Study of the Monotypic

Fish Family Pholidichthyidae

(Perciformes)

VICTOR G. SPRINGER

and

WARREN C. FREIHOFER

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 216
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SMITHSONIA N CONTRIBUTION S TO ZOOLOG Y • NUMBE R 21 6

Study of the Monotypic

Fish Family Pholidichthyidae

(Perciformes)

Victor G. Springer

and Warren C. Freihofer

ISSUED

FEB 1 0 1976

SMITHSONIAN INSTITUTION PRESS

City of Washington

1976
ABSTRACT

Springer, Victor G., and Warren C. Freihofer. Study of the Monotypic Fish

Family Pholidichthyidae (Perciformes). Smithsonian Contributions to Zoology,

number 216, 43 pages, frontispiece, 23 figures, 1976.—Aspects of the osteology,

cranial nerves 5, 7, 9 and 10, lateral-line canals, free lateralis organs and miscellaneous anatomical features of Pholidichthys leucotaenia (the only species in the

Pholidichthyidae) are described and illustrated.

Pholidichthys is known only from the western Pacific Ocean, from the Philippines east to the Solomon Islands. It has an eellike body form and undergoes

striking ontogenetic changes in color pattern. Anatomically the species is mostnotable for having an autogenous, unpaired ossification of the interorbital

septum (which is not a modified orbitosphenoid); no ascending process on the

parasphenoid; a large complex metapterygoid; fused 5th ceratobranchials (at

sizes at least as small as 16.9 mm); a sagittal sulcus with the ostium completely

separated from the cauda by a raised area; an incomplete, disjunct ring of infraorbital bones and interrupted infraorbital sensory canal; no scales; no spines in

the vertical fins; apparent displacement dorsally and freeing of the lateralis

organs (innervated by the ramus buccalis facialis) of the infraorbital canal in the

gap area and partial invasion of the gap by free lateralis organs innervated by

the ramus buccalis accessorius facialis of the truncus hyomandibularis; presence

of free lateralis organs along the horizontal septum anteriorly ventral to the

dorsal collector lateral-line nerve; Serranus pattern (pattern 9) of the recurrent

facial nerve; return of the dorsal collector lateral-line nerve to the horizontal

septum at a point above, or near, the anus; only two dorsal collector rami joining

the dorsal longitudinal lateral-line nerve; an extremely heavy innervation of the

conjunctiva of the eye; a single nostril on each side.

Based on its pattern 9 recurrent facial nerve, Pholidichthys is a perciform fish

and within that grade is highly specialized. With the possible exception of two

specializations concerning the dorsal longitudinal lateral-line nerve (point of

return to the horizontal septum; number of collector rami), which Pholidichthys

shares only with the tropical blennioids, there is no unequivocal conclusion that

can be drawn about its subordinal relationships. The osteological evidence does

not indicate a close relationship with the tropical blennioids.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 6083. SERIES COVER DESICN:

The coral Montastrea cavernosa (Linnaeus).

Library of Congress Cataloging in Publication Data

Springer, Victor Gruschka, 1928-

Study of the monotypic fish family Pholidichthyidae (Perciformes)

(Smithsonian contributions to zoology ; no. 216)

Includes bibliographical references.

Supt. of Docs, no.: SI 1.27:216

1. Pholidichthys leucotaenia. I. Freihofer, Warren C, joint author. II. Title. III. Series:

Smithsonian Institution. Smithsonian contributions to zoology ; no. 216.

QL1.S54 no. 216 [QL6S8.P55] 591'.08s [597'.58] 75-619210
Contents

Page

Introduction 1

Methods 2

Abbreviations 2

Material of Pholidichthys 2

Comparative Material for Study of Bones 2

Comparative Material for Study of Nerves 3

Acknowledgments 3

Synonymy 4

Descriptions of the Bones 4

The Cranium 4

Superficial Bones, Jaws, and Suspensorium 7

Pectoral and Pelvic-fin Girdles and Supports 11

Gill Arches and Hyoid Apparatus 11

Vertebral Column, Dorsal, Anal, and Caudal Fins 13

Seismosensory Canals and Free Lateralis Organs 15

Descriptions of the Nerves 17

Truncus supraorbitalis 19

Truncus infraorbitalis 21

Ramus oticus 25

Ramus recurrens facialis (Ramus lateralis accessorius) 25

Truncus hyomandibularis 27

Anterior ramus palatinus facialis . , 31

Trunk Lateral-line Nerves 31

Innervation of the Fin Rays 32

Miscellaneous Anatomical Notes 32

Color Pattern Changes 32

Notes on Behavior 34

Relationships of Pholidichthys 34

Summary 40

Literature Cited 41

i n
Pholidichthys leucotaenia, photographed in aquarium.

(Courtesy of T. F. H. Publications, Inc.)
Study of the Monotypic

Fish Family Pholidichthyidae

(Perciformes)

Victor G. Springer

and Warren C. Freihofer

Introduction

The family Pholidichthyidae comprises a single

species, Pholidichthys leucotaenia Bleeker.1 Until

recently (Kailola, 1973), this species was known

in the scientific literature from only three juvenile

specimens (Bleeker, 1856; Herre and Herald,

1951). The lack of specimens for detailed study

probably contributed to the present confusion surrounding the familial placement and relationships

of Pholidichthys. About 1968, specimens of Pholidichthys were first imported into the United States

by the aquarium industry (Michaelis, 1972). Most,

if not all, of these specimens were juveniles and

seem to have been confused by the importers with

cleaner wrasses (Labroides dimidiatus) and reef

'Lockington (1882) described Pholidichthys anguilliformis

from a single specimen from the Gulf of California. No additional specimens have been reported, and the location of the

holotypc (Academy of Natural Sciences of Philadelphia

10843) has been unknown for many years (Smith-Vaniz, in

litt.). Lockington reported that there were only spines (more

than 60) in the dorsal fin, and thus it seems unlikely that his

generic allocation was correct. Jordan (1887), Jordan and

Evcrmann (1896, 1898), Jordan, Evermann and Clark (1930),

and Fowler (1944) all listed P. anguilliformis based on Lockington.

Victor G. Springer, Division of Fishes, National Museum of

Natural History, Washington, D.C. 20560. Warren C. Freihofer, Department of Ichthyology, California Academy of

Sciences, San Francisco, California 94118.

catfishes (Plotosus lineatus) with which they apparently had been caught. The geographic origin of

the aquarium specimens is not clear, but aquarium

dealers report that they received the specimens from

suppliers in the Philippines. The verified distribution of Pholidichthys (Figure 1: we have accepted

Herre and Herald's, 1951, Philippine record, although we have not seen their specimens, which

apparently are lost) does include the southwesternmost of the Philippine Islands, and we have been

told by Philippine aquarium exporters that it occurs as far north as Calatagan, Batangas Province.

In any event, a reasonably large number of Pholidichthys specimens found their way into the hands

of ichthyologists by way of aquarium dealers. In

some instances aquarium specimens were maintained alive, and a record of their growth and radical ontogenetic changes in color pattern were documented in the aquarium literature (Michaelis, 1972;

Brittan, 1972).

During 1970, the Steinhart Aquarium obtained

a large series of live young Pholidichthys, which

were put on display. Freihofer observed these individuals as they grew and changed color pattern

and decided that a description of these changes,

which had not been reported in the scientific literature, and the nerve patterns of the species were

desirable. In 1971, Craig Phillips, then with the

National Aquarium, gave Springer a large aquarium specimen of Pholidichthys for identification.

Initially, Springer believed that Pholidichthys

might be related to the blennioids and he, thus,
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 1.—Distribution of Pholidichthys leucotaenia.

became interested in investigating its relationships

in more detail. On learning of our mutual interests

in Pholidichthys, we decided to pool our efforts in

the investigation of this interesting fish.

METHODS.—The three specimens (16.9, ca. 70,

ca. 140 mm standard length) used for the osteological description of Pholidichthys were cleared

and stained using Taylor's (1967) trypsin technique. The two largest specimens lacked the last few

vertebrae. All of the osteological illustrations, except that of the caudal fin (Figure 11), are based

on the 140 mm specimen. The caudal fin was illustrated from a radiograph of a larger specimen

(CAS 32048). Base drawings of the bones in the

other illustrations were made by Springer using a

Wild M5 stereomicroscope with camera lucida

attachment. The final drawings were inked, contoured, and labeled by J. R. Schroeder under

Springer's supervision. Cartilage is indicated on

these drawings by the use of small, open circles

(for example, see rostral cartilage on Figure 5).

Osteological features on the 140 mm specimen

were checked for consistency with the two smaller

specimens. Vertical-fin ray and vertebral counts

were taken from radiographs and, as possible, from

the cleared and stained specimens.

The five specimens (111-150 mm SL) used for

the description of the nerves of Pholidichthys

were cleared and stained by the Sihler technique

(Williams, 1943; Freihofer, 1966; Fraser and Freihofer, 1971). The nerve illustrations were drawn

by Freihofer.

ABBREVIATIONS.—AMNH = American Museum

of Natural History; ANSP = Academy of Natural

Sciences of Philadelphia; BPBM = Bernice P.

Bishop Museum; CAS = California Academy of

Sciences; NMNH = National Museum of Natural

History, Smithsonian Institution; USNM = former United States National Museum (specimens

in NMNH); SL = standard length.

MATERIAL OF Pholidichthys.—The two largest

cleared and stained specimens used for the bone

descriptions (USNM 206237) were aquarium specimens of unknown origin. The smallest specimen

(out of USNM 212162) was from Darvel Bay, Borneo. The five specimens used for the nerve decriptions were all aquarium specimens (CAS

32048).

Other aquarium specimens (preserved) examined included: USNM 212163 (1: 337 mm), USNM

uncataloged (1: 205 mm), CAS 32048 (9: 58-275).

Specimens examined from known localities include: BPBM 15667 (3: 18-19 mm SL), Florida

Island, Solomon Islands; BPBM 15688 (7: 45-49),

Guadalcanal, Solomon Islands; BPBM 15916 (4:

34-40), Port Moresby, New Guinea; USNM 212162

(6: 15-18), Darvel Bay, Borneo; BPBM 18050

(5: 87-94), Ambon, Indonesia.

Live specimens at the Steinhart Aquarium

(CAS) were the basis for our observations on

behavior.

COMPARATIVE MATERIAL FOR STUDY OF BONES.—

Many diverse fishes were examined, including

whole specimens, partial dissections, radiographs

of specimens, disarticulated skeletons (USNM),

and cleared and stained specimens. In addition,

numerous published osteologies of fishes, which

are not cited, were referred to. Only the cleared

and stained specimens of perciforms are listed

here.

ACANTHOCLINIDAE: Acanthoclinus sp., USNM 200546;

Bclonepterygion fasciolatum, USNM 211306. ALABETIDAE:

Alabes rufus, USNM 201415. AMMODYTIDAE: Ammodytes

americanus, USNM 189223. BATHYMASTERIDAE: Ronquilus sp., USNM 214099. BATRACHOIDIDAE: Opsanus

beta, USNM 104906; Porichthys porosissimus, USNM uncataloged; Thalassophryne maculosa, USNM 200558. BLENNIIDAE: (see Springer, 1968). BOVICHTHYIDAE: Bovichthys

variegatus, USNM 213829. BROTULIDAE: Bidenichthys
NUMBER 216

capensis, USNM uncataloged; Dinematichthys sp., USNM uncataloged. CALLIONYMIDAE: Synchiropus ocellatus, S.

splendidus, both USNM uncataloged. CARACANTHIDAE:

Caracanthus unipinnis, USNM 214028. CEPOLIDAE: Cepola

pauciradiata, USNM 213502. CHAENOPSIDAE: (see Springer,

1968). CHAMPSODONTIDAE: Champsodon capensis, USNM

uncataloged. CHEIMARRICHTHYIDAE: Cheimarrichthys

fosteri, USNM 214024. CICHLIDAE: Cichlasoma cyanoguttatum, USNM 213531. CLINIDAE: (see Springer, 1968). CONGROGADIDAE: Blennodesmus scapularis, USNM 205026;

Congrogadus subducens, USNM 173804; Haliophis gultatus,

USNM 212290. COTTIDAE: Cottus bairdi, USNM 193153;

Myoxocephalus aeneas, USNM uncataloged. CYCLOPTERIDAE: Liparis koefoidi, USNM 157704. DACTYLOSCOPIDAE:

Dactylagnus mundus, USNM uncataloged; Dactyloscopus tridigitatus CAS SU22155. GADIDAE: Rhinonemus cimbrius,

USNM uncataloged; Urophycis tenuis, USNM 200115. GOBIESOCIDAE: Trachelochismus pinnulatus, USNM uncataloged.

GOBIIDAE: Awaous tajasica, USNM 213491. HEXAGRAMMIDAE: Hexagrammos decagrammus USNM 104656. KRAEMERIIDAE: Kraemeria bryani, USNM 143153. LABR1DAE:

Labrichthys unilineatus, USNM 208451; Pseudolabrus japonicus, USNM 208589; unidentified post larvae, USNM uncataloged. LEPTOSCOPIDAE: Leptoscopus macropygus, USNM

213490. MELANONIDAE: Melanonus sp., USNM uncataloged.

MACROURIDAE: Bathygadus macrops, USNM 202778; Steindachneria sp., USNM 186365. MASTACEMBELIDIDAE: Mastacembelus armatus, AMNH 10274. MORIDAE: Lotella

fernandeziana, USNM uncataloged. MUGILOIDIDAE: Parapercis cephalopunctata, USNM 140786. NOTOGRAPTIDAE:

Notograptus guttatus, USNM 173798. OPHIDIIDAE: Ophidion holbrooki, USNM 196039. OPISTOGNATHIDAE:

Opistognathus aurifrons, ANSP 94307; O. maxillosus, ANSP

120715; O. whitehursti, ANSP 120714; Stalix moenensis,

USNM 211963. PHOLIDAE: Xererpes fucorum, CAS 27861.

PLESIOPIDAE: Plesiops caeruleopunctatus, USNM 211304.

POMACENTRIDAE: Abudefduf saxatilis, USNM 192029.

PSEUDOCHROMIDAE: Pseudochromis flavivertex, USNM

211305. SCIAENIDAE: Aplodinotus grunniens, USNM 172278;

Pogonias cromis, USNM uncataloged. SCORPAENIDAE:

Setarches guentheri, USNM 157704. SCYTAL1NIDAE: ScytaUna cerdale, USNM 213832. STICHAEIDAE. Chirolophis

nugator, CAS 30962; Poroclinus rothrocki, CAS 15099; Lumpenella longirostris, USNM 213535; Lumpenus medius, USNM

213534; Vivaria subbifurcata, USNM 201949; Xiphister mucosus, USNM 213533. SYNBRANCHIDAE: Synbranchus

marmoratus, USNM 213805. SYNANCIIDAE: Synanceia vexrucosa, USNM 149901. TRACHINIDAE: Trachinus draco,

USNM 201573. TRICHODONTIDAE: Trichodon trichodon,

USNM 213532. TRICHONOTIDAE: Crystallodytes enderburyensis, USNM 202584. TRIPTERYGIIDAE: Forsterygium

varium, USNM 204997 (see also Springer, 1968). URANOSCOPIDAE: Astroscopus y-graecum, USNM 185669; Kathelostoma albigulta, USNM 185666; Uranoscopus scaber, USNM

198087. ZOARCIDAE: Lycodes turneri, USNM 165153.

COMPARATIVE MATERIAL FOR THE STUDY OF

NERVES (unless noted otherwise, the material is

CAS uncataloged).—

APHREDODERIDAE: Aphredoderus sayanus. APOGONIDAE: Apogon atradorsatus. ARRIPIDAE: Arripis georgianus.

ATHERINIDAE: Atherinops affinis. BATRACHODIDAE:

Porichthys notatus. BLENNIIDAE: Entomacrodus caudofasciatus, Salarias fasciatus. CALLIONYMIDAE: Synchiropus

splendidus. CHAETODONTIDAE: Chelmon rostratus. CIRRHITIDAE: Cirrhites rivulatus. CLINIDAE: Gibbonsia metzi,

Malacoctenus zonifer, Neoclinus blanchardi. CORYPHAENIDAE: Coryphaena hippurus. COTTIDAE: Scorpaenichthys

marmoratus. DACTYLOSCOPIDAE: Gillellus rubellulus, CAS

32306. GASTEROSTEIDAE: Gasterosteus aculeatus. GOBIESOCIDAE: Gobiesox maeandricus. GOBIIDAE: Bathygobius

lineatus, Gobiodon histrio, Gobionellus sp. HOLOCENTRIDAE: Holocenlrus sp. KUHLIIDAE: Kuhlia rupestris.

KYPHOSIDAE: Kyphosus analogus. LABRIDAE: Labroides

dimidiatus, Lepidaplois mesothorax, Novaculichthys taeniourus. LOBOTIDAE: Datnioides microlepis. LUTJANIDAE:

Lutjanus vaigiensis. MALACANTHIDAE: Malacanthus nordtii. MASTACEMBELIDAE: Mastacembelus sp. MERLUCCI1DAE: Merluccius productus. MONODACTYLIDAE:

Monodactylus argenteus. MORIDAE: Physiculus talarae.

