Novtautesamerican MUSEUM PUBLISHED by the AMERICAN MUSEUM of NATURAL HISTORY CENTRAL PARK WEST at 79TH STREET, NEW YORK, N.Y

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NovtautesAMERICAN MUSEUM PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2722, pp. 1-24, figs. 1-1I1 January 29, 1982 Studies on the Paleozoic Selachian Genus Ctenacanthus Agassiz: No. 2. Bythiacanthus St. John and Worthen, Amelacanthus, New Genus, Eunemacanthus St. John and Worthen, Sphenacanthus Agassiz, and Wodnika Miunster

JOHN G. MAISEY1

ABSTRACT Some of the finspines originally referred to Eunemacanthus St. John and Worthen is revised Ctenacanthus are reassigned to other taxa. Sev- to include some European and North American eral characteristically tuberculate lower Carbon- species. Sphenacanthus Agassiz is shown to be iferous finspines are referred to Bythiacanthus St. a distinct taxon from Ctenacanthus Agassiz, on John and Worthen, including one of Agassiz's the basis of finspine morphology, and its wide- original species, Ctenacanthus brevis. Finspines spread occurrence in the Carboniferous of North referable to Bythiacanthus are known from west- America is demonstrated. Similarities are noted ern Europe, the U.S.S.R., and North America. between the finspines of Sphenacanthus and Amelacanthus, new genus, is described on the Wodnika, and both taxa are placed provisionally basis of finspines from the United Kingdom. Four in the family Sphenacanthidae. A new species of species are recognized, two of which were origi- Wodnika, W. borealis, is recognized on the basis nally assigned to Onchus by Agassiz, and all four of a finspine from the Permian of Alaska. of which were referred to Ctenacanthus by Davis.

INTRODUCTION The present paper is the second in a series Ctenacanthus in an attempt to restrict this of reviews of the Paleozoic chondrichthyan taxon to sharks with finspines that closely Ctenacanthus. The first paper (Maisey, resemble those of the type species, C. ma- 1981) reexamined Agassiz's (1837) genus jor. Agassiz (1837) described some other 1 Assistant Curator, Department of Vertebrate Paleontology, American Museum of Natural History.

Copyright (©) American Museum of Natural History 1982 ISSN 0003-0082 / Price $2.00 2 AMERICAN MUSEUM NOVITATES NO. 2722 spines which were referred to Ctenacanthus, different from that of C. major in shape and although their morphology and ornament ornamentation. Instead of being long and patterns differ greatly from those of C. ma- slender, the spine of C. brevis is squat and jor. Only one of Agassiz's (1837) other Cten- broad, and is ornamented by large round, acanthus species, C. tenuistriatus, is left in striated tubercles arranged in closely spaced that genus by Maisey (1981). However, var- series down the spine, instead of the fine pec- ious spines have been referred to Ctenacan- tinated ribs seen on C. major spines. Since thus by previous authors, with the result that the spines of C. brevis and C. major are so the genus had become reduced to an almost different, retaining C. brevis in the genus undiagnosable state; in particular, Sphen- Ctenacanthus is unjustified. Recent squaloid acanthus has been greatly confused with and heterodontid finspine morphology and Ctenacanthus. The present work therefore ornamentation does not vary below generic reviews finspines that were included in Cten- level. This is apparently also true of hybo- acanthus by Agassiz (1837) but were exclud- dont finspines (Maisey, 1978). ed by Maisey (1981), and also includes a re- Agassiz (1837) never saw the finspine on view of the genus Sphenacanthus. which his description of C. brevis was based before its publication, although it is known ACKNOWLEDGMENTS which specimen this was and it can still be I thank the following people for their as- located (see below and fig. 2B, C). He knew sistance in preparing this work: Ms. Lorraine the specimen only from a drawing sent by Meeker and Mr. Chester Tarka (preparation the Reverend William Buckland, his col- of illustrations), Mr. Walter Sorensen (clean- league. ing and preparation of specimens). The fol- Finspines similar to those in C. brevis lowing have also been most helpful in were later described from North America providing specimens, photographs or and referred to a new genus, Bythiacanthus information; Drs. S. M. Andrews, M. D. St. John and Worthen (1875). Comparison of Crane, C. L. Forbes, W. J. Hlavin, N. Hot- the original descriptions with other finspines ton, D. Sartenaer, B. Schaeffer, G. Schaum- referred to Bythiacanthus in the American berg, K. S. Thomson, M. Williams, R. Zan- Museum of Natural History suggest that gerl and J. Zidek. Abbreviations are: AMNH, Agassiz's (1837) C. brevis should provision- American Museum of Natural History; ally be referred to Bythiacanthus. BMNH, British Museum (Natural History); AMENDED DIAGNOSIS: Elasmobranch rec- CM, Carnegie Museum; USNM, United ognized by having dorsal finspines of stout States National Museum, Smithsonian In- build, rhomboidal outline in lateral view; stitution. thick walls of trabecular osteodentine; anterior face rounded, strongly to moderately compressed laterally, posterior wall convex, BYTHIACANTHUS ST. JOHN AND WORTHEN level of posterior closure very high and the HISTORICAL NOTE: The type species of posterior wall correspondingly short; in Ctenacanthus (Agassiz, 1837) is C. major. transverse section the trunk wall much thick- The second species he described, C. brevis, ened anteriorly; ornament of longitudinal is based on a dorsal finspine which is very rows of rounded, striated tubercles, usually

FIG. 1. A-I, Bythiacanthus vanhornei; holotype, from St. John and Worthen (1875) pl. 17, no. 1. J-L, Bythiacanthus siderius (Leidy); J-K, AMNH 1826, St. Louis Limestone, Alton, Illinois; L, the holotype PAN S 22:17 7835, "Sub-Carboniferous," Glasgow, Tennessee; from Leidy (1873) pl. 32, no. 59. M-N, Bythiacanthus off. ianishevskyi AMNH 9594 (reversed to facilitate comparison with other specimens); Waverly sandstone, ?Marion Co., Kentucky. 1982 MAISEY: CTENACANTHUS AGASSIZ 3

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FIG. 2. A-F, Bythiacanthus brevis (Agassiz); A, from Agassiz (1837) tab. 2, no. 2; B, C, the holotype C 4154 (photographs courtesy of Bristol City Museum and Art Gallery, England). Compare with A which was originally copied from Buckland's drawing of this specimen; D, deta-il of ornament from another specimen, BM(NH) P2226; E, F, from Davis (1883) p1. XLIII, no. 3; this appears to be specimen BM(NH) P2226. G-K, Bythiacanthus ianishevskyi (Khabakob); from Khabakob (1926) pl. III, nos. 5-10. 1982 MAISEY: CTENACANTHUS AGASSIZ 5

