidensis. Brachiopods and corals from 

the Decker Formation indicate a definitive Late Silurian age. 

The overlying Rondout and lower Manlius formations have 

only yielded fossils of limited biostratigraphic utility. Thus 

the Silurian-Devonian boundary is within a 30-m interval. 

For reasons cited above, we suspect the first appearance of 

I. woschmidti is higher within the woschmidti Zone in this 

area than to the south and possibly the west. The position 

of the Silurian-Devonian boundary is less precisely located 

here than elsewhere in the study areas. Collections from the 

Mohonk Lake quadrangle, New York (fig. 1, section 20), 

however, once again permit a more precise placement of the 

boundary. Oulodus elegans was recovered from within the 

Glasco Member of the Rondout Formation (USGS colln. 

11815-SD) at Accord, N.Y. (fig. 1, section 20), indicating 

a definitive Late Silurian age for a relatively high level within 

the Rondout Formation. About 5.5 km northeast of Accord, 

M, S, and fragments of Pa elements of Icriodus have been 

recovered from two samples, 1 and 2.5 m above the base 

of the Manlius Formation (USGS collns. 11818-SD, 

11819-SD), indicating a Devonian age for the entire Manlius. 

Thus, in this area, the Silurian-Devonian boundary lies within 

a 5- to 7 -m interval that includes the upper beds of the Glasco 

Member and the entire Whiteport Dolomite Member of the 

Rondout. We depart somewhat from the interpretation used 

by Rickard (1975) and Berg and others (1983) in placing the 

base of the Devonian System not at the base of the Rondout 

Formation, but rather within the Whiteport Dolomite 

Member of the Rondout, as did Oliver and others (1967) or 

at the base of the overlying Mashipacong Member (=base 

of Manlius Limestone in eastern New York). The Whiteport 

Dolomite Member consists of mud-cracked, laminated 

dolomudstone that probably represents maximum regression 

near the Silurian-Devonian boundary. This unit corresponds 

to some level in the upper limestone member of the Keyser 

Limestone associated with lowest conodont diversity in the 

more consistently normal marine sections in the southern 

study area near the basin axis. 

SYSTEMATIC PALEONTOLOGY 

All figured specimens are reposited in the U.S. National 

Museum, Washington, D.C. (USNM). 

Genus ICRIODUS Branson and Mehl, 1938 

Icriodus woschmidti woschmidti Ziegler, 1960 

Plate 1, figures A-H 

Remarks.-The elements of representatives of Icriodus 

woschmidti woschmidti in our collections from the central 

and northern Appalachian basin conform in virtually all 
respects to elements of the subspecies figured by Serpagli 

(1983) from Sardinia and to the elements we assign to the 

subspecies figured by Ziegler (1960, pl. 13, figs. 6, 17; pl. 

14, figs. 11, 19, 21; pl. 15, figs. 12, 16-22) from the Gedinnian of the Rheinisches Schiefergebirge in the Federal 

Republic of Germany. Our collections contain Pa elements 

and four symmetry transition series in what we consider the 

Pb, M, and two Sa-Sd series positions. The latter consist 

of an adenticulate and denticulate series (pl. 1, figs. E-H). 

Although Serpagli (1983) figured many morphotypes of the 

denticulate S series, he may have included some members 

of the adenticulate S series in his e-position series (fig. 4A?). 

Unfortunately, representatives of both S series are rare in 

our collections; it appears, however, there are at least three 

elements in the denticulate series and four in the adenticulate 

series. 

Genus OULODUS Branson and Mehl, 1933 

Remarks.-We follow the multielement diagnosis given 

by Sweet and Schonlaub (1975) for the genus Oulodus which 

permits a wide range in apparatus composition and morphotype and thus accommodates many types of digyrate apparatuses of Middle Ordovician through Devonian age. We 

emend their multielement diagnosis to allow two types of 

Pb elements in the same species and a vacancy in the M as 

well as the Pa position. Sweet and Schonlaub acknowledged, 

however, the possibility that the inclusion of post-Silurian 

species in Oulodus may be a polyphyletic grouping. Klapper 

and Philip (1971) established the genus Delotaxis for Type 

3 apparatuses of Silurian and Devonian age ( = digyrate 

apparatuses) and designated Ligonodina elegans Walliser the 

type species of the genus. The apparatus to which L. elegans 

belongs is equally dissimilar to Ordovician and Late Devonian digyrate apparatuses. We believe, however, that the Late 

Silurian and earliest Devonian digyrate apparatuses, particularly in the aspect of their Pb element(s), form a continuum 

with Ordovician and older Silurian representatives of 

Oulodus. 

Oulodus cristagalli (Ziegler) 

Plate 1 , figures I-T 

Pa element 

1960. Lonchodina walliseri Ziegler, p. 188-189 (part), only pl. 14, fig. 2. 

?1968. Lonchodina serbica Schulze, p. 198, pl. 17, figs. 25, 27. 

Pb1 element 

1960. Lonchodina cristagalli Ziegler, p. 189-190, pl. 14, figs. 1, 3, 5. 

1964. Lonchodina cristagalli Ziegler. Walliser, p. 43, pl. 9, fig. 23. 

1968. Lonchodina cristagalli Ziegler. Schulze, p. 196, pl. 17, fig. 23. 

1970. Lonchodina cristagalli Ziegler. Epstein, p. 174-176, pl. 5, figs. 1, 2. 

1975. Falcodus sp. Hamdi, pl. 1, fig. 2. 

1980. Delota.xis walliseri (Ziegler). Pickett, p. 79-81, fig. 10M. 

1981. Delota.xis excavata cristagalli (Ziegler), Pb element. Cook, p. 68-71, 

pl. 2, figs. 1, 4. 

1986. Oulodus greilingi hirpex Mawson, p. 46, pl. 1, fig. 4. 

1988. Oulodus cristagalli (Ziegler), Pb1 element. Elbert and others, pl. 1, 

figs. H-J. 

Pb2 element 

1960. Lonchodina walliseri Ziegler, p. 188-189, pl. 14, figs. 6, 7. 

1970. Lonchodina walliseri Ziegler. Epstein, p. 179-181 (part), pl. 5, fig. 3, 

pl. 4, fig. 16. 

1980. Delota.xis walliseri (Ziegler). Pickett, p. 79-81, figs. IOJ, IOK. 

1981. Delota.xis excavata cristagalli (Ziegler), Pa element. Cook, p. 68-70, 

pl. 2, fig. 7. 

1981. Delota.xis excavata cristagalli (Ziegler), M element. Cook, p. 68-72, 

pl. 2, fig. 5. 

1986. Oulodus greilingi hirpex Mawson, p. 46, pl. 1, figs. 2?, 3. 

?M element 

1960. Prioniodina excavata Branson and Mehl. Ziegler, p. 192, pl. 15, 

fig. 5. 

?1986. Oulodus walliseri (Ziegler), M element. Mawson, p. 48, pl. 9, fig. 5. 

Sa element 

1960. Trichonodella inconstans Walliser. Ziegler, p. 197, pl. 14, figs. 14, 

17. 

1970. Trichonodella inconstans Walliser. Epstein, p. 232-235, pl. 6, figs. 

7-10. 

1981. Delota.xis excavata cristagalli (Ziegler), Sa element. Cook, p. 72, 

pl. 2, fig. 3. 

Sb element 

1960. Lonchodina greilingi Walliser. Ziegler, p. 188, pl. 14, figs. 15, 16, 

18, 20. 

1970. Lonchodina greilingi Walliser. Epstein, p. 176-179, pl. 5, fig. 10. 

1981. Delota.xis excavata cristagalli (Ziegler), Sb element. Cook, p. 69-72, 

pl. 2, fig. 2. 

1988. Oulodus cristagalli (Ziegler), Sb element. Elbert and others, pl. 1, 

fig. K. 

Sc element 

?1960. Ligonodina diversa Walliser. Ziegler, p. 186-187, pl. 14, figs. 8, 12. 

1960. Ligonodina n. sp. Walliser. Ziegler, p. 187, pl. 14, figs. 9, 10. 

1960. Ligonodina n. sp. a, Ziegler, p. 187, pl. 14, fig. 13. 

1970. Ligonodina salopia Rhodes. Epstein, p. 170-174 (part), pl. 7, figs. 

1, 2, 6, 7. 

1981. Delota.xis excavata cristagalli (Ziegler), Sc element. Cook, p. 69-73, 

pl. 2, fig. 6. 

Description.-Robust multielement species with Pa 

(rare), Pb1, Pb2, Sa, Sb, and Sc elements; M position 

appears to be vacant or rarely occupied. Pa element angulate 

(priniodiniform); Pb elements digyrate (oulodontiform), Pb1 

( cristagalliform) element processes have greater inversion 

of attachment surface, are more twisted and form a smaller 

angle than processes ofPb2 (walliseriform); Sa element alate 

(trichonodelliform); Sb element digyrate (lonchodiniform); 

Sc element bipennate (ligonodiniform). 

All elements have discrete denticles that are subround 

to oval in cross section. All elements, except the Pa element, 

have been adequately described previously. The Pa element 

is angulate with processes of nearly equal length; lower 

margin of cusp is slightly flared; basal cavity extends as a 

slit to the end of the anterior process and is wider and weakly 

inverted on the posterior process; cusp only slightly wider 

and higher than largest process denticles; process denticles 

extremely variable in size (pl. 1, fig. I); posterior process 

denticles may be bowed inward. 

Remarks. -Representatives of Oulodus are characteristic of high-energy, shallow-water biofacies and are generally hydraulically sorted and broken. Consequently apparatus 

reconstruction and adequate description of even discrete 

elements is difficult. Thus far, only three geographically 

widespread multielement species of Oulodus have been 

Conodont-Based Determination of the Silurian-Devonian Boundary, Valley and Ridge Province B9 
documented in Upper Silurian and lowermost Devonian 

rocks: Oulodus elegans (Walliser) (Jeppsson, 1969, 1974; 

Sweet and Schonlaub, 1975; Cook, 1981; Bultynck, 1986), 

which ranges from the late Ludlovian to the latest Pridolian; 

Oulodus siluricus (Branson and Mehl) (Chlupac and others, 

1980, pl. 17, fig. 20) which ranges from the middle Ludlovian to at least the early Pridolian; and Oulodus cristagalli 

(Ziegler) (Pickett, 1980; Cook, 1981; Mawson, 1986; Elbert 

and others, 1988) which ranges from the latest Pridolian to 

at least middle Lochkovian. The apparatus composition and 

element morphotype of Oulodus cristagalli is closer to 0. 

siluricus than 0. elegans. Even though 0. elegans is common in our sections and overlaps the lowest part of the range 

of 0. cristagalli, and though 0. siluricus has not been 

recognized in the central Appalachian basin, it seems more 

likely that 0. cristagalli evolved from 0. siluricus or related 

forms. Plate 1 shows the apparatus composition of 0. elegans 

and 0. cristagalli in samples from the central Appalachian 

basin. 

Our reconstruction of the apparatuses of 0. cristagalli 

and 0. elegans is based on large collections with low species 

diversity. In these collections, all other elements not assigned 

to Oulodus belong to other well known multielement species. 

The sample which forms the basis of our reconstruction of 

0. elegans is from the upper limestone member of the Keyser 

Limestone at Lambert Gap, W. Va., of late Pridolian age 

(USGS colin. 10669-SD). This collection contains abundant 

representatives of 0. elegans and only a few ramiform element fragments of Ozarkodina remscheidensis (Ziegler) and 

decoriconids. Our reconstruction agrees in element composition with that of Cook (1981), except that we place both 

oulodontiform elements in the Pb position whereas she 

assigned our Pb1 to an Sd position. The sample that produced abundant representatives of 0. cristagalli is from the 

New Creek Limestone near McDowell, Va., of earliest 

Devonian age (USGS colin. 11549-SD). In addition to abundant 0. cristagalli, the sample contains abundant Icriodus 

woschmidti woschmidti Ziegler, lesser numbers of Ozarkodina remscheidensis (Ziegler), and a few representatives each 

of Belodella sp. and Pseudooneotodus beckmanni (Bischoff 

and Sannemann). In this collection, there are 3 Pa, 11 Pb1, 

46 Pb2, 17 Sa, 45 Sb, and 62 Sc elements of 0. cristagalli. 

We could not identify any specimens assignable to the M 

position. In addition to the apparent absence of an M element in our collections, Pa elements appear to be underrepresented in this species. Because other species of Oulodus 

may contain two Pb elements (for example, 0. elegans, pl. 

