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550,5 

F1 GE0L06Y LIBRARY 

n.s. 

no. 35 



FIELDIANA 



Geology 

NEW SERIES, NO. 35 



Cervifurca nasuta n. gen. et sp., an 
Interesting Member of the Iniopterygidae 
(Subterbranchialia, Chondrichthyes) 
from the Pennsylvanian of Indiana, U.S.A. 



Rainer Zangerl 



en 



a. 

35 



March 31, 1997 
Publication 1483 



PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY 



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Croat, T. B. 1978. Flora of Barro Colorado Island. Stanford University Press, Stanford, Calif., 943 pp. 

Grubb, P. J., J. R. Lloyd, and T D. Pennington. 1963. A comparison of montane and lowland rain forest in 
Ecuador. I. The forest structure, physiognomy, and floristics. Journal of Ecology, 51: 567-601. 

Langdon, E. J. M. 1979. Yage among the Siona: Cultural patterns in visions, pp. 63-80. In Browman, D. L., 
and R. A. Schwarz, eds., Spirits, Shamans, and Stars. Mouton Publishers, The Hague, Netherlands. 

Murra, J. 1946. The historic tribes of Ecuador, pp. 785-821. In Steward, J. H., ed., Handbook of South 
American Indians. Vol. 2, The Andean Civilizations. Bulletin 143, Bureau of American Ethnology, 
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J.IN0IS LIBRA* 
URBANA-CHAMP/ 



FIELDIANA 



Geology 

NEW SERIES, NO. 35 



Cervifurca nasuta n. gen. et sp., an 
Interesting Member of the Iniopterygidae 
(Subterbranchialia, Chondrichthyes) 
from the Pennsylvanian of Indiana, U.S.A. 

Rainer Zangerl 

Curator Emeritus 

Department of Geology 

Field Museum of Natural History 

Roosevelt Road at Lake Shore Drive 

Chicago, Illinois 60605-2496 

Present address: 

R.R. 4 

Box 252A 

Rockville, Indiana 47872 



Accepted May 21, 1996 
Published March 31, 1997 
Publication 1483 



PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY 



© 1997 Field Museum of Natural History 

ISSN 0096-2651 

PRINTED IN THE UNITED STATES OF AMERICA 



Table of Contents 



GEOLOGY LIBRARY 



Abstract 

Introduction 

Systematic Paleontology 

Cervifurca, gen. nov 

Diagnosis 

Etymology 2 

Cervifurca nasuta, sp. nov 2 

Diagnosis 2 

Etymology 2 

Holotype 2 

Referred Specimens 2 

Description 5 

Discussion 15 

Conclusions 23 

Acknowledgments 23 

Literature Cited 23 



List of Illustrations 



1. Cervifurca nasuta, holotype, fmnh 
PF13228, X-ray 3 

2. Cervifurca nasuta, referred specimen 
uimnh 11378, partial skeleton 4 

3. Cervifurca nasuta, drawing of uimnh 
11378 4 

4. Cervifurca nasuta, isolated neurocran- 

ium, PF13233, X-ray enlargement 6 

5. Cervifurca nasuta, neurocranial out- 
lines, plate and counterplate, PF 13233 .... 7 



6. Outline of the skull of Raja 8 

7. Outline of the neurocranium of Cervi- 
furca nasuta 9 

8. Radiograph tracings, plate and counter- 
plate, PF13236, Cervifurca nasuta 10 

9. Cervifurca nasuta, PF 13230, X-ray of 
plate 11 

10. Cervifurca nasuta, PF 13230, X-ray of 
counterplate 12 

11. Cervifurca nasuta, dentition, PF 13228, 
PF13237, PF13230, PF13229 13 

12. Cervifurca nasuta, minute denticles, 
PF13229 14 

13. Cervifurca nasuta, visceral cartilages, 
PF6455 15 

14. Cervifurca nasuta, tentative reconstruc- 
tion of ventral visceral elements 16 

15. Cervifurca nasuta, tracing of vertebral 
column, PF13228 16 

16. Cervifurca nasuta, X-ray shadow trac- 
ings, fins and rasps, PF13228 17 

17. Cervifurca nasuta, outline drawings of 

rasp and tenacular hooks, PF 13230 17 

18. Cervifurca nasuta, rasp and tenacular 
hooks, PF13238, PF13229 18 

19. Cervifurca nasuta, terminal segment of 
pterygopodium, PF13236 19 

20. Cervifurca nasuta, long pterygopodial 
segment, PF13228 20 

21. Cervifurca nasuta, reconstruction of 
skeleton in ventral view 21 

22. Cervifurca nasuta, reconstruction of 
skeleton in lateral aspect 22 



vm^**"**" 



in 



IV 



Cervifurca nasuta n. gen. et sp., an 
Interesting Member of the Iniopterygidae 
(Subterbranchialia, Chondrichthyes) from the 
Pennsylvanian of Indiana, U.S.A. 

Rainer Zangerl 



Abstract 

A new member of the family Iniopterygidae from the Excello Shale (Carbondale Formation, 
Westphalian lower D, Pennsylvanian) of the Bethel Quarry, southern Pike County, Indiana, is 
described. This taxon is remarkable for its dorsoventrally flattened body habitus and probably 
(functionally) correlated enormous size of the pterygopodia, and for orbits that face dorsolat- 
erad. The neurocranium is provided with very prominent nasal capsules, and the pelvic fins 
consist of a few very short and stout radials. Cervifurca nasuta was probably a member of the 
mobile benthos. 



Introduction 

During the field seasons of 1982 and 1983 my 
wife Ann and I, with occasional help from col- 
leagues, students, and friends, quarried the highly 
fossiliferous Excello Shale at the Field Museum 
of Natural History's Bethel Church locality in 
southern Pike County, Indiana. This locality is of 
particular interest because it contains an abun- 
dance of iniopterygians, both species already de- 
scribed (Iniopteryx rushlaui, Promexyele peyeri, 
Sibyrhynchus denisoni, Iniopera richardsoni; 
Zangerl & Case, 1973) and several new taxa. 
Among the latter is a highly distinctive new mem- 
ber of the family Iniopterygidae, Cervifurca na- 
suta, in which the palatoquadrates are separate 
cartilages attached to the neurocranium by joints, 
and the dentition teeth are not fused to form tooth 
whorls. Cervifurca nasuta combines a number of 
anatomical features suggestive of a benthic habitat 
for this species. 

At the time when E. S. Richardson and I stud- 
ied the paleoecological aspects of the carbona- 
ceous, sheety black shales (Mecca and Logan 
Quarry shales; Zangerl & Richardson, 1963), we 
tacitly assumed that the fishes entombed in these 
deposits had been regular inhabitants of the ex- 



tensive epicontinental marine basin complex (Il- 
linois basin; Forest City basin, etc.) of the north- 
central United States. There are, however, indi- 
cations that part of this fish fauna may have en- 
tered the epicontinental realm from more distant 
oceanic waters during repeated transgressions; 
this applies particularly to the iniopterygians. 



Systematic Paleontology 

Subclass Subterbranchialia Zangerl, 1979 
Order Iniopterygida Zangerl & Case, 1973 
Family Iniopterygidae Zangerl & Case, 1973 



Cervifurca, gen. nov. 
Type Species 

Cervifurca nasuta, sp. nov. 