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i FIG. 3. A, B, Bythiacanthus solidus (Eastman); A, the holotype, USNM 3383; B, paratype, from Eastman (1903) p1. 7, no. 3. C-F, Bythiacanthus peregrinus (Khabakob); from Khabakob (1928) pl. III, nos. 1-4. G, Bythiacanthus lucasi (Eastman); from Eastman (1902) pl. 6, no. 1. less than their own diameter apart; rows in- Asteracanthus siderius Leidy, 1873, p. 313; creased proximally by primary bifurcation C. solidus Eastman, 1902, p. 90; Incertae anteriorly and by being inserted between sedis, aff. Bythiacanthus; Glymmatacan- other rows marginally. thus irishii St. John and Worthen, 1875, p. TYPE SPECIES: Bythiacanthus vanhornei 447; G. rudis St. John and Worthen, 1883, St. John and Worthen, 1875, p. 445, St. p. 249; G. petrodoides St. John and Wor- Louis Limestone, Alton, Illinois. then, 1883, p. 250. REFERRED SPECIES: Ctenacanthus brevis DISCUSSION: Leidy (1873, p. 313) referred Agassiz, 1837, p. II; C. ianishevskyi Kha- a coarsely tuberculated finspine, PAN S bakob, 1928, p. 23; C. lucasi Eastman, 1902, 22:13 7835, from the "Sub-Carboniferous" p. 80; C. peregrinus Khabakob, 1928, p. 25; of Glasgow, Tennessee, to a new species, 6 AMERICAN MUSEUM NOVITATES NO. 2722

Asteracanthus siderius. Apart from the pres- relatively even deeper cross-sections are ence of tubercles, however, there is nothing also known. to suggest that this spine is referable to As- Bythiacanthus solidus (Eastman, 1902, p. teracanthus, which is otherwise a Mesozoic 90) is based on finspines USNM 3383 (the taxon and which has distinctive hybodontid holotype) and USNM 4833 (paratype). East- finspines (Maisey, 1978). Leidy's (1873) man's (1902, fig. 13) transverse section is specimen of a spine resembles that of By- taken near the base of the type finspine, but thiacanthus vanhornei, described by St. does not indicate the full depth of the spine John and Worthen (1875, p. 445), who sug- anteroposteriorly. Eastman (1902, pl. 2, fig. gested that these spines might belong to the 3) did not otherwise figure the type speci- same species. Another almost complete fin- men, which is illustrated here (fig. 3A). The spine, AMNH 1826, closely resembles Lei- ornament of the holotype is slightly less pro- dy's (1873) specimen, and is referred to By- nounced than that of the paratype (fig. 3B), thiacanthus siderius. Finspines referred to and is similar to the ornament of B. lucasi, this taxon are more densely covered by tu- also described by Eastman (1902, p. 80, pi. bercles than those in B. vanhornei. Because 6, fig. 1, also text-fig. 9). The ornamentation of the differences in their tubercle arrange- of B. solidus, however, is less regular than ment and density, I disagree with St. John that of B. lucasi (fig. 3G). A primary row of and Worthen's (1875) suggestion that these tubercles is present anteriorly on finspines of species are synonymous (fig. lA-L). both species. Both are provisionally referred Agassiz's (1837) figure of "Ctenacanthus" to Bythiacanthus although their ornamenta- brevis is reproduced here (fig. 2A), along tion is more regular than in the type species, with illustrations of the actual specimen (fig. B. vanhornei. 2B, C). This represents the first time that the Bythiacanthus ianishevskyi (Khabakob, type specimen has been properly figured. 1928, p. 23) is also founded on a fragmentary The coarsely tuberculate ornament is shown finspine with coarse, tuberculate ornament in detail (fig. 2D). It agrees closely with that and an extremely deep anteroposterior di- of Bythiacanthus finspines. In transverse mension in transverse section (fig. 2G-K). section, B. siderius and B. vanhornei fin- Another finspine of equally peculiar shape is spines are laterally compressed, whereas AMNH 9594, apparently from the Waverly those of B. brevis are rounded and little com- Sandstone of Marion Co., Kentucky (fig. pressed. All these finspines have an ex- IM, N). This spine is referred to Bythiacan- tremely high level of posterior closure, so thus and is probably close to B. ianishevskyi. that the posterior opening is very long and Bythiacanthus peregrinus (Khabakob, the complete posterior wall is short. In all 1928, p. 25) is provisionally included here cases the posterior wall is convex. Bythi- because of similarities in the finspine orna- acanthus brevis finspines are stout, thick mentation in B. brevis, B. solidus, and B. walled, and strongly recurved toward the tip. lucasi. In transverse section B. peregrinus Tubercles on these spines are arranged in finspines resemble those of B. brevis quite rows which increase in number proximally closely, and these species may eventually by two methods; bifurcation of new rows prove to be synonymous. Khabakob's (1928) from a primary row anteriorly; and marginal illustrations are shown in figure 3C-F. introduction of new rows posterolaterally The type species of Glymmatacanthus, G. (cf. Sphenacanthus marginal rib insertion irishii, is based on a fragmentary finspine, pattern described below). USNM 13537. Its flattened shape in trans- Bythiacanthus vanhornei and B. siderius verse section, and ornamentation pattern are finspines are laterally compressed, but are reminiscent of Bythiacanthus (fig. 4D-G). very deep anteroposteriorly. This is evident Another species also founded on a similar in transverse sections (e.g., fig. IG, H). Oth- fragment of spine, is G. rudis (fig. 4A-C). er finspines with similar ornamentation but Bythiacanthus and Glymmatacanthus are 1982 MAISEY: CTENACANTHUS AGASSIZ 7

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.4 1-1 J Z,, 4 " JI_LA I 1 cm L- -- FIG. 4. A-C, Glymmatacanthus rudis; from St. John, Worthen and Miller (1883) pl. XXV, no. 1; section C is diagrammatic and cannot be located accurately on original specimen USNM 13504. D-G, Glymmatacanthus irishii; from St. John, Worthen and Miller (1875) pl. 17, no. 2; specimen now USNM 13537. H-K, Glymmatacanthus petrodoides; from St. John, Worthen and Miller (1883) pl. XXV, no. 2. provisionally retained as separate taxa, but vanian) of Indiana, however, has coarsely may prove to be synonymous. Some species, tuberculate finspines which may ally it to such as G. petrodoides St. John and Wor- Bythiacanthus. There is some similarity be- then (1883, p. 250) are based on very frag- tween Bythiacanthus finspines and those of mentary material about which little can be Goodrichthys eskdalensis (Moy-Thomas, said (fig. 4H-K). 1936, pl. II). Both have an extremely high level of posterior closure, and a relatively short ornamented region. Whether these ARTICULATED OR ASSOCIATED similarities are of systematic significance is REMAINS unknown. None of the finspines discussed here has been described from associated or articulat- AMELACANTHUS, NEW GENUS ed remains. Therefore, the relationships of EUNEMACANTHUS ST. JOHN AND WORTHEN taxa based on these remains are highly spec- HISTORICAL NOTE: Amelacanthus, new ulative. An as yet undescribed shark, FMNH genus, is defined on the basis of finspines. PF 8170, from the Mecca Shales (Pennsyl- Four species from the British lower Carbon- 8 AMERICAN MUSEUM NOVITATES NO. 2722

