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Ctenacanthus and other chondrichthyan spines and denticles from the () of Colorado

Article in Journal of Paleontology · May 2003 Impact Factor: 1.28 · DOI: 10.1666/0022-3360(2003)077<0524:CAOCSA>2.0.CO;2

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Available from: Wayne Itano Retrieved on: 10 May 2016 J. Paleont., 77(3), 2003, pp. 524±535 Copyright ᭧ 2003, The Paleontological Society 0022-3360/03/0077-524$03.00

CTENACANTHUS AND OTHER CHONDRICHTHYAN SPINES AND DENTICLES FROM THE MINTURN FORMATION (PENNSYLVANIAN) OF COLORADO

WAYNE M. ITANO,1 KAREN J. HOUCK,2 AND MARTIN G. LOCKLEY2 11995 Dartmouth Ave., Boulder, Colorado 80305, Ͻ[email protected]Ͼ and 2Dept. of Geography, Geology, and Environmental Science, University of Colorado, Denver 80217

ABSTRACTÐChondrichthyan spines and dermal denticles are reported from the Middle Pennsylvanian Minturn Formation, Eagle County, Colorado. The most common element is a dorsal ®nspine referred to Ctenacanthus buttersi St. John and Worthen, 1883. Some of the specimens are more complete distally than the holotype and only previously ®gured specimen of C. buttersi. Less common remains include a dorsal ®nspine referred to Acondylacanthus nuperus St. John and Worthen, 1883, a smooth-ribbed dorsal ®nspine close to ``Ctenacanthus'' furicarinatus Newberry, 1875, a spine fragment probably referrable to Physonemus sp., and two large-noded dorsal ®nspines probably referrable to two different species of Bythiacanthus. Dermal denticles are referred to Petrodus patelliformis M'Coy, 1848. Ctenacanthus buttersi ®nspines and some large cladodont teeth, referred to ``'' occidentalis (Leidy), 1859, may belong to the same species. This conjecture is based mainly on the relative abundances of chondrichthyan teeth found at the same locality.

INTRODUCTION (McNulty, 1963; Dalquest et al., 1993), Oklahoma (Zidek, 1978, DIVERSE marine chondrichthyan assemblage has been found 1993; Hansen, 1980), Nebraska (Ossian, 1974; Maisey, 1983; A in the Minturn Formation (middle Pennsylvanian) of Eagle Johnson, 1984), and Kansas (Miller, 1957; Chorn and Frailey, and Routt Counties, Colorado, near the town of McCoy (Fig. 1). 1978; Maisey, 1989; Robb, 1992; Schultze and West, 1996). The remains consist of isolated teeth, spines, and dermal denticles. Much of the modern research has concentrated on a few un- Six distinct spines and one dermal denticle are described and ®g- usual localities, such as the late Bear Gulch Lime- ured in this report. The teeth will be described in a future pub- stone of Montana (Lund, 1999) and the Pennsylvanian black lication. Many of the specimens discussed here were found at a shales of Indiana, Illinois, and neighboring states (Zangerl and single locality, associated with a prominent bed. All of Richardson, 1963; Williams, 1985), where articulated chondri- the specimens were found within a radius of a few kilometers of chthyan skeletons are sometimes preserved. Other marine chon- McCoy, Eagle County, Colorado, in marine shales and , drichthyan assemblages have not been studied to the same degree, associated with invertebrate including , brachio- largely because the remains nearly always consist of isolated pods, molluscs, and . A preliminary report on the vertebrate teeth, spines, and dermal denticles. Still, it may be possible to assemblage appeared in an informal publication, which included obtain a fairly complete inventory of the species present at a given a faunal list and sketches of specimens (Lockley, 1984). Since locality from such isolated remains. An example is Hansen's that report appeared, several new taxa have been identi®ed. (1986) comprehensive study of the microscopic and macroscopic The published record of chondrichthyans from chondrichthyan remains from the Pennsylvanian marine carbonate Colorado is rather sparse. The ®rst record appears to be the de- formations of Ohio. The Minturn Formation assemblage, which scription of Cladodus girtyi by Hay (1900), based on a tooth from includes six distinct spine taxa, is unusually diverse for this geo- ``the Coal Measures of Colorado.'' Eastman (1903) believed Cla- graphic region and time period. dodus girtyi to be ``scarcely distinct'' from Cladodus occidentalis STRATIGRAPHIC SETTING Leidy. C. girtyi is the only ®sh from Colorado listed in The Pennsylvanian Minturn Formation consists of a complex a review of the ®shes ( and extant) of the Rocky Mountain sequence of conglomerates, sandstones, shales, and marine lime- region (Cockerell, 1907). Some chondrichthyan teeth from the stones, deposited at the eastern margin of the Central Colorado Minturn Formation of Colorado, referred to ohioensis Basin, adjacent to the Ancestral Front Range (De Voto, 1980). Safford are reposited in the University of Colorado Museum. Ste- The Minturn Formation was originally described by Tweto (1949) vens (1958) ®gured teeth referred to Petalodus destructor New- in the vicinity of Minturn and Pando, Eagle County, Colorado. berry and Worthen (probably a junior synonym of P. ohioensis) The fossiliferous Pennsylvanian deposits in the vicinity of Mc- and to Cladodus sp. and a fragment of a dorsal ®nspine, referred Coy, Eagle County, Colorado, were studied by Roth and Skinner to Ctenacanthus sp., all from the Minturn Formation near McCoy, (1930), who named these beds the McCoy Formation. Stevens Colorado. Bass and Northrop (1963) noted the presence of Penn- (1958) and Chronic and Stevens (1958) recognized their equiva- sylvanian chondrichthyans in the Glenwood Springs, Colorado lence with those at Minturn, and designated them as the Minturn area, including Peripristis semicircularis Newberry and Worthen, Formation. They also designated 19 numbered stratigraphic units, in the Belden Formation, and Petalodus ohioensis in the Paradox containing both marine and nonmarine sediments (Fig. 2). Houck Formation. (1997) was able to correlate several of the marine transgressions The record of Carbonifererous chondrichthyans in neighboring with the fusulinid biozones of Ross and Ross (1987) and show states is only slightly better. Eastman (1903) provided a survey that the middle part of the Minturn Formation (units 3 through 7 for the central western United States. Reviews covering individual of Stevens, 1958) ranges from the late Atokan age to the Des- states have been given for (Zidek and Kietzke, moinesian age of the Pennsylvanian Period. 1993), Utah (Sumida et al., 1999), and Oklahoma (Zidek, 1973, 1976, 1977). In addition to the occurrences noted in these reviews, SYSTEMATIC PALEONTOLOGY there have been reports of isolated teeth and spines, a few de- Other than for Ctenacanthus, which is known from articulated scriptions of articulated remains, and a few extensive faunal re- specimens, the taxonomic groupings within the ports from particular localities from Arizona (Elliott and Bounds, to which the following spines and denticles are assigned are high- 1987), New Mexico (Zidek, 1992; Lucas and Estep, 2000), Utah ly uncertain, even when they can be assigned to nominal genera (Miller, 1981), Wyoming (Branson, 1916; Santucci, 1998), Texas or even species. For that reason, their assignment to families, 524 ITANO ET AL.ÐCHONDRICHTHYAN SPINES FROM COLORADO 525 orders, and even subclasses is kept to a minimum. We follow Zangerl (1981) for the classi®cation of Ctenacanthus. All speci- mens collected for this study are reposited in the Denver Museum of Nature and Science (DMNH) or the American Museum of Natural History (AMNH). All of these specimens are from the Minturn Formation, Eagle and Routt Counties, Colorado, near the towns of Bond and McCoy. Precise locations of individual spec- imens are on ®le at the respositories. DMNH specimens for which names of collectors are not noted were found by Martin Lockley, Karen Houck, and students of the University of Colorado at Den- ver. Where known, the units are given in terms of the named members of the Minturn Formation (Tweto, 1949), the numbered units of Stevens (1958) and Houck (1997), and the ages within the Pennsylvanian Period (Atokan or Desmoinesian). In addition, some specimens at the University of Colorado Museum (UCM), the United States National Museum of Natural History (USNM), and the New Mexico Museum of Natural History and Science (NMMNH) were examined.