1, figs. V, W) as well as an M element (pl. 1, fig. X), we 

did not place either of the oulodontiform elements in the M 

position. Cook (1981, pl. 2, fig. 5) figured an incomplete 

digyrate specimen as an M element of 0. cristagalli. 

Moreover, she stated that all specimens assigned to the M 

position in her collections are broken and resemble what we 

consider the Pb2 element. We interpret her material to be 

incomplete Pb2 elements. 

810 Shorter Contributions to Paleontology and Stratigraphy 

Pickett (1980) placed the cristagalliform and walliseriform elements described by Ziegler (1960) in the Pb and 

Sb positions of an apparatus that he designated Delotaxis 

walliseri (Ziegler). His material, from three limestone units 

in the Cobar Supergroup of central New South Wales, 

Australia, consisted of22 specimens distributed in 13 samples 

through at least 100 m of section that ranges from the 

woschmidti Zone into the pesavis Zone. Apparatus reconstruction based on a few specimens from samples that are 

widely separated stratigraphically and chronologically is 

risky, particularly for apparatuses that apparently possess as 

many vicarious elements as digyrate apparatuses. Consequently, the only specimens figured by Pickett ( 1980) that 

are included in our synonymy for 0. cristagalli are those 

we consider Pb1 and Pb2 elements. Although Pickett's 

collections contained no forms that he could assign to an M 

position, he placed elements assigned to Prioniodina excavata 

by Ziegler (1960, pl. 15, fig. 5) in theM position of Delotaxis 

walliseri. Because specimens referred to Prioniodina excavata by Ziegler (1960) occur in topotype material with all 

the other elements we include in the apparatus of 0. 

cristagalli and because these specimens resemble elements 

of 0. cristagalli, it seems possible that M elements may have 

occurred, though rarely, in some individuals of this species. 

Mawson ( 1986) reported five species of Oulodus from 

beds representative of the eurekaensis and delta Zones in the 

Windellama Limestone of central eastern New South Wales, 

Australia. Mawson included cristagalliform and walliseriform elements in an apparatus she designated Oulodus greilingi (Walliser) and which, we believe, she erroneously 

considered synonymous with the apparatus of Oulodus 

elegans. We consider that these elements, and probably 

several other S elements figured by her, belong in 0. 

cristagalli. None of the specimens figured in Mawson's plates 

are characteristic of forms we and other workers (for example, Sweet and Schonlaub, 1975), with the exception of 

Pickett (1980, fig. 9), include in 0. elegans. Examination 

of Mawson's plates indicates her collections contain at least 

three species of Oulodus, one of which is Oulodus cristagalli 

as we interpret it. Moreover, specimens that may belong to 

0. cristagalli appear to have been included in other species 

of Oulodus (particularly specimens assigned to the Pa and 

Pb positions of 0. spicula Mawson). As in the case of 

Pickett's material, we have only synonymized the cristagalliform and walliseriform elements of Mawson's material 

and we have refrained from including even all of these 

elements in our synonymy. This is because samples that contained the most abundant representatives of Oulodus were 

assigned, by Mawson, to three or four species per sample. 

Mawson (1986) synonymized Delotaxis walliseri of Pickett 

( 1980) with her Oulodus walliseri and assigned M elements 

in her collections to this species. These specimens resemble 

elements included in Prioniodina excavata Branson and Mehl 

by Ziegler (1960) which possibly confirms Pickett's (1980) 

interpretation discussed above. 
LOCALITY REGISTER 

Section numbers keyed to index map (fig. 1). 

Section 1. Price's Bluff, Botetourt Co., Va., lat 37°42.5' N., long 79°49.6' 

W., Eagle Rock, Va .. 7.5-minute quadrangle. Chesapeake & Ohio 

Railroad cut, above the James River near Va. Rte. 622, 1.3 km from 

U.S. Rte. 220 and 2.4 km north of Gala, Va. Measured and columnar 

section in Cook (1981). 

Section 2. Iron Gate, Alleghany Co., Va., lat 37°48.3' N., long 79°47.8' 

W., Clifton Forge, Va., 7.5-minute quadrangle. Chesapeake & Ohio 

Railroad cut along west side of Jackson River below U.S. Rte. 220, 

immediately north of Iron Gate, Va. 

Section 3. McDowell, Highland Co., Va., lat 38°19.4' N., long 79°27.4' 

W., McDowell, Va., 7.5-minute quadrangle. Roadcut on north side 

of U.S. Rte. 250, 4.6 km (road distance) east of McDowell, Va. 

Section 4. Strait Creek, Highland Co., Va., lat 38°25.9' N., long 79°32.1' 

W., Monterey, Va.-W.Va., 7.5-minute quadrangle. Roadcut on Va. 

Rte. 629, approximately 1.6 km southeast of intersection with U.S. 

Rte. 220, 5.6 km north of Monterey, Va. Measured and columnar section in Cook (1981). 

Section 5. Smoke Hole, Pendleton Co., W. Va., lat 38°50.5' N., long 

79°15.9' W., Upper Tract, W.Va., 7.5-minute quadrangle. Roadcut 

on W. Va. Rte. 2, 3 km west of intersection with U.S. Rte. 220. 

Columnar section in Helfrich (1978). 

Section 6. New Creek, Mineral Co., W. Va.,lat 39°22.1' N.,long 79°01.9' 

W., Antioch, W.Va., 7.5-minute quadrangle. Abandoned quarry on 

north side of U.S. Rte. 50, 100 m east of New Creek stream and 

immediately south of New Creek, W. Va. 

Section 7. Keyser, Mineral Co., W.Va., lat 39°26.3' N., long 78°57.5' 

W., Keyser, W. Va.-Md., 7.5-minute quadrangle. Westernmost of two 

abandoned quarries (city dump), approximately 1.5 km east of Keyser, 

on the south side of the Baltimore & Ohio Railroad tracks. Columnar 

section in Helfrich (1978). 

Section 8. Altoona, Blair Co., Pa., lat 40°29.6' N., long 78°24.3' W., 

Hollidaysburg, Pa., 7 .5-minute quadrangle. Abandoned quarry and 

streamcut on west side of parking lot behind Altoona Bible Church within 

city limits of Altoona. Church on Pa. Rte. 36 (Union Ave.) and 1.4 km 

north of intersection with U.S. Rte. 220. 

Section 9. Mexico, Juniata Co., Pa., lat 40°31.8' N., long 77°21.5' W., 

Mexico, Pa., 7 .5-minute quadrangle. Small abandoned quarry on south 

side of Penn Central Railroad tracks and south side of Juniata River, 

about 1 km southwest of Mexico, Pa. 

Section 10. Tyrone, Blair Co., Pa., lat 40°41.3' N., long 78°14.7' W., 

Tyrone, Pa., 7.5-minute quadrangle. Abandoned quarry (town baseball 

field) and streamcut of Sink Creek behind American Legion building, 

0.2 km west of intersection of Lincoln and 15th Streets (Pa. Rte. 453). 

Section 11. Godfrey Ridge, Monroe Co., Pa., lat 40°59.6' N., long 75°09.1' 

W., Stroudsburg, Pa.-N.J., 7.5-minute quadrangle. Streamcut on 

southeast bank of Brodhead Creek, approximately 0.2 km above dam. 

Measured and columnar section in Epstein and others (1967, section 

15-c). 

Section 12. Shawnee on Delaware, Monroe Co., Pa., lat 41 °00.5' N., long 

75°06.9' W., Bushkill, Pa.-N.J., 7.5-minute quadrangle. Roadcut on 

northwest side of road, 1 km southwest of Shawnee on Delaware, Pa. 

Measured and columnar section in Epstein and others (1967, section 

14-b). 

Section 13. Wallpack Bend, Monroe Co., Pa., lat 41 °05.4' N., long 74°58.7' 

W., Flatbrookville, N.J.-Pa., 7.5-minute quadrangle. Outcrop in woods 

on northeast side of secondary road along ascent of Wallpack Ridge 

in Pennsylvania, immediately southwest of where Delaware River cuts 

through the ridge. Measured and columnar section in Epstein and others 

(1967, section 11). 

Section 14. Flatbrookville, Sussex Co., N.J., lat 41 °06.7' N., long 76°56.8' 

W., Flatbrookville, N.J.-Pa., 7.5-minute quadrangle. Roadcut on 

northwest side of county road which extends along southwest side of 

Wallpack Ridge, 2.4 km northwest ofFlatbrookville, N.J., and 0.2 km 

southwest of V -shaped bend in road. Measured and columnar section 

in Epstein and others (1967, section 10). 

Section 15. Cliff section, Sussex Co., N.J., lat 41 o 10.5' N., long 74 °52.2' 

W., Culvers Gap, N.J.-Pa., 7.5-minute quadrangle. Series of ledges 

on steep southeast slope of Wall pack Ridge at an elevation of about 

620ft, 2.7 km (road distance) southwest of Peters Valley, N.J. Columnar 

section in Epstein and others ( 1967, section 6). 

Section 16. Peters Valley, Sussex Co., N.J., lat41 °12.2' N., long 74°50.8' 

W., Culvers Gap, N.J.-Pa., 7.5-minute quadrangle. Series ofledges 

along hillside above small abandoned quarry at an elevation of about 

600 ft, 1 km northeast of Peters Valley, N.J. Columnar section in Epstein 

and others (1967, section 5). 

Section 17. Montague, Sussex Co., N.J., lat 41 °17.7' N., long 74°46.7' 

W., Milford, Pa.-N.J., 7.5-minute quadrangle. Section on southwest 

side of county road and in woods on northeast side of road, about 1.6 km 

southeast of Montague, N.J. Columnar section in Epstein and others 

(1967, section 4). 

Section 18. Nearpass quarries, Sussex Co., N.J., lat 41 °20.1' N., long 

74°42.3' W., Port Jervis South, N.J.-N.Y.-Pa., 7.5-minute quadrangle. 

Abandoned quarry on southwest slope of Wallpack Ridge, approximately 

3 km southwest of Dutton ville, N.J. Measured and columnar section 

in Epstein and others ( 1967, section 3). 

Section 19. Tristates, Orange Co., N.Y., lat 41 °21.8' N., long 74°42.3' 

W., Port Jervis South, N.J.-N.Y.-Pa., 7.5-minute quadrangle. Abandoned quarries on northwest side of Lime Kiln Road, on southeast slope 

of Trilobite Mountain, Port Jervis, N.Y. Measured and columnar section in Epstein and others (1967, section 2). 

Section 20. Mohonk Lake, Ulster Co., N.Y., Mohonk Lake, N.Y., 

7 .5-minute quadrangle, composite section. Glasco Member of the 

Rondout Formation exposed in abandoned quarry, 0.7 km westsouthwest of town center of Accord, lat 41°47.0' N., long 74°13.5' 

W.; Whiteport Dolomite Member of the Rondout Formation and Manlius 

Limestone exposed in bed of small tributary of Rondout Creek, 0.3 km 

northwest of Epworth Church, lat 41 °48.7' N., long 74°10.2' W. 

Section21. Mount Ida quarry, Columbia Co., N.Y., lat42°15.6' N., long 

73°43.8' W., Stottville, N.Y., 7.5-minute quadrangle. Southeast side 

of abandoned quarry, Mount Ida, 2. 9 km south-southeast of Stottville, 

N.Y. 

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faunas from Windellama, New South Wales: Geologica et 

Palaeontologica, v. 20, p. 39-71. 

Oliver, W.A., Jr., 1976, Biogeography of Devonian rugose corals: 

Journal of Paleontology, v. 50, no. 3, p. 365-373. 

Oliver, W.A., Jr., and Pedder, A.E.H., 1979, Biogeography of 

Late Silurian and Devonian rugose corals in North America, 

in Gray, Jane, and Boucot, A.J., eds., Historical biogeography, 

plate tectonics, and the changing environment: Corvallis, Ore., 

Oregon State University Press, p. 131-145. 

Oliver, W.A., Jr., and others, 1967, Devonian of the Appalachian 

basin, United States, in Oswald, D.H., ed., International Symposium on the Devonian System: Calgary, Alberta, Alberta 

Society of Petroleum Geologists, v. 1 , p. 1001-1040. 

Pickett, John, 1980, Conodont assemblages from the Cobar 

Supergroup (Early Devonian), New South Wales: Alcheringa, 

v. 4, no. 1, p. 67-88. 

Reeside, J.B., Jr., 1917, The Helderberg Limestone of central Pennsylvania: U.S. Geological Survey Professional Paper 108-K, 

p. 185-225. 

Rickard, L.V., 1962, Late Cayugan (Upper Silurian) and 

Helderbergian (Lower Devonian) stratigraphy in New York: 

New York State Museum Bulletin 386, 157 p. 