MUGILIDAE: Xenomugil thoburni, CAS 14407. MUGILOIDIDAE: Parapercis cylindrica. OGCOCEPHALIDAE: Zalieutes elater. OPHIDIIDAE: Brotula clarkae, Dicrolene intronigra, Lepophidium prorates. PERCICHTHYIDAE: Morone

saxatilis. PERCOPSIDAE: Percopsis omiscomaycus. POLYCENTRIDAE: Polycentrus schomburgkii. POLYNEMIDAE:

Polydactylus approximans. POMACANTHIDAE: Holacanthus

tricolor. POMADASYIDAE: Plectorhynchus chaetodontoides.

PHOLIDAE: Apodichthys flavidus, Xererpes fucorum. PRISTOLEPIDAE: Pristolepis fasciatus, CAS 32307. RACHYCENTRIDAE: Rachyccntron canadum. SALMONIDAE:

Oncorhynchus tshawytscha. SCIAENIDAE: Larimus pacificus.

SCORPAENIDAE: Pterois antennata, Sebastes sp. SIGANIDAE: Siganus guttatus. SPHYRAENIDAE: Sphyraena barracuda. TRYPAUCHENIDAE: Ctenotrypauchen microcephalus.

ZOARCIDAE: Lycodopsis pacifica.

ACKNOWLEDGMENTS.—Our study has been helped

immeasurably by the contributions of many individuals. To them we express our appreciation.

For loan or donation of specimens: B. B. Collette

and D. M. Cohen, National Marine Fisheries Service Systematic Laboratory; W. P. Davis, John's

Island, South Carolina; W. N. Eschmeyer, CAS;

T. H. Fraser, General Development Corporation;

R. Giles, Salt Water City Aquarium, San Francisco;

T. Goyne, San Francisco; J. E. Morrow, University

of Alaska; C. Phillips, Division of Fish Hatcheries,

United States Fish and Wildlife Service; J. E. Randall, BPBM; W. F. Smith-Vaniz, ANSP. For curatorial assistance, including clearing and staining

of specimens: J. F. McKinney, NMNH and L. J. V.

Compagno, Stanford University. For photographs

or preparation of prints: W. E. Burgess, T. F. H.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Publications, Inc.; M. Giles, CAS; J. F. McKinney,

NMNH. For informative discussions: B. B. Collette and D. M. Cohen; L. J. Dempster, CAS: J. E.

Fitch, State of California, Department of Fish and

Game; T. H. Fraser, G. J. Nelson and D. E. Rosen,

AMNH; N. B. Marshall, Queen Mary College,

University of London; S. H. Weitzman and S.

Zehren, NMNH.

Secretarial assistance was rendered by D. Dunn,

NMNH.

Drafts of the entire manuscript were read and

constructively criticized by D. E. Rosen, S. H.

Weitzman, and R. H. Gibbs, Jr.

The nerve portion of our study was supported

by a National Science Foundation grant GB3O551

to W. C. Freihofer.

Synonymy

There are no junior synonyms of Pholidichthyidae, Pholidichthys or P. leucotaenia. We have,

therefore, lumped all references to these taxa in

the synonymy that follows, which purports to be

complete:

Pholidichthys leucotaenia Bleeker, 1856 [description of genus

and species; Kajeli, Boeroe].—Troschel, 1857 [listed].—

Bleeker. 1857 [listed]; 1859 [listed]; 1865 [listed].—Ciinther,

1861 [based on Bleeker].*—Jordan, 1887 [based on Bleeker].—

Jenkins and Evermann, 1889 [similar to Psednoblennius].—

Jordan and Evermann, 1896 [listed].—Jordan and Evermann, 1898 [genus based on Bleeker; Pholidichthyinae].—

Boulenger, 1904 [listed, misspelled].—Weber, 1913 [based on

Bleeker].—Jordan, 1919 [listed]; 1923 [included in Chaenopsidae].—Jordan, Evermann, and Clark, 1930 [listed].—De

Beaufort, 1951 [holotype redescribed, figured, Pholidichthyidae.]—Herre and Herald, 1951 [Candaraman Bay off

Albay Island, Philippines; description].—Herre, 1953

[listed].—Gosline, 1955 [excluded from gobioids by inference].—Norman, 1966 [included in Blenniidae incertae

sedis].—Greenwood et al., 1966 [synonym of of Microdesmidaej.—SchulU, 1966 [redescription of holotype; dentition

figured; classification].—Lindberg, 1971 [included in Microdesmidae].—Michaelis, 1972 [color pattern, aquarium behavior, photograph of adult].—Brittan, 1972 [color pattern,

aquarium behavior, photographs of juveniles and adult].—

Burgess and Axelrod, 1972 [Philippine Islands, photograph

of juveniles]; 1973 [photographs of juveniles and adults].—

Kailola, 1973 [Yule Island, Samarai, and Port Moresby,

Papua; description, photograph, illustrations].—Miller, 1973

placed in Microdesmidae].—Freihofer and Lin, 1974 [placed

in super family Blennioidea]. See also footnote 1.

Descriptions of the Bones

THE CRANIUM (Figures 2 and 3).—Anteriorly,

there is a large mass of ethmoid cartilage, which is

bordered dorsoanteriorly by the median ethmoid,

ventrally by the vomer, laterally by the lateral

ethmoids, and posteriorly by the septal bone. The

anteriormost portion of the ethmoid cartilage is

not sheathed by bone, nor is a small, slender section that reaches the dorsal surface of the cranium

between the anterior ends of the frontals. The

cartilage is continuous posteriorly as the interorbital septum, which extends below the septal

bone and above the parasphenoid, and envelops a

low, long, thin dorsomedian crest on the parasphenoid. The ethmomaxillary ligament originates

dorsolaterally on the median ethmoid and inserts

on the maxillary in the region of the maxillopalatine articulation.

The septal bone is an unpaired, median ossification of the interorbital septum. Anteriorly the

bone bifurcates laterally into two thin flanges that

embrace the posterior portion of the ethmoid

cartilage. Dorsally the septal bone joins, and is

slightly overlapped on each side by, the frontals.

The septal bone extends ventroposteriorly as a

ventrally open, trough-shaped arm whose posterior end is sheathed dorsally by the anterior end

of the basisphenoid.

In the 16.9 mm SL juvenile with a skull length

of 4 mm, the septal bone consists of a small, unpaired, thin, bladelike island of bone in the cartilage of the interorbital septum, with the posterior

margin of the bone bordered by the anterior margin of the membranous portion of the interorbital

septum.

The lateral ethmoid bears two thin, internal

processes, dorsal and ventral, that abut on the

anterolateral surface of the septal bone. The lateral ethmoid is perforated anteromedially by a

large canal (anterior myodome) into which the

superior and inferior oblique muscles of the eye

enter and attach, and through which the olfactory

tract passes. Medially, the lateral ethmoid also

joins the frontal, median ethmoid, ethmoid cartilage and vomer.

The most noteworthy feature of the frontal is

an irregular, dorsally open trough on its dorsoanterior surface, along which the supraorbital sensory canal passes. Posteriorly, the frontal overlaps
NUMBER 216

SUPRAOCCIPITAL EXOCCIPITAL

MEDIAN

ETHMOID

LATERAL

ETHMOID

BASIOCCIPITAL

FRONTAL SPHENOTIC PARIETAL PTEROTIC EPIOTIC

MEDIAN

ETHMOID

SUPRAOCCIPITAL

- INTERCALAR

EXOCCIPITAL

VOMER

LATERAL

ETHMOID

PARASPHENOID

^SPHENOID SPHENOTIC

BASIOCCIPITAL

EXOCCIPITAL

BASISPHENOID

EPIOTIC

FRONTAL PARASPHENOID INTERCALAR

FIGURE 2.—Pholidichthys leucotaenia: dorsal, lateral, and ventral views of skull.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FRONTAL ( LEFT

SPHENOTIC

PTEROSPHENOID

PROOTIC

MEDIAN ETHMOID

PARASPHENOID VOMER

FIGURE 3.—Pholidichthys leucotaenia: lateral view of anterior portion of right side of skull with

right lateral ethmoid and right frontal bones removed. Dashed line dorsally represents limit of

left frontal bone overlapped by seplal bone and cartilage; dashed line ventroanteriorly represents

limit of median dorsal crest on parasphenoid overlapped by ventroposterior arm of septal bone

and cartilage of interorbital septum; dashed line dorsoposteriorly represents limit of septal

bone overlapped by basisphenoid.

flanges of the sphenotic, parietal, supraoccipital,

and pterosphenoid; medially it abuts against, but

does not overlap, its fellow on the opposite side.

The sphenotic bears a shallow trough dorsally,

along which the unroofed (by bone), autogenous

dermosphenotic loosely attaches. A large fenestra

completely penetrates the sphenotic at about the

center of the trough. Ventrally the sphenotic contributes to the dorsal portion of the socket into

which the anterior condyle of the hyomandibular

inserts.

The pterotic bears a shallow trough dorsally

that is continuous with the sphenotic trough and

which underlies the sensory canal continuing from

the sphenotic. A shallow depression on the ventrolateral surface of the pterotic serves as the point

of attachment of the posterodorsal condyle of the

hyomandibular.

The parietals are completely separated by the

low-crested supraoccipital. Each parietal is perforated by a small centrally located foramen through

which the recurrent facial nerve passes and extends

to the dorsal fin.

The exoccipitals are separated ventrally by the

basioccipital and dorsoanteriorly by the supraoccipital. They form a narrow synchondral joint

dorsoposteriorly. Just dorsoanteriorly to the exoccipital condyle is a foramen for passage of the

occipital nerves (Figure 2, lateral view, not

labeled). The vagal foramen is present in the exoccipital just posterior to the posterior end of the

intercalar (Figure 2, ventral view, not labeled)

and the glossopharyngeal foramen lies in the joint

between the prootic and exoccipital (Figure 2,

lateral view, not labeled).

The epiotic bears a rather large articulating surface dorsally, which joins the ventral surface of the

dorsal arm of the posttemporal.

The intercalar overlies portions of the prootic,

pterotic, and exoccipital. Posteriorly, the intercalar bears a thickened ridge, which serves as the

point of attachment for the ligament that inserts

on the ventral arm of the posttemporal.

The prootic is quite large and extends for twothirds the postorbital length of the cranium. In

the medial wall of the pars jugularis, the prootic

bears two foramina, through which the V-VII

complex of nerves passes. The larger (anterior) of

the two foramina is occluded from lateral view by

the lateral wall of the pars jugularis. The larger
NUMBER 216

foramen is not (yet) completely bordered by bone

anteriorly in the 70 mm specimen. The prootic

contributes the ventral portion of the socket with

which the anterior condyle of the hyomandibular

articulates; the dorsal portion is formed by the

sphenotic. The prootic does not have a ventromedially projecting flange and, hence, does not

contribute to the osseous roof of the posterior

myodome. The prootic and pterosphenoid enter

the orbital region of the skull without restriction

as there is no ascending process on the parasphenoid; however, there is a low ascending parasphenoid process, which partially borders the prootic,

in the 70 mm specimen.

The parasphenoid extends for most of the skull

length. On its dorsal surface, from the region overlapped by the belophram of the basisphenoid to a

point just posterior to the region of the broad anterior end of the vomer, the parasphenoid bears a

low, thin median crest that is completely enveloped by the cartilage of the interobital septum

(Figure 3). At about its midlength, the parasphenoid bears a foramen (on each side) that leads

to a canal that opens internally between the parasphenoid and basisphenoid (internal carotid foramen). Posteriorly, the parasphenoid overlaps the

median anterior portion of the basioccipital.

Laterally and dorsally, for about three-fourths

its length, the toothless vomer is overlapped by the

parasphenoid. Dorsolaterally, on each side, the

vomer bears a flange that joins the lateral ethmoid posteriorly and anteriorly cups the ventral

portion of the ethmoid cartilage.

The basioccipital is relatively short. It bears the

concave articulating surface that joins the centrum

of the first vertebra. This surface is well separated

from the exoccipital condyles. Just anterior to the

basioccipital concave surface and ventrolaterally

on each side, the basioccipital bears a low, knoblike process on which Baudelot's ligament originates. The ligament inserts on the dorsoanterior

internal surface of the cleithrum.

The basisphenoid is a complex bone. It bears a

broad, dorsolaterally extending wing (meningost)

on each side of its median, anteriorly and ventrally

extending portion (belophram), which overlaps

the posterior end of the septal bone. The meningosts articulate dorsally with the pterosphenoids

and posteroventrally with the parasphenoid. Ventrally, each meningost forms a narrow, medially

extending projection that meets its fellow at the

midline of the skull just ventral and posterior to

the belophram. In so doing, the meningosts create

a small foramen between themselves and the belophram, and a narrow, roofing shelf over the parasphenoid. The only osseous contributions to the

roof of the posterior myodome are derived from

the meningosts (the wings and medial projections). The posterior extent of the myodome was

not determined, but appears to lie within the

cranium a short distance posterior to the medial

projections of the meningosts, and well in advance

of the anterior end of the basioccipital (there is

no passageway for the eye muscles from the inside

to the outside of the cranium via the ventral surface of the basioccipital, as occurs in some fishes).

The sagitta (Figure 4) has roughly parallel dorsal and ventral margins; its posterior end is evenly

rounded except for minor irregularities; its rostrum is short and bluntly pointed. The antirostrum scarcely projects. The medial and lateral

surfaces of the sagitta are convex, and the lateral

surface has a small, rounded depression slightly in

advance of its midlength, but is otherwise lacking

in distinctive features. The sagitta is narrowly ellipsoidal in cross section. The sulcus is slightly

sigmoidal with the ostium and cauda separated by

a raised central portion. The ostium is a flatbottomed channel, widest anteriorly, converging

posteriorly, and the cauda is a round-bottomed

trough, widest posteriorly, and terminating more

than a sulcus width in advance of the posterior

end of sagitta. The crista superior is moderately

strong, and most prominent between the midpoints

of the ostium and cauda. Measurements (in mm) of

right sagittae from three individuals are:

Fish length

Sagitta length

Sagitta height

Sagitta thickness

Ostium length

Cauda length

Sulcus length

not taken

2.75

1.31

0.70

1.10

0.85

2.35

not taken

2.06

1.01

037

0.83

0.65

1.70

3

ca. 140

2.69

1.30

0.65

1.05

0.99

2.47

• Data furnished by John E. Fitch.

SUPERFICIAL BONES, JAWS, AND SUSPENSORIUM

(Figure 5).—There are four infraorbital bones.

These are thin and unroofed (by bone), and none

is in bony contact with another. The lacrymal articulates loosely with a facet on the lateral ethmoid.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

SULCUS

I

OSTIUM CAUDA

ANTIROSTRUM

ROSTRUM

CRISTA SUPERIOR

FIGURE 4.—Pholidichthys leucotaenia: medial and dorsal views of right sagitta.

The next two infraorbitals posteriorly are suspended in the skin and neither bears a subocular

shelf. The infraorbital sensory canal passes along

these three bones. The dorsalmost infraorbital is

well separated from the others, lies in the skin, and

is loosely connected dorsally to the frontal, dermosphenotic and sphenotic. The infraorbital sensory

canal is interrupted between the third and the

dorsalmost infraorbital. The canal passes along

the dorsalmost infraorbital and is continuous with

the supraorbital canal anteriorly and the canal of

the autogenous dermosphenotic posteriorly. On

the left side of the illustrated specimen, there is a

minute osseous inclusion between the second and

third infraorbitals. The inclusion is not present

on the right side or on either side of the 70 mm

specimen.

The nasal bone is a thin, trough-shaped bone

with a nonstaining ventral portion. The sensory

canal that passes along the nasal bone is continuous with the anterior end of the supraorbital canal.

There are two trough-shaped extrascapulars

(on each side), which lie loosely in the skin, perpendicular to each other and dorsal to the pterotic

and epiotic. The medial extrascapular is widely

separated from its fellow on the opposite side of

the skull, and there is no supratemporal commissural sensory canal between the medial extrascapulars. The sensory canals of the medial and lateral

extrascapulars are continuous via the sensory canal

that passes along the pterotic.

The premaxillary bears a relatively high ascending process (hidden from view by the nasal bone

in Figure 5). The large, unpaired rostral cartilage

is attached to the posterior surface of the ascending

process and the palatopremaxillary ligament inserts on the dorsal end of the process. The teeth

are caniniform, slightly compressed, and with

slightly recurved tips. In specimens 140 mm and

larger there is an outer row of teeth, which decrease in size posteriorly, on the outer margin of

the premaxillary, and an inner row of smaller teeth

posterior to the outer largest teeth. In specimens

up to about 100 mm, the teeth on the lateral margin of the premaxillary are arranged in three rows.