Diagnosis 

Iniopterygid with dorsoventrally flattened body. 
Neurocranium in dorsoventral preservation about 



FIELDIANA: GEOLOGY, N.S., NO. 35, MARCH 31, 1997, PP. 1-24 



as wide as long; orbits facing dorsolaterad; nasal 
capsules prominently projecting from neurocrani- 
um anterolateral^ ; no or very short rostrum. 
Well-defined articular facets for attachment of pal- 
atoquadrates posterior to orbits. Meckel's cartilage 
slightly curved, rather sturdy. Ceratohyals about 
as large as Meckel's cartilages, articulate with tri- 
angular basihyal. Fairly large hyoid rays project- 
ing posteroventrad from hyoid elements, probably 
supporting opercular flaps as in other members of 
the order. 

Dentition teeth, probably 36 in number, rela- 
tively very large, consisting of sharp-cusped, 
probably backward-curved crowns and widely 
flaring bases; most likely forming single rows of 
functional teeth on biting edge of each jaw. 

Vertebral column consisting of paired neural 
arch cartilages, declining in height from neck re- 
gion to tail peduncle, and paired (as preserved) 
more or less rectangular cartilages, probably lo- 
cated ventrolateral to notochord. Number of ver- 
tebral elements approximately 50, exclusive of tail 
fin. 

Scapulocoracoid relatively wide at midlength, 
strongly curved forward at both ends as in other 
iniopterygians. A hemispherical joint boss for ar- 
ticulation of basipterygium of pectoral fin occurs 
a short distance from dorsal end. As in Iniopteryx 
rushlaui, basipterygial region of pectoral fin con- 
sisting of relatively large anterior cartilage and 
much smaller posterior element. Along anterior 
edge of larger plate is a joint pan for articulation 
with scapulocoracoid, and along posterior edge a 
strongly projecting joint knob for articulation with 
first strongly enlarged fin ray (in males, "rasp"). 
Rasp with sharp reduction in diameter in distal 
half, much as in Promexyele bairdi, but with rel- 
atively small number of hooks, about 18-20 per 
rasp, with the proximal 7 very much enlarged. 
About 11 distally very slender radials forming 
main supports of fin web. At trailing side of fin, 
four radials proximally fused to form a structure 
reminiscent of a deer antler. Similar proximal fu- 
sion of radials occurs by convergence in Squati- 
nactis, another Carboniferous form of batoid hab- 
itus (Lund & Zangerl, 1974). These fused radials 
and two or three adjacent ones are attached to the 
smaller basal plate. 

Pelvic girdle elements consisting of sturdy car- 
tilages, twice as wide distally as proximally, 
pierced by three or four foramina (perhaps zonal 
nerve canals). Distally attached are approximately 
triangular basipterygial plates of the pelvic 
"fins," each probably studded with some 25 te- 



nacular hooks (in life) consisting of stout, yet 
acutely pointed, strongly curved crowns and 
large, bulbous bases. Ten very short and robust 
radials and two or three slender ones constitute 
the pelvic fin complex. 

Pterygopodia enormously enlarged, consisting 
of two rhomboidal connecting links, followed by 
a very long clasper cartilage; the terminal struc- 
ture, not consisting of calcified cartilage (see be- 
low), is about half as long as the preceding clasper 
element and is provided with three barbs near its 
end. 

Dorsal fin consisting of series of about six fair- 
ly sturdy radials. 



Etymology 

cervus = deer; furca = fork. 

Cervifurca nasuta, sp. nov. 
Diagnosis 

Same as for genus. 

Etymology 

nasutus — (large) nosed. 

Holotype 

fmnh PF13228 (X-ray [XR]: B83-996) 6\ a 
partial, slightly disarticulated skeleton lacking the 
anterior end of the skull (Fig. 1). 

Horizon — Excello Shale (equivalents: black 
shale over coal IV A, Indiana; black shale over 
coal IV, Illinois), Carbondale Formation, Des- 
moines Series, Westphalian lower D, Pennsylva- 
nian. 

Locality — Bethel Quarry, excavated during 
1982-1983 by Rainer and Ann Zangerl with oc- 
casional help from colleagues, friends, and a few 
devoted amateur collectors. Strip-mine headwall, 
about center of NWV 4 of sec. 3, T3S, R7W (Au- 
gusta quadrangle), about 1 km SE of Bethel 
Church, Pike County, Indiana. 

Referred Specimens 

Horizon — Preserved in a fragment of a siderite 
concretion from a black shale above the Spring- 



FIELDIANA: GEOLOGY 




20 mm 



? V PS 



Fig. 1. Cervifurca nasuta. X-ray positive of the plate of the holotype fmnh PF13228 (XR: B83-996); the missing 
parts of the shoulder girdle and pectoral fin are on the counterplate. The radiograph shows shadows of structures not 
belonging to Cervifurca, such as L, "flag" denticles of Listracanthus hystrix; PGR, plaeoniscoid gastric residue mass; 
PS, a scatter of palaeoniscoid scales; and a background scatter of very large numbers of tiny cladodont denticles that 
are the topic of a separate account (Zangerl, 1995). 



field (no. 5) coal; Carbondale Fm., Desmoines Se- 
ries, Pennsylvanian. Locality — Fulton County, 
about 20 mi south of Galesburg, Illinois. The label 
mentions Fred R. Jelliff, Galesburg, Illinois, who 
may have been the collector. Specimen — Univer- 



sity of Illinois Museum of Natural History 
(uimnh) 1 1378 (Figs. 2, 3). Part of a three-dimen- 
sionally preserved, 6 specimen, consisting of part 
of the vertebral column, the pelvic fin complex, 
parts of both pterygopodia, and the dorsal fin. 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 




Fig. 2. Cervifurca nasuta, uimnh 11378, partial, mostly articulated skeleton preserved in a fragment of a large 
siderite concretion. 




Fig. 3. Drawing of the preserved parts of uimnh 1 1378. The pelvic area is somewhat distorted, probably because 
of the presence of a large coprolitic mass (cop). The question marks indicate very indistinctly outlined cartilages, 
probably the pelvic cartilages and the basal plate of the pelvic fin of the opposite side, ptp, long elements of the 
pterygopodia. 



FIELDIANA: GEOLOGY 



Horizon — Excello Shale (equivalent: black 
shale over coal IV A, Indiana) Carbondale Fm., 
Desmoines Series, Westphalian lower D, Penn- 
sylvanian. Locality — Barret Cemetery: Strip- 
mine headwall, NWV4, sec. 3, T3S, R7W (Augusta 
quadrangle), NW of Barret Cemetery, Pike Coun- 
ty, Indiana. Specimens — fmnh PF6455 (XR: Bar- 
ret no. 1 1 ), fair 8 specimen including dorsoven- 
trally preserved braincase and some visceral ele- 
ments. Collected 1970, by Field Museum party. 
fmnh PF6456 (XR: Barret no. 7), disarticulated, 
partial 8 skeleton. Collected 1970 by Field Mu- 
seum party. 

Locality — Bethel Church: Strip-mine headwall, 
about center of NW% of sec. 3, T3S, R7W (Au- 
gusta quadrangle), about 1 km SE of Bethel 
Church, Pike County, Indiana. Specimen — fmnh 
PF6618 (XR: Bethel no. 51), chewed, disarticu- 
lated partial 8 specimen. Collected 1970 by Field 
Museum party. 