Class CHONDRICHTHYES Huxley, 1880 Subclass Bonaparte, 1838 Order Hay, 1902 Superfamily CTENACANTHOIDEA Zangerl, 1981 Family CTENACANTHIDAE Dean, 1909 CTENACANTHUS Agassiz, 1837 Type species.Ctenacanthus major AGASSIZ, 1837. Discussion.The type species, Ctenacanthus major, is founded on an isolated Lower Carboniferous ®nspine having ornament consisting of numerous closely spaced longitudinal ribs pectinated with minute tuberculations. Spines of C. major have never been found associated with other remains, such as teeth. However, ar- ticulated specimens of Ctenacanthus compressus Newberry, 1889 and Ctenacanthus clarkii Newberry, 1889 (now considered to be a junior synonym of C. compressus) are known from the upper Cleveland Shale. These specimens have ®nspines con- forming closely to C. major. Maisey (1981, 1982, 1984) reeval- uated the nominal species referred to Ctenacanthus and excluded most of them from that genus on the grounds that they did not conform closely to C. major. FIGURE 1Ð1, Map of Colorado showing locations of the town of McCoy CTENACANTHUS BUTTERSI St. John and Worthen, 1883 and of Eagle and Routt Counties. 2, Enlarged view of the vicinity of Figures 3.1±3.9, 4.1, 4.2, 5 the towns of McCoy and Bond. CTENACANTHUS BUTTERSI ST.JOHN AND WORTHEN, 1883, p. 240±241, pl. 22, ®g. 2a±2e (Fig. 5). Several ®nspine fragments in the UCM collections, two Description.Finspines ornamented with regular rows of fragments labeled 8821, three fragments labeled 8910a (Fig. 4.1± rounded tubercles. Margin between ornamented and unornament- 4.2). The most complete specimen, AMNH 19236, 17 cm long, ed regions very oblique, with unornamented region extending missing about 5 cm from distal end and part of the proximal, very far distally along the posterior margin. Anterior edge nearly inserted end (Fig. 3.1±3.5). Fragment of anterior part with exter- straight for most of the length. Row of tubercles along the anterior nal mold of left lateral face, DMNH 44646 (Fig. 3.9). External margin similar in ornament to lateral rows, but somewhat wider mold of portion near distal end, DMNH 44647 (Fig. 3.6). Frag- on some specimens. Tubercles on anterior row moderately com- ment near distal end, showing full cross-section, DMNH 44649 pressed, with their major axes perpendicular to the length of the (Fig. 3.7±3.8). Fragment of middle ornamented portion, DMNH spine. Tubercles on lateral rows nearest the anterior edge mod- 44648. Other spine fragments, DMNH 45051, 45052, 45053, erately compressed, oriented at an oblique angle with respect to 45054, 45061. the tubercle rows. These tubercles are oriented along a distal- Occurrence.USNM 16033, 16034, Lower Coal Measures, posterior to proximal-anterior axis. Tubercles on the more poste- roof shales above Coal No. 5 (Spring®eld Coal Member), Car- rior lateral rows oval to round. Lateral rows nearest the posterior bondale Formation, Desmoinesian, Carlinville, Illinois, collected margin de¯ected proximally and posteriorly. Cross-section stout, by F. Springer. UCM 8821, Robinson Member, (Unit 7 of Stevens, subtriangular, lateral surfaces slightly convex. Position of poste- 1958), Minturn Formation, Desmoinesian, sec. 6, T2S, R83W, Ea- rior closure not far from distal end. Posterior face moderately to gle County, Colorado, collected by J. Henderson and N. Hinds. strongly convex. Denticles not observed on posterior face or UCM 8910a, Minturn Formation, Resolution Member (Unit 3 of along the postero-lateral margins on any known specimens. Stevens, 1958; Unit 3a of Houck, 1997) sec. 5, T2S, R83W, Eagle Material examined.Fragments of ®nspine, near distal end, County, Colorado, collected by J. Henderson and N. Hinds. USNM 16033 and 16034. USNM 16034 is labeled ``syntype'' and AMNH 19236, unnamed shale bed in Unit 2 of Stevens (1958) carries a note stating that it was used in the original description below Resolution Member, Minturn Formation, late Atokan, sec. 526 JOURNAL OF PALEONTOLOGY, V. 77, NO. 3, 2003

part of the lateral, ornamented surface, mostly as an external mold, appears to belong to a spine referrable to the same species as AMNH 19236, but larger by approximately a factor of 1.5. The specimens from Colorado all lack most of the unornamented, proximal end, but some include portions of the distal end not present in the holotype. Specimen DMNH 44647 (Fig. 3.6) is an external mold showing the rapidly tapering distal end not pre- served on either the holotype or on AMNH 19236. One fragment from near the distal end, DMNH 44649 (Fig. 3.7±3.8), displays the complete cross-section and shows the posterior face to be strongly convex distally. The posterior face just above the level of closure on AMNH 19236 is moderately convex. Ctenacanthus buttersi does not seem to have been reported pre- viously outside of the type locality, Carlinville, Illinois. The Col- orado specimens which we assign to C. buttersi share several distinctive features with the holotype. These features include the nearly straight anterior margin, the long unornamented regions at the posterior margins of the lateral faces, the high level of pos- terior closure, and the details of the ornamented rows, including the de¯ection of the rows near the posterior margin and the shapes of the tubercles, which are more rounded than in typical Ctena- canthus. The tubercles vary in shape from round to moderately compressed, but are never sharply compressed to a ridge as in, for example, Ctenacanthus venustus Eastman, 1902. The oblique orientation of the lateral tubercles, noted in the original descrip- tion and seen clearly in USNM 16034 (Fig. 5) is also seen in the Colorado specimens UCM 8910a (Fig. 4) and AMNH 19236. The ratio of the anterior-to-posterior thickness to the lateral width is somewhat smaller at the position of maximum thickness (about FIGURE 2ÐColumnar section of the Minturn Formation as it occurs in the area around McCoy, Colorado. The 19 units were delineated by 1.6) than that of typical Ctenacanthus (2 to 3). The lateral tubercle Chronic and Stevens (1958). The positions of stratigraphic horizons rows of UCM 8910a (Fig. 4.1) become somewhat irregular near bearing ®nspines are also shown. The ®nspines were found in gray the posterior border between the ornamented and unornamented marine limestones and shales that formed during marine transgressions parts of the lateral face. This probably is a result of a slowing of in the Central Colorado Basin. the rate of growth at maturity. Maisey (1975) divided most elasmobranchs into three orders, the Euselachiformes, Hybodontiformes, and , 16, T2S, R83W, Eagle County, Colorado, collected by W. Itano. de®ned partially by ®nspine morphology. The ®nspine of Cten- DMNH 44646, 44647, Robinson Member, (Unit 7 of Stevens, acanthus buttersi possesses features typical of both the Ctenacan- 1958), Minturn Formation, Desmoinesian, sec. 31, T1S, R83W, thiformes and the Hybodontiformes sensu Maisey (1975). Maisey Routt County, Colorado, collected by M. Lockley. DMNH 44649, (1984) considered C. buttersi to be a hybodont, based on the 45051, 45052, 45053, 45054, 45061, Robinson Member, (Unit 7 convexity of the posterior face. However, the ®ne, pectinate or- of Stevens, 1958), Minturn Formation, Desmoinesian, sec. 1, T2S, nament in C. buttersi is like that in Ctenacanthus sensu stricto. R84W, Eagle County, Colorado. DMNH 44648, Unit 3b of Such ornament is not known in any undoubted hybodonts. Also, Houck, (1997), Minturn Formation, late Atokan, sec. 5, T2S, C. buttersi seems to lack denticles on the posterior face, which R83W, Eagle County, Colorado, collected by D. Nelson. are present in many hybodont ®nspines. Thus, C. buttersi may Discussion.Most of the chondrichthyan spines known from not be a hybodont (Maisey, personal commun.). For now, C. but- the Minturn Formation are referred to this species. Most of the tersi is retained in Ctenacanthus sensu stricto. other Minturn taxa are founded on spines presently known only A ®nspine from the Seminole Formation (Missourian) of Tulsa from single specimens. The holotype of C. buttersi is an incom- County, Oklahoma was reported by Zidek (1977) to resemble C. plete ®nspine from the Pennsylvanian (Lower Coal Measures buttersi. He noted that it differed in that its ornament reached the above Coal Number 5, Desmoinesian, Carbondale Formation) of posterior margin, whereas C. buttersi has an unornamented region Carlinville, Illinois (Fig. 6.1±6.3). The holotype is missing much along the posterior margin. The Pennsylvanian chondrichthyan of the distal end and is smaller than many of the specimens from fossils described by Zidek (1977) have recently been transferred Colorado. However, the existence of fragments of larger speci- from a private collection to the American Museum of Natural mens apparently belonging to the same species was noted in the History. We have examined the ®nspine from the Seminole For- original description. The present location of the holotype is un- mation, now designated AMNH 19587, and ®nd that it differs known, and it may have been lost or destroyed during an unsu- from C. buttersi in several respects. The posterior face is concave, pervised relocation of the Worthen collection in 1887. The history with rows of small denticles along the postero-lateral margins; C. of the Worthen collection and its present status is discussed by buttersi has a convex posterior face and seems to lack such den- Leary and Turner (1996). The National Museum of Natural His- ticle rows. AMNH 19587 appears to be closer to Ctenacanthus tory collections contain two ®nspine fragments labeled Ctenacan- lamborni Wells, 1944, which is founded on the distal part of a thus buttersi, USNM 16034 and 16033. Both are from the Lower ®nspine from the Ames Limestone (late Virgilian) of Ohio. Coal Measures, Carlinville, Illinois. Of these, USNM 16034 (Fig. The question arises as to which of the various chondrichthyan 5) is better preserved, and a note states that it was used in the teeth known from the Minturn Formation might have belonged to original description. the same species as the C. buttersi ®nspines. By far the most One Colorado specimen, DMNH 44646 (Fig. 3.9), showing common large teeth are Petalodus sp. and some cladodont teeth. ITANO ET AL.ÐCHONDRICHTHYAN SPINES FROM COLORADO 527