The teeth in the anteriormost row are the largest

of the three rows and this row overlaps the anterior

end of the next row of teeth, which are slightly
NUMBER 216

DERMOSPHENOTIC

MESOPTERYGOID HYOMANDIBULAR

LACRYMAL

NASAL

INFRAORBITALS

PALATINE

EXTRASCAPULARS

OPERCLE

MAXILLARY

ECTOPTERYGOID

/ T**qFF ^ypiild**^ \ \ . \ PREOPERCLE

/ ANGULAR \ A METAPTERYGOID \ INTEROPERCLE

ARTICULAR QUADRATE SYMPLECTIC

FIGURE 5.—Pholidichthys leucotaenia: lateral view of skull and superficial bones.

SUBOPERCLE

smaller. The second row of teeth overlaps the anterior end of the third row, which is formed by the

smallest teeth. Anteriorly on the premaxillary are

several teeth, the largest, and just behind these

large teeth is an irregular row of very small teeth.

The arrangement of the teeth in juveniles has been

illustrated by Schultz (1966, fig. 133) and Kailola

(1973, fig. 1).

The dentary forms an open, lengthwise trough

ventrolaterally, along which the anterior portion

of the mandibular sensory canal passes. The canal

is continuous with that of the opposite dentary

and the two canals open by a common pore at the

symphysis. At its posterior end, the dentary forms

a triangular pocket, open laterally, closed medially,

into which the anterior end of the articular inserts.

The dentary teeth are similar in shape to the premaxillary teeth. There is an outer row of teeth,

which increase in size as one progresses anteriorly,

except that the two anteromedialmost teeth (possibly atypical) are abruptly smaller. There is a

second row of smaller teeth anteriorly behind the

largest teeth, and a third, inner row consisting of

only one or two small teeth. The disposition of the

dentary teeth in small specimens is similar to that

described above for the premaxillary (disposition

of dentary teeth in juveniles is illustrated by Schultz

1966, and Kailola, 1973).

The articular bears an open trough ventrolaterally along which the posterior portion of the mandibular sensory canal passes. There is a small, irregularly shaped sesamoid articular (coronomeckelian) on the posteroventral medial surface of the

dentary (not illustrated).

The toothless palatine has a facet dorsally at the

point where the anterolaterally extending arm,

which overlaps the anterior end of the maxillary,

joins the internal, posteriorly projecting portion

of the palatine. This facet articulates loosely with

a similar facet on the proximal, ventral portion of

the lateral ethmoid. The palatopremaxillary ligament originates on the palatine close to the palatine facet and inserts on the dorsal end of the premaxillary ascending process. The palatine forms a

loose, but strong, joint on its ventroposterior medial surface with the conjoined anterior ends of the

ectoptergoid and mesopterygoid.

The mesopterygoid is sharply differentiated into
10

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

a ventral staining portion and a dorsal nonstaining

portion. The nonstaining portion is very thin,

broad, medially curved and has its lower boundary

along a level that connects the dorsal margin of

the ectopterygoid with the dorsal margin of the

ventroanterior portion of the metapterygoid (the

staining and nonstaining portions of the mesopterygoid are not differentiated in Figure 5). The staining portion of the mesopterygoid is elongate anteriorly where it is joined to the dorsomedial surface

of the ectopterygoid for the entire anterior extent

of the ectopterygoid. Ventrally, the staining portion is broadly overlapped by the quadrate, and

posteriorly, it is slightly overlapped by the metapterygoid.

The ectopterygoid broadly overlaps and clasps

the anterior portion of the quadrate. The ectopterygoid tapers anteriorly, and at its anterior end,

with the mesopterygoid, forms a loose connection

with the palatine.

The quadrate is a relatively large bone that forms

broad, overlapping syndesmotic joints with the

ectopterygoid, mesopterygoid, symplectic, and preopercle, a condylar connection with the articular,

and a synchondral joint with the metapterygoid.

The symplectic is an elongate bone that extends

from just below the ventral end of the hyomandibular, with which it forms a synchondral joint, to

a position on the medial surface of the quadrate

that is just dorsal to the anterior end of the preopercle. At this position the quadrate forms a pocket into which the cartilaginous end of the symplectic inserts and ligamentously attaches. For most

of its length, the symplectic bears a thin, broad

flange that joins the medial surface of the metapterygoid and quadrate.

The hyomandibular bears three condyles, two

dorsally and one posteriorly. These condyles articulate with sockets on the skull and with the opercle.

The posterior surface of the ventral shank of the

hyomandibular attaches to the anterodorsal surface

of the preopercle. Just dorsal to the ventral end of

the shank is the ventral, external opening of the

canal for the truncus hyomandibularis nerve. The

dorsal entrance to this canal is on the medial surface of the hyomandibular somewhat ventral to

the anteriormost condyle. Just anterior to the

canal's ventral opening is a shallow pocket into

which a flange of the metapterygoid inserts. This

metapterygoid flange forms the lateral and anterior margins of a short passageway whose posterior

margin is formed by the anterior surface of the

ventral shank of the hyomandibular, and whose

medial margin is formed by a medial flange of the

metapterygoid. The structures, if any, passing

through this passageway were not investigated.

The cartilaginous ventral end of the hyomandibular forms a synchondral joint with the cartilaginous dorsal end of the interhyal. A small cartilaginously tipped process on the posteromedial margin

of the metapterygoid articulates with this synchondral joint. Anteriorly on its medial surface, the

hyomandibular forms a suturing joint with a

dorsoposterior medial flange of the metapterygoid.

The metapterygoid is an unusually large and

complex bone consisting primarily of a smaller,

irregularly surfaced and margined lateral portion

and a larger, flattened medial portion. The metapterygoid synchondrally joins only the dorsoposterior end of the quadrate. On its posteromedial surface the metapterygoid bears a small cartilaginously

tipped process that articulates with the synchondral joint between the hyomandibular and symplectic. The syndesmotic articulations of the metapterygoid are with the hyomandibular, symplectic

and mesopterygoid.

The preopercle bears a shallow, trough-shaped

channel, which is almost divided into two portions

by a raised, flattened area at its middle. The sensory canal of the preopercle passes along this channel and is continuous with the canal coming from

the articular, but ends dorsally a short distance

dorsal to the preopercle. The preopercle is strongly

joined to the quadrate and hyomandibular, but

only weakly attached to the other opercular bones.

The opercle is a thin, broad, flat bone whose posterior and ventral margins change imperceptibly

into the membrane that connects it with the dorsolateral surface of the subopercle. Dorsoanteriorly,

the opercle joins the posterior condyle of the hyomandibular.

The subopercle is roughly a reversed L-shaped

bone with the short, strong shank of the L rising

dorsally; the long shank is thin and horizontal. The

subopercle forms a shallow depression at the junction of its two shanks into which the opercle fits

and attaches. The posterior end of the subopercle

becomes very thin and threadlike, and attaches for

most of its length to the medial surface of the opercle, which is thin and membranous in this area.
NUMBER 216 11

The interopercle is a long, flat bone whose dorsal margin is overlapped by, and connected to, the

preopercle. A ligament attaches on the dorsomedial

surface just anterior to the posterior end of the

interopercle and extends to a point just anterior to

the dorsoposterior end of the epihyal. Another

ligament extends from the anterior end of the

interopercle to the angular. Less discrete ligamentous tissue connects the interopercle to the subopercle.

PECTORAL AND PELVIC-FIN GIRDLES AND SUPPORTS

(Figure 6).—The posttemporal is thin and depressed anteriorly where it articulates with the

epiotic. Posterolaterally, the posttemporal forms a

laterally open trough, along which the posteriormost portion of the laterosensory canal of the head

passes. Posteroventrally, the posttemporal forms

a strong process that is attached by a ligament to

the intercalar. On its posteromedial surface, the

posttemporal joins the bladelike supracleithrum,

which in turn attaches to the dorsolateral surface

of the cleithrum.

The cleithrum is roughly arc shaped with a lateral ridge ventroanteriorly. Ventromedially, the

cleithrum is broadly trough shaped. Baudelot's ligament attaches to the dorsoanteriormost surface of

the cleithrum and the two cleithra are joined at

their ventroanterior ends. The small, thin, poorly

staining, platelike dorsal postcleithrum is loosely

attached to the dorsoposterior medial surface of

the cleithrum and strongly attached to the distal

end of the first epipleural rib. There is no ventral

postclei thrum. The scapula, which completely encloses the scapular foramen, and dorsoanterior end

of the coracoid join by a large cartilaginous area,

which extends into a shallow pocket on the medial

surface of the cleithrum. The ventral end of the

coracoid, which is tipped with cartilage, attaches

ligamentously to the ventrolateral surface of the

cleithrum. A short ligament connects the midanterior surface of the cleithrum with the posterolateral corner of the fused 5th ceratobraobranchials.

There are four pectoral-fin radials, each with

both ends cartilaginous. The dorsalmost radial

bears marked dorsal and ventral processes that

attach by short ligaments to a process on the scapula and the second from dorsalmost radial, respectively. The second radial is connected to the third,

and the third to the fourth, by similar, but lessdefined ligaments. There are 15 segmented pectoralPOSTTEMPORAL

SUPRACLEITHRUM

CLEITHRUM

POSTCLEITHRUM

SCAPULA

RAYS

SPINE'

FIGURE 6.—Pholidichthys leucotaenia: lateral view of pectoral

and pelvic-fin girdles and supports (fin rays truncated; dashed

lines indicate extent of postcleithrum, scapula, coracoid, and

pelvis overlapped by cleithrum).

fin rays (8 specimens; 15-16 according to Kailola,

1973), all but the dorsalmost one or two and ventralmost of which are branched in large specimens.

Each ray embraces a small, cartilaginous distal

radial (not shown). The two dorsalmost rays are

loosely associated with the scapula.

The pelvis is a long, rod-shaped bone with a

roughly cup-shaped distal end. The proximal end

is tipped with cartilage and is closely joined, ligamentously, to the ventromedial surface of the cleithrum. The proximal ends of the two pelvises are

widely separated from each other and are not connected, but they are joined posteriorly along two

vertical processes (on each pelvis), one dorsal, one

ventral, on the medial surface of the cup-shaped

portion. The cup-shaped portion bears a tiny cartilaginous process (not shown) ventroanteriorly

to which the pelvic-fin elements attach. The fin

consists of a delicate spine with a deeply forked

base and two or three delicate, segmented rays (in

some specimens the fins are malformed on one or

both sides or missing on one side). Cartilaginous

radials, if present, were not apparent.

GILL ARCHES AND HYOID APPARATUS (Figures 7

and 8).—The only cartilage shown in Figure 7 is
12 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

that representing the 4th basibranchial. However,

the following bones bear cartilaginous ends: basihyal, anteriorly only; 1st basibranchial, posteriorly

only (the posterior end of the basihyal and anterior end of the 1st basibranchial appear to be connected by fibrocartilage); 2nd and 3rd basibranchials, both ends; hypobranchials 1-3, both ends;

ceratobranchials 1-4, both ends; the apex and corners of the fused 5th ceratobranchials; epibranchials 1-4, both ends; the uncinate processes of the

1st, 3rd and 4th epibranchials (but not that of the

2nd); the 1st infrapharyngobranchial, both ends;

the three corners of the toothless 2nd infrapharyngobranchial (which articulate ligamentously with

the uncinate process of the 1st epibranchial, distal

end of the 2nd epibranchial and anterodistal end

of the 3rd infrapharyngobranchial, respectively);

the toothed 3rd infrapharyngobranchial, proximally and anterodistally.

There is no interarcual cartilage between the

uncinate process of the 1st epibranchial and the

2nd infrapharyngobranchial.

The teeth of the fused 5th ceratobranchials and

3rd infrapharyngobranchials are similar. The

smaller teeth are round in cross section; the larger

are narrowly elliptical. The teeth are notched anteriorly just below their anteriorly recurved tips.

The 5th ceratobranchials are completely fused

without indication of a median joint. The same

condition exists even in the 16.9 mm early juvenile

(greatest dimension of 5th ceratobranchials 1.2

mm). A short ligament connects each posterolateral corner of the fused 5th ceratobranchials to its

respective cleithrum's anterior surface.

The tooth plate of the 4th infrapharyngobranchial is either fused to the 3rd infrapharyngobranchial or lost; it is not possible to tell which

(the condition is the same in the 16.9 mm juvenile).

The anterior end of the 1st basibranchial lies

ventral to the posterior end of the basihyal. The

EPIBRANCHIALS

4 3 2

FUSED 5th CERATOBRANCHIALS

+ TOOTH PLATES

INFRAPHARYGOBRANCHIALS

— 3(+ TOOTH PLATE OF 4?)

GILLRAKERS

CERATOBRANCHIALSHYPOBRANCHIALS-j 2

Li

CARTILAGE

(BASIBRANCHIAL 4)

--BASIBRANCHIALS

BASIHYAL

.—Pholidichthys Uucotaenia: gill arches (only cartilage shown is that of basibranchial 4;

see text for description of other cartilage; gill rakers removed from left arches).
NUMBER 216 13

HYPOHYAIS

BRANCHIOSTEGALS

FIGURE 8.—Pholidichthys leucotacnia: right hyoid arch

(branchiostegals truncated; urohyal shown in normal position

and separately).

anteroventral surface of the 1st basibranchial is

ligamentously connected to the anterodorsal surface of the urohyal.

The distal portion of the 2nd epibranchial overlies the dorsal surface of the 2nd infrapharyngobranchial. Ligamentous tissue tightly attaches the

cartilaginous distal end of the 2nd epibranchial to

the dorsoposterior surface and posterior, cartilaginous tip of the 2nd infrapharyngobranchial. An

uncinate process arises at about the midposterior

margin of the 2nd epibranchial and is connected

by a ligament to^a process at about the midanterior

margin of the 3rd epibranchial. The uncinate process of the 3rd and 4th epibranchials are closely and

tightly joined by ligaments.

The gill rakers are all simple and there are no

tooth plates on the gill arches.

Dorsally the interhyal bears a plug of cartilage

that joins the synchondral joint between the hyomandibular and symplectic. The ventral end of

the interhyal is cartilaginous and is joined to the

cartilage on the posteromedial surface of the epihyal. There is a ligament connecting the dorsoposterior end of the epihyal to the medial surface

of the interopercle. The epihyal and ceratohyal

are joined dorsally by a suturing joint. Ventral

to this joint the bones are joined synchondrally.

The dorsal and ventral hypohyals tightly clasp the

ceratohyal and form a broad synchondral joint between themselves. There are six branchiostegals.

The anterior two attach on the ventromedial surface of the ceratohyal; the next two attach on a

ventrolateral shelf on the ceratohyal that is continous with a shelf on the epihyal, to which the

posteriormost two branchiostegals attach.

The urohyal is a bladelike bone. A pair of short

ligaments extend from the ventroanterior end of

the urohyal, one ligament to each of the ventral

hypohyals. Anterodorsally, the urohyal bears an

articulating facet that impinges on the ventral surface of the 1st basibranchial. A long ligament extends from the posterior end of the urohyal to the

joined ventroanterior ends of the cleithra.

VERTEBRAL COLUMN, DORSAL, ANAL, AND CAUDAL

FINS (Figures 9-11).—The total number of vertebrae (including urostylar vertebra) varies from

71 to 79 (22 specimens). Precaudal vertebrae vary

from 22 to 26 (24 specimens) and caudal vertebrae,

from 48 to 56 (24 specimens). These counts include each anomalous vertebra (those with two or

three neural and/or hemal spines, Figures 9 and

11) as one vertebra.

Anomalous vertebrae are common in Pholidichthys: at least 14 of the 27 specimens examined

had them, and a specimen might have as many as

three. The anomalous vertebrae occur in both the

precaudal and caudal portions of the vertebral column, but are more common in the caudal portion.

It is not known whether the anomalous vertebrae

represent fusions between two or more vertebrae;

the centra are not noticeably larger than those of

adjacent normal vertebrae. Usually there is only

one dorsal-fin pterygiophore associated with any

given vertebra, but in each of three specimens the

multiple neural spines of a vertebra were each associated with an equal number of pterygiophores.

In another specimen, a vertebra with three neural

spines was associated with only one pterygiophore.

The single specimen with the most vertebrae (79)

had no anomalous vertebrae. Of the five specimens

with 78 vertebrae, four exhibited no anomalous

vertebrae and one had three such vertebrae, all in

the region below the dorsal fin. The single specimen with the least vertebrae (71) had no anomalous vertebrae.

The anteriormost precaudal vertebra bears articulating facets for the exoccipitals and basioccipital, and a posteriorly projecting flange on each

side that connects with the adjacent (second) vertebral centrum. The second vertebra also possesses

a similar, but much reduced, flange. The third
DISTAL

PTERYGIOPHORE

VERTEBRA

(ANOMALOUS)

UNFUSED

NEURAL SPINE

(ANOMALOUS)

FIN RAY

MEDIAL + PROXIMAL

PTERYGIOPHORE

EPIPLEURAL

RIB

EPIPLEURAL RIB PLEURAL

RIBS

TRANSVERSE

PROCESS

FIGURE 9.—Pholidichthys leucotaenia: anteriormost precaudal vertebrae and dorsal-fin elements,

lateral view.