Locality — Bethel Quarry, worked during 
1982-1983 at the site of Field Museum of Natural 
History's Bethel Church locality (see above). 
Specimens— fmnh PF 13229 (XR: B83-133C), 
somewhat disturbed, partial 8 skeleton, fmnh 
PF13230 (XR: B83-135), good, partial 8 skele- 
ton, fmnh PF13231 (B82-384), isolated neuro- 
cranium. fmnh PF13232 (XR: B83-483), incom- 
pletely recovered 8 skeleton, partial vertebral col- 
umn, partial pelvic complex, fmnh PF 13233 (XR: 
B82-240), isolated neurocranium. fmnh PF13234 
(XR: B83-510), incompletely recovered 8 skele- 
ton, partial pectoral fin, partial pterygopodium. 
fmnh PF13235 (B82-561), isolated neurocranium. 
fmnh PF13236 (XR: B83-554), mutilated, incom- 
plete skeleton, fmnh PF13237 (XR: B83-136), 
somewhat disturbed, partial 8 skeleton, fmnh 
PF13238 (XR: B83-1039), badly disturbed, partial 
8 skeleton. 

Horizon — Mecca Quarry Shale, black shale 
over coal III A (Indiana) = Colchester No. 2 (Il- 
linois), Carbondale Fm., Desmoines Series, West- 
phalian upper C, Pennsylvanian. Locality — Chi- 
nook Mine, Ayrshire Colliery, south of Staunton, 
Clay County, Indiana. Specimen — fmnh PF5874 
(XR: Chinook no. 1), disarticulated, partial 8 
skeleton. Collected by Field Museum party. 

Remarks — All specimens other than uimnh 
11378 show the effects of predation (Zangerl & 
Richardson, 1963) as well as some bacterial de- 
composition, the latter affecting especially skele- 
tal elements that had been injured by the predator. 
The remains preserved in the black, sheety Ex- 
cello Shale from the Bethel Church and Barret 



Cemetery localities are covered with an extremely 
thin, smooth, and glossy film of pyrite, and hence 
show excellent surface detail and furnish unusu- 
ally good X-ray pictures. 

It may be noted from the specimen list that all 
remains (other than the isolated neurocrania, for 
which the sex cannot be determined) belong to 
males. Female iniopterygians (of all species) are 
extremely rare in the present collections, and the 
one relatively well-preserved female skeleton, 
fmnh field no. B83-942, from the Bethel Quarry, 
is a sibyrhynchid probably belonging to an as yet 
undescribed species. 



Description 

Neurocranium and Visceral Skeleton — 
Three isolated neurocrania, PF13231, PF13233 
(Figs. 4, 5), PF13235, and two associated with 
partial skeletons, PF13236 and PF6455, are all 
preserved in a dorsoventral burial position. As 
preserved they resemble somewhat the skull of 
Helodus simplex as depicted by C. Patterson 
(1965), but closer study shows beyond question 
that the similarity is superficial: the paired, large 
openings at midlength of the holostylic neuro- 
cranium of Helodus are cranioquadrate passages, 
whereas they are the orbits in the (iniopterygid) 
autodiastylic (deBeer, 1937, p. 422, PI. 142) Cer- 
vifurca skulls. 

A better understanding of the Cervifurca brain- 
case is gained by comparison with the neurocra- 
nium of a modern batoid such as Raja where the 
eyes look out from the dorsal surface of the flat- 
tened head. In Raja the orbits are delimited by 
cartilage only medially and anteriorly, where large 
anterolateral projections enclosing the nasal cap- 
sules jut out. This condition is depicted on the 
right side of Figure 6; on the left side the basic 
Raja pattern is shown as modified in Cervifurca, 
where the orbits are delimited all around by car- 
tilage, and the nasal capsules are in a position 
comparable to that in Raja. In contrast to other 
iniopterygians, the orbits of Cervifurca lack a dor- 
sal cartilage roof, hence the suggestion that the 
eyes faced dorsolaterad, as in batoids. 

Another profound difference between the neu- 
rocrania of Helodus and Cervifurca is the location 
of articular facets for the visceral skeleton. In the 
holostylic Helodus, joint facets for Meckel's car- 
tilages are located anterior and ventral to the or- 
bits and well forward of the cranioquadrate pas- 
sages, whereas in Cervifurca, the joint facets for 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 




Fig. 4. Isolated neurocranium (plate only) of Cervifurca nasuta, PF13233 (B82-240) in dorsoventral burial po- 
sition; X-ray enlargement. The diagonal shadow across the right orbit is a thickness boundary of the shale slab. The 
irregular black areas are cartilage pieces that have broken loose from the counterplate. Extraneous shadows in the 
background belong to palaeoniscoid scales and tiny cladodontid denticles (see note with Fig. 1). X-ray courtesy of 
John D. Knight, Rockville, Indiana. 



the palatoquadrates are situated behind the orbits 
and lateral to the otic capsules (Figs. 5c,d). 

The dorsoventrally preserved neurocrania de- 
scribed above (Figs. 4, 5) are clearly flattened into 
a near two-dimensional state. In Figure 7 I have 
tried to visualize, in principle, the original form 
of the braincase (using modern batoid neurocrania 
for comparison) as depicted in three cross sec- 
tions: across the antorbital region, across the or- 
bits, and across the postorbital region. The cross 
sections, which are, of course, hypothetical, also 



indicate the presumed relationship of the palato- 
quadrates to the neurocranium. In Figure 7B the 
orbits face dorsad and slightly laterad. 

The visceral skeleton is incompletely preserved 
in all specimens. A palatoquadrate could be ten- 
tatively identified only in PF13236 (Fig. 8), where 
a cartilage of the right size and believable outline 
lies next to the braincase and close to a Meckel's 
cartilage. The outline of this element on the X-ray 
film is obscured both fore and aft by skeletal de- 
bris, and its overall form cannot be determined 



FIELDIANA: GEOLOGY 





20mm 




Fig. 5. Neurocranial outlines of Cervifurca nasuta, dorsoventral burial position, a, b, Plate and counterplate of 
PF13233 (B82-240), see Fig. 4; c, d, plate and counterplate of PF13235 (B82-561). Drawings made from the spec- 
imens with the drawing tube of a Wild binocular microscope, afpq, articular facet for the palatoquadrate; nc, nasal 
capsule; o, orbit; ?oc, otic capsule. 



satisfactorily. The outline of the palatoquadrate in 
the lateral view of the skull (Fig. 7) is a hypo- 
thetical interpretation of what the element de- 
scribed above might have looked like. 

Meckel's cartilages are present in PF6455 (Fig. 
13), PF13229, PF13230 (Fig. 9), and PF13236. 
They are elements of simple form, slightly S- 
shaped in dorsoventral aspect; concave articular 
facets are visible at the posterior ends (Fig. 13). 
Anteriorly, several specimens show on X-ray film 
indications of surfaces that probably represent the 
symphysial contacts of right and left elements. 

Dentition — As may be gathered from the de- 
scription of the condition of preservation of the 
jaws, the dentition teeth are not located in situ 
with the jaws in any of the specimens. Neverthe- 
less, some assumptions concerning the dentition 
can be made with some confidence. 

The dentition of Cervifurca nasuta consists of 
a number of relatively large functional teeth (Figs. 



1 If— j), presumably arranged in single rows along 
the crests of the jaws. Smaller teeth (Figs. 11k- 
q) of similar morphology, but less than half the 
size, are intermingled with the larger teeth, and 
probably represent posterior teeth. In addition, 
there are minute teeth (faintly visible on radio- 
graphs) that most likely are mucous membrane 
denticles (Fig. 12). A total of 35 large and smaller 
teeth are preserved in PF 13230 (Fig. 9); in 
PF6455 there are about 34 teeth. If all of these 
had been functional at the time of death, the den- 
tition would have consisted of eight or nine teeth 
along the biting edge of each jaw quadrant, an 
assumption depicted in Figure 7C. 