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FIG. 5. A-E, Amelacanthus sulcatus (Agassiz); A, from Agassiz (1837) tab. 1, no. 6; B, detail of ornament from BM(NH) P2670; C, D, from Davis (1883) pi. XLV, no. 3; specimen now BM(NH) P2670; E, from peel of BM(NH) P2871. F-I, Amelacanthus plicatus (Davis); from Davis (1883) pl. XLV, no. 4. J, K, Amelacanthus laevis (Davis); from peel of BM(NH) P2531. L, Amelacanthus pustulatus (Davis); from peel of BM(NH) P2529, reversed to facilitate comparison with other specimens. iferous are recognized, two of which were thus, but which was subsequently removed originally referred to Onchus (Agassiz, to the new genus (St. John and Worthen, 1837), and all four of which were referred to 1883). Agassiz (1837) listed C. heterogyrus Ctenacanthus by Davis (1883). These species finspines but these were only later described are readily distinguished from Ctenacanthus and figured (McCoy, 1855). This species is major by the extensive- shiny enameled lay- probably referable to Eunemacanthus on the er over much of the smooth finspine orna- basis of its finspine morphology (see below). ment. AMELACANTHUS, NEW GENUS The genus Eunemacanthus is based on a finspine which was originally referred by DIAGNOSIS: Elasmobranch recognized by Newberry and Worthen (1866) to Ctenacan- slender, slightly recurved finspines; anterior 1982 MAISEY: CTENACANTHUS AGASSIZ 9 margin acute but rounded; sides divergent C. pustulatus, were also recognized on the posteriorly but almost flat, giving a subtrian- basis of enameled finspines similar to those gular outline in section; posterior wall con- of 0. sulcatus and 0. plicatus. All these cave or flat, rarely with a low rise mesially; species are referred here to Amelacanthus, ornament of broad, smooth costae (ribs) with new genus. narrow intercostal grooves; costae heavily The principal differences between the fin- enameled and usually displaying growth spines referred here to Amelacanthus are the lines; primary bifurcation of costae occurs at number and breadth of costae and the angles the anterior margin, but a distinct anterior at which the lateral faces of the spines di- rib may be absent; posterolateral margins verge. In Amelacanthus sulcatus the fin- armed apically by small, usually downcurved spines have about 15 costae per side, with a and rounded or pointed denticles. somewhat broader anterior rib from which TYPE SPECIES: Onchus sulcatus Agassiz, three or four lateral ribs arise by primary bi- 1837, vol. 3, p. 8, pl. 1, fig. 6; Onchus sul- furcation (fig. 5A-E). Finspines of A. sulcatus Agassiz; Agassiz, 1837, p. 8; Cten- catus are about twice as deep as broad in acanthus sulcatus (Ag); Davis, 1883, p. 343; transverse section (Davis, 1883, fig. 3A). The C. sulcatus (Ag); Woodward, 1891, p. 101. lateral faces diverge from the leading edge of TYPE: Bristol Museum C4154 lower Car- the finspine at approximately 30 degrees (fig. boniferous Limestone; Gloucestershire, SD). Finspines referred to A. laevis are sim- Shropshire, and Armagh. ilar to those of A. sulcatus in transverse sec- REFERRED SPECIES: C. plicatus (Agassiz, tion (fig. 5K), and the anteriormost lateral 1837); C. laevis Davis, 1883, p. 341; C. pus- costae arise by primary bifurcation from the tulatus Davis, 1883, p. 344. anterior rib, but there are more ribs (approx- DIscUSSION: The finspines referred here to imately 24 per side). The posteriormost ribs Amelacanthus differ profoundly from those are continuous down to the ornament base of Ctenacanthus in their ornamentation. In- in A. laevis finspines (fig. 5J). In A. sulcatus, stead of numerous pectinated or transversely however, the posteriormost one or two ribs tuberculated ribs (typical of Ctenacanthus) terminate at the posterolateral margins the finspines of Amelacanthus are orna- above the ornament base (marginal offlap of mented by broad, smooth costae separated ribs; fig. 5C). Finspines of A. sulcatus and by narrow intercostal grooves. The costae A. laevis are of similar size and the differ- are surfaced by a shiny, thick outer enamel- ences noted are probably not growth related; oid layer. Agassiz (1837) did not refer any of different taxa are undoubtedly represented. these finspines to Ctenacanthus. This was Finspines of Amelacanthus plicatus are not because of the differences in their ribbed somewhat broader posteriorly than those of ornamentation, however, but becau.se he A. sulcatus and A. laevis, and in transverse thought these spines lacked posterolateral section have the form of an equilateral tri- denticles. Two species were referred to On- angle (fig. SF-I). A distinct anterior (prima- chus; 0. sulcatus and 0. plicatus (the latter ry) rib is absent. Lateral ribs increase in by name only). Davis (1883, p. 343) men- number basally by bifurcation rather than by tioned that Agassiz subsequently received a intercalation of new ribs. As a result of this, finspine of 0. sulcatus in which marginal the anterior margin is "formed by the re- denticles were present, and Davis also con- peated inosculation of the lateral ridges" firmed the presence of these denticles on fin- (Davis, 1883, p. 342). In other respects A. spines of this and the other species. On the plicatus finspines resemble those of A. sul- strength of this discovery, Davis (1883) re- catus and A. laevis, and are most like A. ferred 0. sulcatus and 0. plicatus to Cten- laevis finspines in having about 20 costae per acanthus. The possibility that posterolateral side proximally and half that number distal- marginal denticles might be useless as a ge- ly. neric character does not seem to have been Finspines referred to a fourth species, considered. Two other species, C. laevis and Amelacanthus pustulatus, are distinguished 10 AMERICAN MUSEUM NOVITATES NO. 2722