1ST HEMAL

SPINE

MEDIAL + PROXIMAL

PTERYGIOPHORE FIN RAY

FIGURE 10.—Pholidichthys leucotaenia: posteriormost precaudal and anteriormost caudal vertebrae

and anal-fin elements, lateral view.
NUMBER 216 15

through last precaudal vertebrae bear broad,

roughly triangular transverse processes that, except

for the third vertebra, overlap the next vertebral

centrum anteriorly. The transverse processes support the pleural ribs, which commence on the third

vertebra and terminate on the 22nd (next to last)

in the single specimen in which rib counts were

made. The epipleural ribs begin on the first and

terminate on the 19th vertebra in the same specimen. In this specimen the fourth precaudal vertebra had three neural spines and three transverse

processes on each side. Each of the transverse processes supported a pleural rib and its associated

epipleural rib (Figure 9). None of the precaudal

vertebrae has parapophysial stays. The caudal vertebrae all bear hemal arches, none of which are

autogenous.

The urostylar (caudal fin) vertebra consists of a

single element (Figure 11). The hypurals and parhypural are fused into fans that are in turn fused

with the urostylar centrum. There are no epurals

or other autogenous elements associated with this

vertebra except for the 10 segmented, branched fin

rays, 5 each on the dorsal and ventral hypural fans

(21 specimens; 8—10 rays according to Kailola,

1973). There is no hypurapophysis. In the illustrated caudal fin, the hemal spine of the penultimate vertebra is forked; it is normally simple.

The dorsal fin originates dorsal to the level of

the posterior margin of the head, and the anal fin

originates a little anterior to the midpoint of the

body. Both fins are joined membraneously to the

caudal fin.

The dorsal and anal fins contain only segmented

rays; all except the anteriormost one or two

are branched and embrace paired distal radials.

Each ray, except the anteriormost two in each

fin, is associated with its own fused proximal +

medial radials. The anteriormost two rays are

associated with a single fused proximal + medial

radial. The pterygiophores (= distal + medial +

proximal radials) bear a one-to-one relationship

with the vertebrae, except anteriorly, and except

occasionally where a vertebra bears multiple neural

or hemal spines. The number of dorsal-fin rays

varies from 72 to 79 (20 specimens; 66-77 according

to Kailola, 1973), and there are usually fewer rays

than vertebrae, ranging from three less to three

more rays than vertebrae. The number of anal-fin

rays varies from 57 to 62 (17 specimens; 49-62 acFICURE 11.—Pholidichthys leucotaenia: posteriormost two

caudal vertebrae and caudal-fin rays (from radiograph of

USNM 212163; rays truncated; forked hemal spine unusual).

cording to Kailola, 1973), and there are 5 to 10

more rays than caudal vertebrae.

Seismosensory Canals and Free Lateralis Organs

The bony canal elements and bony depressions

on the cranium associated with different parts of the

membranous cephalic canals are shown in Figures

2 and 5. The cephalic membranous canals are

shown in Figure 12. The distributions of the free

lateralis organs of the head and trunk are shown

in Figures 12 and 13. The openings (pores) to the

cephalic canals are shown in Figure 14. Although

the pores are typically simple, small accessory pores

may occur at almost any pore position.

Most of the external openings of the head canals

are large, circular, deep depressions, each with an

almost sphincterlike inner opening at its base. Some

of the pores appear as horizontal slits; others, especially those of the preopercular canal, are noticeably small (Figure 14). The pores shown in Figure

12 are drawn from a Sihler nerve preparation in

which the tissues have been relaxed through maceration and the pores have all become rather large

and round.

A gap occurs in the infraorbital canal (Figure

12). This gap is considered below in connection

with the vertical line of free lateralis organs and

its innervation. There is also a gap between the

mandibulo-preopercular and supratemporal canals.

The canal system of the two sides of the head are

connected dorsally only by an interorbital commissure. There apparently once was a supratemporal

commissure in pholidichthyid ancestry as is indi-
16

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FOSTORBITAL CANAI

FREE LATERALIS ORGANS OVER POSTURBITAL CANAL

LAST IHIBAOBHTAL CANAL ORGAN

MTERORMTAL COMMISSURE

wnucaarrAL CANAL.

WSTTtMPORAL t'ANAI.

T (NASAL) SUnAOMTAL CANAL

niunr unmAoaarTAL CANAL ORGAN

PREE LATERALIS ORGANS VENTRAL TO SUBOPERC1.E

FIGURE 12.—Pholidichthys leucotaenia: lateral view of head showing cephalic lateralis canals,

canal pores, canal organs, and free lateralis (pit) organs.

cated by the three free lateralis organs of each side

of the head extending anteromedially toward the

middorsal line. The anterior end of the mandibulopreopercular canal is connected membranously

across the symphysis of the lower jaw, a pore (Figure 14) occurring at the symphysis. There is no

cross-connection between the nasal canal of each

side. There is only one canal organ in the nasal

canal, a location where the number of canal organs

can be significant in systematic studies.

The free lateralis organs of the head and trunk

are embedded in a thick epidermis consisting

mainly of mucous cells of various sizes, many of

large size. The tip of the lateralis organ is open to

the outside. The organ can be termed a "pit" organ, but we prefer the general term "free lateralis

organ."

Some of the clusters of free lateralis organs of

the head correspond to similar clusters or lines in

other fishes. The row of 4 or 5 organs below the

base of the single nostril (Figure 12) corresponds

to a similar cluster in the percoid Polycentrus

(Freihofer, in press). The row of three organs

above the posterior end of the nasal canal corresponds to a similar cluster in Polycentrus. The vertical line of organs on the cheek corresponds to

such a line on Amia, Polycentrus, and many teleosts. The unusual feature of this line in Pholidichthys is that the organs have partially invaded the

area where the infraorbital canal organs would be

expected to occur. This statement is based on the

fact that these organs are innervated from the

ramus buccalis accessorius facialis of the truncus

hyomandibularis (Figures 13 and 20), not from the

ramus buccalis facialis of the infraorbital trunk.

The row of four free organs lying more dorsally in

the gap of the infraorbital canal is supplied from

the ramus buccalis of the infraorbital trunk (Figure 16). These four free organs apparently represent one or more canal organs of the missing segment of the infraorbital canal.

The single free organ near the anterior end of

the chin corresponds to a large patch of such organs on Polycentrus and some other percoids. The

row of four or five free lateralis organs over the

articular part of the mandibular canal (Figures 12

and 17) corresponds to a larger row in Polycentrus

innervated also by the r. buccalis accessorius facia-
NUMBER 216 17

DORSAL LONGITUDINAL LINE OF FREE LATERALIS ORGANS

DORSAL FIN

LATERAL LINE NERV

POSTERIOR CANAL

ORGAN OF POSTTEMPORAL

SAL LONGITUDINAL COLLECTOR LATERAL LINE NERVE

NERVUS LINAE LATERA

EZONTAL SEPTUM UNB OF FREE

LATERALIS ORGANS

SECOND DORSAL COLLECTOR RAM US

FIGURE 13.—Pholidichthys leucotaenia: complete lateral view showing trunk lateral-line nerves

and lines of free lateralis organs. The dotted line is a continuation of the dorsal collector lateralline nerve more posteriorly on one side of some specimens.

lis. The two free organs in the region external to

the anteroventral area of the subopercle (Figure

12) correspond to a similar patch on Polycentrus.

The two clusters of two organs each, one above the

postorbital canal and the other above the anterior

horizontal segment of the supratemporal canal

(Figure 12), may correspond to the anterior and

middle pit lines of Amia (Allis, 1889).

The trunk lateral line consists of three longitudinal rows of free lateralis organs embedded in a

thick skin containing great numbers of mucous

cells, the lateralis organs opening to the exterior at

the surface of the skin (Figure 13). The first row,

constituting the dorsal-fin lateral line, is short, consisting of only three organs (Figures 12 and 13).

This line curves dorsally from the supracleithral

area up to the front of the dorsal fin. The second

row, constituting the main or dorsal longitudinal

lateral line, curves dorsally from the cleithral area

up to about halfway between the horizontal septum to a point above the anus, or above the fourth

or fifth anal-fin ray on some specimens, and then

returns to the horizontal septum. The third line of

organs, constituting the horizontal septum lateral

line, lies along the horizontal septum. It begins at

a point dorsal to the posterior end of the pectoral

fin and extends along the septum to the base of the

caudal fin. In addition to the three trunk lateral

lines there are three free lateralis organs, forming

a short longitudinal row lying halfway between the

horizontal septum and the dorsal longitudinal lateral line.

There are 138 free lateralis organs along the horizontal septum lateral line on the right side of one

specimen examined and 133 on the left side. The

organs usually occur in a series of from four to six

organs separated by a short space. There were 19

organs on each side along the dorsal longitudinal

lateral line.

Descriptions of the Nerves

The cranial nerves described are the trigeminal

(fifth), facial (seventh) and parts of the glossopharyngeal (ninth) and vagal (tenth). These

nerves have more numerous and complex branches

and offer more promise as a source of systematic

characters than do the other cranial nerves.

The illustrations (Figures 12-13 and 15-21) are

moderately detailed and diagrammatic. The nerves

are shown with the main kinds of functional nerve

fibers their branches contain. In the absence of

serial section preparations, these determinations

were made on the basis of present knowledge of the

distributions of the functional nerve fiber bundles

in fishes for which such information is best known

(see Herrick, 1899, for Menidia, 1900, for Gadus,

and 1901, for Atneiurus).

Analysis and representation of nerves according

to their functional components leads to a ready

understanding of the distribution of the nerves.

For the nerves described, there are four kinds of

functional components present: (1) the general

cutaneous component, represented by nerve fibers
18

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FICUKE 14.—Pholidichthys leucotaenia: lateral, dorsal, and ventral views of head of adult specimen in Figure 23 illustrating cephalic sensory canal openings. Note insertion of pelvic-fin

relative to insertion of pectoral-fin. (Photograph by M. Giles.)
NUMBER 216 19

emanating from the Gasserian ganglion of the trigeminal nerve and going to the skin, where the

fibers have undifferentiated, free endings (that is,

not terminating in multicellular end organs); (2)

the communis or taste component, represented by

nerve fibers emanating from the geniculate ganglion of the facial nerve, from the petrosal ganglion

of the glossopharyngeal nerve and the ganglia of

the vagal branchial rami. The communis nerve

fibers end in either taste buds of the pharynx, buccal cavity, and lips or in the external skin, or by

simple terminations in the mucosa of the mouth

and pharynx; (3) the visceral motor or, simply,

motor component, represented by nerve fibers to

muscles of the gill arches or of former (phylogenetically) gill arches; and (4) the lateralis component, represented by nerve fibers coming from

the lateralis ganglia of the facial and vagal nerves

and going to canal lateralis organs or free lateralis

organs in the skin. A nerve branch may contain

more than one functional component. The symbols

for each component depicted in the illustrations

and for the free and canal lateralis organs are given

in Figure 15.

The nerve terminology follows mainly that of

Herrick (1899). The words "branch" and "nerve"

are used broadly to refer to any separately coursing

group or unit of nerve fibers. The term "truncus"

denotes the most proximal, unbranched part of a

nerve after its cranial exit; the term "ramus" usually denotes a first division branch of a truncus, but

the branches of some major rami are also termed

rami; a "ramulus" is a first division branch of a

ramus.

TRUNCUS SUPRAORBITALIS

The truncus supraorbitalis and the truncus infraorbitalis emerge together from the prootic's trigeminal foramen, which is far posterior to the orbital

socket. The two trunks diverge as they pass anteriorly from the facial foramen.

The truncus supraorbitalis is composed of two

rami: the ramus ophthalmicus superficialis trigeminus, which consists of general cutaneous fibers, and

the ramus ophthalmicus superficialis facialis, which

consists of lateralis fibers. There are no motor fibers

and probably no communis fibers in the truncus

supraorbitalis. The two rami course together

closely and are indistinguishable macroscopically.

Associated with the proximal intracranial part of

the truncus supraorbitalis are the two main

branches of the recurrent facial nerve: the orbitopectoral and the parieto-dorsal branches (Figure

15). The ramus oticus is also associated with the

truncus and with the orbito-pectoral branch of the

recurrent facial nerve. All of these associated

nerves are described following the description of

the two rami of the supraorbital trunk.

Ramus ophthalmicus superficialis trigeminus

There are several intracranial, apparently general cutaneous branches, most rather small, that

course partway toward the cranial roof with the

parieto-dorsal branch of the recurrent facial nerve.

These small branches leave the parieto-dorsal

branch, pass anterodorsally up to the frontal roof

of the cranial cavity, where they exit, and pass to

overlying skin, turning posteriorly in the skin. The

number and exact locations of where they leave the

supraorbital trunk varies on different sides of the

study specimens. A few of these cutaneous branches

leave the ramus ophth. supf. trigeminus separately

and pass anterodorsally to the area of the posterolateral corner of the frontal bone above the posterior end of the eye, where they pass through the

bone to overlying skin, coursing posteriorly in the

skin. One cutaneous branch detaches from the lateralis branch to the sphenotic canal organ, and one

detaches from the lateralis branch to the posteriormost frontal canal organ. Both of these cutaneous

branches pass posteriorly in the skin over the top

of the head. Some of the intracranial cutaneous

branches for the skin over the top of the cranium

are shown in Figure 15. The intracranial vagal

ramus joins the parieto-dorsal branch of the recurrent facial nerve close to the parietal bone and

could not be followed separately in any of the specimens.

There is one fair-sized general cutaneous branch

that leaves the truncus supraorbitalis posterior to

the eye near the branch for the fourth supraorbital

canal organ. This cutaneous branch passes anteriorly medial to the frontal canal and innervates the

skin over the frontal canal for half the distance to

the anterior margin of the eye. Another cutaneous

branch detaches near the third supraorbital canal

organ and innervates the skin of the interorbital

region anterior to the previous cutaneous branch.
20

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

RAM US OTICUS

CANAL ORGAN OF SPIIENOTIC

TO CONJUNCTIVA

BRANCH PROM

RAMUS BUCCAUS FACIA

RAMUS

MAX1LLARIS

SUPER1OR1S

PARIETO-DORSAL BRANCH OP RAMUS RECURRENS FAC1AL1S

ORBITO-PECTORAL BRANCH OP RAMUS RECURRENS PAC1AUS

VAGAL RAMUS

NCUS SUPRAORBITALIS

SYMBOLS FOR FIGURES

LATERALIS BRANCHES ' "•••'•'•

GENERAL CUTANEOUS BRANCHES

TASTE (COMMUNIS) BRANCHES

MOTOR BRANCHES

FREE LATERALIS ORGANS

CANAL LATERALIS ORGANS

FIGURE 15.—Pholidichthys leucotaenia: lateral view of head showing distribution of branches of

truncus supraorbitalis. Symbols for all figures given at lower right-hand corner.

The last noticeable cutaneous branch to the skin

of the supraorbital region detaches near the front

of the orbit and passes to the skin of the snout medial to the frontal and nasal canals.

There are general cutaneous branches that leave

the ramus ophth. supf. trigeminus and pass ventrally to skin of the upper posterior part of the

cheek, to the conjunctiva (and undoubtedly into

the cornea), and to the snout ventral to the nasal

canal. The first of these branches detaches far posterior to the eye, and passes anteriorly up to the

orbital cavity, then over the posterolateral wall of

the cavity where it detaches branches to the adjacent conjunctiva. The remainder then passes posteriorly under the skin over the upper cheek almost

to the preopercular canal. Several more ramuli

leave the ramus ophth. supf. trigeminus along its

orbital course and pass down over the conjunctiva,

innervating it. One of the anterior of these

branches detaches a branch that passes dorsally to

supply the skin above the eye. The anteriormost

of these ventrally directed branches of the ramus

ophth. supf. trigeminus passes mainly to the skin

above the anterior end of the infraorbital canal

(lacrimal) and below the nasal canal. The innervation of the conjunctiva of Pholidichthys is the

heaviest by far that we have seen on any fish. (It

is from one of the posterior of these conjunctival

branches that the orbital cirrhus is innervated on

the blenniid Salarias). Most posteriorly on the tr.

supraorbitalis are general cutaneous branches associated with the ramus oticus. These branches are

part of the ramus ophth. supf. trigeminus, and they

are described with the ramus oticus.

Ramus ophthalmicus superficialis facialis

This ramus courses in intimate contact with

the ramus ophth. supf. trigeminus and is easy to

describe because there are usually far fewer later-
NUMBER 216 21

alis branches than there are cutaneous branches.

The ramus ends anteriorly by innervating the single canal organ of the nasal bone (Figure 15). It

also innervates the three canal organs of the frontal

bone, and close to the base of the ramulus for the

posteriormost of these organs is a ramulus that

passes up through the frontal bone and then posteriorly, ending by innervating the two free lateralis organs on the side of the head dorsal to the

sphenotic and pterotic canal organs.

The supraorbital trunk of Pholidichthys terminates anteriorly, where it does in most fishes, at

about the anterior end of the nasal canal and

rather high on the side of the snout. Also, as in

most other fishes, the rest of the snout, including

its tip and the upper jaw, are the domain of the

infraorbital trunk, as are the free lateralis organs

lying medial to the posterior end of the nasal canal.