The dentition teeth (Figs. 1 If— q) are single 
cusped and provided with extraordinarily large 
bases. The crowns consist of dentine, probably or- 
thodentine (to judge from its appearance on bro- 
ken cusps), surrounding open pulp cavities. A su- 
perficial layer of vitrodentine was not observed 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 




Fig. 6. Outline of the skull of Raja, after Gegenbaur 
(1872, PI. 13, Fig. 1). The left half of the outline is 
modified to reflect the condition in Cervifurca. o, orbit. 



and may have been dissolved after burial. The 
crown cusps are acutely pointed and curved (pre- 
sumably backward) and are of differing lengths, 
probably depending on their position on the jaw. 
The crowns sit on top of asymmetrically conical 
bases (Figs, llk-q), which are strongly flaring. In 
(presumably) older but not much larger individ- 
uals, the bases of these teeth are enormously ex- 
panded in the form of fingerlike projections, so 
that their diameters may reach as much as eight 
times the largest diameters of the crowns. 

None of the specimens show mouth plates (= 
aggregations of basally fused mucous membrane 
denticles) homologous to those in Promexyele and 
the sibyrhynchids; the lining of the mouth cavity 
may, however, have been studded with tiny den- 
ticles, present in large numbers in front of the 
head region of PF13229. These very small den- 
ticles (200-400 u,m base diameter) have bases of 
oval or irregular outline and low, stout crowns 
(Fig. 12). 

Hyoid Arch and Branchialia — These struc- 
tures have not yet been described for the Iniop- 



terygidae; the little that is known pertains to spe- 
cies of the Sibyrhynchidae. Cartilages of the hy- 
oid arch and the branchial basket are seen in sev- 
eral specimens of Cervifurca, but they are not in 
articulation and are frequently obscured on X-ray 
pictures by parts of the neurocranium, the scapu- 
locoracoids, and other elements. In PF6455, how- 
ever, some parts of this complex lie behind the 
two lower jaws, and in front of the nasal projec- 
tions on the neurocranium (Fig. 13). An unpaired 
triangular element has joint facets at the postero- 
lateral corners, but none in front. This clearly un- 
paired element may thus be the basihyal. To either 
side and behind it are elongated cartilages of 
about the same size as the lower jaws; they have 
joint facets in front and taper almost to points at 
the opposite ends. The left one in Figure 13 is 
almost in articulation with the triangular cartilage 
identified as the basihyal. The position of these 
cartilages in this specimen suggests that they ar- 
ticulated in life with the unpaired element be- 
tween them, and thus represent the ceratohyals. If 
this interpretation is correct, both the basihyal and 
the ceratohyals differ considerably in form from 
those of the Sibyrhynchidae (see Zangerl & Case, 
1973, Figs. 46, 72, 73; Zangerl, 1981, Fig. 30). 
The absence of posterodorsal joint facets on the 
presumed ceratohyals may indicate the lack of 
calcification at those ends. Behind these probable 
hyoid elements are a number of very narrow strips 
of cartilage that are perhaps ceratobranchials (Fig. 
13). These are pointed at both ends, which may 
indicate that some uncalcified cartilage was as- 
sociated with them. A search for basibranchial el- 
ements among the present specimens was nega- 
tive. 

Since the original description of members of 
the order Iniopterygida (Zangerl & Case, 1973) 
several specimens have come to light that show 
beyond question that the scapulocoracoids not 
only extend far forward ventrally, but actually ar- 
ticulate by means of ball-and-socket joints with 
what I assume to have been the posteriormost ba- 
sibranchials (Zangerl, 1981, Fig. 30). None of the 
Cervifurca specimens show this connection, but 
the ventral, forward-reaching end of the scapulo- 
coracoid is very much elongated and probably 
had the same relationship to the last basibranchial 
as in Sibyrhynchus. 

The morphology of the ventral visceral arch el- 
ements, as presently understood, is illustrated for 
Cervifurca in Figure 14. Hyoid rays that probably 
supported opercular flaps, as in extant chimae- 
roids, are seen in several specimens, for example, 



FIELDIANA: GEOLOGY 




Fig. 7. A, Outline of neurocranium of Cervifurca nasuta in dorsoventral burial position. B, Position of hypo- 
thetical sections x, y, and z. C, Attempt at reconstruction of the skull in lateral view. The form of the palatoquadrate 
is almost entirely conjectural, o, orbit; pq, palatoquadrate; sc, scapulocoracoid. 



PF13230 (Fig. 10) and PF13237. They are fairly 
sturdy — a little more than 1 mm in width as pre- 
served — and there appear to be about nine rays 
on each side. 

Vertebral Column — The vertebral column is 
most completely preserved in the holotype, 
PF13228, but it is not entirely intact (Figs. 1, 15). 
It consists of paired neural arches and paired ven- 
tral cartilage pieces that may have formed within 
the notochordal territory, or ventrolateral to it in 
the notochordal sheath. 

The precise number of vertebrae cannot be de- 
termined, but a fairly close estimate is possible, 
as follows: there are about 18 prepelvic vertebrae, 
of which the anteriormost 6 may be cervical. Of 
the postpelvic vertebrae, about 14 reach back to 
the dorsal fin; another 10 or more may have 
formed the tail peduncle. The total number of ver- 
tebrae (minus those supporting the tail fin) may 
have been around 50. 

The cervical vertebrae differ from those farther 
back in that the neural arch pieces are longer, have 
enlarged ventral ends, and the neural arches show, 
in lateral aspect, bulges and constrictions (Fig. 
15). The subrectangular ventral cartilages are lon- 
ger than those farther back, indicating that these 



vertebrae were longer as well as taller than the 
thoracic ones. Behind the cervical series the neu- 
ral arches gradually diminish in height and the 
individual arch pieces are of very simple form, 
widest ventrally and tapering to a point dorsally. 
This region of the column is preserved in the con- 
cretion specimen uimnh 11378 (Figs. 2, 3), and 
this specimen shows the right and left neural arch 
elements almost in perfect preburial configura- 
tion — only the slightly diverging dorsal tips show 
that these cartilages are paired. 

Shoulder Girdle and Pectoral Fin — As in all 
other iniopterygians the shoulder girdle cartilages 
differ from the scapulocoracoids of elasmo- 
branchs where the right and left coracoidal por- 
tions meet in a midventral symphysis; in the in- 
iopterygians the ventral halves of the shoulder gir- 
dle cartilages are strongly projected forward (Zan- 
gerl & Case, 1973, Fig. 36) and end in joint pans 
that articulate with paired joint bosses on the sec- 
ond basibranchial element (e.g., in Sibyrhynchus, 
Zangerl, 1981, Fig. 30). 

None of the shoulder girdle cartilages in any of 
the available specimens of Cervifurca is pre- 
served in its entirety and without injury; hence no 
detailed description of this structure can be given. 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 





, 20mm , 




Fig. 8. Radiograph tracings of plate and counterplate of Cervifurca nasuta, PF13236 (XR: B83-554). be, basal 
cartilage of pectoral fin; Mc, Meckel's cartilage; o, orbit; pe, pelvic element; ?pq, very probably the palatoquadrate — 
its outline fore and aft is not well defined; sc, scapulocoracoid; tep, terminal element of the pterygopodium. 