Various holocephalan tooth plates, referred to the genera Laga- except for Agassizodus variabilis, are relatively common there. rodus, Deltodus, and Sandalodus are also moderately common. We have examined the ctenacanthid ®nspines from the Gray Mesa While some holocephalans are known to have had dorsal ®nspi- Formation (Fig. 7.1±7.5; Lucas and Estep, 2000, ®g. 7a, 7b) and nes, none of these spines is known to be similar to those of Cten- ®nd that they are similar both in cross section and in ornament acanthus. Several other genera, such as Edestus, Agassizodus, and to Ctenacanthus buttersi. The cross section near the proximal end the petalodonts Peripristis, Polyrhizodus, and Janassa, are rep- of the ornamented part (Fig. 7.4) is very similar to that of C. resented in the collection mainly by single teeth and hence are buttersi (Fig. 4.2). The lateral nodes (Fig. 7.5) are rounded and unlikely to belong to the same species as the common ®nspine. obliquely oriented as in C. buttersi (Fig. 5). The ornament pattern Dorsal ®nspines have not been observed in any of the few known near the distal end (Fig. 7.2), where it is preserved, matches that articulated petalodonts (Lund, 1989). A dorsal ®nspine resembling of C. buttersi (Fig. 3.7) very closely. However, certain identi®- that of Ctenacanthus was found closely associated with a tooth cation of the Gray Mesa specimens does not seem possible be- of Megactenopetalus, a petalodont (Hansen, 1978). However, this cause of their incomplete and abraded condition. None of the could have been a chance association. fragments preserves the posterior surface. If the Gray Mesa frag- If we eliminate from consideration the teeth belonging to pe- ment shown in Figure 7.2 does belong to C. buttersi, it shows talodonts and holocephalans and those which are rare, the only that C. buttersi ®nspines have an unornamented band along the teeth likely to belong to the same species as the spines referred posterior margin that extends all the way to the distal tip. Of the to Ctenacanthus buttersi are some large cladodont teeth which we chondrichthyan teeth identi®ed from the Gray Mesa Formation refer to ``Symmorium'' occidentalis (Leidy, 1859). Some of the assemblage, only ``Symmorium'' occidentalis is likely to have be- bases of these teeth, when complete, would have been over 4 cm longed to the species that possessed the ctenacanthid spines. For wide. Thus, they provide a good match in size for the Ctenacan- reasons stated previously, Petalodus ohioensis is not a likely can- thus buttersi ®nspines, some of which were probably over 30 cm didate. Agassizodus variabilis belongs to the Order Eugeneodon- long when complete. ``Symmorium'' occidentalis was originally tida Zangerl, 1981, the members of which are believed to lack designated Cladodus occidentalis by Leidy (1859). ``Cladodus'' dorsal ®nspines (Zangerl, 1981, p. 77). An articulated specimen, is considered to be a nomen dubium, as teeth of cladodont form with teeth resembling those of Agassizodus, and originally re- are found in several different lineages of . We follow cur- ferred to that genus, has a single dorsal ®n with no spine (Case, rent practice (Ivanov, 1999; Malysheva, 2001) in the tentative 1970a). This specimen was later referred (Case, 1982, ®g. 24-43) assignment of these teeth to Symmorium. Teeth of this species to Romerodus orodontus Zangerl, 1981, another eugeneodontid, have never been found together with more complete remains, so but it is unlikely that Agassizodus variabilis had a dorsal ®nspine, their true generic assignment is uncertain. ``Symmorium'' occi- given that no other eugeneodontid is known to have had one, and dentalis teeth are similar to, though distinct from, those of Sym- that Romerodus and some other eugeneodontids are known to lack morium reniforme Cope, 1893, which is known from articulated them. remains. In the past, teeth of ``Symmorium'' occidentalis have Figure 8 represents an attempt to reconstruct the entire ®nspine been assigned incorrectly to Symmorium reniforme (Williams, of Ctenacanthus buttersi. Lateral views of six specimens were 1985; Lockley, 1984; Mapes and Hansen, 1984; Zidek, 1992; Lu- combined to form this composite ®gure. The component ®gures cas and Estep, 2000). Ginter (1998, 1999), after examining the were adjusted in scale to obtain the best ®t. This procedure is type specimen of Symmorium reniforme, pointed out that the teeth valid to the extent that the outline of the ®nspine retained the of Symmorium reniforme are easily distinguished from those of same shape during growth. From proximal to distal (right to left), ``Symmorium'' occidentalis. Teeth of ``Symmorium'' occidentalis the ®gures making up the composite ®gure are the holotype, have two widely separated buttons on the upper side of the base, AMNH 19236, USNM 16034, DMNH 44647, and NMMNH P- corresponding to two distinct labio-basal projections. A deep la- 26149 (Figs. 6.1, 3.1, 5, 3.6, 3.7, and 7.2). According to this bial concavity is present between the two projections. Teeth of S. reconstruction, the anterior margin is nearly straight, while the reniforme have neither two buttons nor two distinct labio-basal posterior margin displays more curvature. The greatest deviation projections. Two articulated ctenacanthoid sharks, Ctenacanthus from a good ®t between the component ®gures occurs near the compressus and Ctenacanthus costellatus Traquair, 1884 have cla- proximal end. In the holotype specimen (Fig. 6.1), the anterior dodont teeth with two buttons (Ginter, personal commun.). margin bends sharply backward at the border between the orna- Based on the sizes and relative abundances of the teeth and on mented and unornamented regions. In ANMH 19236 (Fig. 3.1), other known associations of teeth and spines, we believe that the the bend is less sharp. The two specimens are very different in teeth most likely to belong to the same species as the Ctenacan- scale. The holotype is small and presumably represents a juvenile, thus buttersi ®nspines are those of ``Symmorium'' occidentalis. while AMNH 19236 is relatively large and probably represents Symmorium reniforme is known to lack ®nspines, but this does an adult. The difference might therefore be due to a growth-re- not rule out an association of Ctenacanthus buttersi ®nspines and lated change in shape. The difference might also be due to a ``Symmorium'' occidentalis teeth, since ``Symmorium occidental- difference in shape between the anterior and posterior ®nspines is'' teeth are clearly distinguishable from those of Symmorium or simply to individual variation. reniforme. The chondrichthyan assemblage described by Lucas and Estep Superfamily, Family indeterminate (2000) from the uppermost Gray Mesa Formation of the Madera Genus BYTHIACANTHUS St. John and Worthen, 1875. Group of Socorro County, New Mexico is close to the Desmo- Type species.Bythiacanthus vanhornei ST.JOHN AND WOR- inesian-Missourian boundary and is tentatively dated to the Des- THEN, 1875. moinesian. Thus, the assemblage is close, both geographically and Discussion.The type species, Bythiacanthus vanhornei,is chronologically, to that of the Minturn Formation, and it would founded on a dorsal ®nspine which differs from that of Ctena- not be surprising if the two assemblages were found to be similar. canthus in being squat and broad and having ornamentation con- The elements identi®ed from the Gray Mesa Formation assem- sisting of somewhat irregular rows of large, round tubercles. In blage are teeth of Petalodus ohioensis,``Symmorium'' occiden- contrast, Ctenacanthus spines are long, slender, and have regular talis, and Agassizodus variabilis, dermal denticles of Petrodus rows which are ®nely denticulated. Maisey (1982) reevaluated the patelliformis, and some ctenacanthid ®nspines. All of these ele- genus and assigned to it several ®nspines previously assigned to ments have also been identi®ed from the Minturn Formation, and, Ctenacanthus. In all, Maisey (1982) assigned seven species, all 528 JOURNAL OF PALEONTOLOGY, V. 77, NO. 3, 2003 ITANO ET AL.ÐCHONDRICHTHYAN SPINES FROM COLORADO 529