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FIG. 6. A-F, Eunemacanthus costatus (Newberry and Worthen); A, from Newberry and Worthen (1866) pl. XII, no. 5; B-F, from St. John, Worthen and Miller (1883) pi. XXIII,.s no. 2. from the others by its ribs, which are nar- catus, and A. pustulatus. These denticles are rower than the intercostal grooves (fig. 5L). unusual in A. pustulatus in being directed About nine or ten ribs are present on each upward, rather than downward as in most side, their number increasing proximally by Paleozoic shark finspines. lateral intercalation and anterior primary bi- EUNEMACANTHUS furcation. Between some of the more ante- ST. JOHN AND WORTHEN rior ribs are a few discrete enameled tuber- AMENDED DIAGNOSIS: Elasmobranch rec- cles. Posterolateral (marginal) denticles are ognized by stout, elongate and laterally com- present on finspines of A. sulcatus, A. pli- pressed finspines; anterior margin broad, oc- 1982 MAISEY: CTENACANTHUS AGASSIZ I1I

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FIG. 7. A-I, Eunemacanthus heterogyrus (McCoy); A-E, from Davis (1883) pi. XLIV, nos. 1-3; F, G, details of ornament from BM(NH) P2228; H [Royal Mus., Bruxelles] P1321; I, sagittal section through apex of BM(NH) 2528 to show heavy abrasion of dentine. J-M, Eunemacanthus? venator (Khabakob); J-L from Khabakob (1928) pl. IV, nos. 1-3; M, alter- native restoration of section, avoiding need for ribs on posterior wall (cf. L). cupied by a wide, enameled rib; sides nearly (Newberry and Worthen); St. John and Wor- flat, but with a slight convexity; posterior then, 1883, p. 246. surface concave; ornamentation of thick, ir- REFERRED SPECIES: Ctenacanthus hetero- regular enameled ribs interrupted by trans- gyrus, McCoy, 1855, p. 625 (syn. C. dubius verse ridges, sometimes discontinuous; in- Davis, 1883, p. 340; see Woodward, 1891, p. tercostal areas sometimes occupied by 101); Eunemacanthus keyti Branson, 1916, irregularly dispersed tubercles or short p. 655; Ctenacanthus venator Khabakob, lengths of ribbing; primary bifurcation oc- 1928, p. 28. curs anteriorly; marginal denticles occur api- DIscUSSION: Although Newberry and cally. Worthen's (1866) species was designated the TYPE SPECIES: Ctenacanthus costatus type of Eunemacanthus by St. John and Newberry and Worthen, 1866, p. 120, pl. Worthen (1883), it is predated by Ctenacan- XII, fig. 5; Carboniferous, St. Louis Lime- thus heterogyrus which is similar in many stone, Alton, Illinois; Ctenacanthus costa- respects. This species was named by Agassiz tus Newberry and Worthen, 1866, p. 120; (1837, p. 177), but was only later described Ctenacanthus excavatus St. John and Wor- (McCoy, 1855, p. 625). Eunemacanthus het- then, 1875, p. 428; Eunemacanthus costatus erogyrus finspines seem sufficiently distinct 12 AMERICAN MUSEUM NOVITATES NO. 2722 from E. costatus to continue separating them convex rather than concave (possibly a re- specifically. sult of crushing), although the irregular, Eunemacanthus costatus finspines are enameled ribs are similar to E. costatus. moderately recurved posteriorly, taper fairly Ctenacanthus excavatus St. John and rapidly, and have a wedge-shaped transverse Worthen (1875, p. 428) is based on fragments section (fig. 6). The anterior rib is particular- from the tips of finspines, probably E. cos- ly broad, being almost semicircular in sec- tatus. The fewer number of ribs is probably tion, and the spine therefore has a blunt lead- growth related (see Maisey, 1975, 1978). ing edge. St. John and Worthen's (1883) Ctenacanthus dubius Davis (1883, p. 340) description of the ornamentation is clear and similarly can be regarded as an E. hetero- is not repeated here. gyrus finspine at an earlier state of develop- Eunemacanthus heterogyrus finspines are ment. similarly shaped as those in E. costatus, but Ctenacanthus venator Khabakob (1928, p. in many specimens the appearance of a 28) is known only by a fragment from the broad leading edge is further exaggerated by midregion of a finspine (fig. 7J-M). The or- remarkably heavy abrasion (fig. 7A-I). The namentation is said to be "smooth-ribbed," ribs are somewhat less crenulated than in the but whether it is enameled or not is not men- type specimen, although this is not apparent tioned. The posterior wall of the spine is ap- from published figures. In fact, there is con- parently concave. I have not examined the siderable variation in the ornamentation that specimen and provisionally must accept has been illustrated. In McCoy (1855, pl. III, Khabakob's conclusion that it is "nearly al- fig. 32), rather beaded or crenulated ribs are lied to the English Ctenacanthus heterogy- indicated, whereas they are depicted (some- rus McCoy." However, I have reservations what diagrammatically) as straight bars by about including C. venator here, since the De Koninck (1878, pl. VI, fig. 3; cf. fig. 7H published figures are very reminiscent of here). Davis (1883, pl. XLIV, figs. 1-3) illus- Sphenacanthus spp. (see following section trates strongly pectinate finspines, with fairly and figs. 8-11). Khabakob's (1928, fig. 2) regular ribbing. Finspines of E. heterogyrus transverse section is unlikely to be accurate, in the British Museum (Natural History) are since it shows lateral ribbing extending onto much more irregularly ornamented (fig. 7F, the posterior wall, unlike other elasmo- G). Irregular tubercles and short costae are branch dorsal finspines (fig. 7L). An alter- much more common in E. heterogyrus than native restoration of the transverse section in E. costatus. The marginal denticles also is shown in figure 7M. differ, the finspines of E. costatus being re- All the finspines under discussion are char- curved upward slightly, and those of E. het- acteristically ornamented with heavily enam- erogyrus being more rounded. eled costae, and (apart from E. keyti) have An inner layer of nontrabecular dentine a concave posterior wall. None of them is completely fills the finspine central cavity known from articulated or even associated apically in E. heterogyrus, perhaps to count- remains, so their relationships are to a large er the effects of heavy in vivo apical abra- extent untestable. However, in both char- sion; a longitudinal section illustrates how acteristics just mentioned, these finspines re- extensive both the abrasion and the second- semble those of Recent squaloids and het- ary dentine are (fig. 71). Eunemacanthus erodontids, and differ profoundly from those costatus has not been sectioned, and it is not of hybodontids. They are similar also to fin- known whether a comparable plug of dentine spines of Palaeospinax and Nemacanthus, is developed. fossil genera which I have argued elsewhere Eunemacanthus keyti is founded on a tiny (Maisey, 1977) are closely allied to living scrap of finspine (Branson, 1916, p. 655, pl. elasmobranchs. I therefore suggest that IV, fig. 1, text-fig. 1), and is here included Amelacanthus and Eunemacanthus are al- with misgivings since the posterior wall is lied to neoselachians and not to hybodontids 1982 MAISEY: CTENACANTHUS AGASSIZ 13 or Ctenacanthus. Nemacanthus character- species of Ctenacanthus, C. major, and to istically has a broad anterior enameled rib, Newberry's (1873) revision of Ctenacanthus and numerous rounded tubercles arranged in which was based on Sphenacanthus fin- more or less vertical rows laterally. Marginal spines that had been sent him from Scotland denticles are frequently but not invariably and which had previously been misidentified present. The finspines of Geisacanthus bul- as C. major (Maisey, 1981). Confusion over latus St. John and Worthen (1875, p. 441, pl. the identity of Ctenacanthus and Sphen- XVII, figs. 3, 4) have larger, vertically striat- acanthus has also resulted in referral of a ed tubercles (diameters exceeding that of the wide variety of finspines, with differing or- anterior rib, unlike Nemacanthus which has namentation and other morphological char- rather smaller tubercles), which are arranged acters, to Ctenacanthus (e.g., Davis, 1883). in definite axial series. Geisacanthus fin- In fact Ctenacanthus and Sphenacanthus spines may therefore represent a morpholog- finspines are readily distinguishable. It is ical intermediate between those of Eune- now clear that Newberry's (1873) Ctenacan- macanthus and Nemacanthus, although a thus marshi finspine is referable to Sphena- phylogenetic relationship based on these canthus, and that it represents the first pub- similarities would be highly speculative. lished (but by no means the only) occurrence None of the finspines referred to Amela- of Sphenacanthus from Carboniferous de- canthus or Eunemacanthus have been found posits of North America. associated with other remains. However, During the course of the present investi- these spines are considered to pertain to gation, it became evident that Sphenacan- sharks, rather than to some other fish, be- thus finspines closely resemble those of cause of the presence of distinct ornamented Wodnika, a Permian shark now known from (distal) and unornamented (basal) parts (see many complete skeletons (Schaumberg, 1977 Maisey, 1975 for details). and in prep.). Since these genera may be Eunemacanthus seems to have had a fairly closely related, a discussion of Wodnika has wide distribution. Amelacanthus is more re- been added here. stricted. Outside Great Britain and Northern I will attempt to distinguish between Ireland, Amelacanthus is recognized in Sphenacanthus and Ctenacanthus by pre- North America on the basis of a fragmentary senting diagnoses of their finspines. Associ- finspine, University of Nebraska State Mu- ated remains of both genera are known seum no. 82410. (Dick, 1978; Maisey, 1981), and other char- acters such as tooth morphology support the SPHENACANTHUS AGASSIZ AND continued separation of these taxa. In the WODNIKA MUNSTER present work, however, my primary concern is with finspine morphology, and discussion HISTORICAL NOTE: Ctenacanthus and of other anatomical features will be minimal. Sphenacanthus are Paleozoic chondrichthyan taxa, recognized by dorsal finspines. WHAT IS SPHENACANTHUS? These spines were originally described by Agassiz (1837), but the descriptions are The following is the diagnosis of Sphen- founded in each case upon rather poor spec- acanthus presented by Agassiz (1837, p. 5): imens. However, many better preserved "This genus is founded on a single spine, spines have subsequently been referred to from the freshwater Burdiehouse Limestone, these taxa, and some are associated with in the collection of the Royal Society of skeletal remains. Unfortunately, over the Edinburgh. As in Gyracanthus it has well- years Sphenacanthus has become almost defined grooves and ridges; but rather than lost as a synonym of Ctenacanthus. In part, being arranged obliquely across the spine as this is undoubtedly due to Thomson's (1869) in that genus, the grooves and ridges of the confusion of Sphenacanthus with the type Sphenacanth extend longitudinally from the 14 AMERICAN MUSEUM NOVITATES NO. 2722