TRUNCUS INFRAORBITALIS

The truncus infraorbitalis of fishes has three

main rami: ramus maxillaris trigeminus, ramus

buccalis facialis, ramus mandibularis trigeminus.

•The ramus max. trigeminus typically carries general cutaneous fibers (branches shown in black in

Figure 16). The ramus buccalis facialis carries

lateralis fibers (branches stippled in Figure 16).

The ramus mand. trigeminus carries general cutaneous and visceral motor fibers (branches appropriately coded in Figures 17 and 18).

Ramus opercularis trigeminus

This is the first ramus to detach from the truncus infraorbitalis (Figure 16). It has two ramuli

that pass ventrally into the levator arcus palatint

muscle for a considerable distance and innervate

it. At about the point of division of the ramus into

these two ramuli, a third ramulus is detached,

which passes posteriorly lateral to the sphenotic

and hyomandibular bones and innervates the dilatator operculi muscle.

Ramus maxillaris trigeminus

We were unable to determine if communis fibers

are present in the ramus max. trigeminus, but

there is no reason to expect any as there are no

barbellike developments on the upper jaw. In

drawing the branches of the ramus max. trigeminus, the cutaneous fibers are shown as two separate

divisions at the base of the tr. infraorbitalis. These

join at some point (not illustrated) more proximal in the truncus. The ramus max. trigeminus

has three ramuli.

The first ramulus of the ramus max. trigeminus

detaches far posteriorly on the truncus and passes

anteriorly alongside the cranium up to the orbital

cavity, where it curves laterally over the orbital

rim and then courses ventroposteriorly beneath

the skin, which it innervates at the posterior part

of the cheek region (Figure 16). Before curving

over the orbital rim it detaches some small branches

to the conjunctiva at the posterior end of the eye.

The second ramulus to detach, shown leaving

the ventral surface of the tr. infraorbitalis, passes

anterolaterally over the orbital rim and medial to

the posterior end of the infraorbital canal lying

before the gap in this canal. Before reaching the

infraorbital canal, the ramulus divides into a ventroposterior branch, which innervates the skin of

the cheek anterior to the ventral ramulus of the

ramus mand. trigeminus, and an anteroventral

ramulus, which innervates the skin of the cheek

below the infraorbital canal but some distance

above the angle of the mouth.

The third ramulus of the ramus max. trigeminus

courses as part of the lateralis branch of the ramus

buccalis to the second infraorbital canal organ. It

leaves this buccalis ramulus and innervates the

skin below and between the second and third infraorbital canal pores. A second cutaneous branch

detaches from this same buccalis ramus that innervates the second infraorbital canal organ. This

second cutaneous branch innervates a small part

of the conjunctiva in the anteroventral quadrant

of the eye, which it reaches by first coursing for a

short distance in the ramulus that innervates the

four free lateralis organs along the base of the

nostril.

The ramus maxillaris next divides into its two

major parts: the ramulus maxillaris superioris trigeminus and the ramulus maxillaris inferioris

trigeminus.

RAMULUS MAXILLARIS INFERIORIS TRIGEMINUS.—

This ramulus passes anteroventrally toward the

upper jaw and divides into a large anterior and a

smaller posterior branch /.(Figure 16). The latter
22

RAMULUS MAXILLARIS [NFERIORIS TRIGEMINUS

ANTERIOR RAMUS PALAT1NUS

I01NING RAMUS MAXILLARIS 1NFERIORIS

RAMULUS MAXILLARIS

SUPERIORIS TRIGEMINUS (V),

TO ORAL MEMBRANE

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

RAMUS BUCCALIS FACIALIS (STIPPLED BRANCHES)

RAMUS MAXILLARIS TRIGEMINUS

(BLACK BRANCHES)

TRUNCUS INFRAORB1TAL1S

— ^AMUS OPEKCUIARIS TRIGEM1NUS

TO DILATATOR OPERCUl.I

RAMUS MANDIBULARIS TRIGEMINUS (V)

ITJ LEVATOR ARCUS PALATINI

CANAL LATERAL1S ORGAN

FIGURE 16.—Pholidichthys Uucotaenia: lateral view of head showing distribution of branches of

truncus infraorbitalis except for the ramus mandibularis trigeminus (see Figure 17). See Figure

15 for symbols designating nerve components, free lateralis organs, and canal organs.

passes ventrally toward the maxillary bone and

then distally along the dorsal edge of the maxillary,

crossing the maxillary near its end and passing

into the tissue at the junction of the posterior ends

of the upper and lower lips. En route it gives off

a branch to the skin between the third and fourth

infraorbital canal pores.

The anterior, larger branch of the ramulus

passes ventrally medial to the second intraorbital

canal pore, and detaches two branches to the skin,

one anterior and one posterior to the second pore.

The main part of the ramulus continues across the

medial surface of the maxillary bone. In the intervening jaw membrane it breaks up into several

branches for the upper lip, teeth, and alveolar

tissue. One large branch continues onto the lateral

surface of the premaxillary and breaks up into

branches innervating the posterior half of the

upper lip. The other large branch continues onto

the medial side of the premaxillary, where it divides into two branches: one coursing along the

alveolar region toward the symphysis and, apparently, innervating the teeth, and one coursing distally and innervating the oral membrane and mucosa of the premaxillary. Just before the ramulus

max. inferioris crosses the maxillary bone, it detaches a branch that passes anteriorly in the jaw

membrane along the dorsal edge of the maxillary

bone and out toward the bone's posterior end. Before passing the maxillary bone, the ramulus max.

inferioris receives the remainder of the anterior

ramus palatinus facialis (see under this heading),

which carries communis fibers to the upper jaw.

RAMULUS MAXILLARIS SUPERIORIS TRIGEMINUS.—

This large ramulus leaves the ramulus max. inferioris and continues anteriorly in a medial position over the palatine bone (Figure 16). It passes

under the lateral ethmoid and over the maxillary
NUMBER 216 23

process of the palatine bone, lying en route medial

to the nasal organ. It passes onto the external

surface of the premaxillary and over the premaxillary-maxillary articulation, not far from the

symphysis. It then divides into several branches.

One penetrates the bone and, beneath the teeth,

divides, sending one branch toward the symphysis

and another branch, which innervates teeth, distally under the rear edge of the premaxillary alveolar region. The rest of the ramulus breaks up into

branches supplying the lip tissue and skin of the

external surface of the premaxillary lying anterior

or medial to that supplied by the ramulus max.

inferioris. On its way down the snout, the ramulus

max. superioris detaches two small cutaneous

branches. One branch supplies the skin medial to

the anterior end of the nasal bone and the other

supplies the skin lateral to the nasal bone, after

which the ramulus continues ventrally and passes

into the premaxillary bone near the symphysis. Before the ramulus turns downward toward the premaxillary, a branch of the ramus buccalis facialis

coursing with it leaves and passes medial to the

nasal canal and ends by innervating the two free

lateralis organs above and a little ahead of the posterior end of the nasal canal.

Ramus buccalis facialis

This ramus innervates all four of the infraorbital

canal lateralis organs lying anterior to the gap separating the two parts of the canal (Figure 16). It

also supplies the free lateralis organs associated

with the infraorbital and nasal canals, but not

those free organs that lie at the edge of the gap.

The organs at the edge of the gap are part of the

vertical line of free lateralis organs, as evidenced

by their innervation from the ramus buccalis accessorius facialis. The ramus buccalis facialis splits

into three ramuli.

The first ramulus passes ventrally and supplies

part of the innervation to the fourth infraorbital

canal organ. On its way to the fourth organ it detaches a branch that supplies the four free organs

located opposite the gap in the canal.

The second ramulus, which is moderately large,

splits into three branches. The posterior branch

(Figure 16) innervates the fourth canal organ

(which is also innervated by the first ramulus!)

and supplies half the innervation of the third

canal organ. The middle branch supplies the rest

of the innervation of the third canal organ. The

anterior branch, which also carries some general

cutaneous fibers, courses anteriorly and divides into

three more branches. One of these branches supplies the second canal organ. Another branch

(general cutaneous) supplies skin between the

second and third canal pores, and the third branch,

which passes anteriorly some distance, innervates

the four free organs along the base of the nostril.

In the macerated Sihler specimen, the free organs

are not visible, but the type of nerve ending, plus

the fact that this is the only lateralis branch supplying this area, makes the identification of the

source for innervation reasonably certain. The

branch that supplies the free lateralis organs of

the nostril also detaches a branch to the adjacent

skin and conjunctiva of the anteroventral quadrant of the eye.

The third and most anteriorly coursing ramulus

of the ramus buccalis facialis detaches from its association with the ramulus max. superioris at the

anterior end of the orbit and divides into two

branches. One branch supplies the first organ of

the infraorbital canal and the other passes dorsally,

medial to the posterior end of the nasal canal, and

innervates the two free organs in this area.

Ramus mandibularis trigeminus

The functional components of this large ramus,

as far as can be determined, are only motor and

general cutaneous (Figure 17). Communis fibers

are probably lacking.

Herrick (1899) suggested that the ramus opercularis trigeminus be treated as a branch of the

ramus mand. trigeminus instead of its usual treatment as an independent ramus of the truncus infraorbitalis. We prefer the usual treatment and

describe it under the tr. infraorbitalis.

The first ramulus (here unnamed) of the ramus

mand. trigeminus directly divides into three large

branches, which innervate the adductor mandibulae muscle. The remainder of the ramus mand. trigeminus continues ventrally toward the angle of

the jaw, above which it detaches its second branch,

the ramulus mandibularis cutaneus trigeminus, a

moderate-sized general-cutaneous nerve.

RAMULUS MANDIBULARIS CUTANEUS TRIGEMINUS.—

En route to the angle of the jaw this ramulus de-
24

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

RAMUS MAND1BULAR1S TRIGEMINUS (R. MAND. TR1.)

BRANCHES OP R. MAND. TRl. TO ADDUCTOR

MANDIBULAE MUSCLES

RAMUS BUCCALIS ACCESSORIUS FAC1ALIS

RAMUS MANDIBULARIS INTERNUS PACIALIS

RAMUS MANDIBULARIS EXTERNUS FACIAL1S

RAMULUS MANDIBULARIS CUTANEUS TRIGEMINUS

ANEOUS BRANCHES OF R. MAND. TRI. TO ANGLE OF

JAW AND ARTICULAR AND DENTARY

FREE LATERALIS ORGANS OF ARTICULAR AREA

FIGURE 17.—Pholidichthys Uucotaenia: lateral view of head showing proximal half of ramus

mandibularis trigeminus. See Figure 15 for meaning of symbols.

taches a small nerve (Figure 18) that passes ventrally toward the articulating head of the quadrate,

breaking up in tissue that appears to be in an area

near the base of the maxillary tendon. The rest of

the ramulus cutaneus continued toward the angle

of the jaw (Figure 17), where it divides into four

smaller branches. The first of these is an anterior

branch that divides very shortly into two twigs.

The first twig follows a dorsal curve in the skin

behind the end of the maxillary bone. The second

twig passes anteroventrally onto the posterior end

of the lower jaw and innervates the skin dorsal

to the mandibular canal. The second branch

detaching from the ramulus cutaneus passes dorsoposteriorly, innervating the skin of the anteroventral area of the cheek anterodorsal to the quadrate articulating head. The third branch, the

largest, detaches at the posterior end of the articular,

comes into contact with the dentary branch of the

ramus buccalis accessorius facial is, apparently

gives off some branches to it, and continues anteriorly along the ventrolateral side of the articular

and onto the dentary, where it innervates the skin.

The fourth branch and remaining part of the ramulus cutaneus passes ventrally medial to the

articular canal and innervates skin over the ventroposterior part of the articular.

The ramus mand. trigeminus next passes onto

the medial side of the lower jaw (Figure 18), crossing some distance dorsoanterior to the quadratearticular articulation and divides into two large

ramuli: the ramulus mandibularis externus trigeminus, which innervates the lip, the skin ventral

to the lip, and the teeth of the lower jaw; and the

ramulus mandibularis internus trigeminus, which

innervates the intermandibularis and protractor

hyoidei muscles and the skin of the floor of the

mouth.

RAMULUS MANDIBULARIS INTERNUS TRIGEMINUS.—

This ramulus passes laterally down the side and

medially under Meckel's cartilage, and then slants

anteromedially toward the belly of the intermandi-
NUMBER 216 25

bularis muscle. As it leaves the area of Meckel's

cartilage, a lateral is branch from the ramus mandibularis externus facialis joins it. This lateralis

branch detaches well anteriorly and innervates by

three different branches the anterior dentary free

lateralis organ (Figure 18), the first dentary canal

organ, and the free lateralis organ of the chin near

the symphysis. The ramulus internus, after leaving

the side of the dentary and detaching the preceding

lateralis branches, passes in the membrane of the

jaw floor. There it detaches a general cutaneous

branch, which passes anteriorly to near the symphysis of the lower jaw together with the lateralis

branch to the free lateralis organ of the chin. The

cutaneous branch continues anteriorly beyond the

detachment of the lateralis branch and innervates

the skin ventroposterior to the lip. (This portion

of the skin is located more or less on the curvature

of the dentary helow the lip.) The rest of the

ramulus internus supplies several branches to the

muscles and skin of the floor of the lower jaw. The

first of these branches innervates the anterolateral

slip of the protractor hyoidei muscle. The next,

more medial, larger branch innervates the intermandibularis muscle and overlying skin, being

joined at the center of the muscle by a corresponding branch from the opposite side. The most medial, largest branch curves anteromedially and

enters the anterior end of the dividing protractor

hyoidei muscle (Figure 18). It then sends a branch

to the anteromedial slip of the muscle and is met

by a corresponding branch from the opposite side

of the specimen. The two corresponding nerves,

however, exchange branches in a cross innervation

of the two halves of the protractor hyoidei muscle.

The nerve then passes back in the muscle to the

muscle's attachment to the ceratohyal and innervates en route both the muscle and overlying skin.

The nerve is not met posteriorly by an anteriorly

coursing branch of the ramus hyoideus as occurs

commonly in fishes. In Pholidichthys the ramus

hyoideus branch to the protractor hyoidei muscle

only innervates skin over the muscle. In most fishes

it is reported to share with the trigeminal ramulus

in the innervation of the posterior part of this

muscle.

RAMULUS MANDIBULARIS EXTERNUS TRIGEMINUS.—

This ramulus departs from the medial trigeminal

mandibular ramulus and passes down the medial

side of the articular to the top of Meckel's cartilage.

Before reaching Meckel's cartilage it detaches a

small branch that innervates a rather small mentalis (Aw) division of the adductor mandibulae

muscle (Figure 18). The ramulus then continues

anteriorly toward the tip of the lower jaw, detaching shortly before reaching it a branch that curves

posterolaterally in the bone of the dentary and

innervates teeth. The remainder and much larger

part of the external ramulus continues anteriorly

through the dentary near the symphysis and, coursing in the lip tissue, gives off numerous branches

to papillae and skin. As there is no apparent connection of the ramulus mand. exter. trigeminus

with the ramus mand. internus facialis, which

carries the communis component, it is not evident

that there are any taste fibers in the ramus mand.

exter. trigeminus. If there are, and the nerve is of

considerable size (although this may be the result

of a large general cutaneous component), the taste

fibers would have had to enter the infraorbital

trunk intracranially and then been carried by the

ramus mand. trigeminus.

RAMUS OTICUS

The ramus oticus (Figure 15), which has a

lateralis and a general cutaneous component,

passes together with the orbito-pectoral branch of

the recurrent facial nerve into the orbital cavity

through the trigeminal foramen. Both of these

nerves are on the dorsal surface of the truncus

supraorbitalis. These two rami directly leave the

truncus and together pass dorsolaterally into a bony

passageway through the sphenotic, emerging on

the dorsal surface of this bone beneath the dermosphenotic, where the ramus oticus divides into

three ramuli: one going to the dorsalmost (last)

infraorbital canal organ, one to the dermosphenotic canal organ, and the third to the pterotic canal

organ. The ramuli to the dermosphenotic and

pterotic canals each detach a general cutaneous

branch, the former innervating skin over the area

of the leva tor operculi muscle and the latter innervating skin over the dilator operculi muscle.

RAMUS RECURRENS FACIALIS

(RAMUS LATERALIS ACCESSORIUS)

The orbito-pectoral branch (RLA-OP, Figure

15) of the ramus recurrens facialis leaves the ramus
26

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TO LOWER LIP.