1975, Correlation of the Silurian and Devonian rocks 

in New York State: New York State Museum and Science 

Service Map and Chart Series no. 24, 16 p., 4 pis. 

Schulze, Rudolf, 1968, Die Conodonten aus dem Palaozoikum der 

mittleren Karawanken (Seeberggebiet): Neues Jahrbuch fiir 

Geologie und Palaontologie Abhandlungen, v. 130, no. 2, p. 

133-245. 

Serpagli, Enrico, 1983, The conodont apparatus of Icriodus 

woschmidti woschmidti Ziegler: Fossils and Strata, no. 15, p. 

155-161. 

Sorauf, J.E., and Oliver, W.A., Jr., eds., 1983, Silurian and Devonian corals and stromatoporoids of New York: Washington, 

D.C., Fourth International Symposium of Fossil Cnidaria, 

179 p. 

Stock, C.W., and Holmes, A.E., 1986, Upper Silurian/Lower 

Devonian Stromatoporoidea from the Keyser Formation at 

Mustoe, Highland County, west-central Virginia: Journal of 

Paleontology, v. 60, no. 3, p. 555-580. 

Swartz, C.K., 1913, The Lower Devonian deposits of Maryland, 

correlation of the Lower Devonian, in Maryland Geological 

Survey, Lower Devonian: p. 96-123. 

Swartz, C.K., and others, 1942, Correlation of the Silurian formations of North America: Geological Society of America 

Bulletin, v. 53, p. 533-538. 

Swartz, F.M., 1929, The Helderberg Group of parts of West 

Virginia and Virginia: U.S. Geological Survey Professional 

Paper 158-C, p. 27-75. 

Swartz, F.M., and Whitmore, F.C., Jr., 1956, Ostracoda of the 

Silurian Decker and Manlius limestones in New Jersey and 

eastern New York: Journal of Paleontology, v. 30, no. 5, p. 

1029-1091. 

Sweet, W. C., and Schonlaub, H.P., 1975, Conodonts of the Genus 

Oulodus Branson & Mehl, 1933: Geologica et Palaeontologica, 

v. 9, p. 41-59. 

Ulrich, E.O., 1911, Revisions of the Paleozoic Systems: Geological 

Society of America Bulletin, v. 22, p. 281-680. 

Walliser, O.H., 1964, Conodonten des Silurs: Hessisches 

Landesamt fiir Bodenforschung Abhandlungen, no. 41, 106 p. 

1971, Conodont biostratigraphy of the Silurian of 

Europe, in Sweet, W.C., and Bergstrom, S.M., eds., Symposium on conodont biostratigraphy: Geological Society of 

America Memoir 127, p. 195-206. 

Walmsley, V.G., Aldridge, R.J., and Austin, R.L., 1974, 

Brachiopod and conodont faunas from the Silurian and Lower 

Devonian of Bohemia: Geologica et Palaeontologica, v. 8, p. 

39-47. 

Woodward, H.P., 1943, Devonian system of West Virginia: West 

Virginia Geological Survey, v. 15, 655 p. 

Ziegler, Willi, 1960, Conodonten aus dem Rheinischen Unterdevon 

(Gedinnium) des Remscheider Sattels (Rheinisches Schiefergebirge): Palaontologische Zeitschrift, v. 34, no. 2, p. 169-201. 

Conodont-Based Determination of the Silurian-Devonian Boundary, Valley and Ridge Province B13 

PLATE 1 

Contact photographs of this plate are available, at cost, from U.S. Geological Library, Federal 

Center, Denver, Colorado 80225 
PLATE 1 

Conodont indices to the Silurian-Devonian boundary interval, Valley and Ridge province, Appalachians 

[SEM photomicrographs of specimens coated with carbon and gold] 

FIGURES A-T. Earliest Devonian conodonts from 1.7 m above the base of the New Creek Limestone, 

near McDowell, Va. (USGS colln. 11549-SD). 

A-H. Icriodus woschmidti woschmidti Ziegler. 

A. Upper view of Pa element (lower margin incomplete), x50, USNM 

418409. 

B. Upper view of Pa element with seven transverse rows of nodes and a 

prominent inner lateral spur, X40, USNM 418410. 

C. Outer lateral view of Pb element, x50, USNM 418411. 

D. Inner lateral view of M element, X 50, USNM 418412. 

E. Outer lateral view of Sb1 element (adenticulate series), X 100, USNM 

418413. 

F. Lateral view of slightly asymmetric Sd1 element, x50, USNM 418414. 

G, H. Inner and outer lateral views of Sb2 elements (denticulate series), X 50 and 

x75, USNM 418415-16. 

I-T. Oulodus cristagalli (Ziegler). 

I, J. Inner lateral views of rare Pa elements (J is complete), X40 and X 50, 

USNM 418417-18. 

K, L. Inner and outer lateral views of Pb1 (cristagalliform) elements, X40, 

USNM 418419-20. 

M-0. Two inner and one outer lateral views of Pb2 (walliseriform) elements; M, 

X50, USNM 418421; N, 0, x40, USNM 418422-23. 

P. Posterior view of Sa element, X40, USNM 418424. 

Q, R. Inner lateral views of Sb elements, x40, USNM 418425-26. 

S, T. Inner lateral view of Sc elements, X40 and x50, USNM 418427-28. 

U-AA. Oulodus elegans (Walliser), from 1.4 m above the base of the upper limestone member 

of the Keyser Limestone (upper Pridolian), Lambert Gap, West Virginia (USGS colln. 

10699-SD); all specimens incomplete and X75. 

U. Inner lateral view of Pa element, USNM 418600. 

V. Oblique inner lateral view of Pb1 element, USNM 418601. 

W. Inner lateral view of Pb2 element, USNM 418602. 

X. Inner lateral view of M element, USNM 418603. M elements of Appalachian 

basin 0. elegans have an adenticulate anticusp, whereas some European 

representatives of this species have M elements with a denticulate anticusp 

(Jeppsson, 1969, fig. 4B; 1974, pl. 3, fig. 4). 

Y. Posterior view of Sa element, USNM 418604. 

Z. Inner lateral view of Sb element, USNM 418605. 

AA. Inner lateral view of Sc element, USNM 418606. 
U.S. GEOLOGICAL SURVEY BULLETIN 1837- B PLATE 1 

ICRIODUS, OULODUS 

CHAPTER C 

Homeognathodus peniculus (Conodonta), 

a New Earliest Pridolian Index Species, 

and the Ludlovian-Pridolian Boundary in the 

Central Appalachian Basin 

By KIRK E. DENKLER and ANITA G. HARRIS 

U.S. GEOLOGICAL SURVEY BULLETIN 1837 

SHORTER CONTRIBUTIONS TO PALEONTOLOGY AND STRATIGRAPHY 

CONTENTS 

Abstract Cl 

Introduction Cl 

Lithostratigraphy C2 

Conodont biostratigraphy and the Ludlovian-Pridolian boundary C3 

Conodont zonation CS 

Lower remscheidensis Subzone CS 

peniculus Subzone of the remscheidensis Zone CS 

Systematic paleontology CS 

Genus Homeognathodus n. gen. CS 

Locality register C6 

References cited C7 

PLATE 

[Plate follows References Cited] 

1. Some biostratigraphically significant conodonts from the Tonoloway Limestone 

and equivalents, central Appalachian basin. 

FIGURES 

1. Map showing Silurian outcrop belt and location of measured sections that yielded 

representatives of Homeognathodus peniculus n. sp. in the central 

Appalachians C2 

2. Chart showing conodont -based correlation of uppermost Ludlovian to lowermost 

Lochkovian stratigraphic units in the east -central Appalachians C3 

3. Chart showing stratigraphic range of important conodont indices across the 

Ludlovian-Pridolian boundary in key European and North American sections C4 

TABLE 

1. Locality and sample data for Homeognathodus peniculus n. sp. C7 

Contents Ill 

Homeognathodus peniculus (Conodonta), 

a New Earliest Pridolian Index Species, 

and the Ludlovian-Pridolian Boundary in the 

Central Appalachian Basin 

By Kirk E. Denkler and Anita G. Harris 

Abstract 

A new index species, Homeognathodus peniculus, is 

described and its stratigraphic distribution documented from 

eight localities, all from within the middle member of the 

Tonoloway Limestone and its equivalents, in the central Appalachian basin. The latest Silurian conodont zonation is revised; 

the eosteinhornensis Zone is renamed the remscheidensis Zone 

and its base is placed at the lowest occurrence of Ozarkodina 

remscheidensis in the latest Ludlovian. Two new subzones are 

established for the latest Ludlovian and earliest Pridolian part 

of the remscheidensis Zone: the Lower remscheidensis Subzone 

represents the interval of overlap of the name bearer with 

subspecies of 0. snajdri; the succeeding peniculus Subzone is 

defined by the range of the name bearer and its lower boundary approximates the base of the Pridolian. H. peniculus is 

probably an Appalachian endemic; thus, recognition of the 

peniculus Subzone is most likely limited to the Appalachian 

basin. 

INTRODUCTION 

Precise correlation of Ludlovian and Pridolian rocks 

of the central Appalachian basin with other regions has defied 

paleontologists for over a century. Although these Silurian 

rocks are widespread (fig. 1), relatively well exposed from 

Maryland to northernmost Tennessee, and as much as 

1,000 m thick, they are only locally fossiliferous and contain chiefly endemic species. Because other fossil groups have 

been unable to provide detailed correlation, conodonts have 

been utilized (Helfrich, 1975) to effect a biostratigraphic correlation of the carbonate rocks in these series in part of the 

central Appalachians. In this area, however, carbonate rocks 

are only abundant in the late Ludlovian and Pridolian, in the 

Wills Creek, Tonoloway, and Keyser formations and their 

equivalents. 

Berry and Boucot ( 1970) placed the LudlovianPridolian boundary within the Wills Creek Formation 

primarily on the basis of the similarity of its eurypterid fauna 

with that of the Syracuse Formation in New York. They 

assumed that the presence of Ozarkodina remscheidensis 

(Ziegler) group conodonts in the Syracuse Formation 

indicated an age no older than Pridolian for that unit. The 

most recent correlation charts for the Appalachian basin also 

show the Ludlovian-Pridolian boundary within the Wills 

Creek Formation (American Association of Petroleum 

Geplogists, 1985a, b). In contrast, Helfrich (1975) placed 

the base of the Pridolian in the middle of the overlying 

Tonoloway Limestone on the basis of the occurrence of latest 

Ludlovian conodonts (Ozarkodina snajdri crispa (Walliser), 

in particular) in the lower half of the formation. In the same 

paper, Helfrich reported a new species, herein designated 

Homeognathodus peniculus, from a single collection in the 

lower part of the upper Tonoloway; he suggested the new 

species descended from 0. s. crispa and was Pridolian in age. 

In 1982, W. B. Brent, Tennessee Division of Geology, 

submitted a sample of coralline-stromatoporoid limestone 

from the lower half of the Sneedville Limestone of Stafford 

(1856) in Tennessee for biostratigraphic analysis. The corals, 

identified by W. A. Oliver, Jr., indicated a Late Silurian age. 

The conodont faunule included representatives of Ozarkodina 

confluens (Branson and Mehl) and H. peniculus, suggesting 

an early Pridolian age based on Helfrich's (1975) conodont 

biostratigraphy. Because this distinctive species was 

recovered from two widely separated localities and because 

the 0. s. crispa-H. peniculus lineage proposed by Helfrich 

appeared to have biostratigraphic potential for defining the 

Ludlovian-Pridolian boundary, we undertook to find this 

species succession in other sections in the central 

Appalachians. 

Homeognathodus peniculus (Conodonta), a New Earliest Pridolian Index Species Cl 
LITHOSTRATIGRAPHY 

Uppermost Ludlovian and Pridolian rocks in the study 

area are represented, at their thickest, by 280 m of the 

Tonoloway and most of the overlying Keyser Limestones. 

The Tonoloway Limestone and its equivalents decrease in 

thickness southwestward, from 200 m in western Maryland 

to less than 30m in northeastern Tennessee (fig. 2). Where 

thickest, the Tonoloway is subdivided into three informal 

members. The lower and upper members consist chiefly of 

thin-bedded carbonate mudstone and calcareous shale that 

are generally laminated, stromatolitic, mud-cracked, and 

poorly fossiliferous. The middle member is composed of a 

wider variety of carbonate rock types containing, in part, 

a diverse marine fauna representing a transgression that proVIRGINIA 

--TENNESSff 

duced normal marine subtidal facies between the peritidal 

mudflat facies of the lower and upper members. Distinctions 

between members gradually disappear as the Tonoloway 

thins southwestward. In the northern part of the study area, 

the Tonoloway is sharply to gradationally overlain by 

fossiliferous wackestone to grainstone of the Keyser Limestone. Southwest of central Virginia, an unconformity of 

increasing magnitude separates the Tonoloway and its 

equivalents from younger rocks (fig. 2). Details of the areal 

distribution, thickness, and vertical and lateral relationships 

and measured sections of these rocks can be found in 

Maryland Geological Survey (1923), Woodward (1941), 

Colton (1970), and Smosna and others (1977). 