] El c-i0

5mm 3mm

FIG. 8. A, Sphenacanthus serrulatus Agassiz; from Agassiz (1837) tab. 1, no.. 11; B-G, Sphen- acanthus hybodoides; B, drawing of BM(NH) P5572 (reversed for ease of comparison); C, AMNH 9591; D, BM(NH) P8172; E, detail of ornament from BM(NH) P8172; F, BM(NH) Wild Coll. slide no. 459; section above level of posterior closure; G, BM(NH) P10016, section below level of.posterior closure. base to the apex of the spine, which is round- squarely on its posterior face. These char- ed on its sides and anterior margin, but cut acters draw it much to the hybodes 1982 MAISEY: CTENACANTHUS AGASSIZ 15

[hybodonts] from which it differs in that instead of large teeth in its posterior border, only a delicate crenellation is noted.... This spine is shaped like a wedge which ta- pers gradually to its extremity, and which is round on three of its faces and cut squarely on its fourth. The truncated side is smooth, and on its margins a slight serration is noted. The ridges which project on the sides and anterior border are gradually lost on the posterior margin towards the tip; they are rounded on the anterior margin and on the sides of the tip of the spine; while, on the sides of the middle and lower part, particularly on the posterior margins, they are slightly crenel- lated." Agassiz (1837) commented on the similarities between the ribbing of Sphenacanthus and Hybodus finspines, but also noted that large downcurved posterior denticles (characteristic of hybodontid finspines) are absent from Sphenacanthus spines. The fine cren- ulation of some of the ribs in S. serrulatus is rarely seen in other finspines referred to Sphenacanthus. Although it is true that the ribbing of Sphenacanthus finspines resembles that of Hybodus, the arrangement and modes of increase in the number of ribs is different in these taxa. In Sphenacanthus finspines, new ribs appear down the posterolateral margins and subsequently run onto the lateral spine wall (figs. 8A, C, D; 9A; lOA, D, E; llA, B). This mode of increase, which I term "marginal rib insertion," is apparently confined to Sphenacanthus. It can be seen in several ex- amples figured here and is apparent in Agas- siz's (1837) type specimen (fig. 8A). Marginal ribs pass distally into posterolateral denticle rows which are always present. In addition to marginal rib insertion, rib numbers in- 2cm crease down the of the both a I length spine by FIG. 9. A, B, Sphenacanthus hybodoides? bifurcation and intercalation. Like Hybodus AMNH 523, one of Newberry's specimens origi- and unlike Ctenacanthus, there is no pri- nally misidentified as Ctenacanthus major. mary rib down the anterior midline of a Sphenacanthus finspine. Unlike Hybodus finspines, those of Sphenacanthus lack a lat- dontid finspines the ribbing is not completely eral field of fine, narrow ribs. In large Sphen- smooth, and there are rugosities and nodal acanthus finspines there are frequently as points which in some spines are organized many as 20 to 25 ribs per side. As in hybo- into a definite pattern suggestive of pauses 16 AMERICAN MUSEUM NOVITATES NO. 2722

