Bull. Tohoku Univ. Museum. No. 18, pp. 1‒4, 2019© by The Tohoku University Museum

Grafordites mcleodi, a new Pennsylvanian cephalopod
from Texas, southern Midcontinent, North America
Shuji Niko* and Royal H. Mapes*** Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima
739-8521, Japan, ** American Museum of Natural History, Central Park West at 79th Street, New York, 10024-5192, U.S.A.
Abstract: A unique specimen of middle Missourian (Late Pennsylvanian; Late Carboniferous)
orthoconic cephalopod was collected from the Lake Bridgeport Shale of the Graford Formationin north-central Texas, southern Midcontinent, North America. On the basis of this specimen wedescribe Grafordites mcleodi gen. et sp. nov., whose important diagnostic features are imbricatedsurface bands, very deep and conical septum, and narrow siphuncle having a supracentral position.
The higher taxonomic placement of Grafordites is unclear.

Introduction

Systematic Paleontology

The Pennsylvanian Graford Formation (Plummer, 1919;
Plummer and Moore, 1921) is a shallow marine deposit
consisting mainly of shale and limestone with minor amountsof sandstone. It is widely exposed in Palo Pinto, Jack andWise Counties, north-central Texas, southern Midcontinent,North America. Scott and Armstrong (1932) subdivided theformation into five units on the basis of lithologies; theseare the Lake Bridgeport Shale, the Rock Hill Limestone,
the Jasper Creek Shale, the Chico Ridge Limestone, andthe Devil’s Den Limestone. The purpose of this paper isto describe a unique specimen of orthoconic cephalopod
from the Lake Bridgeport Shale which represents the lowest
unit of the formation and belongs to the Preshumardites
Ammonoid Zone indicating middle Missourian (earlyKasimovian; Late Carboniferous) age (Boardman et al.,1994). The new specimen was obtained from a low-water
outcrop of nodular reddish-brown shale exposed along
the southwest shore of Lake Bridgeport at Runaway Bay,
Wise County (Figure 1). Together with orthoconic nautiloid
cephalopods, this locality also yields a molluscan dominatedinvertebrate fauna including gastropods (Worthenia,Trepospira and Glabrocingulum), coiled nautiloids, andgoniatitid ammonoids (McLeod, personal communication).
This new cephalopod and the Graford fauna described byprevious workers (e.g., Petty, 1975; Hoare et al., 1996;Rigby et al., 2008) represent a biotic community that lived
in the neritic zone along the southern margin of Laurentia(Erxleben, 1973).

Class Cephalopoda Agassiz, 1847
Subclass and order uncertain
Family Dentoceratidae Ruzhentsev and Shimansky, 1954?
Genus Grafordites gen. nov.
Type species.─Grafordites mcleodi sp. nov., by monotypy.
Diagnosis.─Orthoconic longicone having moderateconch expansion, subcircular cross sections and very long
body chamber; transverse imbricated bands of surfaceornamentation indicate dorsolateral (= ocular) and ventral (=hyponomic) sinuses; septum very deep, conical; siphuncle
narrow, supracentral located near midway between center ofconch and dorsal margin.
Etymology.─The generic name is derived from the Graford
Formation.
Discussion.─The living orientation of the present
specimen can be inferred by the sinuses on the exterior
surface of the conch. The specimen has subcircular crosssections which bear two kinds of sinuses; one is at the antisiphuncular side of the conch and the other is on the lateralside of the conch. The counterpart of the lateral sinus is
not observable because the bilaterally symmetrical part ofshell is embedded in concretionary matrix. We determinedthat the former is the ventral hyponomic sinus and the latterforms an ocular sinus.
Very deep and conical septum with bluntly pointed apexof Grafordites gen. nov. excludes it from almost all known
Late Palaeozoic genera of longiconic cephalopods. The
only known exception is the Permian genus Dentoceras
Ruzhentsev and Shimansky, 1954, which has similar septal

2Shuji Niko and Royal H. Mapes

Figure 1. Location map showing fossil locality (asterisk) on the southwest shore of Lake Bridgeport in Wise County,
north-central Texas. Inset maps indicate the general position of the area.
character as Grafordites. The higher taxonomic placementof Dentoceras is currently uncertain. Ruzhentsev andShimansky (1954) originally assigned the genus to thefamily Dentoceratidae of the Nautiloidea. Subsequently,
Kummel (1964) placed the genus in the Scyphoceratidae,
whose family also belongs to the Nautiloidea. On the otherhand, Flower (in Gordon, 1964) treated it as a genus of
the Oncocerida. Although Dentoceras is distinguishedfrom Grafordites at the generic (and familial?) level by
the possession of a gently cyrtoconic conch and a single
longitudinal groove on the ventral side of septum, they may
belong to an identical group (family?). Therefore, the higher
taxonomic placement of Grafordites is also unclear andadditional and more complete specimens of Dentoceras andGrafordites are required to solve these questions.
Grafordites mcleodi sp. nov.
Figure 2Diagnosis.─As for the genus.
Description.─An incomplete longiconic orthocone wasavailable for study; it is 45.5 mm in length, consisting of
the last septum and very long body chamber, the latterof which indicates moderate expansion of approximately
5°; cross sections of conch are subcircular and may havefaintly angulate ventrolateral and dorsolateral corners;