The Tonoloway Limestone and its equivalents were 

deposited in a generally shallow-water, restricted foreland 

0 

I 

0 

+38' 

100 MILES 

I 

100 KILOMETERS 

Figure 1. Silurian outcrop belt (shaded) and location of sections that yielded representatives of Homeognathodus peniculus n. 

sp. in the central Appalachians. See locality register for geographic description. Sections are: GR, Grasshopper Run, W. Va.; PI, 

Pinto, Md.; PH, Powers Hollow, W. Va.; LG, Lambert Gap, W. Va.; FR, Fulks Run, Va.; M, McDowell, Va.; HF, Hatfield farm, 

Tenn.; SN, Sneedville, Tenn. 

C2 Shorter Contributions to Paleontology and Stratigraphy 
basin, bounded on the east by low-relief uplands and on the 

north and west by the craton; marine waters entered the basin 

from the southwest. In the study area, the clastic-to-carbonate 

ratio increases toward the eastern limit of the Silurian outcrop belt; grain size of the clastic rocks generally increases 

southward. An evaporite basin lay north and west of the study 

area, where equivalent facies consist of dolostones and 

evaporites (Salina Formation). 

CONODONT BIOSTRATIGRAPHY AND THE 

LUDLOVIAN-PRIDOLIAN BOUNDARY 

Walliser (1964) was the first to propose a conodont 

zonation for the entire Silurian, based on one rather complete section at Cellon, Austria, and additional collections 

from key areas in central Europe. The upper Ludlovian, as 

used by Walliser (1964), included what is now upper Ludlovian and Pridolian. He included the upper part of the siluricus 

Zone and the succeeding latialata, crispa, and eosteinhornensis Zones in this interval. At that time, Walliser presumed 

the base of ef32 in Bohemia (=base of Pridoli Formation) 

coincided with the base of the latialata Zone. In 1971 , based 

on new data, Walliser revised the base of ef32 to approximate 

the base of his eosteinhornensis Zone. Moreover, he was 

also aware of the co-occurrence of 0. r. eosteinhornensis 

and 0. s. crispa in collections from Gotland (Walliser, 1971, 

p. 200). As a result, he expressed doubt about the validity 

SYSTEM 

CJ) SERIES CONODONT 

~ ZONES a: OR w AND CJ) STAGE SUBZONES 

WESTERN MARYLAND 

of the crispa Zone as well as its relationship to the eosteinhornensis Zone; that is, does the range of 0. r. eosteinhornensis partly or completely overlap the range of 0. s. 

crispa. In the same year, Rexroad and Craig ( 1971) reported 

0. r. eosteinhornensis together with 0. s. snajdri in collections from the upper Bainbridge Formation in Missouri and 

speculated that 0. r. eosteinhornensis could range as low 

as the upper siluricus Zone. 0. s. snajdri and 0. r. eosteinhornensis were found together once again in the Kokomo 

Limestone Member of the Wabash Formation in Indiana, as 

used by Pollock and Rexroad (1973). 

Klapper and Murphy (1975) noted that in the type area 

of the Pridolian, 0. r. eosteinhornensis extends downward 

into the top of the Kopanina Formation where it occurs with 

0. s. crispa. Nonetheless, they showed the LudlovianPridolian boundary, at Cellon, at the boundary between the 

crispa and eosteinhornensis Zones. Since then, many authors 

have reported a considerable overlap of the ranges of 0. s. 

crispa and 0. r. eosteinhornensis (fig. 3). For example, at 

the Muslovka quarry in the type Pridolian of Czechoslovakia, 

the lower range of 0. r. eosteinhornensis completely overlaps 

the range of 0. s. crispa and extends 3m below the base 

of the Pridoli Formation; moreover, 0. s. crispa extends upward into the basal 0.5 m of the Pridoli Formation (Chlupac 

and others, 1980). Consequently, neither the first or last 

occurrence of these zonal indices, nor of other conodont 

species reported from the type Pridoli Formation, could be 

used to mark the base of the Pridolian. In 1980, Chlupac 

WEST -CENTRAL 

VIRGINIA AND 

EAST -CENTRAL 

WEST VIRGINIA 

SOUTHWESTERN 

VIRGINIA 

NORTHEASTERN 

TENNESSEE 

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3 KOVIAN ~-----l-=-+------1----- w B UPPER LS. 

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Figure 2. Conodont-based correlation of uppermost Ludlovian to lowermost Lochkovian stratigraphic units in the east-central 

Appalachians. 

Homeognathodus peniculus (Conodonta), a New Earliest Pridolian Index Species CJ 
and others proposed reducing the crispa Zone to a subzone 

of the eosteinhomensis Zone and that the base of the eosteinhomensis Zone, following Walliser (1964), be taken at the 

first occurrence of that species within the latest Ludlovian, 

a proposal followed by Harris and others (1983). In 1984, 

the Subcommission on Silurian Stratigraphy formally 

established the Pridolian Series and placed its base at the first 

appearance of Monograptus parultimus in the Pozary section in the Barrandian area, Czechoslovakia (Holland, 1985). 

Kfiz and others (1986) published a detailed biostratigraphic 

analysis of fossils in the Ludlovian-Pridolian boundary beds 

in many sections in the Barrandian area. These authors also 

changed the name of the Pridoli Formation to the Pozary Formation in order to avoid duplication of formation and series 

names. Their data showed that representatives of subspecies 

of Ozarkodina snajdri do not extend into the parultimus 

Zone, but range to within 50 em of the base of the zone at 

the Pozary section. 

In our sections in the central Appalachians, 0. r. remscheidensis and 0. r. eosteinhomensis are coeval and intergradational ecophenotypes that repeatedly replace one 

another in shallowing-upward or transgressive-regressive 

cycles from the latest Ludlovian through early Lochkovian 

(Denkler and others, 1983; Denkler and Harris, 1985), from 

within the lower member of the Tonoloway Limestone 

through the Keyser Limestone. As a result, we have changed 

the name of the latest Silurian conodont zone to the remscheidensis Zone to better reflect the concurrent range of both 

subspecies. Moreover, in these same sections~ 0. s. snajdri 

precedes, occurs together with and considerably above 0. 

s. crispa, extending as high as the upper meter of the lower 

member of the Tonoloway. In central European sections 

(Kfiz and others, 1986), in contrast, 0. s. snajdri precedes 

and only overlaps the lowest part of the range of 0. s. crispa 

and 0. s. crispa extends to very near the top of the Ludlovian (fig. 3). In both the central Appalachians and central 

Europe subspecies of 0. remscheidensis overlap the upper 

part of the range of subspecies of 0. snajdri. In the central 

Appalachians, 0. s. snajdri appears to extend to the top of 

the Ludlovian, overlapping and extending well beyond the 

range of 0. s. crispa. Consequently, we prefer to designate 

the interval of overlap of subspecies of 0. remscheidensis 

with subspecies of 0. snajdri, the Lower remscheidensis Subzone thereby avoiding confusion with the central European 

concept of a crispa Zone or Subzone that only contains 0. 

s. snajdri in its lower part. Homeognathodus peniculus appears to be restricted to the middle member of the Tonoloway 

Limestone and its equivalents and can occur throughout an 

WORLDWIDE 

SERIES CONODONT 

ZONATION 

1 

BOHEMIA, 

2 

CELLON, 

3 

GOTLAND, 

4 

ROBERTS 

5 

CENTRAL 

APPALACHIAN 

BASIN 

CENTRAL 

APPALACHIAN 

ZONATION 

CZECHOSLOVAKIA 

AUSTRIA 

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American sections. References for columns are: 1, Kri:z and others (1986) and Mehrtens and Barnett (1976); 2, Walliser (1964); 

3, Jeppsson (1983); 4, Klapper and Murphy (1975); 5, Helfrich (1975) and this report. 

C4 Shorter Contributions to Paleontology and Stratigraphy 
interval about 30m thick. In all sections, H. peniculus first 

appears above the upper limit of representatives of its probable ancestor, 0. snajdri. At McDowell, Va., these species 

are separated by an interval only 1 m thick. Consequently, 

we propose to use H. peniculus as a subzonal indicator for 

the early Pridolian and to use its lowest stratigraphic occurrence as the base of the Pridolian in the central Appalachians. 

The base of the Pridolian Series in at least three sections in 

the Barrandian area of Czechoslovakia is 30 to 50 em above 

the last occurrence of 0. s. crispa. Significantly, the biostratigraphic horizon we have chosen to approximate the base 

of the Pridolian in the central Appalachians is 1 m above 

the last occurrence of 0. s. snajdri. 

CONODONT ZONATION 

Lower remscheidensis Subzone 

This zone equals the former crispa Subzone of Harris 

and others (1983, fig. 2). 

Lower boundary.-The first appearance of Ozarkodina 

remscheidensis remscheidensis (Ziegler) or 0. r. eosteinhomensis (Walliser) and transitional forms in the presence 

of subspecies of 0. snajdri (Walliser). 

Upper boundary.-The first appearance of Homeognathodus peniculus n. sp. in the central Appalachians; 

elsewhere, the last occurrence of subspecies of Ozarkodina 

snajdri (Walliser). 

Associated conodonts.-Oulodus elegans (Walliser), 

Ozarkodina conjluens (Branson and Mehl), and Panderodus 

spp. are present throughout the subzone and Distomodus 

dubius (Rhodes) and Ozarkodina highlandensis (Helfrich) 

appear to be limited to the lower part of the subzone in the 

central Appalachians. Elsewhere, Belodella spp. (Pollock and 

Rexroad, 1973)~ Ozarkodina excavata (Branson and Mehl) 

(Chlupac and others, 1980; Jeppsson, 1974; Walliser, 1964) 

and Ozarkodina wimani (Jeppsson, 1983) occur in the 

subzone. 

Remarks~-Because Homeognathodus peniculus is 

probably an Appalachian endemic and is known only from 

beds above the last occurrence of the cosmopolitan subspecies 

of 0. snajdri, the upper boundary of this subzone elsewhere 

can be taken as the last occurrence of 0. snajdri subspp. 

From the data of Rexroad and Craig ( 1971, table 1), it. is 

possible that 0. r. eosteinhomensis extends into the upper 

limit of the range of Polygnathoides siluricus Branson and 

Mehl; they report P. emarginatus (Branson and Mehl) s.f. 

(which we interpret as the Pb element of P. siluricus) above 

and together with representatives of 0. r. eosteinhomensis 

and 0. s. snajdri. 

The subzone is present at various levels throughout the 

lower member of the Tonoloway Limestone and its 

equivalents in the central Appalachians and in the Kokomo 

Limestone Member of the Wabash Formation, north-central 

Indiana (Pollock and Rexroad, 1973), upper part of the Bainbridge Formation, Missouri (Rexroad and Craig, 1971), the 

Hamra b through Sundre Beds, Gotland (Jeppsson, 1983), 

and the upper Kopanina and very lowermost Pozary Formations, Bohemia (Walliser, 1964; Mehrtens and Barnett, 1976; 

and Chlupac and others, 1980; Kfiz and others, 1986). 

peniculus Subzone of the remscheidensis Zone 

Lower boundary.-The first appearance of Homeognathodus peniculus n. sp. 

Upper boundary.-The last occurrence of H. peniculus. 

Associated conodonts.-Oulodus elegans (Walliser), 

Ozarkodina confluens (Branson and Mehl), Ozarkodina 

remscheidensis remscheidensis (Ziegler) and 0. r. eosteinhomensis (Walliser) and transitional forms, and Panderodus 

spp. occur in many samples with H. peniculus. 

Remarks.-We are using the lowest occurrence of H. 

peniculus to approximate the base of the Pridolian in the central Appalachians. Thus far, the subzone is restricted to the 

middle member of the Tonoloway Limestone and is represented by a maximum thickness of about 30 m. The subzone 

occurs within 1 m of the base and 7 m of the top of the 

member at McDowell, Va., and Lambert Gap, W. Va., 

respectively. The zone occurs in eight sections, from 

Grasshopper Run, W. Va., at the northern limit of the study 

area, to Sneedville, Tenn., 400 km southwest (fig. 1). Five 

other sections of the Tonoloway and its equivalents within 

the study area were sampled for conodonts, but did not yield 

H. peniculus. Equivalent strata at many localities in Pennsylvania, from the Allegheny front to the eastern limit of 

Silurian outcrop, were examined for possible conodont 

sampling, but were of inappropriate lithofacies. The recognition of the subzone is probably limited to the Appalachian 

basin. 