The shoulder girdle cartilage is rather wide at 
midlength, and in PF 13228 one of them is pre- 
served in articulation with the basal cartilage of 
the pectoral fin (Fig. 1). In all iniopterygians the 
joint boss is located on the posterolateral edge of 
the dorsal half of the scapulocoracoid and artic- 
ulates with the joint pan on the anteromedial side 
of the basal cartilage of the pectoral fin. 

The basal cartilage bears a pronounced joint 
boss at its anterolateral corner; this prominent 
boss articulates by means of a well-developed 
joint pan on the much enlarged first fin ray, the 
rasp, of the pectoral fin of the males (Fig. 16). 
Behind the joint boss the lateral edge of the basal 
cartilage is irregularly concave and shows attach- 
ment facets for about eight fin rays. As in Iniop- 
teryx rushlaui, where the last four pectoral radials 
are attached to a small second basal cartilage 
(Zangerl & Case, 1973, Fig. 22), there is a second 
basal cartilage in Cervifurca that bears three ra- 



dials and the "antler" complex at the trailing side 
of the fin (Figs. 1, 16B). 

The pectoral fin web is relatively large, being 
supported, in males, by an enlarged first radial 
(rasp), about 11 fairly slender radials, and the 
"antler" complex Figs. 1, 16B, 21, 22). The ball- 
and-socket joint between the basal cartilage and 
the rasp is so prominent that there is the possibil- 
ity that the rasp was not included in the fin web 
and may have been capable of independent move- 
ment. Cervifurca has the most extensive pectoral 
fin web of all presently known iniopterygians, if 
the above interpretation of the number of radials 
is correct. 

The rasp is relatively thick in its proximal half, 
then tapers to a long, slender distal portion (Fig. 
16A). Its shape is thus similar to that of the rasp 
of Promexyele bairdi (Zangerl & Case, 1973, 
Figs. 40, 41), but it differs much from the latter 
by the form, size, and number of the hooks. In 



10 



FIELDIANA: GEOLOGY 







1 "•£ ' 



40. mm 






Fig. 9. Cervifurca nasuta, PF13230 (XR: B83-135); X-ray positive of plate. This specimen shows a large portion 
of the dentition but it is not possible to determine to which jaw the longitudinal rows of teeth belong, dt, dentition 
teeth; Mc, Meckel's cartilage; P, palaeoniscoid element. 



Cervifurca, as in Iniopteryx rushlaui, there are 
about 10 hooks in but a single row. The hooks on 
the proximal half of the rasp are very large (Figs. 
lie, 16, 17e-i, 18A-C), and consist of sharply 
pointed, rather stout crowns and enormously ex- 
panded bases that may measure as much as 6 mm 
in length and 2 mm in width. The total height of 
these denticles (tip of crown to bottom of base) 



may measure more than 2 mm. The bases grew 
both proximad and distad in the form of finger- 
shaped projections (Figs, lie, 17, 18) that fused 
to form a large platform. Broken crowns of these 
rasp hooks show a thick layer of dentine (proba- 
bly orthodentine) surrounding a rather narrow, 
open pulp cavity (Fig. 18). The base consists of 
trabecular dentine. The hooks diminish in size 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 



11 




hr 







lv 



40mm 

1 



%£ 




12 



FIELDIANA: GEOLOGY 




Fig. 1 1. Outline of dentition teeth, and tenacular and rasp hooks of Cervifurca nasuta. a, b, Tenacular hooks; c, 
large rasp hook of PF13228 (XR: B83-996). d, e, Tenacular hooks; f, dentition tooth of PF13237 (XR: B83-136). g- 
j, Dentition teeth of PF13230 (XR: B83-135). k-q, dentition teeth of PF13229 (XR: B83-133C). The drawings are 
tracings from X-ray films, using a Wild binocular microscope drawing tube. 



where the rasp cartilage tapers to a thin rod (Fig. 
16), and the most distal hooks measure about 1 
mm in base length. 

Pelvic Cartilages, Pelvic Fins, Pterygopo- 
dia — The pelvic cartilages of Cervifurca have a 
characteristic shape that is easy to identify on 
X-ray films (Figs. 1, 16C): a proximal, more or less 
parallel-sided shaft is distally expanded to about 
\Vi times the shaft diameter, and where the element 
expands in width there are several (often four) fo- 
ramina that may have allowed the passage of zonal 
nerves and perhaps blood vessels (Fig. 16C). 

The pelvic fin of this species is unique among 
presently known iniopterygians. It consists of a 
triangular basal cartilage (Fig. 16C) that probably 
carried a battery of tenacular hooks, and has, 
along its lateral border, attachment facets for 10 



radials, all short and stout except for the first and 
two slender ones at the posterior end of the fin 
(Figs. 2, 3, 16C, 21, 22). The radials of this pelvic 
fin complex are so short and stout that it seems 
unlikely that they supported a fin membrane, and 
that the structure as a whole functioned as a fin. 
It seems possible that the sturdy radials were stiff 
in life and may have been used for crawling or 
some other activity not related to swimming. 

Ceratotrichia, present in the pelvic fins of In- 
iopteryx rushlaui, could not be found in any spec- 
imen of Cervifurca, including the concretion 
specimen uimnh 11378. 

Cervifurca has a large number of tenacular 
hooks that are highly characteristic in form (Figs. 
11, 17, 18, 20, 21). The numbers range from ap- 
proximately 36 (= 18 pairs in PF 13237) to ap- 



FiG. 10. Cervifurca nasuta, PF13230 (XR: B83-135); X-ray positive of counterplate. This shows the hyoid rays 
(hr). The skull is badly mutilated. 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 



13 





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1 


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1 

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5mm 















jtf 


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Fig. 12. X-ray positive of anterior end of specimen PF13229 (XR: B83-133C) showing a large number of minute 
denticles of the general form of the dentition teeth of Cervifurca nasuta. They might be mucous membrane denticles 
of the mouth cavity. 



proximately 44 (= 22 pairs in PF13228) to ap- 
proximately 50 (= 25 pairs in PF13230). The 
crown of these denticles extends from one end of 
the base (probably the forward end), and curves 
(? backward) over the base so that the apex in 
many cases is above the midlength point of the 
base (Figs. 11, 17, 18); more rarely the base is 
elongated and the crown reaches only a short dis- 
tance over the base. The crowns are circular to 
slightly oval in cross section and vary somewhat 
in size relative to the bases (Figs. 17, 18). The 
base exhibits a number of highly characteristic 
features. It has lateral and basal bulges and often 
a rather pronounced ridge that runs clear around 
the base just below the crown — base junction 
(Figs. 11, 17, 18). In any given specimen the te- 
nacular hooks tend to be fairly uniform in size, 
but smaller hooks are present in PF 13229 and 
PF13230 (Figs. 17, 18). I assume that these den- 
ticles were borne on the basal cartilages of the 
pelvic fins because there is no evidence of sepa- 
rate tenacula. 

The pterygopodium (Figs. 1-3, 16C, 19-21) is 
of enormous size relative to the size of the fish. 