dorsoventral diameter at the apical end is 7.0 mm; peristome
not preserved; ratios of preserved length of body chamber
per dorsoventral conch diameter at the adoral end areapproximately 5.5. Shell surface ornamented by imbricatedand relatively wide bands, 0.6‒1.3 mm in width; the bands
are roughly transverse and with a very shallow to shallow
dorsolateral (= ocular) sinus and a very shallow ventral (=hyponomic) sinus; each band has gentle adapical slope
and steep adoral one. Suture is not observable; septum
very deep, conical with bluntly pointed apex; ratio of septal
depth per maximum septal width is approximately 0.8;
weak adapical projection occurs on septum at siphuncularforamen; siphuncle supracentral and located near midway
between center of conch and dorsal margin; diameter ofsiphuncle is narrow, approximately 0.6 mm at foramen;
septal neck and connecting ring are not preserved; neither
endosiphuncular and cameral deposits are observable. Shellultrastructure not preserved.
Material examined.─Holotype, AMNH 6015, which isreposited in the American Museum of Natural History in New
York.
Etymology.─The specific name honors Mr. John McLeod,
who discovered the holotype.
Age.─Middle Missourian (Late Pennsylvanian; LateCarboniferous).

New Pennsylvanian cephalopod from Texas

3Figure 2. Grafordites mcleodi gen. et sp. nov., holotype, AMNH 6015. A. Lateral view, venter on right. B. Septal viewof apical end, venter down, arrow indicates siphuncle. C. Details of apical shell, partial enlargement of A, arrow indicatessiphuncular position. D. Details of apical shell, dorsal view; arrow indicates siphuncle. E. Details of adoral shell, partialenlargement of A, arrows indicate respectively ocular (left) and hyponomic (right) sinuses. F. Details of adoral shell, partial
enlargement of A, note surface ornamentation consisting of imbricated bands. Scale bar is 20 mm in A; 8 mm in B and E; 10mm in C and D; 4 mm in F.

4Shuji Niko and Royal H. Mapes

Acknowledgements
We gratefully acknowledge Mr. John McLeod, of Tulsa,Oklahoma, who kindly donated the holotype of Grafordites
mcleodi gen. et sp. nov. and provided geologic informationon the Lake Bridgeport Shale. Our thanks are also due to Dr.
Masayuki Ehiro for his helpful comments on the manuscript.

References
Agassiz, L., 1847, An Introduction to the Study of NaturalHistory, in a Series of Lectures Delivered in the Hall of
the College of Physicians and Surgeons, 58 p. Greeley
and McElrath, New York.
Boardman, D. R., Work, D. M., Mapes, R. H. and Barrick,J. E., 1994, Biostratigraphy of Middle and LatePennsylvanian (Desmoinesian- Virgilian) ammonoids.
Kansas Geological Survey, Bulletin 232, p. 1‒121.
Erxleben, A. W., 1973, Depositional systems in thePennsylvanian Canyon Group of north-central Texas. InBrown L. F. et al., eds., Guidebook 14. Pennsylvanian
Systems in North Central Texas: A Guide for Interesting
Terrigenous Clastic Facies in a Craton Basin, p. 43‒56.
University of Texas, Bureau of Economic Geology,Austin.
Gordon, M. Jr., 1964, Carboniferous cephalopods ofArkansas. United States Geological Survey Professional
Paper, no. 460, p. 1‒322, pls. 1‒30.
Hoare, R. D., Mapes, R. H., Yancey, T. E. and Nestell, M. K.,
1996, Late Paleozoic turrilepadid machaeridians fromNorth America. Acta Palaeontologica Polonica, vol. 41, p.
127‒145.
Kummel, B., 1964, Nautiloidea―Nautilida. In Teichert, C.
et al., eds., Treatise on Invertebrate Paleontology, PartK, Mollusca 3, p. K383‒K457. Geological Society ofAmerica, New York, and University of Kansas Press,Lawrence.
Petty, A. J. Jr., 1975, Biostratigraphy of the Graford
F o r m a t i o n , M i s s o u r i a n , W i s e C o u n t y, Te x a s .
Unpublished MS Thesis, the University of Texas at El
Paso, 76 p.
Plummer, F. B., 1919, Preliminary paper on the stratigraphyof the Pennsylvanian formations north-central Texas.
Bulletin of the American Association of Petroleum
Geologists, vol. 3, p. 133‒145.
Plummer, F. B. and Moore, R. C., 1921, Stratigraphy of thePennsylvanian formations of north-central Texas. The
University of Texas Bulletin, no. 2132, p. 1‒237.
Rigby, J. K., McKinzie, M. G. and Britt, B. B., 2008,
Pennsylvanian sponges from the Graford Formation,
Wise County, Texas. Journal of Paleontology, vol. 82, p.
492‒510.
Ruzhentsev, V. E. and Shimansky, V. N., 1954, Lower
Permian coiled and curved nautiloids of thesouthern Urals. Akademiya Nauk SSSR, Trudy
Paleontologicheskogo Instituta, vol. 50, p. 1−152, pls.
1−15. (in Russian)Scott, G. and Armstrong, J. M., 1932, The Geology of WiseCounty, Texas. The University of Texas Bulletin, no.
3224, p. 1‒77.