Mississippian, to Bythiacanthus. Maisey (1983) assigned a ®n- spine fragment from the Kiewitz Shale or Stoner Limestone (Pennsylvanian) of Cass and Sarpy Counties, Nebraska, to By- thiacanthus sp. This specimen is small and slender, has only ®ve or six lateral tubercle rows, and may represent a juvenile. A large ®nspine from the Coffeyville Formation (Missourian) of Tulsa County, assigned to Ctenacanthus sp. by Zidek (1977), has been reassigned to Bythiacanthus sp. (Maisey, private communication). This specimen is now reposited at the American Museum of Nat- ural History and is designated AMNH 19586. The various species of Bythiacanthus vary somewhat in shape and in regularity of the rows of tubercles but have in common large, round tubercles, often radially striated. None of the species of Bythiacanthus are known from articulated or associated remains. However, a Penn- sylvanian elasmobranch described by Williams (1985) as Phoe- bodus heslerorum has ®nspines that resemble Bythiacanthus. Gin- ter (1998) has noted that the teeth of ``Phoebodus'' heslerorum differ strongly from those of Phoebodus and thus belong in a different genus and also that the species appears to be a junior synonym of ``Cladodus'' divergens Trautschold, 1879. Thus, it may be that Bythiacanthus ®nspines belong to a having FIGURE 4ÐFragment of Ctenacanthus buttersi dorsal ®nspine from Min- cladodont teeth. turn Formation, Colorado, in 1, right lateral; and 2, proximal views. Two fragments of ®nspines with ornament resembling those One of three specimens labeled UCM 8910a. Scale bar is 1 cm. assigned to Bythiacanthus are known from the Minturn Forma- tion. Because they are too incomplete to be clearly assignable to any of the recognized species of Bythiacanthus, they are simply referred to as Bythiacanthus sp. 1 and sp. 2 here. (Leidy, 1873) from the Mississippian of Tennessee, which also has radially striated tubercles. BYTHIACANTHUS sp. 1 Figure 9.1±9.3 BYTHIACANTHUS sp. 2 Description.Dorsal ®nspine with regular rows of closely- Figure 9.7±9.10 spaced, large tubercles, radially striated. Very compressed later- Description.Dorsal ®nspine, moderately compressed lateral- ally. Symmetrical pair of rows of round tubercles along the an- ly, with regular rows of round, radially striated tubercles. Anterior terior ridge. Tubercles on anteriormost lateral row larger than margin has a single row of tubercles, some of which are fused those on anterior margin, somewhat elongated perpendicular to together. Tubercles decrease in size away from the anterior mar- the direction of the row. Tubercles decrease in size posteriorly. gin. On the lateral surfaces, the tubercles are widely spaced. Material examined.A single ®nspine fragment, DMNH Material examined.A single ®nspine fragment, DMNH 45056, preserving part of the anterior margin and some of the 45055, preserving part of the anterior margin and right and left right lateral surface (Fig. 9.1±9.3). lateral surfaces (Fig. 9.7±9.10). Occurrence.DMNH 45056, Robinson Member, (Unit 7 of Occurrence.DMNH 45055, Robinson Member, (Unit 7 of Stevens, 1958), Minturn Formation, Desmoinesian, sec. 1, T2S, Stevens, 1958), Minturn Formation, Desmoinesian, sec. 1, T2S, R84W, Eagle County, Colorado. R84W, Eagle County, Colorado, collected by M. Lockley. Discussion.This spine differs dramatically from the Ctena- Discussion.This spine differs from the one referred to By- canthus buttersi ®nspines found more commonly in the Minturn thiacanthus sp. 1 in having a single rather than a double row of Formation, especially in the size of the tubercles. DMNH 45056 tubercles along the anterior margin and in having more closely has 2.9 tubercles per cm along the anterior margin, whereas a spaced tubercles. There are 4.7 tubercles per cm in the row on relatively large C. buttersi spine, AMNH 19236, has 9.7 tubercles the anterior margin, except where they are fused together at the per cm near the proximal limit of the ornamented portion. Only distal end of the fragment. Fusion of anterior tubercles does not three rows of tubercles are preserved, but the lateral surface seem to have been observed previously in Bythiacanthus ®nspi- shows scars from abraded tubercles indicating that the tubercles nes, although it is present in spines of Ctenacanthus lamborni decrease in size away from the anterior margin. The tubercles are (Wells, 1944) and Ctenacanthus amblyxiphias (Cope, 1891). (The poorly preserved, most of them having the tips broken off or latter spines do not otherwise resemble those of Bythiacanthus.) abraded, but a few of them show radial striations on the surface. Most of the tubercles are incomplete, but some of them preserve Figure 9.3 is a view from the right side of the spine of two of radial striations on the surface. Two of the lateral tubercles that the tubercles of the middle of the three preserved tubercle rows. are complete are shown in Fig. 9.10. The ornament of Bythia- The tips of the tubercles are broken off, but radial striations are canthus sp. 2 resembles that of Bythiacanthus solidus (Eastman, visible on the part of the surface that is preserved. The size and 1902), from the Mississippian of Iowa and Illinois, in terms of density of the tubercles is similar to that of Bythiacanthus siderius the density of rows and tubercles. Bythiacanthus solidus is also

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FIGURE 3ÐDorsal ®nspines of Ctenacanthus buttersi from Minturn Formation, Colorado. 1±5, AMNH 19236, in 1, right lateral; 2, anterior; 3, posterior; 4, distal; and 5, proximal views. 6, DMNH 44647, external mold, lateral view (mirror-reversed for easier comparison with other specimens). 7±8, DMNH 44649, segment near distal end, 7, right lateral; and 8, proximal views. 9, DMNH 44646, incomplete, broken spine and external mold, lateral view. Scale bars are 1 cm. 530 JOURNAL OF PALEONTOLOGY, V. 77, NO. 3, 2003