It is more than three times the length of the neu- 
rocranium and consists of three cartilaginous el- 
ements (Figs. 16C, 21) and an elongated barbed, 
terminal one that consists of a tissue other than 
calcified cartilage (Fig. 19). Of the calcified car- 
tilage elements two proximal pieces are short and 
of rhombic outline (as preserved), and a third is 
a very long rod about \Vi times the length of the 
braincase. The calcification of these elements con- 
sists of fine-grained "prisms" (Fig. 20) that give 
these structures a characteristic appearance on 
X-ray film. As preserved, all described pieces are 
flat, but in life they were no doubt more or less 
circular in cross section, surrounding a canal for 
the transmission of seminal fluid. The terminal el- 
ement is preserved only in one specimen, 
PF13236, where it is not associated with the other 
pterygopodial structures (Fig. 8). However, its ap- 
pearance on X-ray film matches terminal clasper 
elements observed, for example, in Sibyrhynchus 
denisoni (fmnh B83-961 and B83-811) from the 
Bethel Quarry, where these structures are pre- 
served in situ. Along one side and near the end 
of this terminal clasper piece are three serrations 



14 



FIELDIANA: GEOLOGY 




Fig. 13. Visceral cartilages of Cervifurca nasuta, PF6455, traced from an X-ray enlargement, bh, basihyal; ch, 
ceratohyal; Mc, Meckel's cartilage. At bottom front end of neurocranium. 



or barbs (Fig. 19). This element is preserved in 
the form of a carbonaceous film. Because uncal- 
cified cartilage is not preserved in the black shales 
containing this fauna, it may be assumed that the 
structure in question consisted of some other, per- 
haps ceratinous, tissue. 

Unpaired Fins — The dorsal fin, located some 
distance behind the position of the pelvic fins, is 
preserved in situ in the concretion specimen 
uimnh 11378 (Figs. 2, 3), and in disarticulated 
state in PF13228 (Fig. 15). In uimnh 11378, the 
dorsal fin consists of eight radials that are pointed 
ventrally; dorsally they end abruptly, as if cut by 
shears. The radials of PF13228 have exactly the 
same shapes, suggesting that the dorsal tips re- 
mained uncalcified. 

The tail fin is missing in all specimens available 
at present. 

Reconstruction — The reconstruction draw- 
ings, Figure 21 in ventral view and Figure 22 in 
lateral view, are based on all available specimens, 
but of course primarily on the most completely 
preserved skeletons, and on uimnh 11378. Over- 
all, I believe, the drawings correctly represent the 
skeletal morphology of this animal, but because 
not every detail is actually documented in a spec- 



imen (e.g., the placement of the tenacular hooks, 
or the exact number of radials in the pectoral fin), 
future revisions may well be required. 



Discussion 

The skeleton of Cervifurca nasuta conforms 
perfectly to the morphotype (sensu Kalin, 1945) 
of the family Iniopterygidae in that its jaw sus- 
pension is autodiastylic — that is, the palatoquad- 
rate is attached to the neurocranium by a joint 
(Stahl, 1980) — and the dentition teeth do not fuse 
to form tooth whorls across the jaws. The roof 
and floor of the mouth cavity are free of charac- 
teristically shaped armor plates, the products of 
fusion of large numbers of mucous membrane 
denticles, present in the members of the family 
Sibyrhynchidae, and in orimental development 
perhaps seen in Promexyele peyeri among the In- 
iopterygidae. (Oriment, from oriri = to rise, is a 
term proposed by Othenio Abel (1914) for a struc- 
ture in early phylogenetic development, in con- 
trast to rudiment, which is consistently used in the 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 



15 




Fig. 14. Tentative reconstruction of ventral visceral 
elements, bb I and II, basibranchials I and II (not yet 
observed in this taxon); bh, basihyal; cbr I-V, cerato- 
branchials I-V; ch, ceratohyal; Mc, Meckel's cartilage; 
sc, scapulocoracoid. 



German literature for a phylogenetically vanish- 
ing structure.) 

Cervifurca nasuta differs, however, from all 
other presently known members of the order by 
its dorsoventrally flattened body shape, most 
strikingly apparent in the character of the brain- 



case with orbits that suggest dorsolaterad-directed 
eyes, as in modern batoids; in all other species of 
iniopterygians where the skull is known, the or- 
bits are roofed over by cartilage, thus restricting 
upward viewing. Also, a dorsoventral burial po- 
sition occurs in every specimen where the neu- 
rocranium is preserved more or less intact. A ba- 
toid habitus is further suggested by the large pec- 
toral fin web, modified pelvic fins that could hard- 
ly have been used in swimming, and the 
enormously enhanced pterygopodia. It may thus 
be concluded that Cervifurca nasuta was an in- 
habitant of the benthic realm (though probably not 
at great depth), a member of the mobile benthos. 

Dentition — The dentition as depicted in Figure 
7C looks rather formidable. However, what is 
missing in that illustration are the soft tissues, the 
submucosa and the mucosa. In life these soft tis- 
sues covered the large tooth bases entirely, so that 
only the tooth crowns were visible and came into 
contact with prey. The largest diameters of the 
crowns, in the largest teeth, are only about 1 mm, 
and their length was not much greater. The den- 
tition therefore, was not as impressive as Figure 
7C would suggest, but it was no doubt quite ef- 
fective in holding and piercing struggling prey. 

The question arises: why the large tooth bases? 
In the two other genera of the family, the dentition 
teeth are minute in Iniopteryx, and are small, tri- 
cuspid denticles with small bases in Promexyele. 
In the Sibyrhynchidae, where the bases of entire 
tooth families are fused to form tooth whorls, the 
volume of the combined base may exceed many 
times that of the tooth crowns (Zangerl & Case 
1973, Figs. 47i' and 47i"). 

The tooth base serves, in chondrichthyans, to 
anchor the tooth by means of numerous collagen 
fiber bundles within the submucosa and the peri- 
chondrial membrane of the jaw skeleton. A large 
tooth base, therefore, affords a much firmer at- 
tachment of the tooth to the jaw than a small base. 



% f^C 




40 mm 



Fig. 15. Tracing of vertebral column of Cervifurca nasuta, PF13228 (XR: B83-996) from X-ray enlargement. 
Cervical vertebrae to the left. See also Figure 1 . 



16 



FIELDIANA: GEOLOGY 






-^ ^^ 



62? 

\ 

Fig. 16. X-ray shadow tracings, Cervifurca nasuta, PF13228 (XR: B83-996). A, Rasps with broken distal sections 
reassembled. B, Right pectoral fin as preserved. C, Pelvic area with one of the pelvic fins and proximal elements of 
one of the pterygopodia as preserved. D, Pelvic fin reassembled, be, basal cartilage of pectoral fin; pe, pelvic cartilage; 
pef, pelvic fin; ptp, (part of) pterygopodium; r, rasp; sc, scapulocoracoid. 



This, however, is not the whole explanation. Spec- 
imen PF13229 is about % the size of PF13230, 
but the tooth bases of PF13229 are only about Vi 
the diameter of those of PF 13230, whereas the 



basal diameters of the tooth crowns are about the 
same in both specimens. Because both sets of 
teeth appear to have been functional at the time 
of death, the tooth bases of the larger individual 




Fig. 17. Outline drawings of rasp and tenacular hooks of PF13230 (B83-135), showing variation in form and 
size, a-d, tenacular hooks; e-i, rasp hooks. 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 



17 




, 1mm i 

Fig. 18. Rasp and tenacular hooks rendered from specimens of Cervifurca nasuta with the aid of a Wild binocular 
microscope drawing tube. A, Large, proximal rasp hooks, PF13238 (B83-1039); B, C, large and small rasp hooks of 
PF13229 (B83-133C), one of them showing pulp cavity; D, tenacular hook of PF13238 (B83-1039); E, tenacular 
hooks of PF 13229 (B83-133C). 