FIRST CANAL ORGAN OF DENTARY—

FREE I.ATERALIS ORGAN OF CHIN

TO ANTEROI.ATERAL Sill1 OF

I'RO TRACTOR IIYOIDEI MUSCLE

TO INTLRMANWBULARIS MUSCLE

RAMl'LUS MANDIBlll-AWIS EX I'LRNUS 1KIGEN.INUS

AMUS MANDIBULARIS TRIGEMINUS

TO AREA OF BASE OF MAXILLARY TENDON

RAMUS MANOIBUIAR1S

EXTERNUS I-ACIALIS

TR1GEMINAL BRANCH TO PROTRACTOR

HYOIDE1 MUSCLE

ANTERIOR DENTARY FREE LATERAl-lS ORGAN

CROSSING OVER OF TRIGEMINAL FIBERS

FOR PROTRACTOR MYOIDEI MUSCLE

MECKEL'S CARTHAGE

RAMULUS MANDIBULARIS 1NTERNUS TRIGEMINUS

FIGURE 18.—Pholidichthys leucotaenia: lateral view of lower jaw showing branches of ramus

mandibularis trigeminus and ramus mandibularis facialis to lower jaw. See Figure 15 for meaning

of symbols.

oticus and continues posteriorly under the dermosphenotic canal, then under the anterior end of the

bony pterotic canal. It crosses diagonally in a bony

passageway underneath the pterotic canal, reaching the medial side of the pterotic canal, where it

passes posteriorly beyond the pterotic through

muscle. It continues rather deeply below muscle

medial to the supratemporal (extrascapular) canal

and onto the medial side of the epiotic arm of the

posttemporal bone. It then continues ventrally

down the medial side of the posttemporal, supracleithrum and cleithrum, passing lateral to the

nervus linae lateralis (the lateral line nerve of the

trunk, Figure 13) and, finally, not far above the

base of the pectoral fin, RLA-OP gives off two

branches. The first branch, which is thin, passes

posteriorly and a little ventrally toward the bases

of the dorsalmost pectoral-fin rays, which it apparently enters. The second branch splits off a little

further along and detaches another branch that

joins a branch of the pectoral plexus (not illustrated) passing out the medial side of the muscular

base of the fin toward the bases of the ventral and

medial pectoral-fin rays, which it apparently innervates. Most of RLA-OP passes medially and joins

a nerve made up of a joint branch from the fourth

and fifth ventral spinal rami (assuming that the

occipital nerves are made up of three ventral spinal

rami). This combined branch, which most of

RLA-OP enters, passes posteroventrally out the

muscular base of the pectoral fin and supplies finray innervation to the middle and ventral pectoralfin rays. By backtracking in branches of the pectoral plexus, fibers of RLA-OP could reach the pelvic

fin, but no distinct RLA-OP branch to the pelvic

fin was observed. There is no branch of RLA-OP

to the anal fin. The details varied on another specimen, but the main branches of RLA-OP to the pectoral fins are apparently essentially the same.

The parieto-dorsal branch (RLA-PD, Figure

15) is formed from two separate branches that

course with the truncus supraorbitalis up to, or

almost to, the trigeminal foramen. The two nerves

either enter the foramen and then directly reenter
NUMBER 216 27

the cranial space through the prootic bone or they

do not enter the foramen but leave the truncus

supraorbitalis as two branches, which shortly unite

and pass up through the cranial cavity dorsoposteriorly to the cranial exit for RLA-PD in the

parietal bone. Near the parietal exit, RLA-PD

meets a small intracranial vagal ramus. The vagal

ramus, after joining RLA-PD, could not be followed separately. The vagal ramus may detach from

RLA-PD on the top of the head and innervate

the skin, as it has been observed to do in some

other perciforms (Freihofer, in press). Outside the

parietal, RLA-PD courses up through muscle to

the overlying skin and then back close to the middorsal line, where it passes alongside the dorsal-fin

pterygiophores for apparently the length of the fin.

TRUNCUS HYOMANDIBULARIS

The truncus hyomandibularis has two intracranial branches that join as they pass anteriorly

into the prootic (Figures 19 and 20). These two

branches constitute the anterior ramus palatinus

facialis, which is described separately. As the truncus hyomandibularis leaves the facial foramen it is

joined by the ramus communicans from the Gasserian ganglion (not illustrated) of the trigeminal

nerve. The ramus communicans is the source of

general cutaneous fibers for the truncus hyomandibularis. The first external cranial branch of the

truncus is the posterior ramus palatinus facialis.

Posterior ramus palatinus facialis

This short ramus (Figure 19) detaches from the

truncus hyomandibularis shortly after the truncus

leaves the facial foramen and directly meets a very

large palatine ramus from the glossopharyngeal

nerve a little anterolaterally to the truncus. The

two nerves form Jacobson's anastomosis close to the

dorsal end of the large and well-developed pseudobranch (Figure 19). We are tentatively calling the

resulting compound nerve the pseudobranch nerve.

The glossopharyngeal palatal ramus supplies innervation to the pseudobranch (Laurent and Dunel,

1966). The compound nerve supplies communis

innervation to the mucosa of the rear palatal area,

hyoid arch and rear floor of the mouth. Shortly

after formation of Jacobson's anastomosis, a branch

is detached posteriorly that courses to the mucosa

dorsal and medial to the pseudobranch. Another

branch passes ventroposteriorly near the vertical

base of the pseudobranch. This branch continues

around the ventral end of the interhyal on one

side of the specimen; on the other side it ended

close to the ventral end of the pseudobranch. The

main part of the pseudobranch nerve passes ventrally near the anterior base of the pseudobranch,

giving off en route several branches that pass well

anteriorly in the palatal mucosa and include a

large branch that passes near the lateral edge of

the palate. The remainder of the nerve passes onto

the hyoid arch, detaches branches to the medial

side of the arch that extend down to the heads of

the branchiostegals and anterolaterally into the

mucosa of the floor of the mouth between the hyoid

arch and the dentary. The pseudobranch nerve

ends about three-fourths of the way along the arch.

The next branch that detaches from the truncus

hyomandibularis, shortly after the posterior palatine ramus, is the ramus opercularis profundus

facialis. '

Ramus opercularis profundus facialis

This ramus consists of two large branches: one

anterior and one posterior (Figure 19). The anterior branch innervates the adductor arcus palatini

muscle, which is much the thickest posteriorly. The

posterior branch courses a considerable distance

posteriorly, where it innervates the levator operculi

and adductor operculi muscles.

Ramus opercularis superficialis facialis

The next branch of the truncus hyomandibularis

is the ramus opercularis superficialis (Figure 20),

which contains lateralis and general cutaneous components and detaches at a level just below the dorsal end of the preopercular canal. This ramus

passes posteriorly under the preopercular canal,

detaching a lateralis branch to the last (eighth)

mandibulo-preopercular canal organ. The rest of

the ramus continues ventroposteriorly under the

skin over the anterior end of the opercle, where it

supplies the skin of this area and two (Figure 12)

or three (Figure 20) free lateralis organs located

about over the anterior end of the subopercle. The

posterior part of the skin over the opercle is sup
28

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

RAMUS COMMUN1CANS,

POSTERIOR RAMUS PALATINUS FAC1AL1S

RAMUS OPERCULARIS PROFUNDUS FAC1AUS

ANTERIOR RAMUS PALATINUS FACIALIS

RAMUS

MAXILLAR1S

[NFERIORIS

RAMUS OPERCULARIS PROFUNDUS FACIALIS

I.EVATOR OPERCULl MUSCLE

ADDUCTOR OPERCUL1 MUSCLE

RAMUS OPERCUI.AIUS PROFUNDUS FACIALIS

PALATAL (PSEUDOBRANCH) RAMUS OF N. IX

FIRST INI'RAPIIARYNGOBRANCIIIAL

FIGUKE 19.—Pholidichthys Uucotaenia: lateral view of head showing distribution of anterior and

posterior ramus palatinus fadalis and the palatal ramus of the glossopharyngeal nerve. See

Figure 15 for meaning of symbols.

plied by the ramus opercularis vagi, which is not

discussed.

The next branch of the truncus hyomandibularis

goes to the seventh mandibulo-preopercular canal

organ. It is just ventral to this organ, but still some

distance above the upper end of the interhyal, that

the truncus divides into the anteriorly coursing

ramus mandibularis facialis and the ramus hyoideus, which passes ventrally onto the hyoid arch

(Figure 20).

Ramus hyoideus

The ramus hyoideus carries visceral motor and

general cutaneous components. After detaching

from the truncus hyomandibularis it passes ventrally posterior to the interhyal. At the ventral end

of the interhyal it turns anteriorly, coursing close

to the bases of the branchiostegal rays, and gives

off branches carrying motor fibers for the welldeveloped hyoidei adductores and abductores muscles of the branchiostegal rays (Figure 21). Its first

branch (Figure 20), however, detaches shortly after

it leaves the truncus, and is a general cutaneous

nerve coursing ventrally between the operde and

preoperde, supplying skin in this area as far ventrally as the angle of the preoperde. Much further

anteriorly, a branch detaches between the second

and third branchiostegals, passes anteriorly along

the ventral edge of the protractor hyoidei muscle,

innervating skin, but not the muscle, and ends below the hypohyals. Most of the hyoidei adductores

and abductores muscles are not indicated in Figure 21.
NUMBER 216 29

TRUNCUS HY0MANDIBULAR1S

ANTERIOR RAMUS 1'AI.ATINUS FAC1ALIS

POSTERIOR RAMUS I'AIATINUS FACIAUS

RAM US

MANDIBUI.ARIS

FACIA 1.1S

LOSSOPIIARYNGEAL NERVE

FIRST 1NFRAPIIARYNGOBRANC1IIAL

FIRST BRANCH OF

RAMUS HYOIDEUS

RAMUS MANDIBULAR1S

EXTERMUS FACIA LIS

DENTARY LINE OF FREE LATERAUS ORGANS

RAMUS BUCCALIS ACCESSORIUS FACIALIS

FIGURE 20.—Pholidichthys leucotaenia: lateral view of head showing proximal half of distribution

of truncus hyomandibularis. See Figure 15 for meaning of symbols.

Ramus mandibularis facialis

Beyond the detachment of the ramus hyoideus

the truncus hyomandibularis, now called the ramus

mandibularis facialis, curves ventroanteriorly and

passes in a bony canal in the preopercle dose to

the preopercular lateralis canal. The ramus detaches the ramus buccalis accessorius facialis, a lateralis branch.

Ramus buccalis accessorius facialis

This ramus (Figure 17) innervates the 6 or 7

free lateralis organs, which form a rather welldeveloped vertical line on the cheek. It also innervates four free lateralis organs over the posterior

end of the mandibular canal on the lower jaw. The

dorsal organs of the vertical cheek line appear to

have invaded part of the area of the infraorbital

canal. They are, at least, in the area of the gap in

this canal, which is complete in most fishes. The

ramus contacts a general cutaneous branch of the

ramus mand. trigeminus at the posterior end of the

lower jaw (Figure 17) and apparently receives

some general cutaneous fibers from it. The ramus

buccalis accessorius should not carry general cutaneous fibers in its branch supplying the vertical

free lateralis organ line, as this branch is in the
30

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FROM RAMUS MANDBULAR1S TRIGEMINUS

MOTOR FIBERS

GENERAL CUTANEOUS FIBERS

PROTRACTOR

HYOIDEI MUSCLE

BRANCH TO SKIN

ALONG PROTRACTOR

HYOIDEI MUSCLE

<LS ML'SCl.l

FIGURE 21.—Pholidichthys leucotaenia: lateral view of hyoid arch showing distribution of ramus

hyoideus. See Figure 15 for meaning of symbols.

area of general cutaneous nerves of the intraorbital

trunk.

Shortly after detachment of the ramus buccalis

accessorius the ramus mand. facialis divides around

the symplectic bone (as it does in most teleosts)

into the ramus mandibularis internus facialis and

the ramus mandibularis externus facialis (Figure

20).

Ramus mandibularis internus facialis

This ramus carries communis fibers for taste buds

of the floor of the mouth and lower lip. It passes

anteriorly dorsal to the symplectic and approaches

the ramus mand. externus as both rami pass anteriorly dorsal to the quadrate articulating head and

onto the medial side of the lower jaw (Figures 18

and 20). The ramus mand. internus facialis contacts the ramus mand. externus facialis slightly on

the medial side of the articular bone and continues

anteriorly to near the symphysis of the lower jaw.

Near the symphysis the ramus internus curves laterally in the oral membrane, innervating taste

buds on it and, apparently, taste buds around the

teeth and probably out on the lower lip, although

no branches could be seen reaching the lip. As the

ramus passes the articulating head of the quadrate

it detaches a branch dorsally to the mucosa of this

part of the mouth.

Ramus mandibularis externus facialis

This ramus separates from the ramus mand.

internus above the symplectic and courses anteriorly ventral to this bone. It carries mainly a lateralis component and some general cutaneous fibers.

The cutaneous fibers detach as two cutaneous

branches along the horizontal arm of the preopercle, innervating skin (Figure 20). No cutaneous

fibers are apparently left in the ramus at the point

of its crossing onto the lower jaw. The ramus innervates the sixth mandibulo-preopercular canal

organ and farther on the fifth organ (Figure 20).

The ramus passes anteroventrally above the articulating head of the quadrate and onto the lower

jaw (Figure 18). Just beyond the quadrate it sends

a branch to innervate the last (fourth) mandibular canal organ, which lies in the articular bone.

Further anteriorly, coursing underneath Meckel's

cartilage, the ramus detaches a branch to the third
NUMBER 216 31

mandibular canal organ (in the dentary). A little

anterior to the origin of the fourth canal organ

branch is a lateralis branch, which courses with the

ramulus mandibularis medialis trigeminus that

innervates the protractor hyoidei and intermandibularis muscles. The lateralis branch extends anteriorly as three lateralis ramuli. The posteriormost

ramulus innervates the anterior free lateralis organ

of the dentary (Figure 18); the middle ramulus

innervates the first canal organ of the dentary; and

the anteriormost ramulus innervates the free lateralis organ near the anterior end of the chin

(general cutaneous fibers from the ramus mandibularis trigeminus continue anteriorly beyond the

third ramulus to supply the skin of the anterior

end of the chin). The remainder of the ramus

mandibularis externus facialis continues anteriorly

under Meckel's cartilage as far as the second dentary canal organ, which it supplies.

ANTERIOR RAMUS PALATINUS FACIALIS

This ramus (Figure 19) carries communis fibers.

It originates intracranially as two branches from

the truncus hyomandibularis, which join in the

bone of the prootic and form a ramus that passes

through the anterior wall of the prootic and into

the orbital cavity. The ramus continues forward

on the dorsolateral side of the parasphenoid across

the floor of the orbital cavity. It detaches en route

three large branches that pass ventrally through

the adductor arcus palatini muscle to the mucosa

of the palate. Beneath the vomer the ramus sends

a number of thin branches to the mucosa. It continues anterolaterally under the vomer, joining the

ramus maxillaris inferioris trigeminus as this nerve

crosses the ventral surface of the maxillary.

TRUNK LATERAL-LINE NERVES

The nervus linae lateralis (Figure 13), which

innervates the lateralis organs of the trunk, emerges

from the cranium on the posterodorsal side of the

vagus (tenth) nerve (not illustrated). The nervus

linae lateralis directly leaves the vagus, passes posteriorly and laterally toward the pectoral girdle,

and detaches the ramus supratemporalis vagi,

which we do not describe further. Shortly before

the cleithrum, the nervus linae lateralis detaches

the dorsal-fin branch, which innervates three free

lateralis organs (Figure 13). Medial to the cleithrum, the nervus linae lateralis detaches the first

dorsal longitudinal collector lateral-line nerve. The

remainder of the n. linae lateralis continues posteriorly as the horizontal septum lateral-line nerve

along the horizontal septum to the end of the

trunk, innervating en route the overlying free lateralis organs. Above the end of the pectoral fin the

second dorsal collector lateral-line nerve detaches

from the horizontal septum nerve and joins the

first dorsal collector nerve. The second collector

nerve is noticeably smaller than the first. The dorsal collector lateral-line nerve ends above the anus

on one side and somewhat posterior to the anus on

the other side of two specimens examined.

The trunk lateral-line nerve pattern of Pholidichthys has the main characteristic of the acanthopterygian pattern: the dorsal longitudinal "collector" lateral-line nerve (Figure 13). In generalized

percoids, such as Perca flavescens (Freihofer, 1972,

fig. 7), this collector nerve typically leaves the main

trunk lateral-line nerve (the horizontal septum

lateral-line nerve) medial to the supracleithrum,

curves dorsoposteriorly to a point about halfway

between the horizontal septum and the dorsal contour of the trunk, and continues in a gradually

descending course toward the horizontal septum, to

which it returns at the beginning of the caudal

peduncle. En route, the dorsal longitudinal collector

lateral-line nerve is usually joined by four or five

dorsal segmental rami that detach from the horizontal septum. The beryciform Holocentrus also

has a dorsal longitudinal collector lateral-line nerve.

The pattern in Pholidichthys differs from the

generalized acanthopterygian pattern in that the

dorsal longitudinal collector nerve collects only two

dorsal rami. The line of free lateralis organs in

Pholidichthys appears to be breaking up and the

organs moving toward the horizontal septum. This

movement is suggested by the presence of at least

three free organs lying midway between the dorsal

longitudinal collector nerve and the horizontal septum nerve (Figure 13). It is also evidenced by the

presence of a line of free organs along the horizontal

septum beginning below the tip of the pectoral fin

and extending to the point of return of the dorsal

collector nerve to the horizontal septum above the

anus or somewhat posterior to it. In the more generalized percoids, there are no lateralis organs,

either free or in tubed scales, along the horizontal
32 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

septum on its course below the dorsal longitudinal

collector nerve.