FIGURE 6ÐHolotype of Ctenacanthus buttersi in 1, right lateral; 2, an- terior; and 3, posterior views, ϫ0.75. Reproduced from St. John and Worthen (1883), pl. 22, ®gure 2. FIGURE 5ÐFragment of dorsal ®nspine, Ctenacanthus buttersi syntype, USNM 16034, lateral view. Mirror-reversed for easier comparison with other ®gures. From Lower Coal Measures (Pennsylvanian), Carlinville, Illinois. Scale bar is 1 cm. Description.Dorsal ®nspine, laterally compressed, cross-sec- tion nearly elliptical, posterior face concave, single smooth rib similar to Bythiacanthus sp. 2 in having a single row of large along anterior margin, parallel smooth ribs on lateral faces, single tubercles on the anterior margin. rows of denticles along the right and left posterolateral margins, Superfamily, Family, Genus indeterminate pulp cavity small. Material examined.A single ®nspine fragment, DMNH cf. ``CTENACANTHUS'' FURCICARINATUS Newberry, 1875 Figure 9.11±9.14 Ctenacanthus furcicarinatus NEWBERRY, 1875, p. 54±55, pl. 59, ®g. 2±2c Description.Finspine with smooth, somewhat irregular, ribs, not densely pectinated as in Ctenacanthus sensu stricto. Level of posterior closure near inserted end. Material examined.A single ®nspine fragment, DMNH 45062, including part of the inserted portion and the proximal part of the ornamented portion. Occurrence.DMNH 45062, Robinson Member, (Unit 7 of Stevens, 1958), Minturn Formation, Desmoinesian, sec. 1, T2S, R84W, Eagle County, Colorado. Discussion.``Ctenacanthus'' furcicarinatus is based on dorsal ®nspines from the Sunbury Shale, Kinderhookian (Mississippian) of Kentucky, which were found associated with the teeth of Or- odus variabilis Newberry, 1875. Thus, the spines and teeth may belong to the same species. Ctenacanthus furcicarinatus was re- garded by Maisey (1984) as differing so greatly in ornamentation from Ctenacanthus sensu stricto as to belong in another genus, although a new genus has not been named. DMNH 45062 is sim- ilar to the holotype of ``C.'' furcicarinatus in the general shape and in the appearance of the ribs. It differs in having ribs that are not as deeply pectinated and in having ribs that increase in num- ber proximally by insertion rather than by bifurcation. Without more complete material, it is not possible to tell whether DMNH 45062 represents the same species as ``C.'' furcicarinatus.Ifit does, then it extends the stratigraphic range of this species to the Pennsylvanian. Subclass, Order, Family indeterminate Genus ACONDYLACANTHUS St. John and Worthen, 1875 Type species.Acondylacanthus gracilis St. John and Worthen, 1875. FIGURE 7ÐCtenacanthid ®nspines from the Gray Mesa Formation, So-  corro County, New Mexico. 1, Lateral; and 4, proximal, views of most Discussion. Acondylacanthus is known only from dorsal ®n- proximal piece of ®nspine NMMNH P-26149, ϫ1.8. Thin line in 1 spines, which are slender and smooth-ribbed. marks the approximate boundary between the ornamented and unor- namented parts. 2, Lateral; and 3, proximal views of most distal piece ACONDYLACANTHUS NUPERUS St. John and Worthen, 1883 of ®nspine NMMNH P-26149, ϫ1.8. 5, Lateral tubercle rows of ®n- Figure 10.1±10.3 spine NMMNH P-26150, oriented with distal end to left and anterior Acondylacanthus nuperus ST.JOHN AND WORTHEN, 1883, p. 242±243, upward, ϫ5.3. All photographs mirror-reversed for easier comparison pl. 26, ®g. 3a±3c., Hansen, 1996, ®g. 21±5.8 with other ®gures. ITANO ET AL.ÐCHONDRICHTHYAN SPINES FROM COLORADO 531

FIGURE 8ÐReconstructed ®nspine of Ctenacanthus buttersi formed from a composite of six specimens. 1±6, Individual images of specimens, scaled so as to ®t together. 1, holotype (St. John and Worthen, 1883, pl. 22, ®g. 2b); 2, AMNH 19236; 3, USNM 16034; 4, DMNH 44647; 5, DMNH 44649; 6, NMNHM P-26149. 7, Composite ®gure generated by displacing 1±6 vertically to bring them together. 8, Enlarged view of distal end of composite ®gure.

45057, showing the entire cross-section and preserving the sur- PHYSONEMUS sp. face ornament, except for the posterior denticles, which are bro- Figure 9.4±9.6 ken.   Description. Spine with laterally compressed transverse Occurrence. DMNH 45057, Robinson Member, (Unit 7 of cross-section, tapered, surface showing irregularly arranged small Stevens, 1958), Minturn Formation, Desmoinesian, sec. 1, T2S, tubercles. Some tubercles display radial striations (Fig. 9.6). R84W, Eagle County, Colorado.   Material examined. A single spine fragment, DMNH 45058, Discussion. Though small, this spine fragment seems readily much abraded, but preserving some surface ornament. assignable to Acondylacanthus nuperus, because the ornament Occurrence.DMNH 45058, Robinson Member, (Unit 7 of agrees with that of the holotype and because of its similarity in Stevens, 1958), Minturn Formation, Desmoinesian, sec. 1, T2S, transverse cross-section, which has the shape of a laterally com- R84W, Eagle County, Colorado. pressed ellipse. Other species of Acondylacanthus have a cross- Discussion.This fragment is provisionally assigned to Phy- section which is subtriangular. The holotype of A. nuperus is from sonemus, though it is not possible to assign it to any particular the LaSalle Limestone Member of the Bond Formation, Missour- species. We interpret it as part of the extreme distal end of a large ian (Pennsylvanian), Peru, Illinois. A ®nspine from the Cambridge Physonemus spine, perhaps Physonemus mirabilis (St. John and Limestone (Conemaugh Group) middle to late Missourian, Tus- Worthen, 1875). The left edge of Figure 9.4 is interpreted as the cawaras County, Ohio, has been assigned to A. nuperus (Hansen, anterior margin because of the similarity of the shape of the trans- 1996). Hansen (1986) has also noted the presence of A. nuperus verse cross-section (Fig. 9.5) to that of Physonemus mirabilis (cf. in the Putnam Hill Limestone (Allegheny Group, early Desmo- Dalquest et al., 1993, ®g. 4). The transverse cross-section is in- inesian), the Vanport Limestone (Allegheny Group, early Des- complete on the posterior side. When complete, it probably would moinesian), the Washingtonville Shale (Allegheny Group, late have appeared more compressed laterally, as is typical of Phy- Desmoinesian), and the Brush Creek Formation (Conemaugh sonemus. It is probably not referrable to Batacanthus St. John and Group, early Missourian) of Ohio. Worthen, 1875, which has a more oval transverse cross-section.

Genus PHYSONEMUS M'Coy, 1848 Genus PETRODUS M'Coy, 1848 Type species.Physonemus arcuatus M'COY, 1848. Type species.Petrodus patelliformis M'COY, 1848. Discussion.The form genus Physonemus includes bilaterally Discussion.Isolated chondrichthyan dermal denticles belong- symmetrical, laterally compressed, forward-curving spines, or- ing to the form genus Petrodus are widespread and common in namented with tubercles. They have never been found together the Carboniferous. American specimens have often been referred with more complete remains. Other form genera, including Dre- to Petrodus occidentalis Newberry and Worthen, 1866. However, panacanthus Newberry and Worthen, 1866, and Xystracanthus P. occidentalis is so similar to the type species P. patelliformis, Leidy, 1859, are probably junior synonyms of Physonemus. that it is probably a junior synonym of the latter (Zidek, 1973). 532 JOURNAL OF PALEONTOLOGY, V. 77, NO. 3, 2003 ITANO ET AL.ÐCHONDRICHTHYAN SPINES FROM COLORADO 533

Chorn and Reavis (1978) have reviewed possible af®nities of Pe- trodus, but, lacking more complete remains, no ®rm conclusions can be drawn.