18 



FIELDIANA: GEOLOGY 




Fig. 19. X-ray negative enlargement of the terminal segment of the pterygopodium of Cervifurca nasuta, PF1 3236 
(XR: B83-554), which does not consist of calcified cartilage. Shadows of unrelated structures: Pp, dermal denticle 
of Petrodus patelliformis; cs, ?pectoral fin cartilage, and below it near edge of picture, a compound dermal denticle 
of a caseodontid shark; in background miscellaneous debris and large numbers of tiny cladodont denticles (see caption 
of Fig. 1). 



must have continued to grow to twice the diam- 
eter of those of the smaller specimen while in 
functional state. 

This speaks for a rather slow rate of tooth re- 
placement, even though the tooth crowns show no 
wear facets. These observations suggest that the 
large size of the tooth bases has little to do with 
requirements for strong attachment but is the re- 
sult of continued sclerotization past the functional 
need for tooth stabilization. Cervifurca nasuta 
most likely preyed on soft-bodied invertebrates 
and immature fishes. 

The above explanation of continued growth of 
tooth bases past the point of secure fastening of 
these structures to the substrate may apply as well 
to the specialized dermal denticles of the rasp and 
the tenacular hooks. These organs also have large 
bases, and those of the proximal rasp hooks, in 
particular, show finger-shaped projections both 
fore and aft, indicating continuing growth in both 
directions (Fig. 18). 

Pterygopodia — The pterygopodia of iniopte- 
rygians are structurally simple organs that consist 
of a variously jointed cylinder containing a lumen 
for the transmission of sperm. The segments con- 



sist of a finely granular calcified cartilage, but in 
at least one species the terminal section is either 
sheathed in dentine or perhaps bone (Iniopera 
richardsoni), or consists of a substance other than 
cartilage, perhaps a ceratinous tissue {Sibyrhyn- 
chus denisoni, Cervifurca nasuta, and three as yet 
undescribed sibyrhynchids) that tends to be pre- 
served as a carbonaceous film. 

There are no characteristic familial or generic 
patterns to the pterygopodia; instead, the details 
of clasper organization, including the secondary 
sexual features, tenacular and rasp hooks, are typ- 
ical for each species. The evolution of species- 
specific copulatory organs parallels a more com- 
mon phenomenon in closely related insects, where 
it is thought to discourage or prevent hybridiza- 
tion. 

Numerical Disparity Between the Sexes — As 
was pointed out earlier (p. 5), no female speci- 
mens of Cervifurca have been identified, and this 
is not solely due to the fact that partial and mu- 
tilated specimens lacking pterygopodia, rasp, and 
tenacular hooks cannot be recognized as females, 
let alone (if they also lack dentition teeth) as fe- 
males of a particular species. The present collec- 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 



19 




Fig. 20. X-ray positive enlargement of long pterygopodial segment of PF 13228 (B83-996) to show the charac- 
teristic texture of the calcified cartilage "prisms" of these structures. 



tions, indeed, contain very few adequately com- 
plete and well-preserved skeletons of iniopteryg- 
ians that lack the mentioned characteristic male 
sex organs, and are hence unquestionable females. 
One such specimen (fmnh field no. B 83-942) 
shows that the pelvic skeleton differs greatly, as 
should be expected, from those of males. Because 
adequately preserved female specimens are very 
rare it has not been possible, except in Iniopteryx 
rushlaui, to assign them to described species. 

The great numerical disparity between the sex- 
es of all iniopterygian taxa in the present collec- 
tions is real, rather than the result of our inability 
to recognize females among incomplete or poorly 
preserved specimens. The disparity existed in the 
burial environment that produced the black shales, 
and this raises the question why the females failed 
to be attracted to this unstable and no doubt hos- 
tile environment. 

A discussion of this question requires a state- 
ment concerning the broader problems of where 
the fishes entombed in the black shales came 



from. Zangerl and Richardson (1963) reached the 
conclusion that the burial environment could not 
have been the normal habitat of any of the fishes 
of the Mecca fauna, for reasons that are briefly 
summarized below. 

There is much important evidence that the 
black carbonaceous Mecca and Logan Quarry 
shales, and similar shales at other stratigraphic 
levels, including the Excello Shale, were formed 
on freshly leveled coal-forest surfaces, shallowly 
inundated during marine transgressions. These 
marginal basin environments became covered by 
floating vegetation (flotants) that produced large 
quantities of black muds beneath them. Holm et 
al. (1969) published measurements of modern flo- 
tant productivity of more than 30 cm of organic 
mud per year beneath a floating mat of water hy- 
acinth (Eichhornia crassipes (Mart.) Solms). The 
Pennsylvanian flotant (which probably was algal 
in composition) eliminated wave disturbance of 
the bottom mud, and the interstitial water of the 
mud was highly charged with hydrogen sulfide, 



20 



FTELDIANA: GEOLOGY 




Fig. 21. Reconstruction of the skeleton of Cervifurca nasuta, in ventral view. 



toxic to all forms of infauna, but an ideal envi- 
ronment for bacteria and other decomposers. Be- 
cause of the unusually rapid deposition of organic 
debris, the mud environment was very favorable 
for the preservation of fish skeletons, including 
the calcified cartilage of chondrichthyans. For ev- 
idence supporting the above conditions and a de- 
tailed analysis of the paleoecological parameters 
of the black shales, see Zangerl and Richardson 
(1963); Coveney and Glascock (1989) corrobo- 
rated many of the findings of Zangerl and Rich- 
ardson using entirely different evidence. 

Given the stated aspects of the black shale de- 
positional environment, one must conclude that 
the animals entombed in the shales were not reg- 



ular inhabitants of those environments, but rather 
were visitors from the deeper, more central parts 
of the basins that entered these marginal areas. 
There many, perhaps most, of the invaders be- 
came entrapped in residual ponds and succumbed 
to predation and injuries inflicted by predators 
(Zangerl & Richardson, 1963). 

There is, however, some evidence that not all 
of the fishes preserved in the black shales were 
inhabitants of the epicontinental waters of the 
central North American basin complex. The pres- 
ence of teeth of such sharks as Cobelodus aculea- 
tus (Cope), Stethacanthus altonensis (St. John and 
Worthen), and Phoebodus sp. in the wash residues 
of central United States Pennsylvanian carbonates 



ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 



21 




Fig. 22. Reconstruction of the skeleton of Cervifurca nasuta, in lateral aspect. 



and drab shales suggests that these taxa inhabited 
the epicontinental marine basins and were widely 
distributed within them (Tway & Zidek, 1982, 
1983a,b; Hansen, 1986). But remains of the most 
conspicuous and very abundant elements of the 
Mecca fauna, namely the iniopterygians, are miss- 
ing in the mentioned wash residues. 

The depositional history of the Pennsylvanian 
rock sequence of the structural Illinois basin, for 
example, includes numerous transgressions of ma- 
rine waters over a large, shallow, subsiding epi- 
continental pan. These transgressions inundated 
and destroyed the coal forests that grew on the 
low and swampy lands adjacent to the deeper 
parts of the pan. The muds that accumulated on 
the former forest floor beneath mats of floating 
vegetation, and which have become the black car- 
bonaceous shales, represent the initial conse- 
quences of some of the periodic transgressions. 

It is thus entirely possible that the iniopteryg- 
ians and some other cartilaginous fishes in the 
Mecca fauna (e.g., the caseodontoid and edestoid 
eugeneodontids) entered the epicontinental waters 
from deeper, oceanic realms during episodes of 
transgressive inundation, and were not denizens 
of the shallow basin provinces, but were members 
of the oceanic fish community of that time. 