and interruptions in finspine development. pattern, beginning with an interrupted series The nodes of one rib often correspond with of denticles and becoming more continuous, nodes on adjacent ribs, giving rise to a dis- is the opposite of the usual hybodontid pat- continuous growth line (varix) across all the tern where the ribs are initially continuous ribs but not intercostally (figs. 8D; 9A; IOA, but become discontinuous later in develop- D, E). These varices are as important as ment (discussed in detail by Mai- growth lines in interpreting morphogenetic sey, 1978). processes of fossil finspines, and were used Following Agassiz's (1837) description of in an earlier study of hybodontid finspines S. serrulatus, Egerton (1853) erected two (Maisey, 1978). Although each rib is inde- further species, also based on finspines, pendent of its neighbors, development of all named S. hybodoides and S. nodosus. the ribs was clearly governed by a single, Stratigraphically these were younger than S. synchronized developmental pattern. Some serrulatus, being from the upper rather than spines of S. hybodoides have numerous lower Carboniferous. The majority of beadlike nodes along the ribs, especially on Sphenacanthus finspines in collections are the more lateral ones but sometimes more of Pennsylvanian age. The holotype of S. anteriorly, e.g., BM(NH) P 3117, P 3119. nodasus, BM(NH) P3121, has more regularly Sphenacanthus nodosus finspines are beaded ribbing than typical S. hybodoides. strongly beaded. Generally, the ribs of Such regular beading is also apparent on Sphenacanthus finspines lack a shiny enam- BM(NH) P2223 (two finspines) and P2120. eloid layer, except at the nodes; one of New- Woodward (1889, p. 242) made S. nodosus berry's specimens from the Scottish Coal a synonym of S. hybodoides, using the ar- Measures, AMNH 523, has more completely gument that one was probably founded on a enameled ribs than most Sphenacanthus fin- posterior finspine and the other on an ante- spines. rior spine. This speculation is unfounded, Marginal denticles of Sphenacanthus fin- however, since no specimens show this to be spines extend from near the spine tip to just the case, and both species are therefore pro- above the level of posterior closure, as in visionally retained here. many other Paleozoic finspines. These mar- Some S. hybodoides finspines have been ginal denticles sometimes comprise several crushed so that their posterior wall seems short series, so that the marginal "row" may convex, e.g., BM(NH) P3232, P5552. How-. consist of several sections (figs. 8B, C, D; ever, all uncrushed Sphenacanthus finspines lOD). Each of these short denticle series is have a flat or slightly concave posterior wall, proximally continuous with one of the mar- and lack a median keel or ridge. An incom- ginally inserted ribs. The developmental im- plete spine, S. hybodoides BM(NH) P8172 plication of this denticle arrangement is that has heavy but symmetrical abrasion of its the marginal row was not the product of a apex, presumably acquired during life (fig. single scleroblastic center, but that after an 8D). Egerton (1853, p. 281) noted similar initial period of denticle formation the mar- abrasion of the holotype of S. nodosus, ginal scleroblastic tissue was displaced BM(NH) P3121. Transverse sections through around onto the lateral surface of the spine, the apical region of Sphenacanthus finspines by a newly differentiated scleroblastic pri- reveal thick deposits of non-trabecular cir- mordium, as the dimensions of the spine in- cumpulpar dentine (e.g., fig. 8F), which in creased proximally. Thus the marginal den- some cases completely plugs the spine cen- ticles and marginally inserted ribs of tral cavity apically. In these sections another Sphenacanthus finspines may be regarded as peculiar feature of Sphenacanthus finspines a product of several anlagen. This pattern of is evident. Anterior to the spine central cav- rib insertion provides an important differ- ity is a prominent region of spongy trabecu- ence between Sphenacanthus and typical lar dentine, in which the denteonal trabecu- hybodontid finspines (e.g., Hybodus, Acro- lae are much thinner than elsewhere (fig. 8F, dus, Asteracanthus). The Sphenacanthus G). 1982 MAISEY: CTENACANTHUS AGASSIZ 17

A E I E C0 .0

FIG. 10. A-C, Sphenacanthus marshi (Newberry); A, the holotype, from peel of YPM 2873; B, C, from Newberry (1873) pl. 36, no. 3; D, Sphenacanthus hybodoides? AMNH 524, the other Newberry specimen originally misidentified as Ctenacanthus major, for comparison with S. marshi; E, Sphen- acanthus off. marshi, from peel of USNM 299644, Kinderhook Fm., ?Iowa (St. John Coll.).

Historically, the next species of Sphen- acteristic of Sphenacanthus finspines. I have acanthus to be described (as Ctenacanthus) no doubt that Newberry's (1873) specimen was Newberry's (1873) C. marshi. I have is referable to this genus (fig. IOA-C). examined the holotype, Peabody Museum In an attempt to compare his material with no. 1896, and a cast (AMNH 1166) of a re- the type species of Ctenacanthus, C. major, ferred specimen. The pattern of ornamenta- Newberry acquired two specimens (now tion (particularly the rib arrangement and AMNH 523, fig. 9; and 524, fig. IOD). These marginal insertion pattern), straight posterior finspines are from the Scottish Coal Mea- margin and concave posterior wall are char- sures and are referable to Sphenacanthus, 18 AMERICAN MUSEUM NOVITATES NO. 2722