SYSTEMATIC PALEONTOLOGY 

Homeognathodus peniculus n. sp. is represented only 

by Pa elements in our collections; its suprageneric classification, therefore, cannot be determined at this time. 

All figured specimens are reposited in the U.S. National 

Museum, Washington, D.C. (USNM). 

Genus HOMEOGNATHODUS n. gen. 

Type species.-Homeognathodus peniculus n. sp. 

Derivation of name.-For its similarity to the gnathodid 

cup of many Carboniferous and Permian conodont genera. 

Diagnosis.-A genus of conodont with a carminiscaphate Pa element having a somewhat irregularly ornamented 

upper platform and a carina that is subterminal. Apparatus 

unknown, possibly unimembrate. 

Homeognathodus peniculus (Conodonta), a New Earliest Pridolian Index Species C5 
Remarks.-This genus is known only from a single 

species. Forms linking this genus to representatives of other 

genera have not yet been found, but we suspect that the genus 

is descended from Ozarkodina snajdri by the posterior 

expansion of the platform and development of ornamentation on its upper surface. Homeognathodus resembles the 

Permian genus Sweetognathus (whose apparatus is also 

probably unimembrate), but the former differs in having a 

longer free blade and more irregular platform ornament. 

Discussion.-Along with Helfrich (1975), we believe 

Homeognathodus ( = N. Gen. et n. sp. of Helfrich) descended 

from Ozarkodina snajdri crispa (Walliser). Contrary to Clark 

and others (1981, p. W 165), we do not believe that forms 

with carminiscaphate Pa elements, such as 0. s. crispa and 

0. s. snajdri, belong in Ozarkodina. It is, however, inappropriate to undertake a major revision of this multispecific 

genus at this time. Nonetheless, we want to emphasize that 

Homeognathodus did not evolve directly from a generalized, 

carminate ozarkodinid, but rather from an intermediate form 

with an expanded posterior platform such as ''0. '' snajdri, 

which we would either place in a separate genus or include 

in Homeognathodus. 

Homeognathodus peniculus n. sp. 

Plate 1, figures A-1 

1975. N. Gen. et n. sp. Helfrich, p. 86 of appendix 1, text-fig. 17F, pl. 

16, figs. 1-3, 6. 

Types.-Holotype, USNM 403810 (pl. 1, figs. A-C); 

paratypes, USNM 403811-403814. 

Derivation of name.-Latin peniculus, meaning brush. 

In oblique lateral view, Pa element resembles a hair brush. 

Type locality.-Roadcut on north side of U.S. Highway 

250, about 4.6 km east of McDowell, Highland Co., Va., 

USGS colln. 11272-SD. From a stromatoporoid-coralline 

biolithic wackestone, approximately 0. 7 m above the base 

of the middle member of the Tonoloway Limestone. Only 

a single specimen of H. peniculus has been recovered from 

the type locality. This specimen was selected as the holotype 

because it is the best preserved in our collections and is from 

the lowest known stratigraphic level of the peniculus 

Subzone. 

Reference locality.-H. peniculus is most abundant, 

although not as well preserved as the holotype, in two collections from intraclastic packstone to wackestone at 23 m 

(98 specimens) (pl. 1, figs. D-H) and 25m (21 specimens) 

above the base of the middle member of the Tonoloway 

Limestone on the north side of the Baltimore & Ohio Railroad 

cut, about 0.3 km east-southeast of the Pinto Post Office, 

Allegany Co., Md. 

Diagnosis.-Diminutive (average length 0.5 mm), 

carminiscaphate Pa element with ratio of free blade to platform length varying from 2:1 in juveniles to 1:1 in adults. 

Height of free blade decreases posteriorly except for a single 

denticle at the blade-platform junction (pl. 1, fig. G) which 

is nearly twice as high as adjacent denticles or nodes. In 

C6 Shorter Contributions to Paleontology and Stratigraphy 

lateral view, upper platform margin straight. Platform elliptical to subcircular with steep, slightly concave sides (pl. 1, 

fig. G). Upper surface ornamented with a nodose (pl. 1, fig. 

D) to adenticulate (pl. 1, figs. A, I) carina and a variable 

number of subcircular to transversely elongate marginal 

nodes or ridges. Lower platform margin extends out as an 

apronlike shelf. Gnathodid basal cavity with pit at anterior 

edge of platform (pl. 1, figs. B, H). In lateral view, lower 

platform margin descends in gentle convex arc to lowest point 

at junction with free blade; lower margin of free blade is 

straight or rises slightly anteriorly. 

Remarks.-The largest specimens in our collections are 

slightly more than 1 mm in length. Some variation in platform ornament appears to be ontogenetic; small specimens 

tend to have nodes whereas larger specimens may develop 

transverse ridges. The carina may be adenticulate or nodose 

in all growth stages. No evolutionary trends in ornamentation were observed through 30 m of section. 

Most of our specimens are poorly preserved; they are 

commonly abraded and corroded and generally have an 

incomplete free blade and lower margin. Their color alteration index is 1.5 at the Tennessee localities and 3.5 to 4 at 

all other localities. H. peniculus is a very rare component 

of the middle Tonoloway conodont fauna (table 1). Our most 

abundant collections were recovered from lag concentrates, 

and we believe most specimens are present as a result of postmortem transport. Although it is likely that H. peniculus 

evolved during the transgressive event represented by the 

middle member of the Tonoloway Limestone, it was apparently not a significant component of the conodont biofacies 

represented in these rocks. Thus, when present it is 

represented by no more than 1 or 2 specimens per kilogram 

(table 1). 

Occurrence.-Throughout the middle member of the 

Tonoloway Limestone in the central Appalachians. Table 1 

lists all collections from which H. peniculus has been 

recovered (see locality register for sample locations). 

Material.-152 specimens from 12 samples distributed 

among eight localities. 

LOCALITY REGISTER 

Grasshopper Run, Morgan Co., W.Va., lat 39°40.5' N., long 78°12.3' 

W., Hancock, W. Va.-Md.-Pa., 7.5-minute quadrangle. South side 

of Baltimore & Ohio Railroad cut, 2.3 km south-southwest of south 

end of U.S. Highway 522 bridge across Potomac River. Entire 

Tonoloway Limestone exposed and is 181 m thick: lower member 48 m; 

middle member, 39m; upper member, 94 m. USGS colln. 11271-SD 

from 29 m above base of middle member. 

Pinto, Allegany Co., Md., lat 39°34.0' N., long 78°50.2' W., Cresaptown, 

W. Va.-Md., 7.5-minute quadrangle. North side of Baltimore & Ohio 

Railroad cut, 0.3 km east-southeast of Pinto Post Office. Entire 

Tonoloway Limestone exposed and is 181 m thick: lower member, 

79 m; middle member, 29 m; upper member, 73 m. USGS colln. 

10685-SD from 23m and USGS colln. 10686-SD from 25m above 

base of middle member. 
Table 1. Locality and sample data for Homeognathodus peniculus n. sp. 

Locality1 USGS collection Sample Number of Associated conodonts 

number weight (kg) specimens (in order of decreasing abundance) 

Pinto, Md. 10685-SD 39.0 

10686-SD 45 .5 

Grasshopper Run, W. Va. 11271-SD 12.4 

Powers Hollow, W. Va. 10692-SD 8.4 

Lambert Gap, W. Va. 11273-SD 10.6 

11274-SD 8.0 

11687-SD 11.3 

Fulks Run, Va. 11270-SD 7.4 

McDowell, Va. 11271-SD 8.7 

11589-SD 7.9 

Hatfield farm, Tenn. 11269-SD 11.9 

Sneedville, Tenn. 10417-SD 15.8 

1

See figure 1 and locality register for location and geographic description. 

Powers Hollow, Grant Co., W.Va., lat 38°59.9' N., long. 79°13.0' W., 

Petersburg West, W.Va., 7.5-minute quadrangle. Active quarry on 

northwest side of West Virginia Route 28, opposite Cabins, W. Va. 

Base of vertical quarry wall exposes beds of middle member of 

Tonoloway Limestone; section not measured because of inaccessibility. USGS colln. 10692-SD, from within middle member. 

Lambert Gap, Pendelton Co., W. Va ., lat38°41.1' N., long79°28.6' W., 

Circleville, W.Va., 7.5-minute quadrangle. On north side of private 

dirt road that parallels north side of Morgan Run, 2.4 km south (road 

distance) along West Virginia Route 28 from intersection of West 

Virginia Route 28 and U.S. Highway 33, and then about 0.3 km east 

of West Virginia Route 28 . Entire Tonoloway Limestone exposed and 

is about 174m thick: lower member, 80 m; middle member, 37m; 

upper member, about 57 m. USGS colln. 11278-SD from 58 m above 

base of lower member; USGS colln. 11273-SD from 4 m, USGS colin. 

11687-SD from 27.7 m, and USGS colin. 11274-SD from 30.2 m above 

base of middle member. 

Fulks Run, Rockingham Co., Va. , lat 38°40.3' N., long 78°55.6' W., Fulks 

Run, Va., 7.5-minute quadrangle. Roadcut on east side of Virginia Route 

259, 2.6 km (road distance) west of intersection of Virginia Route 259 

and Virginia Route 612. Most of Tonoloway Limestone is exposed, 

but lower part of lower member may be concealed; 125.5 m exposed: 

lower member (part?), 46 m; middle member, 40.5 m; upper member, 

39 m. USGS colin. 11270-SD from 20m above base of middle member. 

McDowell, Highland Co., Va., lat 38°19.4' N., long 79°27.4' W., 

McDowell, Va., 7.5-minute quadrangle. Roadcut on north side of U.S. 

Highway 250, 4.6 km (road distance) east of McDowell, Va. Incomplete 

exposure of Tonoloway Limestone 111 m thick: lower member (part), 

13 m; middle member, 25 m; upper member, 73 m. USGS colin. 

11272-SD from within 1 m of base of middle member and USGS colin. 

11589-SD from 3.8 m above base of middle member. Type locality 

of Homeognathodus peniculus n. sp. 

Hatfield farm, Hancock Co., Tenn., lat 36°33.6' N., long 83°14.3' W., 

Sneedville, Tenn.-Va., 7.5-minute quadrangle. Streamcut in Blackwater 

Creek, 0.7 km east ofGollihon Cemetery at the intersection of Newman 

Ridge Rd. and Blackwater Creek Rd. Incomplete exposure of Sneedville Limestone 22 m thick; lower contact with Rockwood Formation 

exposed, upper contact missing. USGS colin. 11279-SD from 5 m and 

USGS colin. 11269-SD from 12.3 m above base of Sneedville 

Limestone. 

98 Ozarkodina remscheidensis group, 0. confluens, Oulodus 

elegans, and Panderodus sp. 

21 0. remscheidensis group, 0. confluens, and Panderodus sp. 

2 0. remscheidensis group 

10 0. remscheidensis group and 0. conjluens 

4 0. remscheidensis group 

1 0. remscheidensis group 

2 0. remscheidensis group and Oulodus elegans 

6 

5 

0. remscheidensis group and Oulodus elegans 

0. remscheidensis group, Oulodus elegans, and Panderodus sp. 

0. remscheidensis group, Panderodus sp., and Oulodus elegans 

0. confluens 

0. confluens and 0. remscheidensis group 

Sneedville, Hancock Co., Tenn., lat 36°31.8' N., long 83°13.0' W., Sneedville, Tenn.-Va., 7.5-minute quadrangle. Roadcut on north side of 

county road to Campbell Cemetery, 0.3 km north-northwest of its intersection with Tennessee Route 33. Only 2m of the Sneedville Limestone 

is exposed. USGS colin. 10417-SD from within 1 m of base of exposure. 

REFERENCES CITED 

American Association of Petroleum Geologists, 1985a, Northern 

Appalachian region [correlation chart]: Tulsa, Okla., 1 sheet 

(in jacket). (Correlation of Stratigraphic Units of North America 

(COSUNA) Project.) 

1985b, Southern Appalachian region [correlation chart]: 

Tulsa, Okla., 1 sheet (in jacket). (Correlation of Stratigraphic 

Units of North America (COSUNA) Project.) 

Berry, W.B.N., and Boucot, A.J., eds., 1970, Correlation of the 

North American Silurian rocks: Geological Society of America 

Special Paper 102, 289 p. 