In addition to the two trunk lateral-line nerves

just discussed, Pholidichthys has a third, the dorsalfin lateral-line nerve. It is in the form typical for

many teleosts (Figure 13).

There are other perciforms with a trunk lateralline development similar to that in Pholidichthys.

Although they are not particularly elongate fishes,

they show a tendency toward elongation. The comparisons are discussed in another section.

INNERVATION OF THE FIN RAYS

All the fin rays of Pholidichthys are innervated

by the fin-ray nerves coursing external to the fin

rays, not down the hollow center of the rays as the

fin-ray nerves do in many fishes.

Pectoral and Peltric-fin Innervation

The complex of occipital and spinal nerves making up the pectoral plexus was not studied in detail.

The innervation was examined in the hope of gaining some indication of whether or not the pelvic

fins of Pholidichthys show any signs of being or

having been more forward than are percoid pelvic

fins. A nerve marker was sought that might enable

a comparison of the pelvic-fin position in Pholidichthys with the position of this fin in percoids and

blennioids. A marker chosen for comparison was the

particular ventral spinal ramus that enters the medial base of the last pelvic-fin ray and supplies finray innervation to the medial pelvic-fin rays.

The spinal nerves were numbered by assuming

that the occipital nerves consist of three spinal

nerves. Herrick (1899) states that there are at least

three spinal nerves represented in the occipital

nerves. Whatever the number actually is, according

to Ray (1950) it is apparently rather constant for

most bony fishes. The occipital nerves are the first

postvagal segmental nerves that leave the cranium

through the exocdpital bone.

In Pholidichthys it is the seventh ventral spinal

ramus that enters the base of the last pelvic-fin ray.

Miscellaneous Anatomical Notes

The following brief description of the swim

bladder of Pholidichthys was provided us by N. B.

Marshall: bladder divided into anterior and posterior chambers by a fragile diaphragm; retia in anterior chamber; retia have common origin; gas gland

with six or seven lobes.

The gill openings are wide but restricted ventrally (gill membranes attached lateral to isthmus)

and there is a large opening (slit) posterior to the

fourth gill arch. The pseudobranchiae have welldeveloped gill filaments that extend into the gill

cavity.

The adductor mandibulae muscles of the cheek

are massive. There is no indication of an AjP

division. A large part of the A2A3 divisions insert

on the coronoid process of the dentary.

Color Pattern Changes

The smallest specimens of Pholidichthys (15-49

mm SL) are characterized by having two longitudinal dark stripes, separated by a luminous white

stripe, on the body (Figure 22). The dorsal dark

stripe is narrower and extends along the dorsal

body contour. At this stage the anal fin is unmarked

and the dorsal fin is either unmarked or faintly

dusky; the belly is white. Between 49 and 108 mm

SL the dark stripes break up into rows of dark spots,

and some faint dark spots appear in the dorsal fin,

which has a narrow, pale distal margin (Figure 23;

Kailola, 1973, pi. 4, shows a striped phase, wild

caught specimen 123 mm total length). At larger

sizes the color pattern is quite variable, but, in general, the dark spots on the body increase in size

(especially those in the ventral row), grow together

to form irregular vertical spots and bars, and may

send out dorsal and lateral extensions (Frontispiece and Figure 23). There is a row of dark spots

along the dorsal fin, which extend onto the body

dorsally, and a lateral row of large spots, which tend

to fuse with one another posteriorly and with the

posterior dorsal-fin spots. The anal fin also exhibits

irregular dark spots, and there is a continuous, narrow, pale distal margin around the vertical fins.

Burgess and Axelrod (1973, fig. 265) show a large

specimen with a pattern of broad black bands separated by narrow pale bands posteriorly on the body,

and white spots on the dorsum and belly anteriorly.

In living adults the dark areas are dark brownish

and the pale areas are whitish, yellowish, or pale

chartreuse.
FICUKE 22.—Pholidichthys leucotaenia: swarm of juveniles, Honiara, Guadalcanal, Solomon

Islands. (Courtesy of T.F.H. Publications, Inc.)

FICUKE 2S.—Pholidichthys levcoUenia: lateral views of adult, 205 mm SL, exhibiting banded

color pattern, and preadult, 108 mm SL, exhibiting spotted color pattern. Aquarium raised

specimens. (Photograph by M. Giles.)
34 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Notes on Behavior

Striped phase juvenile Pholidichthys have been

captured inadvertently by collectors seeking plotosid catfishes, which the juveniles resemble in color

pattern and in forming large aggregations. Swimming behavior apparently changes with growth.

Striped phase and preterminal color pattern juveniles have been observed in the wild swimming in

the open water, usually close to the substrate and in

large schools. The adults apparently remain hidden

and no sightings of adults in the wild have been

reported.

In aquaria, Pholidichthys has been observed to

move mouthfuls of sand and gravel from their hiding places and discharge them some distance away,

a habit that has earned Pholidichthys the name

"engineerfish" among Philippine aquarists. Adults

exposed to a current of water over sandy bottom

exhibited "nervous" short backward and forward

movements. The main means of propulsion was a

lateral undulation moving along the entire body.

Backward movement was usually initiated by reversing the direction of movement of the pectoral fins.

In backward swimming the tail end becomes the

fulcrum and the undulations of the body proceed

anteriorly; the head moves through the widest lateral swing. Specimens we attempted to catch in

aquaria sometimes did not turn around and flee but

moved backward, avoiding obstacles. The row of

free lateral is organs on the side of the body in

Pholidichthys probably aids in sensing obstacles

during backward swimming.

The dorsal and anal fins have a specialized role

in swimming. These fins are relatively tall and very

flexible and can be turned to a 90° angle to the

body, both fins sometimes tilted to the same side.

Relationships of Pholidichthys

Based on its general morphology, and especially

the pattern of the recurrent facial nerve (RLA)

and the anterior postition of its pelvic fins, we

place Pholidichthys among the Acanthopterygii,

in which we include the Paracanthopterygii of

recent authors (Greenwood et al., 1966; Rosen and

Patterson, 1969). Within the Acanthopterygii we

recognize two groups (grades): the Beryciformes

and Perciformes.2

*For the purposes of our study we do not distinguish the

In a study of the patterns of the recurrent facial

nerve, Freihofer (1963) found the Serranus-type

pattern (pattern 9) only among the perciform

fishes. Pholidichthys has the Serranus-type pattern.

Patterson (1964) characterized the Perciformes (as

opposed to the Beryciformes) on the basis of their

having lost the orbitosphenoid and reduced the

number of segmented pelvic-fin rays to 5 and the

number of principal caudal-fin rays to 17. Pholidichthys has no orbitosphenoid, has further reduced the number of pelvic and caudal-fin rays,

and has developed what appears to be a de novo

ossification, the septal bone, in the interorbital

septum. On these grounds we consider Pholidichthys to be a specialized perciform. Further comment on the possibility that the septal bone is a

modified beryciform orbitosphenoid is in order.

Whatever its other articulations, the orbitosphenoid of beryciforms, and other more primitive

fishes, articulates with the pterosphenoids (and

frontals). The septal bone of Pholidichthys does

not articulate with the pterosphenoids.

The orbitosphenoid, like the septal bone, is an

autogenous ossification formed in the interorbital

septum. The orbitosphenoid may originate as a

bilateral pair of ossifications that ankylose medially

(Goodrich, 1930, for Salmo; De Beer, 1937, for

Ameiurus = Ictalurus; Daget, 1964, for Coregonus) or from what appears to be a single center

of ossification in an unidentified engraulid we examined (there is no information on the ontogeny

of the orbitosphenoid of beryciforms, although in

a 12 mm specimen of Adioryx we examined, the

orbitosphenoid was an unpaired median ossification; smaller specimens should be examined for

this bone). The rhinosphenoid of characins,

which is probably a separate ossification of the

orbitosphenoid (Daget, 1964), also originates as a

bilateral pair of ossifications that ankylose medially

(Weitzman, 1962). The septal bone originates as

a single, median ossification, which originates at

Paracanthopterygii as separate from the Acanthopterygii.

This consideration does not reflect our individual beliefs

concerning the validity of the Paracanthopterygii as a

phylogenetic group. Freihofer accepts the group (at a preperciform grade), but Springer does not. Our treatment of

the Paracanthopterygii within the Acanthopterygii does not

affect our conclusions concerning the relationships of Pholidichthys, but avoids lengthy discussions that are tangential

to our primary concerns. In the ordinal classification we use,

the Paracanthopterygii would fall into the perciform grade.
NUMBER 216 35

the junction of the posterior membranous and

anterior cartilaginous portions of the interorbital

septum and spreads anteriorly, ultimately cupping

the posterior portion of the ethmoid cartilage

(Figure 3).

The orbitosphenoid of the beryciforms, except

Paratrachichthys, Cleidopus, and Anoplogaster,

articulates only (exclusive of cartilage) with the

frontals and pterosphenoids (S. Zehren, pers.

comm.). In Paratrachichthys it articulates also

with the basisphenoid, and in Cleidopus, also with

the lateral and median ethmoids. In Anoplogaster,

the orbitosphenoid articulates with the frontals,

pterosphenoids, basisphenoid, parasphenoid, and

lateral ethmoids, and the orbitosphenoid, basisphenoid, and pterosphenoids form a double bony

orbital septum with the anterior part of the brain

lying between (Woods and Sonoda, 1973). Except

that it does not articulate with the pterosphenoids,

the septal bone of Pholidichthys articulates with

the same bones as the orbitosphenoid of Anoplogaster, but it does not form a double septum, except for a short distance anteriorly, and the brain

is entirely restricted to the cranium posterior to

the septal bone. The articulations of the orbitosphenoid in Anoplogaster appear to represent a

specialized condition for beryciforms.

While the possibility that the septal bone is a

specialized orbitosphenoid that has lost its connections with the pterosphenoids cannot be excluded, we believe it unlikely. Patterson (1975),

who was unaware of Pholidichthys, reported that

the only possible example of fragmentation or

increase in the bones of the occipital, otic, and

orbitotemporal regions of teleosts is the rhinosphenoid of characins.

Among the perciforms the gadoid fishes have

been described as having an ossified interorbital

septum (Svetovidov, 1948). This ossification is not

autogenous, however, but represents paired, thin,

dorsal crests on the parasphenoid. The median

ethmoid of callionymids is highly modified and has

a ventral flange that forms a bony interorbital

septum (Starks, 1923, fig. 5). We have no basis for

relating either of these interorbital ossifications to

the septal bone of Pholidichthys.

The family relationships of Pholidichthys have

received little critical attention in the literature,

probably because few specimens, until recently,

were available for study. Assignments of Pholidichthys to a family often reflected indecision and

were based only on external characters (often

erroneously recorded) or assumed states of internal characters. In the following discussion we

briefly summarize all the references that relate to

the systematic position of Pholidichthys.

Bleeker (1856) first described Pholidichthys

leucotaenia (both the genus and the species) based

on a 97 mm juvenile. He placed the genus in his

family Blennioidei and stated that Pholidichthys

was between Pholis and Petroscirtes in its relationships, but also exhibited similarities to Zoarces,

Iluocoetes, and Phycocoetes. Bleeker (1859) placed

Pholidichthys in his subfamily Blenniiformes, in

which he also included Gunnelichthys (presently

classified in the Microdesmidae). Gunther (1861)

based on Bleeker (1856), included Pholidichthys

in the Blenniidae. Jordan and Evermann (18%)

included it in the Chaenopsidae, but Jordan and

Evermann (1898) included it under the Blenniidae in their subfamily Pholidichthyinae (first

appearance of a family-group name based on

Pholidichthys), which also included Psednoblennius

( = Emblemaria, a chaenopsid) as the only other

genus. Interestingly, Jordan and Evermann (1898)

recognized the Chaenopsinae as distinct from the

Pholidichthyinae.

Boulenger (1904) and Weber (1913) included

Pholidichthys in the Blenniidae, but Jordan (1923)

and Jordan, Evermann and Clark (1930) assigned

Pholidichthys to the Chaenopsidae, which Jordan

(1923) considered to be a provisional group of

forms perhaps unrelated among themselves, and

in which he also included, among other genera,

Gunnellichthys. Herre and Herald (1951) also included Pholidichthys in the Chaenopsidae, but

Herre (1953) included it in the Blenniidae. De

Beaufort (1951) placed Pholidichthys in the

Pholidichthyidae (first appearance as a family)

under the order Blennioidea, and included Gunnellichthys as the only other genus in the family.

Gosline (1955) removed Gunnellichthys from the

Chaenopsidae and Pholidichthyidae and placed it

properly in the Microdesmidae, which he demonstrated to be allied to the gobioid fishes, but mentioned nothing about the relationships of the

Pholidichthyidae (by inference he eliminated it

from the gobioid fishes). Norman (1966, posthumous) included Pholidichthys and Gunnellichthys

in the Blenniidae as incertae sedis. Gosline (1968)
36 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

noticeably ignored the Pholidichthyidae in his

treatment of the suborders of perciform fishes,

even though its characteristics as reported by earlier authors should have caused him to consider it

among the families he included in his suborder

Blennioidei. Greenwood et al. (1966) and Lindberg (1971) either overlooked or disagreed with

Gosline (1955) and included the Pholidichthyidae

as a synonym of the Microdesmidae. Schultz (1966)

examined the holotype of P. leucotaenia and tentatively allocated it to his gobioid suborder Gobiina without mention of its family placement.

Brittan (1972) briefly noted the previous confusion surrounding the relationships of Pholidichthys. Miller (1973) stated that there was no osteological evidence to support the removal of

Pholidichthys from the Microdesmidae and he,

therefore, included the Pholidichthyidae as a synonym of that family.

Finally, Freihofer and Lin (1974) included the

Pholidichthyidae as one of the six families in their

superfamily Blennioidea; the Notograptidae was

another of the six.

Pholidichthys, thus, has been assigned only to

the blennioid or gobioid fishes, or to its own

family, Pholidichthyidae, with no mention of its

ordinal-group relationships. Gosline's (1955) characterization of the gobioids (particularly the lack

of parietals) adequately serves to exclude Pholidichthys from the gobioids.

The assignments of Pholidichthys to the blennioids were based primarily on observations that

the pelvic fins are inserted slightly in advance of

the pectoral fins. We find that the position of the

pelvic fins varies from slightly in advance of the

pectoral fins (striped juveniles) to directly under

the pectoral fins (banded subadults or adults).

This is more variation than we have encountered

in other fishes usually placed among the blennioids,

which always have the pelvic fins noticeably in

advance of the pectoral fins. This variation might

be considered sufficient to exclude Pholidichthys

from the blennioids, but more discussion of this

matter is required.

The innervation of the posteriormost pelvic-fin

ray in Pholidichthys is by the 7th ventral spinal

ramus, just as it is in blennioids and many other

perciforms with jugular pelvic fins. Those perciforms with the most anterior pelvic fins (for instance brotulids) may have the posteriormost

pelvic-fin ray innervated by the 6th ventral spinal

ramus, and those with nonjugular pelvic fins by

the 8th, or a more posterior, ventral spinal ramus.

If, therefore, the position of the pelvic fins is considered as a segmental, rather than a positional

character, Pholidichthys cannot be excluded from

relationship with the blennioids.

Gosline (1968) most recently treated the classification of the blennioids and defined them on the

basis of the following three specializations: (1)

pelvic fins, when present, inserted ahead of the

pectoral fins; (2) dorsal and posterior soft anal-fin

rays exactly equal in number to the vertebrae

between them; (3) caudal fin usually rounded.

Gosline, however, excluded several fish families

that exhibited these three specializations because

they also exhibited other specializations that made

their inclusion among the blennioids unsatisfactory to him. Gosline's actions resulted in his blennioid fishes being a residual group with unclear

relationships. Hennig (1966) has shown that in

determining phylogenetic relationships, characters

treated as specialized (apomorphic) at one level

of classification must be treated as unspecialized

(plesiomorphic) at the next higher level. Therefore, when a broader spectrum of specialized characters is examined, it is possible that some of the

residual families that constitute Gosline's Blennioidei may be found to be more closely related to

some of the excluded families (or even to some of

the families Gosline did not consider) than they

are to other residual families.

There are other problems with Gosline's definition of the Blennioidei. In particular, his character

concerning the relationship of the dorsal and analfin elements to vertebrae is difficult to apply. For

instance, a number of blenniids and clinids would

be excluded from the blennioids because the last

dorsal and/or anal-fin pterygiophore supports two

rays that are related to only one vertebra (while

procedurally in ichthyology these two rays in

either fin are often counted as one ray, each of the

two rays is a bilaterally paired structure and anatomically each must be considered as a separate

ray). Gosline's fin-ray-to-vertebra character is a

simplification that obscures complex situations

that might have phylogenetic import. In Pholidichthys, for example, the dorsal fin originates

above the second or third vertebra and the fin rays

bear a one-to-one relationship with the vertebrae,
NUMBER 216 37

except that the anteriormost two or three rays are

crowded and may associate with only one or two

vertebrae. Yet, the number of rays at the anterior

end of the fin equals the number of vertebrae in

the same area (see Figure 9, but ignore the anomalous fourth vertebra with three neural spines and

three associated fin rays). Does this condition in

Pholidichthys actually violate Gosline's character

for the blennioids, or does it only appear to do so?