PETRODUS PATELLIFORMIS M'Coy, 1848 Figure 9.15, 9.16 Petrodus patelliformis M'COY, 1848, p. 132. Petrodus occidentalis NEWBERRY AND WORTHEN, 1866, p. 70±71, pl. 4, ®g. 15±15b. Petrodus buttersi NEWBERRY, 1889, pl. 27, ®g. 1, 2. Petrodus sp. CASE, 1970b, ®g. A. Petrodus patelliformis M'COY, 1848. Lucas and Estep, 2000, ®g. 7C. Description.Dermal denticles, circular to elliptical in outline, ridges radiating from central region to outer edges. Material examined.Two denticles, DMNH 45059 (Fig. 9.15), 45060 (Fig. 9.16). Occurrence.DMNH 45059, 45060, Unit 3c of Houck (1997), Minturn Formation, late Atokan, sec. 5, T2S, R83W, Eagle Coun- ty, Colorado, collected by D. Nelson. Discussion.The two specimens, DMNH 45059 and DMNH 45060, are of about the same size and were found at the same locality and unit. It seems highly probable that they belong to the same species, perhaps coming from different parts of the body. DMNH 45059 is indistinguishable from Petrodus patelliformis (cf. Newberry and Worthen, 1866, pl. 4, ®g. 15±15b), other than having a broken apex. DMNH 45060 has a smooth central region, and is indistinguishable from Petrodus buttersi Newberry, 1889. FIGURE 10ÐFragment of Acondylacanthus nuperus dorsal ®nspine, DMNH 45057, in 1, proximal; 2, left lateral; and 3, posterior views. However, lacking suf®cient grounds for separating the two spec- Scale bar is 1 cm. imens, we provisionally refer both of them to Petrodus patelli- formis. Missourian rocks in Illinois (St. John and Worthen, 1875; C. P. SIGNIFICANCE OF THE MINTURN ASSEMBLAGE Weibel, personal commun.), and in both Desmoinesian and Mis- This assemblage of ®nspines and denticles from the Central sourian rocks in Ohio (Hansen, 1986, 1996). The single specimen Colorado Basin is signi®cant for several reasons. Pennsylvanian of A. nuperus from the Minturn Formation was found in rocks of fossil chondrichthyans are poorly known from the western United Desmoinesian age. ``Ctenacanthus'' furcicarinatus occurs in States as a whole, and this is the ®rst published report of ®nspines rocks of Kinderhookian (Early Mississippian) age. If the Minturn and denticles from Colorado. The assemblage is also unusually specimen is indeed ``C.'' furcicarinatus, then the stratigraphic diverse, containing six spine taxa and one denticle taxon. As such, range is extended to the Desmoinesian. If not, then it represents it adds signi®cantly to our understanding of the geographic and a new taxon. Bythiacanthus, Physonemus, and Petrodus patelli- stratigraphic ranges of these taxa, as well as to our understanding formis are long-ranging taxa that are known from throughout the of the ®nspine morphology and the af®nities of Ctenacanthus but- Pennsylvanian Period. tersi, and to our knowledge of the relative abundances of the The numerous specimens of Ctenacanthus buttersi from the spine-based taxa in the Minturn Formation. Minturn Formation provide additional information about the ®n- The Minturn ®nspines and denticles extend the known geo- spine morphology of this species. The type specimen is composed graphic ranges of all seven taxa. Ctenacanthus buttersi was of only the proximal two-thirds of the spine. From the large Min- known previously only from Illinois, and Acondylacanthus nu- turn specimen (AMNH 19236) and the smaller fragments, it is perus from Illinois and Ohio. ``Ctenacanthus'' furcicarinatus was possible to reconstruct the appearance of an entire spine (Fig. 8). known only from Kentucky. Bythiacanthus, Physonemus, and Pe- The Minturn specimens show that the distal ends of the spines trodus patelliformis are geographically widespread taxa, but had taper rapidly, and that posterior faces of the distal ends are strong- not been previously reported from Colorado. ly convex. This suggests that Maisey's (Maisey, 1975) classi®- The Ctenacanthus buttersi and Acondylacanthus nuperus spec- cation of selachian ®nspines into three categories (ctenacanthi- imens from the Minturn Formation are similar in age to their form, hybodontiform, and neoselachian) is in need of modi®ca- counterparts in Illinois and Ohio. Ctenacanthus buttersi occurs in tion, because the C. buttersi ®nspines have features typical of both Desmoinesian rocks in Illinois (St. John and Worthen, 1883), but ctenacanthiform and hybodontiform ®nspines. in both Atokan and Desmoinesian rocks in the Minturn Forma- Prior to this study, it was not known which teeth belonged to tion. The stratigraphic range of C. buttersi is therefore extended the species that bore the Ctenacanthus buttersi ®nspines. The rel- downward into the Atokan. Acondylacanthus nuperus occurs in ative abundances of the various ®nspines and teeth in the Minturn