Chlupat, Ivo, Ktiz, Jiti, and Schonlaub, H.P., 1980, Field Trip 

E-Silurian and Devonian conodont localities of the Barrandian, in Schonlaub, H.P., ed., Second European Conodont 

Symposium (ECOS H)-Guidebook, Abstracts: [Austria] 

Geologische Bundesanstalt Abhandlungen, v. 35, p. 147-180. 

Clark, D. L., and others, 1981, Conodonta, Supplement 2 of 

Robison, R.A., ed., Treatise on invertebrate paleontology, Part 

W, Miscellanea: Boulder, Colo., and Lawrence, Kans., 

Geological Society of America and University of Kansas, 

202 p., 122 figs. 

Colton, G.W., 1970, The Appalachian basin-Its depositional 

sequences and their geologic relationships, in Fisher, G. W., 

and others, eds., Studies of Appalachian geology-Central and 

southern: New York, lnterscience, p. 5-47. 

Denkler, K.E., and Harris, A.G., 1985, Conodont biofacies and 

biostratigraphy of upper Ludlow-Pridoli shallow-water carbonates in the central Appalachians, U.S.A. [abs.], in Aldridge, 

Homeognathodus peniculus (Conodonta), a New Earliest Pridolian Index Species C7 
R.J., and others, eds., Fourth European Conodont Symposium 

(ECOS IV), Nottingham [England], 1985, Abstracts: 

Southampton, England, University of Southampton, p. 8- 9. 

Denkler, K.E., Harris, A.G., and Lierman, R.T., 1983, Conodont 

biofacies of a Late Silurian carbonate mudflat [abs.]: Geological 

Society of America Abstracts with Programs, v. 15, no. 4, 

p. 220. 

Harris, A.G., Hatch, N.L., Jr., and Dutro, J.T., Jr., 1983, Late 

Silurian conodonts update the metamorphosed Fitch Formation, Littleton area, New Hampshire: American Journal of 

Science, v. 283, p. 722-738. 

Helfrich, C.T., 1975, Silurian conodonts from Wills Mountain 

anticline, Virginia, West Virginia, and Maryland: Geological 

Society of America Special Paper 161, 82 p. (microfiche, 

86 p.). 

Holland, C.H., 1985, Series and stages of the Silurian System: 

Episodes, v. 8, no. 2, p. 101-103. 

Jeppsson, Lennart, 1974, Aspects of Late Silurian conodonts: 

Fossils and Strata, No. 6, 54 p., 12 pis. 

1983, Silurian conodont faunas from Gotland, in 

Martinsson, Anders, and Bengtson, Stefan, eds., Taxonomy, 

ecology and identity of conodonts-Proceedings of ECOS III, 

Lund, 1982: Fossils and Strata, No. 15, p. 121-144. 

Klapper, Gilbert, and Murphy, M.A., 1975, Silurian-Lower Devonian conodont sequence in the Roberts Mountains Formation 

of central Nevada: California University Publications in 

Geological Sciences, v. 111, 62 p. [ 197 4 imprint]. 

Kfiz, Jifi, Jaeger, Hermann, Paris, Florentin, and Schonlaub, H.P., 

1986, Pridoli-The fourth subdivision of the Silurian System: 

Jahrbuch der Geologischen Bundesanstalt, v. 129, no. 2, p. 

C8 Shorter Contributions to Paleontology and Stratigraphy 

291 - 360. 

Maryland Geological Survey, 1923, Silurian: Baltimore, Johns 

Hopkins Press, 794 p. 

Mehrtens, C.J., and Barnett, S.G., 1976, Conodont subspecies from 

the Upper Silurian- Lower Devonian of Czechoslovakia: Micropaleontology, v. 22, p. 491-500. 

Pollock, C.A., and Rexroad, C.B., 1973, Conodonts from the Salina 

Formation and the upper part of the Wabash Formation 

(Silurian) in north-central Indiana: Geologica et Palaeontologica, v. 7, p. 77-92. 

Rexroad, C.B., and Craig, W.W., 1971, Restudy of conodonts from 

the Bainbridge Formation (Silurian) at Lithium, Missouri: Journal of Paleontology, v. 45, no. 4, p. 684-703. 

Smosna, R.A., Patchen, D.G., Warshauer, S.M., and Perry, W.J., 

Jr., 1977, Relationships between depositional environments, 

Tonoloway Limestone, and distribution of evaporites in the 

Salina Formation, West Virginia, in [AAPG] Studies in 

Geology, No. 5, p. 125-143. 

Stafford, J. M., 1856, A geological reconnaissance of the State of 

Tennessee: Being the author's first biennial report: Nashville, 

Tenn., 164 p. 

Walliser, O.H., 1964, Conodonten des Silurs: Hessisches 

Landesamt fiir Bodenforschung Abhandlungen, No. 41, 106 p., 

32 pis. 

1971 , Conodont biostratigraphy of the Silurian of 

Europe, in Sweet, W.C., and Bergstrom, S.M., eds., Symposium on conodont biostratigraphy: Geological Society of 

America Memoir 127, p. 195-206. 

Woodward, H.P., 1941, Silurian System of West Virginia: West 

Virginia Geological Survey, v. 14, 326 p. 
PLATE 1 

Contact photographs of this plate are available, at cost, from U.S. Geological Survey Library, 

Federal Center, Denver, Colorado 80225 
PLATE 1 

Some biostratigraphically significant conodonts from the Tonoloway Limestone and equivalents, central 

Appalachian basin 

[Scanning electron micrographs of specimens coated only with carbon] 

FIGURES A-1. Homeognathodus peniculus n. sp., from middle member of Tonoloway Limestone. 

A-C. Upper, lower, and lateral views of holotype, X85, USNM 403810, USGS 

colln. 11272-SD. 

D-H. Paratypes, USGS colln. 10685-SD. 

D. Upper view, x70, USNM 403812. 

E, F. Upper and lower views, x70, USNM 403813. 

G, H. Lateral and lower views, x95, USNM 403814. 

I. Upper view of paratype, X50, USNM 403811, USGS colln. 11273-SD. 

J, K. Ozarkodina snajdri crispa (Walliser), from 5.8 m above base of lower member of 

Tonoloway Limestone at Lambert Gap, W. Va. Upper and lateral views, x75, USNM 

403815 and 403816, USGS colln. 11278-SD. Note similarity with lateral views of 

Homeognathodus peniculus shown in figures C and G. 

L. Ozarkodina snajdri snajdri (Walliser), from lower part of Sneedville Limestone at 

Hatfield farm, Tenn. Upper view, X 100, USNM 403814, USGS colln. 11279-SD. 
U.S. GEOLOGICAL SURVEY BULLETIN 1837-C PLATE 1 

HOMEOGNATHODUS, OZARKODINA 

CHAPTER D 

Occurrence of the Early Cretaceous 

Ammonite Venezoliceras in Puerto Rico 

By WILLIAM A. COBBAN and GLENN R. SCOTT 

Descriptions and illustrations 

of two species of Albian age 

U.S. GEOLOGICAL SURVEY BULLETIN 1837 

SHORTER CONTRIBUTIONS TO PALEONTOLOGY AND STRATIGRAPHY 

Occurrence of the Early Cretaceous Ammonite 

Venezoliceras in Puerto Rico 

By William A. Cobban and Glenn R. Scott 

Abstract 

Several crushed specimens of Venezoliceras were collected 

from the Fajardo Formation near Fajardo in eastern Puerto Rico. 

This genus, of late middle Albian to early late Albian age, has 

not been previously recorded from Puerto Rico. The specimens 

are compared to Venezoliceras commune (Renz) and V. texanum 

Young. 

INTRODUCTION 

Ammonites are scarce in the Lower Cretaceous rocks 

of Puerto Rico. Young (1972) recorded two collections from 

near Aibonita in south-central Puerto Rico. One of the 

collections, from southeast of Aibonita, contained Eogaudryceras? sp., Puzosia cf. P. planulata (Bayle), and Engonoceras spp. Young assigned an early Albian age to this lot. 

The other collection, from north of Aibonita, contained two 

fragments of Manuaniceras closely related to M. supani 

(Lasswitz), a species that occurs in the youngest part of the 

middle Albian of Texas. 

While vacationing in Puerto Rico in May 1968, Glenn 

and Juanita Scott collected several specimens of the Albian 

ammonite Venezoliceras near Fajardo in eastern Puerto Rico. 

The nearest localities where the genus is known are 

Venezuela, Colombia, Peru, Ecuador, and Texas. Owing to 

the scarcity of ammonites in the Lower Cretaceous rocks of 

Puerto Rico, the discovery of Venezoliceras is worth 

recording. 

The two specimens illustrated in this report are kept 

in the National Museum of Natural History, Washington, 

D.C., where they have the catalog numbers 409327 and 

409328. R.E. Burkholder of the U.S. Geological Survey 

photographed the specimens. 

LOCALITY 

The fossils were collected about 0. 8 km south of 

Fajardo on the north face of a hill south of highway 3. The 

fossils were found in weathered brown shale in the Fajardo 

Formation in a road cut about 3 m below the base of a newly 

constructed steel tower at the top of the hill. At this locality 

the part of the Fajardo Formation that includes the 

fossiliferous bed consists of yellowish-gray, siliceous, silty 

shale and fine-grained sandstone that dip about 45 o to the 

north. The fossils, which are crushed flat, occurred in a thin 

bed of pale-yellowish-brown shale. None of the fossils has 

the sutures preserved. 

SYSTEMATIC PALEONTOLOGY 

Family BRANCOCERATIDAE Spath, 1934 

Subfamily MOJSISOVICZIINAE Hyatt, 1903 

Genus VENEZOLICERAS Spath, 1925 

Type species. -Oxytropidoceras venezolense Stieler, 1920. 

Spath (1925, p. 182) named this genus for Oxytropidoceras venezolense Stieler (1920, p. 394), a compressed, 

high-keeled ammonite. Young (1966, p. 65) gave the following concise generic diagnosis: "Large, widely umbilicated, 

high-keeled ammonites with rounded umbilical periphery. 

The ribs of the adults are large, relatively high, and with 

steeper forward slopes than aborad slopes. There are both 

flank and shoulder tubercles at some stage of growth, but 

these seldom extend onto the adults. There is usually slight 

flexing of ribs at the flank tubercle; and the flexing appears 

earlier, ontogenetically, than do the tubercles and persists 

beyond the tubercles. '' 

Occurrence of the Cretaceous Ammonite Venezoliceras in Puerto Rico 01 
In Texas, where the genus is well represented, Young 

(1966, p. 26) noted a range of late middle Albian to early 

late Albian. Renz (1982, p. 56) recorded Venezoliceras from 

Peru, Ecuador, Colombia, Venezuela, Texas, Madagascar, 

South Africa, Morocco, and France. 

Venezoliceras cf. V. commune (Renz) 

Plate 1 , figure 2 

Type.-Figured specimen USNM 409328. 

Description.-The largest specimen in the collection 

has a diameter of 180 mm and an umbilicus of39.5 mm (ratio 

to diameter of 0.22). Only the outer whorl is preserved, 

which has a high, smooth keel. Ribs on the older half of the 

whorl are wirelike and much narrower than the interspaces; 

they are rursiradiate at first and prorsiradiate later and 

number 26. Most ribs on that part of the whorl begin on the 

umbilical shoulder, but about every fourth rib arises low on 

the flank. The ribs are inclined forward to a position about 

a third of the way to the ventrolateral shoulder, where they 

are flexed a little and may or may not support a small bullate 

tubercle. The ribs then continue to the ventrolateral shoulder 

where they rise into forwardly inclined, arcuate, bullate 

tubercles. Ribs on the younger half of the whorl are 

prorsiradiate and number 20. Each arises on the umbilical 

shoulder or on the umbilical wall. All are flexed a little on 

the lower third of the flank, where each supports a small 

bullate tubercle. The ribs become broader as they cross the 

outer two-thirds of the flank, and their adoral slopes become 

steeper then the adapical slopes. Each rib terminates in an 

arcuate ventrolateral tubercle. 

In its general appearance and rib density, this specimen 

resembles Venezoliceras commune Renz (1968, p. 639, pl. 

4, fig. 2a, b; pls. 5-7; pl. 8, fig. 3a, b; text figs. 5f-k, 6b). 

The ventrolateral tubercles, however, are more arcuate on 

the Puerto Rican specimen. 

Venezoliceras cf. V. texanum Young 

Plate 1, figure 1 

Type.-Figured specimen USNM 409327. 

Description.-This sparsely ribbed specimen consists 

of an outer whorl that encloses half of the penultimate whorl. 