B F H

7 El c 7 E 0I 0 j ci 1. 14 /1r I'.K". 5'di 7'.'S

1mm 1 mnrmi 2 mmri

FIG. 11. A, Sphenacanthus aequistriatus (Davis); peel of holotype, BM(NH) P7705; B-E, Sphen- acanthus costellatus (Traquair), from Traquair (1884) pl. II, nos. 2-5; F, Wodnika borealis, new species, the holotype, USNM 299646, Permian, Siksikput Fm., Lisburne Hills, Alaska; G, H, Wodnika striatula section and finspine in Schaumberg coll. perhaps S. serrulatus (although AMNH 524 spines of C. major. Newberry's (1837) is more like the nodular finspines of S. hy- concept of C. major was therefore based bodoides). Unfortunately, Newberry's Scot- upon finspines of Sphenacanthus, the genus tish specimens were misidentified as fin- to which his "C. marshi" finspines coinci- 1982 MAISEY: CTENACANTHUS AGASSIZ 19 dentally belong. It is worth repeating New- CM26049, a finspine with a concave pos- berry's (1873, p. 327) remarks in the light of terior wall, marginal tubercles and several this discovery: faint ribs. In the general character of the surface markings, CM26816-8, a slab containing, among var- these spines resemble those figured and de- ious teeth, a finspine referable to Sphen- scribed by Agassiz under the name of Ctena- acanthus. canthus major; and they agree also with Agas- USNM 299644, a finspine from the Kin- siz's description so far as regards the derhook Formation of ?Iowa, collected by ornamentation, but not in regard to form or the Orestes St. John (fig. lOE). At present it is "acute posterior margin"-the latter being a not possible to assign these spines to new most anomalous feature in the spines of Cten- species; provisionally all are referred to S. acanthus, all of which, so far as I know, have marshi. a flattened posterior surface.... I have some Davis (1879a, p. 185) proposed another large and massive spines from the Coal Mea- sures of Scotland, which, with nearly identical species, Ctenacanthus aequistriatus, which surface markings, are twice as long as these, is also founded on a finspine, BM(NH) P and they have the posterior margins, not acute, 7705, from the lower Coal Measures (Penn- as Prof. Agassiz represents his specimens of sylvanian) of Lowmoor, Yorkshire. There Ctenacanthus major, but broadly concave, as are only about a dozen ribs per side; these in the specimens before us. The spines come to are straighter and much more regular than in me as Ctenacanthus major, and suggest the other Sphenacanthus finspines (fig. I1 A). probability that Prof. Agassiz was misled by the Each rib is very thin, with no pectinations, imperfect exposure of the specimen he figures, beading, or varices. The ornament terminates and that if this were properly developed, it abruptly at its lower end. Marginal denticles would show a flattened, striated posterior sur- are present and several ribs are introduced face, as do the other species of this genus. marginally. Another specimen, BM(NH) I cannot agree that the ornament of New- P15504, from Bradford, Yorkshire, is similar berry's (1873) specimens resembles that of to the holotype, but is incomplete (only an C. major finspines; he was probably allowing apical piece a few inches long is preserved). the misidentified referred specimens from The posterior wall of these spines is con- Scotland to influence him more than Agas- cave. In view of the distinctive ornamenta- siz's (1837) diagnosis. I cannot trace any cor- tion, S. aequistriatus is retained here as respondence to suggest who supplied New- another Sphenacanthus species (agreeing berry with misidentified material. However, with Woodward, 1889, p. 244). some significance may be attached to Thom- Ctenacanthus minor Davis (1879b, p. 531) son's (1869) paper, in which Sphenacanthus was referred to Sphenacanthus by Wood- hybodoides finspines were misidentified as ward (1889, p. 244); it is probably an imma- belonging to Ctenacanthus major. ture Sphenacanthus finspine, since it has Sphenacanthus hybodoides is generally re- smooth ribs and a concave posterior wall, garded as a Pennsylvanian species like S. and is only 1.4 inches long. As an immature marshi. However, Newberry's Scottish specimen, this spine would not be expected specimens (if their locality data are accurate) to display the marginal rib insertion pattern and several new discoveries in North Amer- which, as discussed above, would develop ica suggest that very similar spines also oc- progressively as the finspine enlarged. In all cur in the Mississippian. These finds may probability S. minor is not a valid species, broaden the range of S. hybodoides and S. and may be synonymous with S. hybodoides marshi and these species may eventually which is found in the same horizon. prove to be synonymous. Four other North A complete fossil shark Ctenacanthus American finspines referable to Sphenacan- costellatus from the lower Carboniferous of thus are: Eskdale, Dumfriesshire, was described by 20 AMERICAN MUSEUM NOVITATES NO. 2722