In some tripterygiids, the anteriormost dorsalfin spines are inserted in advance of the first vertebra, and these spines exceed in number the vertebrae anterior to the vertebra that begins the series

relating one-to-one with the remaining dorsal-fin

elements. Does this condition only superficially

conform to Gosline's character? In many fishes, for

example some labrids and acanthoclinids, which

Gosline excluded from the blennioids, the dorsal

fin begins immediately behind the head and the

ratio of dorsal-fin elements to vertebrae is one-toone except that well anteriorly there is always one

vertebra associated with two elements. If the anterior portion of the dorsal fin of such a form

became reduced during the course of evolution,

the form might be allied to the blennioids (following Gosline) because the only dorsal-fin elements

remaining would bear a one-to-one relationship

with the vertebrae.

Without further belaboring the critique of Gosline's characters, suffice it to say that we believe

his case for the homogeneity, or approximate completeness, of his Blennioidei is inadequately defended. Based on Gosline's definition, Pholidichthys might be a blennioid, but based on other

specializations we believe that it shows equal evidence of relationships with certain fishes that have

never been considered blennioid relatives.

Pholidichthys exhibits a number of specializations that remove it from the basal perciform level

of organization. Most of these are of little help in

establishing its suprafamilial relationships as the

specializations are either unique (autapomorphic)

or shared by various, apparently unrelated groups

of perciforms. The most prominent autapomorphic characters are : (1) The presence of a septal

bone. (2) The lack of an ascending process on the

parasphenoid in adults (at least 140 mm) and resulting entry, unimpeded, of the exceptionally long

prootic and large pterosphenoid into the orbital

region. The gobiesocids and alabetids also lack an

ascending process on the parasphenoid. These

fishes have the cranium greatly depressed, however,

and what might be the parasphenoid's ascending

processes are lateral projections. Both of these families also lack pterosphenoids. In some gadoids, the

parasphenoid appears to lack an ascending process

(Svetovidov, 1948). In these gadoids the pterosphenoid is almost entirely anterior, and dorsal, to the

prootic, and the position of these two bones relative to each other is entirely unlike their position in

Pholidichthys. In the highly specialized Mastacembelidae and Chaudhuriidae the parasphenoid also

lacks an ascending process, but either the prootic

is entirely blocked by the pterosphenoid-pleurosphenoid bones from entering the postorbital

margin or the pterosphenoid-pleurosphenoid bones

are absent (D. E. Rosen, pers. comm.). (3) the

large, complex metapterygoid. (4) Apparent displacement dorsally and freeing of the lateralis organs (innervated by the ramus buccalis facialis) of

the infraorbital canal in the gap area and partial

invasion of the gap by free lateralis organs innervated by the ramus buccalis accessorius fadalis of

the truncus hyomandibularis. (5) Presence of free

lateralis organs along the horizontal septum anteriorly ventral to the dorsal longitudinal collector

lateral-line nerve.

Other specializations that we believe offer no

evidence of relationships are the following apparently convergent or autapomorphic characters:

(1) Single nostril (also present in such diverse

groups as cichlids, congiopodids, and zoarceoids).

(2) Eel-like form (also in congrogadids, alabetids, blennioids, and microdesmids). (3-5) Gosline's (1968) blennioid specializations (see discussion on page 36). (6) Reduction of postcleithra.

We have not seen an exact duplication of the

pholidichthyid postdeithrum, but various perciforms have reduced the postcleithra; see SmithVan iz and Springer (1971, fig. 15) for certain

blenniids; trichonotids, leptoscopids, and alabetids,

among others, have no postcleithra. (7) Reduction of caudal-fin structure. We have not seen

an exact duplication of the pholidichthyid caudalfin structure, but various combinations of fusions

and losses in the structure of this fin occur within

and among a large number of families of fishes.

The fusion of the ventral hypural plate to the urostylar centrum and loss of a few fin rays in the eellike Notograptus (Notograptidae) would result
38

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

in a caudal-fin structure similar in appearance to

that of Pholidichthys, as would the loss of an

epural and a few procurrent fin rays in the blenniid Xiphasia, which is also eel-like. Caudal-fin

reduction is apparently often correlated with an

eel-like body form. (8) Reduction of cephalic

seismosensory canals and associated loss of some

circumorbital bones. We have not seen an exact

duplication of the pholidichthyid cephalic seismosenory canal system, but an incomplete circumorbital canal with loss of some circumorbital bones

also occurs in the dinid Exerpes, the ammodytids,

some stichaeoids, the callionymids and the gobiesocids. Lack of a connection between the preopercular and more dorsal head canals occurs in Exerpes

(Clinidae), the ophidioid Brotulataenia (Cohen,

1974) and stichaeoids (Makushok, 1961). Lack of

a supratemporal commissure occurs in many fishes,

for example, pseudochromids. (9-21) Lack of:

scales, predorsal bones (Smith and Bailey, 1961),

a subocular shelf (Smith and Bailey, 1962), vomerine and palatine teeth, dorsal and anal-fin spines,

and a lateral-line canal on the body; fusion of:

associated proximal and medial dorsal and analfin radials, and all hemal arches with their respective centra; possession of: a nonprotractile premaxillary and restricted gill opening. All these

are characters found variously in a wide variety of

perciform fishes. (22) Lack of a medially projecting flange on the prootic and consequent lack of

an osseous contribution by the prootics to the roof

of the posterior myodome (also, at least, found in

some blenniids (Springer, 1968), gobiesocids, and

dactyloscopids). (23) Wide separation, from each

other, of the anterior ends of the (rodlike) pelvises

(also found in cryptacanthodids and Notograptus). (24) Innervation of the posteriormost pelvicfin ray by the seventh ventral spinal ramus (also

in Blenniidae, Coryphaenidae, Mugiloididae, Rachycentridae).

We have found three specializations exhibited

by Pholidichthys that we believe must be considered in a review of its subordinal relationships.

These are the completely fused 5th ceratobranchials (and other gill-arch specializations), the

interrupted sulcus of the sagitta, and the trunk

lateral-line nerve pattern. A discussion of these

characters follows.

GILL-ARCH SPECIALIZATIONS.—Fusion of the 5th

ceratobranchials has been reported previously

among the perciforms only in the families Pomacentridae, Embiotocidae, Labridae, Odacidae, and

Scaridae.3 Nelson (1967 and pers. comm) investigated the gill arches of these families in an

attempt to determine whether they were closely

related. He concluded that aside from the fused

ceratobranchials there was little in gill-arch structure to indicate that these families were, or were

not, closely related. He did note that among these

families there was a tendency for the 1st basibranchial to be displaced downward and for the

2nd infrapharyngobranchial to lose its typical connection with the 1st epibranchial.

The gill-arch structure of Pholidichthys exhibits

a number of similarities, aside from its fused 5th

ceratobranchials, with the structure of the families

Nelson treated. Nelson (1967) did not discuss the

Odacidae, although he included it among the labroids (1969). He has since commented (pers.

comm.) that its gill arches were not appreciably

different from those of the labrids and scarids.

Most of the anterior end of the 1st basibranchial

of Pholidichthys is ventral to the basihyal, just as

it is in the pomacentrids, but the 1st basibranchial

lacks the posterior process of that bone as found

in the pomacentrids. In contrast, the 1st basibranchial is entirely ventral to the basihyal and 2nd

basibranchial in the embiotocids, but is only expanded ventrally (both anteriorly and posteriorly)

in the labroids.

a

 Norman (1966) reported fused lower pharyngeals in the

sciaenid genera Pogonias and Aplodinotus. Juveniles of these

two genera have distinctly separate 5th ceratobranchials.

Gosline (1955) reported completely fused 5th ceratobranchials

in the gobioid Kraemeria samoensis. We did not have that

species available, but in an adult K. bryani we examined, the

5th ceratobranchials were completely separate. Matsubara

and Iwai (1959) described and illustrated the osteology of

Krameria sexradiata. They also reported that the 5th ceratobranchials were separate in their species. Gosline also reported that the tooth plates of the 5th ceratobranchials were

fused in the gobioid Awaous stamineus but that a suture

was evident between the bones on their ventral surface. A

juvenile A. tajasica we examined had the 5th ceratobranchials

completely separate. Cichlids are often reported to have fused

5th ceratobranchials. In a juvenile Cichlasoma cyanoguttatum

we examined, the 5th ceratobranchials (and their associated

tooth plates) were closely joined, but a suture was evident

between them both dorsally and ventrally, and the two bones

were easily separated. In contradistinction, the 5th ceratobranchials are completely fused, without a joint between, in

the earliest stages of the Pomacentridae, Embiotocidae,

labroid fishes, and Pholidichthys.
NUMBER 216

In Pholidichthys there is no interarcual cartilage

between the uncinate process of the 1st epibranchial and the 2nd infrapharynobranchial, and the

uncinate process is ligamentously attached to the

2nd infrapharyngobranchial. The uncinate process and interarcual cartilage are both present and

attach to the 2nd infrapharyngobranchial in the

pomacentrids. Neither the uncinate process nor

cartilage are present in the embiotocids, and the

1st epibranchial is not connected to the 2nd infrapharyngobranchial; the condition is essentially the

same in the labroids except that there is an uncinate process on the 1st epibranchial which attaches

ligamentously to the 2nd epibranchial.

The 2nd infrapharyngobranchial bears no teeth

in Pholidichthys and the labroids, but is toothed

in the pomacentrids and embiotocids.

The tooth plate of the 4th infrapharyngobranchial is either fused to the 3rd infrapharyngobranchial or lost (not possible to tell which) in

Pholidichthys and the labroids, but is autogenous

in the pomacentrids and embiotocids.

Thus, the gill-arch structure of Pholidichthys

is somewhat intermediate between that of the

Pomacentridae and Embiotocidae, on the one

hand, and the labroids, on the other, but perhaps

more similar to that of the labroids.

All of those gill-arch specializations, except the

fused 5th ceratobranchials, shown by these families occur in various other families. For example,

the ventral displacement of the 1st basibranchial

occurs in many diverse families, including, among

others, the Sciaenidae, Cepolidae, Opistognathidae,

and Blenniidae; a toothless 2nd infrapharyngobranchial is present in Synanceia and some Apogonidae (Fraser, 1972) and Opistognathidae; the

interarcual cartilage is absent in a large variety of

fishes including (but not limited to) the Blenniidae, Batrachoididae, Callinonymidae, Cottidae,

Trichonotidae, Trichodontidae, Uranoscopidae,

in which the uncinate process of the 1st epibranchial is variously present or absent, but when

present attaches ligamentously to the 2nd infrapharyngobranchial. Similarly, the 4th infrapharyngobranchial tooth plate is either missing or fused

with the 3rd infrapharyngobranchial (not possible

to tell which) in many families (e. g., Batrachoididae, Blenniidae, Callinonymidae, Cottidae, Gobiesocidae). The presence or state of the 1st infrapharyngobranchial in perciforms is widely variable;

for instance, it is present (as cartilage) in the dinids

but absent in the related blenniids.

We conclude that the gill-arch structure of

Pholidichthys offers no unequivocal information

concerning its relationships.

Among the families with fused 5th ceratobranchials, only Pholidichthys and the labroids

bear an essentially one-to-one relationship between the dorsal and anal-fin elements. We have

already discussed the problems of using this specialization as a basis for relating groups of fishes.

We know of no other specializations, except the

single nostril of pomacentrids (also present in

zoarceoids, congiopodids, and notothenioids),

shared by Pholidichthys and the other fishes with

fused 5th ceratobranchials.

T HE SAGITTA.—Mr. J. E. Fitch provided us with

his assessment of the relationships of Pholidichthys

based on his examination of the sagitta. He informed us that the overall configuration and

arrangement of the sagittal sulcus is the most important otolith character for determining teleost relationships; however, he noted that similarities in

the sulcus of two forms does not necessarily indicate relationship, nor do dissimilarities necessarily

indicate nonrelationship. To his knowledge, the

only fish with a sulcus similar to that of Pholidichthys is Cepola (Cepolidae).

Fitch informed us that the Cepola sagitta differs

from that of Pholidichthys in that the Cepola

ostium opens more dorsad on the anterior margin,

the crista superior is less pronounced, and the sulcus is more curved (sigmoid).

We have examined a cleared and stained specimen of Cepola and a whole specimen and radiograph of Acanthocepola (the only two genera in

the Cepolidae) in a search for other shared specializations that might indicate a close relationship

between the cepolids and Pholidichthys. In general, cepolids are much less specialized than Pholidichthys.* They are elongate, like Pholidichthys,

'Okada and Suzuki (1956) synonymized the Owstoniidae

with the Cepolidae based on osteological characters. We are

inclined to agree that the owstoniids are more closely related

to the cepolids than they are to the opistognathids, near

which they have often been classified. We do not have skeletal material of the owstoniids available, but based on Okada

and Suzuki's study and our examination of radiographs and

whole specimens of Owstonia weberi and Sphenanthias sibogae, we find that the owstoniids are even less specialized than

the cepolids, and offer less evidence of relationships with
40 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

and have reduced the number of dorsal-fin spines

to 2 and anal-fin spines to 1, which shows a trend

toward only segmented rays in these fins, the condition found in Pholidichthys. Except anteriorly,

the dorsal and anal-fin elements bear a one-toone relationship with the vertebrae in Cepola

(like Pholidichthys), but in Acanthocepola the

dorsal-fin elements bear a 1.44 to 1, and the analfin elements (posteriorly) a 1.25 to 1, relationship

with the vertebrae, an apparently less specialized

condition. The cepolids (and owstoniids) have a

single postcleithrum, but this element appears to

occupy the extent of both the dorsal and ventral

postcleithra of those fishes that have two postdeithra. Although Pholidichthys also has a single

postcleithrum, it is represented only by a small,

thin plate of bone dorsally. It is not possible to tell

whether this plate represents a reduction of the

single cepolid postcleithrum or the remains of a

dorsal postcleithrum and associated loss of a separate ventral postcleithrum. As noted above, the

first basibranchial of Cepola is ventral in position,

even more so than in Pholidichthys, but this specialization does not indicate relationships unequivocally. We found no other shared specializations between the cepolids and Pholidichthys,

nor did we find any others between the cepolids

and the families of fishes with fused 5th ceratobranchials. Thus, we have no evidence that Pholidichthys is any more closely related to cepolids

than to any of the families with fused 5th ceratobranchials.

Pholidichthys than do the cepolids. In addition, owstoniids

have a pattern 8 recurrent racial nerve (Freihofer, unpublished), whereas opistognathids, like Pholidichthys, have a

pattern 9 nerve (Freihofer, 1963). Cepolids do not have a

recurrent facial nerve (Freihofer, unpublished), but if cepolids and owstoniids are derived from an ancestor that had a

pattern 8 nerve, it seems unlikely that these two families are

closely related to either opisthognathids or Pholidichthys.

Owstoniid saggitae have not been described, nor have we or

Fitch seen any.

TRUNK LATERAL-LINE NERVE PATTERN.—In Pholidichthys the trunk lateral-line nerve pattern has

the main feature of an acanthopterygian pattern:

the dorsal collector lateral-line nerve. This nerve

exhibits two specializations in Pholidichthys: it has

only two dorsal rami (versus five rami in a perciform such as Perca) and the nerve returns to the

horizontal septum above the anus, or not far posterior to it (versus returning to the septum far posteriorly, on the caudal peduncle, as occurs in

Perca).

While the information on trunk lateral-line

nerve patterns in fishes is limited, we find that the

pattern of Pholidichthys is duplicated only in

the Clinidae, Blenniidae, and Dactyloscopidae

(Springer, unpublished, considers these three

families, together with the Tripterygiidae and

Chaenopsidae, which have not been examined for

the pattern, to form a closely related group, the

tropical blennioids). On the basis of shared osteological specializations, however, these three families are not closely related to Pholidichthys, and

although it is possible that Pholidichthys could be

a member of the group including the primitive

sister group of the tropical blennioids, considerably more information on other perciform fishes

will be necessary to establish such a relationship.

If the distinctiveness of the nerve pattern holds,

it would furnish evidence for a common derivation of Pholidichthys and the families of tropical

blennioids.

Summary

Based on its having a Serranus-type pattern of

the recurrent facial nerve, Pholidichthys is a perciform fish. Its subordinal relationships are unclear,

but based on limited evidence from the trunk

lateral-line nerve pattern, it shows possible relationship with the tropical blennioid fishes (suborder Blennioidei).
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•A U.«. aOVENMMKMT PMIMTIN* OPPICSt I»T« lll-M»/j

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