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FIGURE 9ÐDorsal ®nspines and dermal denticles from Minturn Formation, Colorado. 1±3, Bythiacanthus sp. 1, DMNH 45056; 1, 2, right lateral and anterior views, ϫ1.3; 3, side view of two tubercles at the anterior margin, ϫ6.2. 4±6, Physonemus sp., DMNH 45058; 4, 5, left lateral and proximal views, ϫ2; 6, detail of lateral denticles, ϫ8. 7±10, Bythiacanthus sp. 2, DMNH 45055; 7±9, anterior, right lateral, and proximal views, ϫ1.9; 10, detail of lateral tubercles, ϫ10. 11±14, cf. ``Ctenacanthus'' furcicarinatus, DMNH 45062; 11±13, proximal, left lateral, and distal views, ϫ1.4; 14, detail of lateral ribs, ϫ3.25. 15, 16, Petrodus patelliformis; 15, DMNH 45059; 16, DMNH 45060; ϫ3.2. 534 JOURNAL OF PALEONTOLOGY, V. 77, NO. 3, 2003 assemblage, combined with information obtained from articulated the McCoy area, Eagle County, p. 86±90. In B. F. Curtis (ed.), Sym- or associated remains found elsewhere, suggest that the C. buttersi posium on Pennsylvanian Rocks of Colorado and Adjacent Areas. spines and ``Symmorium'' occidentalis teeth belong to the same Rocky Mountain Association of Geologists. species. The chondrichthyan assemblage from the Gray Mesa For- COCKERELL, T. D. A. 1907. The ®shes of the Rocky Mountain Region. mation in New Mexico (Lucas and Estep, 2000) also supports this University of Colorado Studies, 3:159±178. COPE, E. D. 1891. On the characters of some Paleozoic ®shes. Proceed- interpretation. ings of the U.S. National Museum, 14:447±463. In comparison with other elements, such as teeth or dermal COPE, E. D. 1893. On Symmorium and the position of the cladodont denticles, dorsal ®nspines are uncommon in chondrichthyan fossil sharks. American Naturalist, 27:999±1001. assemblages. This tends to limit their usefulness in determining DALQUEST, W. W., M. J. KOCURKO, AND P. B UZAS-STEPHENS. 1993. A relative faunal abundances within an assemblage or in comparing new record of the chondrichthyan ®sh Physonemus from the Upper different assemblages. The Minturn assemblage contains enough Pennsylvanian of Texas. Texas Journal of Science, 45:190±194. specimens that it is possible to state, with a fair degree of cer- DE VOTO, R. H. 1980. Pennsylvanian stratigraphy and history of Colo- tainty, that Ctenacanthus buttersi, represented by many speci- rado, p. 71±101. In H. C. Kent and K. W. Porter (eds.), Colorado mens, is more common than Bythiacanthus sp. 1, Bythiacanthus Geology. Rocky Mountain Association of Geologists. DEAN, B. 1909. Studies on fossil ®shes (sharks, chimaeroids and artho- sp. 2, cf. ``Ctenacanthus'' furcicarinatus, and Physonemus sp., dires). Memoirs, American Museum of Natural History, 9:209±287. each represented by a single specimen. Acondylacanthus nuperus EASTMAN, C. R. 1902. Some Carboniferous cestraciont and acanthodian is also represented by only a single specimen, but it may be un- sharks. Bulletin of the Museum of Comparative Zoology, 39:55±99. derrepresented in the collection due to collecting bias, because it EASTMAN, C. R. 1903. Carboniferous ®shes from the central western is so small. Faunal comparisons between the Minturn assemblage states. Bulletin of the Museum of Comparative Zoology, 39:163±226. and other chondrichthyan assemblages will require further study ELLIOTT, D. K., AND S. D. BOUNDS. 1987. Causes of damage to bra- of the Minturn Formation teeth, as comparison based on the chiopods from the Middle Pennsylvanian Naco Formation, central Ar- spines alone would not be particularly useful. izona. Lethaia, 20:327±335. GINTER, M. 1998. Taxonomic problems with Carboniferous ``cladodont- level'' sharks' teeth. Ichthyolith Issues Special Publication, 4:14±16. ACKNOWLEDGMENTS GINTER, M. 1999. - chondrichthyan microremains We thank D. Nelson for donation of specimens and landowners from the eastern Thuringian Slate Mountains. Abhandlungen und Ber- in the McCoy area for access to their property. We thank J. Mais- ichte fuÈr Naturkunde, Magdeburg, 21:25±47. HANSEN, M. C. 1978. A presumed lower dentition and a spine of a Perm- ey for help with identi®cation of the specimens, for supplying ian petalodontiform chondrichthyan, Megactenopetalus kaibabanus. photographs of AMNH 19236, and for reviewing an earlier ver- Journal of Paleontology, 52:55±60. sion of the manuscript. We thank P. Robinson for access to the HANSEN, M. C. 1980. New occurrences of the petalodontiform chondri- UCM collections, R. Purdy for access to the USNM collections, chthyan Megactenopetalus in the Pennsylvanian of Oklahoma and Kan- and S. G. Lucas for loaning specimens from the NMMNH. C. P. sas. Oklahoma Geology Notes, 40:185±189. Weibel (Illinois State Geological Survey) and D. Chesnut (Ken- HANSEN, M. C. 1986. Microscopic chondrichthyan remains from Penn- tucky Geological Survey) provided stratigraphic information. W. sylvanian marine rocks of Ohio and adjacent areas. Unpublished Ph.D. Itano acknowledges the Western Interior Paleontological Society dissertation, Ohio State University, Columbus, 536 p. for its support of the purchase of photographic equipment through HANSEN, M. C. 1996. Phylum ChordataÐVertebrate fossils, p. 288±369. In R. M. Feldmann and M. Hackathorn (eds.), Fossils of Ohio. Ohio a Karl Hirsch Memorial Research Grant. Acknowledgment is Division of Geological Survey, Bulletin 70, Columbus, Ohio. made by M. Lockley and K. Houck to the Donors of the Petro- HAY, O. P. 1900. Descriptions of some vertebrates of the Carboniferous leum Research Fund, administered by the American Chemical So- age. Proceedings of the American Philosophical Society, 39:96±123. ciety, for the support of this research. We thank S. Sumida (Cal- HAY, O. P. 1902. Bibliography and Catalogue of the Fossil Vertebrata of ifornia State University, San Bernadino) and M. Hansen (Ohio . Bulletin of the United States Geological Survey, 179: Geological Survey) for their reviews of the manuscript, which 1±868. materially improved it. HOUCK, K. J. 1997. Effects of sedimentation, tectonics, and glacio-eus- tasy on depositional sequences, Pennsylvanian Minturn Formation, North-Central Colorado. AAPG Bulletin, 81:1510±1533. REFERENCES HUXLEY, T. H. 1880. On the application of the laws of evolution to the AGASSIZ, L. 1833±1844. Recherches sur les poissons fossiles. NeuchaÃtel, arrangement of the Vertebrata, and more particularly of the Mammalia. 5 volumes, 1,420 p. Proceedings of the Zoological Society of London, 1880:649±661. BASS,N.W.,AND S. A. NORTHROP. 1963. Geology of Glenwood Springs IVANOV, A. 1999. Late DevonianÐEarly chondrichthyans of the Quadrangle and vicinity, Northwestern Colorado. U.S. Geological Sur- Russian Arctic. Acta Geologica Polonica, 49:267±285. vey Bulletin, 1142-J, 74 p. JOHNSON, G. D. 1984. A new species of xenacanthodii (Chondrichthyes, BONAPARTE, C. L. 1838. Selachorum tabula analytica. Nuovi Annali delle Elasmobranchii) from the late Pennsylvanian of Nebraska. Special Pub- Scienze Naturali (Bologna), 2:195±214. lication Carnegie Museum of Natural History, 9:178±186. BRANSON, E. B. 1916. The lower Embar of Wyoming and its fauna. LEARY, R. L., AND S. TURNER. 1996. The Worthen Collection of Palaeo- Journal of Geology, 24:639±664. zoic vertebrates at the Illinois State Museum. The Geological Curator, CASE, G. R. 1970a. A fossil shark in Nebraska. Underwater Naturalist, 6:195±205. 6(4):29±30. LEIDY, J. 1859. Descriptions of Xystracanthus arcuatus and Cladodus CASE, G. R. 1970b. The occurrence of Petrodus and other fossil shark occidentalis. Proceedings of the Academy of Natural Sciences of Phil- remains in the Pennsylvanian of Iowa. Annals of Iowa, 40:445±449. adelphia, 3. CASE, G. R. 1982. A Pictorial Guide to Fossils. Van Nostrand Reinhold LEIDY, J. 1873. Contributions to the extinct vertebrate fauna of the west- Company, New York, 514 p. ern territories. First Annual Report of the U.S. Geological Survey of CHORN, J., AND D. FRAILEY. 1978. A large chondrichthyan spine, Phy- the Territories, 1±358. sonemus mirabilis, from the Upper Pennsylvanian of Kansas, U. S. A. LOCKLEY, M. G. 1984. Pennsylvanian predators: a preliminary report on Neues Jahrbuch fuÈr Geologie und PalaÈontologie Monatshefte, 7:385± some Carboniferous shark remains from Colorado. University of Col- 392. orado at Denver Geology Department Magazine, 3:18±22. CHORN, J., AND E. A. REAVIS. 1978. Af®nities of the chondrichthyan LUCAS,S.G.,AND J. W. ESTEP. 2000. Pennsylvanian selachians from the organ-genera Listracanthus and Petrodus. The University of Kansas Cerros de Amado, central New Mexico, p. 21±27. In S. G. Lucas (ed.), Paleontological Contributions, 89:4±9. New Mexico's Fossil Record 2. New Mexico Museum of Natural His- CHRONIC, J., AND C. STEVENS. 1958. Pennsylvanian paleogeography in tory and Science Bulletin 16. ITANO ET AL.ÐCHONDRICHTHYAN SPINES FROM COLORADO 535