The outer whorl has a diameter of 155 mm and an umbilicus 

of 39.8 mm (ratio to the diameter of 0. 26). The keel is high 

and smooth and ends in a conspicuous rostrum. Ornament 

on the penultimate whorl consists of weak, narrow, prorsiradiate ribs of irregular height. The stronger ribs support 

small bullate tubercles at midflank, and all ribs terminate in 

02 Shorter Contributions to Paleontology and Stratigraphy 

ventrolateral clavi. The 12 ribs on the older half of the outer 

whorl are prorsiradiate; most have weak midflank bullate 

tubercles and all end in ventrolateral clavi. Nineteen prorsiradiate ribs are present on the younger half of the outer whorl. 

The ribs are sparse and rather straight at first but then become 

more closely spaced, flexed near midflank, and asymmetric 

with steep adoral faces. A midflank tubercle is present on 

every other rib on most of this half whorl. Ribs on the older 

part end in ventrolateral clavi, whereas those on the younger 

part terminate in arcuate bullae. These changes in ornament 

and the presence of a rostrum suggest that this specimen is 

an adult microconch. 

In its sparse ribbing on the inner and outer whorls and 

in its midflank position of tubercles, this specimen resembles 

Venezoliceras texanum Young (1966, p. 75, pl. 7, figs. 1-3, 

7; pl. 8, figs. 1-4; pl. 11, figs. 3, 4; pl. 34, fig. 3; text figs. 

5a-c, 7d, f, 8b, h). Whether the whorl sections are the same 

cannot be determined owing to the crushed condition of the 

Puerto Rican specimen. 

REFERENCES CITED 

Hyatt, Alpheus, 1903, Pseudoceratites of the Cretaceous, Edited 

by T.W. Stanton: U.S. Geological Survey Monograph44, 351 

p., 47 pls. 

Renz, Otto, 1968, Uber die Untergattungen Venezoliceras Spath 

und I..oraiceras n. subgen. der Gattung Oxytropidoceras Stieler 

(Ammonoidea) aus den Venezolanischen Anden: Eclogae 

Geologicae Helvetiae, v. 61, no. 2, p. 615-655, 13 pls. 

1982, The Cretaceous ammonites of Venezuela: Basel, 

Birkhauser Graphisches Untemehmen, 132 p., 40 pls. 

Spath, L.F., 1925, On Upper Albian Ammonoidea from Portuguese 

East Africa, with an appendix on Upper Cretaceous ammonites 

from Maputo land: Annals of the Transvaal Museum, v. 11, 

p. 179-200, pis. 28-37. 

1934, A monograph of the Ammonoidea of the Gault, 

pt. 11: Palaeontographical Society [London] Monograph, p. 

443-496, pis. 49-56. 

Stieler, Carl, 1920, Uber sogenannte Mortoniceraten des Gault: 

Centralblatt fiir Mineralogic, Geologie und Palaontologie, 

Jahrgang 1920, p. 392-400. 

Young, Keith, 1966, Texas Mojsisovicziinae (Ammonoidea) and 

the zonation of the Fredericksburg: Geological Society of 

America Memoir 100, 225 p., 38 pis. 

1972, Ammonites from Puerto Rico and St. Thomas: 

VI Conferencia Geologica de Caribe, Margarita, Venezuela, 

Proceedings, p. 469. 
PLATE 1 

Contact photographs of this plate are available, at cost, from U.S. Geological Survey Library, 

Federal Center, Denver, Colorado 80225 
PLATE 1 

[Both figures x 0. 78 of natural size] 

FIGURE 1. Venezoliceras cf. V. texanum Young. Figured specimen USNM 409327, from the Fajardo 

Formation about 0.8 km south of Fajardo, Puerto Rico. 

2. Venezoliceras cf. V. commune (Renz). Figured specimen USNM 409328, from the same 

locality. 
U.S. GEOLOGICAL SURVEY BULLETIN 1837-D PLATE 1 

VENEZOLICERAS 

CHAPTER E 

Ammonites in Clasts of the Juana Lopez Member 

of the Carlile Shale (Upper Cretaceous) 

near Pueblo, Colorado 

By WILLIAM A. COBBAN 

Unusually good external molds of mollusks 

date the clasts as middle late Turonian 

U.S. GEOLOGICAL SURVEY BULLETIN 1837 

SHORTER CONTRIBUTIONS TO PALEONTOLOGY AND STRATIGRAPHY 

Ammonites in Clasts of the Juana Lopez Member 

of the Carlile Shale (Upper Cretaceous) 

near Pueblo, Colorado 

By William A. Cobban 

Abstract 

Clasts of hard calcarenite derived from the upper Turonian 

Juana Lopez Member of the Carlile Shale occur sparingly in the 

basal bed of the Fort Hays Limestone Member of the Niobrara 

Formation. The Fort Hays Member, of late Turonian to early 

Coniacian age, rests disconformably on the middle Turonian 

Codell Sandstone Member of the Carlile Shale in the Pueblo area. 

Over most of southeastern Colorado, the Juana Lopez Member 

lies between the Codell Member and the Niobrara Formation. 

The clasts reveal the former presence of the Juana Lopez Member 

in the Pueblo area. 

Impressions of the ammonites Prionocyclus wyomingensis Meek and Scaphites warreni Meek and Hayden on the clasts 

have unusually good detail, which reveal features that have not 

been noted previously. Among these are the presence of double 

umbilical tubercles on P. wyomingensis and details of the 

notching on the keel of this species. 

INTRODUCTION 

Excellent external molds of a bivalve and three species 

of ammonites were collected by G.R. Scott, of the U.S. 

Geological Survey, in 1961 from clasts of hard limestone 

at the base of the Niobrara Formation in the area now 

included in the Pueblo Reservoir State Recreation Area. The 

clasts were derived from a bed or beds of hard limestone 

in the Juana Lopez Member of the Carlile Shale. In the 

Pueblo area, the Fort Hays Limestone Member of the 

Niobrara Formation rests disconformably on the Codell 

Sandstone Member of the Carlile Shale, and the clasts at the 

base of the Fort Hays Member reveal the former presence 

of the Juana Lopez Member in the area. The clasts are also 

of much interest in that external molds of the ammonite 

Prionocyclus reveal the presence of double umbilical 

tubercles as well as details of the ventral keel. 

The specimens described and illustrated in this report 

came from U.S Geological Survey Mesozoic locality D3999 

in the EV2 sec. 26, T. 20 S. , R. 66 W., Pueblo County, Colo. 

The illustrated specimens are kept in the National Museum 

of Natural History in Washington, D.C., where they have 

been given USNM catalog numbers. R.E. Burkholder, of 

the U.S. Geological Survey, made the photographs. 

JUANA LOPEZ CLASTS 

Clasts of limestone derived from the Juana Lopez 

Member of the Carlile Shale lie in the basal 15-30 em of 

the Fort Hays Limestone Member of the Niobrara Formation. The clasts are brownish-gray and very hard. Most are 

lenticular and usually 7-8 em thick and as much as 60-70 em 

in length. The rock is a calcarenite containing abundant 

prisms of calcite that were derived from the disaggregation 

of the shells of Inoceramus. Larger fragments of Inoceramus 

are usually present. The clasts are sparse and lie in a softer 

20- to 40-cm-thick bed of light-gray to brownish-gray, 

burrow-mottled, calcareous mudstone that forms the base of 

the Niobrara Formation and rests disconformably on the 

Codell Sandstone Member of the Carlile Shale (fig. 1). The 

burrows in the basal Niobrara bed are usually lighter or 

darker than the matrix, variable in diameter (5-10 mm), and 

horizontal to inclined. Most could be classified as Ihalassinoides. An occasional specimen of Inoceramus coste/latus 

Woods, of late Turonian age, is present in this bed. 

The clasts of Juana Lopez calcarenite are corroded and 

burrowed. Their upper surface is irregular and pitted with 

the depressions filled by the lighter gray lime mudstone of 

the basal bed of the Fort Hays Member. Molds of ammonites 

have been eroded leaving excellent impressions from which 

good casts can be obtained. The clasts were formed during 

a period of nondeposition before the advent of Niobrara 

deposition. Similar clasts in the base of the Fort Hays 

Member in southwestern Kansas were described by Hattin 

(1975, p. 199, pl. 1, fig. 1). At Pueblo the clasts reveal the 

former presence of the Juana Lopez Member. McLane (1983, 

fig. 6) has shown the feather-edge of the member a few 

kilometers west of Pueblo. 

Ammonites in Clasts of the Juana Lopez Member of the Carlile Shale, Colorado E1 
Figure 1. Fifteen-centimeter-long clast of dark-brownish-gray 

calcarenite derived from the Juana Lopez Member of the Carlile 

Shale lying in the basal 25 em (shadowed) of the Fort Hays 

Limestone Member of the Niobrara Formation in the NW~ SE~ 

SE~ sec. 26, T. 20 S., R. 66 W., Pueblo County, Colo. 

Fossils in the clasts are abundant but of low diversity. 

Only Inoceramus dimidius White, Lopha sp., Prionocyclus 

wyomingensis Meek, and Scaphites warreni Meek and 

Hayden have been observed. This assemblage is characteristic of the late Turonian zone of Scaphites warreni (Cobban 

and Reeside, 1952, p. 1018). 

SYSTEMATIC PALEONTOLOGY 

Family COLLIGNONICERATIDAE Wright and Wright, 1951 

Genus PRIONOCYCLUS Meek, 1871 

Type species. -Ammonites (Pleuroceras ?) serrato-carinatus 

Meek, 1870, p. 429 (non Stoliczka, 1865, p. 57) = Prionocyclus wyomingensis Meek, 1876a, p. 452. 

Prionocyclus wyomingensis Meek 

Plate 1, figures 2-4, 7-9 

Ammonites serrato-carinatus Meek, 1870, p. 429. 

Ammonites (Pleuroceras?) serrato-carinatus Meek. Meek, 1871, p. 298 . 

Prionocyclus wyomingensis Meek. Meek, 1876a, p. 452, footnote . 

Prionocyclus wyomingensis Meek. White, 1880, p. 35, pl. 15, fig. 1a-e. 

Prionocyclus wyomingensis Meek. White, 1883, p. 35, pl. 15, fig. 1a-e. 

Prionocyclus wyomingensis Meek. Stanton, 1893 [1894], p. 171, pl. 40, 

figs. 1-4. 

Prionocyclus wyomingensis Meek. Gilbert, 1896, p. 565, pl. 58, figs. 1-3. 

Prionocyclus wyomingensis Meek. Logan, 1898, p. 463, pl. 106, figs. 1-4. 

Prionocyclus wyomingensis Meek. Johnson, 1903, p. 139. 

E2 Shorter Contributions to Paleontology and Stratigraphy 

Prionocyclus wyomingensis Meek. Barbour, 1903, pl. 5, figs. 4, 5. 

Prionocyclus wyomingensis Meek. Grabau and Shimer, 1910, p. 228, fig. 

1510a-d. 

Prionocyclus wyomingensis Meek. Grabau, 1921, fig. 1697e-h. 

Prionocyclus wyomingensis Meek. Diener, 1925, p. 155. 

Prionocyclus wyomingensis Meek. Roman, 1938, p. 457, pl. 46, figs. 435, 

435a. 

Prionocyclus wyomingensis Meek. Shimer and Shrock, 1944, p. 593, pl. 

247, figs. 3-5. 

Prionocyclus wyomingensis Meek,forma typica . Haas, 1946, p. 200, pl. 

18, figs. 3-6; pl. 19, figs. 8-10; pl. 20, figs. 1, 2, 5; text figs. 93-97. 

Prionocyclus wyomingensis Meek. Wright, 1957, p. 427, fig. 547 (6a, b). 

Prionocyclus wyomingensis Meek. Termier and Termier, 1960, fig. 2418. 

Prionocyclus wyomingensis Meek. Hattin, 1962, p. 90, pl. 25, fig. A. 

Prionocyclus wyomingensis Meek. Matsumoto, 1965, p. 18, pl. 16, fig. 

la-c; pl. 17, fig. 2a-c (not pl. 18, fig. la-c). 

Prionocyclus wyomingensis Meek. Hattin, 1975, pl. 2, fig. 11. 

Prionocyclus wyomingensis Meek. Kauffman, 1977, pl. 26, figs. 2, 3. 

Prionocyclus wyomingensis Meek. Hook and Cobban, 1979, p. 39. 

Not Prionocyclus wyomingensis Meek. Whitfield, 1880, p. 440, pl. 14, figs. 

1-3 [=P. novimexicanus (Marcou, 1858)]. 

Not Prion~cyclus wyomingensis Meek. Luppov and Drushchits, 1958, p. 