Smith et al. (1994) compiled a most interesting 
set of 3 1 paleogeographic maps of the world from 
the Pliocene back to the Early Triassic showing 
the changing configuration of the land masses and 
the paleocoastlines. The Early Triassic map shows 
Pangaea with North America plus Greenland 
tightly joined to Africa and South America, 
which, in the aftermath of a major (Permian) gla- 



ciation, means that the landmasses stood high rel- 
ative to mean sea level. In Pennsylvanian (e.g., 
Desmoinesian) time, by contrast, marine waters 
transgressed repeatedly over much of the lower 
North American continental area. Wanless (1969) 
suggested that two belts of transgression originat- 
ed from an area in southern California or north- 
western Mexico. One arm extended up to Mon- 
tana and from there to the Midwest; the other 
reached eastward south of the Ozark uplift to the 
Appalachian basins. However, the elevation of the 
Ouachita deformed belt blocked the eastern part 
of this seaway, so that Desmoinesian and later 
transgressions had to spread north on the west 
side of the Ozarks to reach the Illinois basin, for 
example. 

If my interpretation of the iniopterygians and 
some of the elasmobranchs of the Mecca fauna as 
denizens of oceanic waters is correct, these fishes 
would have had to travel some 3,000 km or more 
to reach the Illinois basin. More likely seems to 
be the existence of an oceanic geosyncline (per- 
haps alluded to by Wanless [1969, Fig. 1] under 
the name of Possible Gulf of Mexico Basin) from 
which by Desmoinesian time transgressions might 
have surged northward. 

Under this interpretation, the Mecca fish fauna 
would represent a mixture of basin elements and 
truly oceanic ones, a matter of considerable inter- 
est, because the Carboniferous record of oceanic 
chondrichthyans is rather meager indeed. 

Of the oceanic chondrichthyan fish community, 
the Mecca fauna appears to have sampled both 
open water endurance swimmers (e.g., Caseodus 
and relatives) with large forked tail fins at least 



22 



FIELDIANA: GEOLOGY 



as stiff as those of Recent swordfish, as well as 
the iniopterygians, forms that perhaps inhabited 
the shelf areas of an oceanic seaway. 

Extensive collecting at many black shale out- 
crops in Parke, Vermillion, Fountain, Vigo, and 
Pike counties, and four quarries in Parke and Pike 
counties has shown that the various taxa of the 
Mecca fish fauna are not represented in equal pro- 
portions everywhere; rather, in each locality one 
or more taxa are common, whereas the rest are 
rare or absent. This phenomenon probably reflects 
the geographically uneven distribution of the fish- 
es immediately prior to and during the transgres- 
sions, when many of them entered the flotant en- 
vironments. 

Returning to the question of the great rarity of 
female iniopterygians, and also of females of the 
elasmobranch Denaea meccaensis (Williams, 
1985) we can exclude, in the case of the iniop- 
terygians, the possibility of preferential predation 
affecting the unarmored females, because all the 
male specimens represent individuals that died of 
the effects of predator-inflicted injuries. In De- 
naea neither sex has any kind of armature. The 
uneven representation of the sexes perhaps merely 
indicates that the females preferred the deeper and 
presumably clearer waters of the more central 
parts of the basins, shunning whatever induce- 
ments the dark, shallow, and treacherous flotant 
environments offered to some 38 species of chon- 
drichthyans now preserved in the black shales that 
resulted from those rich organic mud accumula- 
tions. 



Conclusions 

The present account introduces a new genus of 
iniopterygian, Cervifurca nasuta, with a some- 
what dorsoventrally flattened body and eyes that 
faced dorsolaterad, very large pectoral fins, a pe- 
culiarly modified pelvic fin skeleton of uncertain 
function, and enormously enhanced pterygopodia. 
This new form enlarges our knowledge of the 
adaptive radiation of the Iniopterygia, which, 
along with some sharks, most likely were not part 
of the fish fauna of the epicontinental basin com- 
plex of North America but may have ventured, 
with repeated transgressions of oceanic waters, 
into the shallow basins with their marginal flotant 
environments. 



Acknowledgments 

I am most grateful to the Trustees of the Inter- 
state Commercial Corporation, who kindly per- 
mitted the establishment of the Bethel Quarry on 
corporate land, and I am especially indebted to 
John L. Barnett, Executive Director of the cor- 
poration, for his enduring interest and help with 
the project. The Indiana Department of Natural 
Resources, in particular John Wade, Manager of 
the Patoka State Fish and Game Area, Winslow, 
Indiana, and his staff, who now constitute the en- 
vironmental custodians of this land, contributed 
most important equipment and manpower re- 
sources to the quarry site preparation, and helped 
out on many occasions with weather-related prob- 
lems concerning the access road. My sincere 
thanks are due to all of them. I also wish to ex- 
press my appreciation to Ralph Langenheim of 
the Department of Geology and the University of 
Illinois Museum of Natural History at Urbana for 
the loan of a most interesting, three-dimensionally 
preserved, articulated, partial skeleton of the here- 
in described species from a western Illinois lo- 
cality, and for searching the correspondence files 
concerning the collection history of the specimen. 
I also wish to thank three anonymous reviewers 
for their helpful suggestions. 



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ZANGERL: CERVIFURCA NASUTA, NEW INIOPTERYGID FROM INDIANA 



23 



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24 



FIELDIANA: GEOLOGY 



A Selected Listing of Other Fieldiana: Geology Titles Available 



A Preliminary Survey of Fossil Leaves and Well-Preserved Reproductive Structures from the Sentinel 
Butte Formation (Paleocene) near Almont, North Dakota. By Peter R. Crane, Steven R. Manchester. 
and David L. Dilcher. Fieldiana: Geology, n.s., no. 20, 1990. 63 pages, 36 illus. 

Publication 1418, $13.00 

A Catalogue of Type Specimens of Fossil Vertebrates in the Field Museum of Natural History. Classes 
Amphibia, Reptilia, Aves, and Ichnites. By John Clay Bruner. Fieldiana: Geology, n.s., no. 22, 1991. 
51 pages, 1 illus. 

Publication 1430, $15.00 

Comparative Microscopic Dental Anatomy in the Petalodontida (Chondrichthyes, Elasmobranchii). By 
Rainer Zangerl, H. Frank Winter, and Michael C. Hansen. Fieldiana: Geology, n.s., no. 26, 1993. 43 
pages, 35 illus. 

Publication 1445, $16.00 

Revised, Phylogeny and Functional Interpretation of the Edrioasteroidea Based on New Taxa from the 
Early and Middle Ordovician of Western Utah. By Thomas E. Guensburg and James Sprinkle. Field- 
iana: Geology, n.s., no. 29, 1994. 43 pages, 18 illus., 1 table. 

Publication 1463, $12.00 

Giant Short-Faced Bear (Arctodus simus yukonensis) Remains from Fulton County, Northern Indiana. 
By Ronald L. Richards and William D. Turnbull. Fieldiana: Geology, n.s., no. 30, 1995. 34 pages, 
20 illus., 9 tables. 

Publication 1465, $10.00 

The Genus Placodus: Systematics, Morphology, Paleobiogeography, and Paleobiology. By Olivier Riep- 
pel. Fieldiana: Geology, n.s., no. 31, 1995. 44 pages, 47 illus., 1 table. 

Publication 1472, $12.00 

The Mammalian Faunas of the Washakie Formation, Eocene Age, of Southern Wyoming. Part III. The 
Perissodactyls. By Steven M. McCarroll, John J. Flynn, and William D. Turnbull. Fieldiana: Geology, 
n.s., no. 33, 1996. 38 pages, 13 illus., 5 tables. 

Publication 1474, $11.00 



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