LUND, R. 1989. New petalodonts (Chondrichthyes) from the Upper Mis- ROTH, R., AND J. SKINNER. 1930. The fauna of the McCoy Formation,

sissippian Bear Gulch Limestone (Namurian E2b) of Montana. Journal Pennsylvanian, of Colorado. Journal of Paleontology, 4:332±352. of Vertebrate Paleontology, 9:350±368. SANTUCCI, V. L. 1998. The Yellowstone Paleontological Survey. Yellow- LUND, R. 1999. diversity of the Bear Gulch Limestone, Namurian, stone Center for Resources, National Park Service, Yellowstone Na- Lower Carboniferous of Montana, USA. Geobios, 32:285±295. tional Park, Wyoming, YCR-NR-98-1, 51 p. M'COY, F. 1848. On some new fossil ®sh of the Carboniferous Period. SCHULTZE, H.-P., AND R. R. WEST. 1996. An eugeneodontid elasmo- Annals and Magazine of Natural History, 2:115±133. branch from the late Paleozoic of Kansas. Journal of Paleontology, 70: MAISEY, J. G. 1975. The interrelationships of phalacanthous selachians. 162±165. Neues Jahrbuch fuÈr Geologie und PalaÈontologie Monatshefte, 9:553± ST.JOHN, O., AND A. H. WORTHEN. 1875. Descriptions of fossil ®shes. 567. Geological Survey of Illinois, Geology and Paleontology, 6:245±488. MAISEY, J. G. 1981. Studies on the Paleozoic selachian genus Ctenacan- ST.JOHN, O., AND A. H. WORTHEN. 1883. Descriptions of fossil ®shes. thus Agassiz, 1, Historical review and revised diagnosis of Ctenacan- Geological Survey of Illinois, Geology and Paleontology, 7:55±264. thus, with a list of referred taxa. American Museum Novitates, Number STEVENS, C. H. 1958. Stratigraphy and Paleontology of the McCoy, Col- 2718, 22 p. orado Area. Unpublished M.A. thesis, University of Colorado, Boulder, MAISEY, J. G. 1982. Studies on the Paleozoic selachian genus Ctenacan- 242 p. thus Agassiz, 2, Bythiacanthus St. John and Worthen, , SUMIDA, S. S., G. M. ALBRIGHT, AND E. A. REGA. 1999. Late Paleozoic new genus, Eunemacanthus St. John and Worthen, Sphenacanthus Ag- ®shes of Utah, p. 13±20. In D. D. Gillette (ed.), Vertebrate Paleontology assiz, and Munster. American Museum Novitates, Number in Utah. Utah Geological Survey Miscellaneous Publication, 99±1. 2722, 24 p. TRAQUAIR, R. H. 1884. Description of a fossil shark (Ctenacanthus cos- MAISEY, J. G. 1983. Some Pennsylvanian chondrichthyan spines from tellatus) from the lower Carboniferous rocks of Eskdale, Dumfriesshi- Nebraska. Transactions of the Nebraska Academy of Sciences, 11:81± res. Geological Magazine, 1:3±8. 84. TRAUTSCHOLD, H. 1879. Die KalkbruÈche von Mjatschkowa. Eine Mon- ographie des oberen Bergkalks. Nouveaux Memoires de la SocieÂte Im- MAISEY, J. G. 1984. Studies on the Paleozoic selachian genus Ctenacan- thus Agassiz, 3, Nominal species referred to Ctenacanthus. American periale des Naturalistes de Moscou, 14:1±82. Museum Novitates, Number 2774, 20 p. TWETO, O. 1949. Stratigraphy of the Pando area, Eagle County, Colorado. Colorado Scienti®c Society, Proceedings, 15:149±235. MAISEY, J. G. 1989. Hamiltonichthys mapesi, g. & sp. nov. (Chondrich- WELLS, J. W. 1944. A new ®sh spine from the Pennsylvanian of Ohio. thyes; Elasmobranchii), from the Upper Pennsylvanian of Kansas. Ohio Journal of Science, 44:65±67. American Museum Novitates, Number 2931, 42 p. WILLIAMS, M. E. 1985. The ``cladodont level'' sharks of the Pennsyl- MALYSHEVA, E. O., A. O. IVANOV,P.A.BEZNOSOV,A.A.BELYAEV, vanian black shales of central North America. Palaeontographica, 190: AND S. N. MITYAKOV. 2001. Facies and ichthyofauna of the Kazanian 83±158. from the Vym' River (Komi Republic, Russia). Ichthyolith Issues Spe- ZANGERL, R. 1981. Chondrichthyes I. Paleozoic Elasmobranchii, p. 1± cial Publication, 6:59±63. 115. In H. P. Schultze (ed.), Handbook of Paleoichthyology, volume MAPES,R.H.,AND M. C. HANSEN. 1984. Pennsylvanian shark-cepha- 3A. Gustav Fischer, Stuttgart and New York. lopod predation: a case study. Lethaia, 17:178±183. ZANGERL, R., AND E. S. RICHARDSON,JR. 1963. The paleoecological MCNULTY, C. L., JR. 1963. Teeth of Petalodus alleghaniensis Leidy from history of two Pennsylvanian black shales. FieldianaÐGeology Mem- the Pennsylvanian of North Texas. Texas Journal of Science, 15:351± oirs, 4:1±352. 353. ZIDEK, J. 1973. Oklahoma paleoichthyology, Pt. 2, Elasmobranchii (Cla- MILLER, H. W. 1957. Petalodus jewetti, a new species of fossil bradyo- dodus, minute elements of cladoselachian derivation, Dittodus, and Pe- dont ®sh from Kansas. Transactions of the Kansas Academy of Science, trodus). Oklahoma Geology Notes, 33:87±103. 60:82±85. ZIDEK, J. 1976. Oklahoma paleoichthyology, Pt. 5, Chondrichthyes. MILLER, W. E. 1981. Cladodont shark teeth from Utah. Journal of Pale- Oklahoma Geology Notes, 36:175±192. ontology, 55:894±895. ZIDEK, J. 1977. Oklahoma paleoichthyology, addendum to part 5. NEWBERRY, J. S. 1875. Description of fossil ®shes. Geological Survey Oklahoma Geology Notes, 37:151±156. of Ohio, 2(2):1±64. ZIDEK, J. 1978. New chondrichthyan spines from the late Paleozoic of NEWBERRY, J. S. 1889. The Paleozoic ®shes of North America. United Oklahoma. Journal of Paleontology, 52:1070±1078. States Geological Survey Monograph, 16:1±340. ZIDEK, J. 1992. Late Pennsylvanian Chondrichthyes, Acanthodii, and NEWBERRY, J. S., AND A. H. WORTHEN. 1866. Description of vertebrates. deep-bodied Actinopterygii from the Kinney Quarry, Manzanita Moun- Geological Survey of Illinois, 2:9±141. tains, New Mexico, p. 145±182. In J. Zidek (ed.), Geology and Pale- OSSIAN, C. R. 1974. Paleontology, paleobotany and facies characteristics ontology of the Kinney Brick Quarry, Late Pennsylvanian, Central New of a Pennsylvanian delta in southeastern Nebraska. Unpublished Ph.D. Mexico. New Mexico Bureau of Mines and Mineral Resources, Bul- dissertation, University of Texas, Austin, 394 p. letin, 138. ROBB, A. J. 1992. Vertebrate fossils from the Lawrence Formation (Doug- ZIDEK, J. 1993. A large stethacanthid shark (Elasmobranchii: Symmori- las Group, Virgilian, Upper Pennsylvanian) in Northeastern Kansas. ida) from the Mississippian of Oklahoma. Oklahoma Geology Notes, Transactions of the Kansas Academy of Science, 95:129±138. 53:4±15. ROSS,C.A.,AND J. R. P. ROSS. 1987. Late Paleozoic sea levels and ZIDEK, J., AND K. K. KIETZKE. 1993. Pre-Permian vertebrates of New depositional sequences, p. 137±149. In C. A. Ross and D. Haman Mexico, with remarks on some early Permian specimens, p. 1±10. In (eds.), Timing and Depositional History of Eustatic Sequences: Con- S. G. Lucas and J. Zidek (eds.), Vertebrate Paleontology in New Mex- straints on Seismic Stratigraphy. Cushman Foundation for Foraminif- ico. New Mexico Museum of Natural History and Science, Bulletin, 2. eral Research, Special Publication, 24. ACCEPTED 12 JULY 2002