123, text fig. 97b; pl. 60, fig. 3a, b =P. novimexicanus (Marcou, 1858). 

Not Prionocyclus wyomingensis Meek. Matsumoto, 1971, p. 132, pl. 21, 

fig . 2a, b; pl. 22, fig. la-c; text fig. 2 =P. novimexicanus (Marcou, 1858). 

Not Prionocyclus wyomingensis Meek. Case, 1982, text fig. 12 (63) =P. 

novimexicanus (Marcou, 1858). 

Diagnosis.-Prionocyclus wyomingensis is a large, 

moderately evolute, rather densely ribbed species that has 

inner and outer ventrolateral tubercles and a finely serrated 

keel. 

Description.-This species was originally described by 

Meek (1870, p. 429) as follows: "Shell attaining a rather 

large size; discoid, with periphery provided with a very 

narrow, prominent, serrated mesial keel, including the 

siphuncle. Volutions increasing rather gradually in size, 

somewhat compressed laterally, and a little excavated without 

being distinctly channeled on each side of the ventral keel; 

inner ones but slightly embraced by each succeeding turn, 

and consequently well exposed in the wide umbilicus. Surface ornamented with numerous unequal costae, some of the 

larger of which bear a small, somewhat elongated node near 

the umbilicus, and two closely approximated small nodes 

around the ventro-lateral margins, where they all curve very 

strongly forward as they pass upon the periphery; spaces 

between each two of the large nodose costae occupied by 

from one to about three smaller ones. Septa unknown." 

No illustrations were given by Meek. Before his death, 

Meek placed the type lot in C.A. White's hands. White 

(1880, p. 35, pl. 15, fig. la-e) redescribed the species and 

illustrated three specimens including the suture of one. All 

or part of White's illustrations have been reprinted by many 

later authors (Stanton, 1893; Gilbert, 1896; Logan, 1898; 

Barbour, 1903; Grabau and Shimer, 1910; Grabau, 1921 ; 

Roman, 1938; Shimer and Shrock, 1944; Wright, 1957; 

Termier and Termier, 1960; Kauffman, 1977). 

Matsumoto (1965, p.l8) designated as lectotype one 

of the specimens figured by White (1880, pl. 15, fig. la). 

This specimen consists of parts of two adjoining whorls, each 
of which is less than half a whorl. The larger whorl is about 

114 mm in length. Whorls are higher than wide with flattened flanks and venter and narrowly rounded umbilical 

shoulder. Ornament consists of conspicuous, narrow, prorsiradiate ribs, elongate umbilical tubercles, inner and outer 

ventrolateral tubercles, and prominent serrated keel. Ribs 

begin on the vertical umbilical wall, where they are inclined 

backward. On the umbilical shoulder, the ribs curve forward 

and then cross the flank with forward inclination; they bend 

forward again on the ventrolateral shoulder and disappear 

at or near the base of the keel. Conspicuous elongated umbilical tubercles are present on ribs at irregular intervals; they 

are separated by one to three nontuberculated ribs. Umbilical 

tubercles begin on the umbilical shoulder and extend on to 

the lower part of the flank, where they rise highest. The ribs 

that support umbilical tubercles also support strong, nodate 

inner ventrolateral tubercles; other ribs have weak nodate 

to bullate inner ventrolateral tubercles. All ribs either have 

weak bullate outer ventrolateral tubercles or incipient ones. 

Ribs probably numbered about 35 per half whorl on the lectotype. The keel is high, bounded by low grooves, and notched 

into clavi that are a little more numerous than the ribs. 

The impressions of Prionocyclus wyomingensis on the 

Juana Lopez clasts closely resemble the lectotype in size and 

general appearance. However, latex casts of the impressions 

reveal more detail than that visible on Meek's types. Ribs 

are mostly narrow and sharp to threadlike (pl. 1, figs. 2, 

4). Most ribs are narrower than the interspaces, and some 

ribs may be flexuous (pl. 1, fig. 4). Ribs that support umbilical tubercles are broader and higher than the others (pl. 1 , 

fig. 8). Umbilical tubercles on some specimens are doubled 

and consist of a bullate inner tubercle on the shoulder and 

a larger nodate one on the lower part of the flank (pl. 1, 

fig. 4). Inner ventrolateral tubercles are nodate and high. 

Some outer ones are also nodate, high, and sharp. Both rows 

may have supported spines. The high, rounded keel is 

notched only on its upper surface. This notching results in 

siphonal tubercles of irregular height and strength. Most of 

these tubercles are low and transverse (pl. 1, figs. 1, 7), but 

some may be high and nodate (pl. 1, fig. 3). The siphonal 

tubercles are usually more numerous than the ribs (pl. 1, figs. 

1, 7), but there are rare exceptions (pl. 1, fig. 3). Only three 

of the impressions consist of a half whorl or more. Ribs per 

half whorl are 38 at a diameter of 74.5 mm (pl. 1, fig. 4), 

34 at 93 mm (pl. 1, fig. 2), and 23 at 120 mm. 

Remarks.-Prionocyclus wyomingensis is the immediate ancestor of P. novimexicanus (Marcou, 1858, p. 35, 

pl. 1, fig. 2, 2a) from which it differs in its slightly more 

robust form and in its double ventrolateral tubercles (Hook 

and Cobban, 1979, p. 39). Prionocyclus macombi Meek 

(1876b, p. 132, pl. 2, fig. 3a-d), which is probably the 

ancestor of P. wyomingensis, differs from it chiefly in having weaker ornament and a more rounded venter. 

Occurrence.-Prionocyclus wyomingensis is known 

from the Juana Lopez Member of the Carlile Shale at many 

localities in eastern Colorado, northeastern New Mexico, and 

southwestern Kansas, and from the Juana Lopez Member 

of the Mancos Shale in northwestern New Mexico, western 

Colorado, and eastern Utah. Farther north, the species is 

abundant in the Wall Creek Sandstone Member of the 

Frontier Formation of southeastern Wyoming and in the 

equivalent part of the Turner Sandy Member of the Carlile 

Shale of the Black Hills area in northeastern Wyoming, 

western South Dakota, and southeastern Montana. The 

species becomes scarce northwestward away from the Black 

Hills, and only a single specimen has been found in northwestern Montana (Mudge, 1972, table 9). A part of a whorl 

from Alberta illustrated by Jeletzky (1970, pl. 26, fig. 3) 

as P. wyomingensis var. robusta Haas lacks double ventrolateral tubercles and may be P. novimexicanus (Marcou). 

Types.-Hypotypes USNM 401077-401082. 

Family SCAPHITIDAE Meek, 187Ga 

Genus SCAPHITES Parkinson, 1811 

Type species.-Scaphites equalis J. Sowerby, 1813, p. 53, 

pl. 18, figs. 1-3. 

Scaphites warreni Meek and Hayden 

Plate 1 , figures 1 , 5, 6 

Scaphites warreni Meek and Hayden, 1860, p. 177. 

Scaphites warreni Meek and Hayden. Meek, 1876a, p. 420, pl. 6, fig. 5. 

Scaphites warreni Meek and Hayden var. wyomingensis Meek, 1876a, p. 

423, text figs. 61-63. 

Scaphites warreni Meek and Hayden. White, 1877, p. 200 (not pl. 19, 

fig. 3a). 

Scaphites warreni Meek and Hayden. Stanton, 1893 [1894], p. 185, pl. 

44, fig. 4 (not figs. 5-7). 

Scaphites warreni Meek and Hayden. Logan, 1898, p. 475, pl. 104, fig. 

4 (not figs. 5-7). 

Scaphites warreni Meek and Hayden. Logan, 1899, p. 210 (not pl. 22, fig. 1; 

pl. 23, fig. 5). 

Scaphites warreni Meek and Hayden. Herrick and Johnson, 1900, pl. 45, 

fig. 4 (not figs. 5-7). 

Holcoscaphites warreni (Meek and Hayden). Nowak, 1916, p. 66. 

Scaphites warreni Meek and Hayden. Diener, 1925, p. 204. 

Scaphites warreni Meek and Hayden. Reeside, 1927, p. 36. 

Scaphites warreni Meek and Hayden. Cobban, 1951b [1952], p. 21, pl. 3, 

figs. 8-21. 

Scaphites warreni var. ubiquitosus Cobban, 1951b [1952], p. 23, pl. 3, 

figs. 26, 27; pl. 4, figs. 1-15. 

Scaphites warreni var. haydeni Cobban, 1951b [1952], p. 23, pl. 3, figs. 

22-25. 

Scaphites warreni Meek and Hayden. Easton, 1960, text fig. 11.28 (2a, b). 

Scaphites warreni var. ubiquitosus Cobban. Hattin, 1975, pl. 2, figs. 8-10. 

Scaphites warreni Meek and Hayden. Cobban, 1976, p. 122, pl. 1, fig. 3. 

Scaphites warreni Meek and Hayden. Kauffman and others, 1976 [1978], 

pl. 5, figs. 11, 12. 

Scaphites warreni Meek and Hayden. Kauffman, 1977, pl. 22, figs. 11, 

12; pl. 23, figs. 5, 6. 

Scaphites warreni Meek and Hayden. Merewether and others, 1979, pl. 

2, figs. 6-9. 

Diagnosis.-This fairly stout, nontuberculated, small 

species has conspicuous ribbing in which ribs that cross the 

venter on the older part of the adult body chamber are more 

widely spaced than those on the younger part. 

Ammonites in Clasts of the Juana Lopez Member of the Carlile Shale, Colorado E3 
Description.-Scaphites warreni has been described in 

detail (Cobban, 1951b, p. 21-23). The species is dimorphic 

and includes stout forms (macroconchs) and smaller, more 

slender forms (microconchs). The holotype (Meek, 1876a, 

pl. 6, fig. 5) is a macroconch. Microconchs were assigned 

the nameS. warreni var. ubiquitosus (Cobban, 1951b, p. 23). 

Ornament consists of narrow, threadlike primary and 

secondary ribs. Body chambers of macroconchs from the 

Carlile Shale of western South Dakota have 6 to 13 primary 

ribs, averaging 8.4, and 27 to 41 secondaries, averaging 34.2 

(Cobban, 1951b, p. 22). Body chambers of microconchs 

from the same area have 5 to 9 primaries and an average 

of 32.2 secondaries. 

Juana Lopez clasts from the Pueblo area have several 

excellent impressions of macroconchs of S. warreni and a 

few poorer impressions of microconchs. The macroconchs 

range in diameter from 32 to 40 mm (pl. 1, figs. 1, 5, 6). 

Body chambers have about 7-9 primary ribs and 38-44 

secondaries. 

Remarks.-The high rib counts on the specimens from 

the clasts suggest that this assemblage of S. warreni is transitional to S. ferronensis Cobban (1951b, p. 23, pl. 4, figs. 

16-29), a densely ribbed species that marks a zone between 

the zone of S. warreni and the younger zone of S. whitfieldi 

Cobban (Cobban, 1951a, fig. 2). Inasmuch as Prionocyclus 

wyomingensis Meek occurs with both S. warreni and S. 

ferronensis, a zone of P. wyomingensis with subzones of S. 

warreni and S. ferronensis has been proposed (Cobban, 1984, 

p. 86). 

Occurrence. -Scaphites warreni is widely distributed 

in the western interior region at most of the localities of 

Prionocyclus wyomingensis. However, S. warreni has not 

been found north of the extreme southeast corner of Montana. 

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Ammonites in Clasts of the Juana Lopez Member of the Carlile Shale, Colorado E5 

PLATE 1 

Contact photographs of this plate are available, at cost, from U.S. Geological Survey Library, 

Federal Center, Denver, Colorado 80225 
PLATE 1 

[All figures natural size] 

FIGURES 1, 5, 6. Scaphites warreni Meek and Hayden. From USGS Mesozoic locality D3999 in the 

E% sec. 26, T. 20 S., R. 66 W., Pueblo County, Colo. 

1. Latex cast of hypotype USNM 401083. 

5. Latex cast of hypotype USNM 401084. 

6. Latex cast of hypotype USNM 401085. 

2-4, 7-9. Prionocyclus wyomingensis Meek. From the same locality. 

2. Latex cast of hypotype USNM 401077. 

3. Latex cast of hypotype USNM 401078. 

4. Latex cast of hypotype USNM 401079. 

7. Latex cast of hypotype USNM 401080. 

8. Latex cast of hypotype USNM 401081. 

9. Latex cast of hypotype USNM 401082. 
U.S. GEOLOGICAL SURVEY 

7 8 

SCAPHITES, PRIONOCYCLUS 

BULLETIN 1837-E PLATE 1 

9 


GPO 585-045/78046