Traquair (1884, p. 4), who noted that its fin- SPHENACANTHUS AGASSIZ spines (fig. IIB-E here) "perhaps ap- proach(es) most nearly the Sphenacanthus REVISED DIAGNOSIS: Shark recognized by serrulatus of Agassiz than any other." Tra- its finspines, which are gradually tapered and quair recorded the presence of marginal den- slightly recurved posteriorly, often with a ticles on the finspine of Agassiz's (1837) ho- straight posterior profile; anterior face acute- lotypes of S. serrulatus, and on the basis of ly rounded, lateral faces slightly convex to this similarity with Ctenacanthus made flat, posterior face strongly concave and Sphenacanthus a synonym of that genus. lacking a pronounced median ridge or con- Woodward (1889, p. 242) was also impressed vexity; cross-section approximately twice as by similarities between S. serrulatus and C. deep as broad; ornament of prominent raised costellatus. This genus, however, was not costae a variable distance apart, but inter- distinguished on the basis of finspine mor- costal grooves generally as wide as or wider phology by Woodward (1889, p. 241): "fin- than costae; no primary anterior rib and pri- spines of this fish are indistinguishable from mary bifurcation is characteristic; costae those named Ctenacanthus by Agassiz." In- branch irregularly, are sometimes nodose stead, the distinction was based on an ex- and discontinuous, and new ones sometimes tremely tenuous proposal that teeth like appear by intercalation and often by addition those of C. costellatus are absent in forma- to the marginal ribs; ribs smooth or nodose, tions yielding Ctenacanthus finspines! never closely pectinated but sometimes Woodward (1889) thus created a non sequi- beaded with small, well-spaced tubercula- tur whereby two taxa are distinguished by a tions which may be thinly enameled and negative character, which is unrelated to the striated; posterolateral margins ornamented means by which the taxa were originally sep- by a row of low, posteriorly directed tuber- arated. Although this method of distinguish- cles or denticles, produced in part by tuber- ing Ctenacanthus from Sphenacanthus is cle series related to marginally inserted cos- unjustifiable, these taxa are nevertheless dis- tae; spine trunk composed of trabecular tinguishable by differences in their finspine dentine with a prominent spongy region an- morphology and ornament patterns. On the teriorly, but lacking any ordered vasculari- basis of these features, the shark described zation other than a median canal anterior to by Traquair (1884) is closer to Sphenacan- the central cavity; an inner lamellar, nontra- thus than to Ctenacanthus. becular layer is characteristically well devel- As mentioned above, there are problems oped. with which species of Sphenacanthus should TYPE SPECIES: Sphenacanthus serrulatus be considered distinct and which should be Agassiz, 1837. placed in synonymy. Thomson (1869) de- SYNONYM: Ctenacanthus serrulatus (Ag); scribed some associated Sphenacanthus fin- Traquair, 1884, p. 6. spines, "Cladodus" mirabilis teeth and sha- OTHER REFERRED SPECIES: S. hybodoides green (as Ctenacanthus major). Dick (1878, (Egerton); Egerton, 1853, p. 280; S. nodosus p. 103) mentions undescribed associated re- (Egerton); Egerton, 1853, p. 281; S. marshi mains of S. serrulatus as teeth (Newberry); Newberry, 1873, p. 326; S. ae- having which quistriatus (Davis); Davis, 1879a, p. 185; S. are easily confused with those of Tristychius minor (Davis); Davis, 1879b, p. 531; S. cos- arcuatus, although S. serrulatus teeth differ tellatus (Traquair); Traquair, 1884, p. 3. from those referred to S. hybodoides and S. costellatus. Thus, there is some evidence that these Sphenacanthus species are valid. So GENUS WODNIKA MUNSTER (1843) far, no associated remains from North Amer- AMENDED DIAGNOSIS: Small Permian ica have been referred to Sphenacanthus. phalacanthous shark attaining lengths of 1982 MAISEY: CTENACANTHUS AGASSIZ 21 about 100 cm.; finspines smooth-ribbed, but now known from a number of complete lacking pronounced posterior denticles, and and partial skeletons (Schaumberg, 1977). with concave posterior wall; teeth low, The teeth are of rounded, non-cuspidate du- rounded, tumid, with crowns of tubular den- rophagous morphology, with a punctate sur- tine apparently lacking an outer enameloid face to the crown and (according to a per- layer, approximately eight or nine replace- sonal communication from W.-E. Reif, ment files in each half-ramus of the jaws; ax- Tiibingen) without an enameloid outer layer. ial skeleton poorly calcified; caudal fin with Although these teeth were originally as- single series of small dorsal arcualia and signed to hybodontids (Acrodus Miinster, longer jointed hypural radials; body scales 1840, p. 123; Strophodus Miinster, op. cit., apparently compound and possibly of grow- p. 123; 1843, p. 50), the tooth morphology ing type (detailed morphology not yet differs in some respects from typical Acro- known). dus, and the postcranial and dermal skeleton TYPE SPECIES: Wodnika striatula Miin- of Wodnika also differs from that of hybo- ster, 1843. dontids. For example, Wodnika lacks ce- Much of the generic diagnosis above is phalic spines and a calcified rib cage, and its based on Schaumberg's (1977) revision of scales are not of hybodontid morphology. Wodnika striatula. Moreover, its finspines are distinguishable from those of Mesozoic hybodontids (see Wodnika borealis, new species Maisey, 1978). Wodnika finspines are ornamented by several fairly smooth, broad ribs, DIAGNOSIS: Wodnika known only from a interrupted only by varices (fig. 1IH). No dorsal finspine, which differs from that of W. marginal denticles are known, and marginal striatula only in the following respects; pos- insertion of new ribs is also unknown. The terolateral ribs as broad as the anterior ribs, posterior wall of the spine is concave (fig. and all ribs stouter and more closely spaced 1IG); its anterior wall is thick and sponge- than in W. striatula; lateral ribbing bifur- like, but not so extensively spongy as in cates from an anterior primary rib. Sphenacanthus. While the ribbing of Wod- It is also noteworthy that W. borealis may nika and hybodontid finspines is similar, it have attained a slightly greater size than W. also agrees with the ribbing of Sphenacan- striatula, since the holotype of W. borealis thus in general appearance, and the shape is a finspine which, when complete, probably and internal morphology of Wodnika and measured over 150 mm. in length whereas Sphenacanthus finspines seen in sections W. striatula finspines are generally some- agree closely (cf. figs. 8F, 1IG). Wodnika what shorter. Wodnika borealis also comes and Sphenacanthus differ in their tooth mor- from a different geographical region from phology; in the absence of marginal rib inser- W. striatula, and considerably extends the tion and denticles from Wodnika finspines known distribution of the genus. and in stratigraphic occurrence. While these HOLOTYPE: USNM 299646; Permian, Sik- two genera are still considered to be distinct, sikpuk Formation, Lisburne Hills, Point similarities in their finspines suggest that Hope Quadrangle, 21 ft. above Lisburne-Sik- Wodnika and Sphenacanthus be referred to sikpuk contact in stream valley, about 3 a higher taxon, termed here the family miles N of Mt. Itsalik, Alaska, coll. K. J. Sphenacanthidae. Bird, 1972; figure l lF. By grouping Wodnika and Sphenacanthus together into a higher taxon, on the basis of ARE SPHENACANTHUS AND similarities in their finspines, the systematic WODNIKA RELATED? position of these two taxa is no longer as Wodnika is a small Permian shark origi- problematic as it was. They differ from hy- nally recognized by its teeth (Miinster, 1843), bodontid sharks and from Ctenacanthus in 22 AMERICAN MUSEUM NOVITATES NO. 2722

several respects, and are probably not with Wodnika suggest these genera are closely related to either. Tooth morphology closely allied to each other. in Wodnika is very different from that of It is interesting to note that the few toler- Sphenacanthus, and the total amount of den- ably complete Paleozoic phalacanthous tal variation among different taxa presently sharks known at present may not be closely included within the Sphenacanthidae is as related to one another, contrary to a popular great as that known within the Hybodonti- belief. Ctenacanthus compressus and C. dae. It is therefore concluded that the ten- clarkii are referred to Ctenacanthus with dency toward a durophagous habitus oc- some degree of confidence (Maisey, 1981). curred independently in Wodnika and in "Ctenacanthus" costellatus is probably hybodontids such as Acrodus and Aster- more closely allied to Sphenacanthus and is acanthus. provisionally placed in that genus (see also Woodward, 1889). In some respects Good- CONCLUSIONS richthys eskdalensis finspines resemble those of Ctenacanthus (e.g., ornament pattern) but Only two of Agassiz's (1837) Ctenacan- in other respects are similar to those of By- thus species based on finspines are retained thiacanthus (e.g., level of posterior closure). in that genus: Ctenacanthus major (the type An undescribed Pennsylvanian form may be species) and C. tenuistriatus (a synonym of closely allied to Bythiacanthus. Other "cten- C. major). Thus only one species of Cten- acanths" show evidence of affinity with Me- acanthus described in that work is still con- sozoic hybodontids (Maisey, 1981 and in sidered valid (Maisey, 1981). Of the remain- prep.). Amelacanthus and Eunemacanthus ing species given by Agassiz (1837), C. finspines are similar in some respects to ornatus is not an elasmobranch but is prob- those of Nemacanthus and Palaeospinax; ably an acanthodian (Pageau, 1969). The oth- the latter genus is well known from articu- er species, Ctenacanthus brevis, is referred lated remains (Maisey, 1977) and has affinity here to Bythiacanthus St. John and Worthen with Recent sharks. It is therefore no longer (1875). Two species were referred to the ge- possible to group all phalacanthous Paleo- nus Onchus by Agassiz (1837) but later de- zoic sharks into a single "ctenacanth" cat- scribed as Ctenacanthus by Davis (1883), egory, even though the interrelationships of along with two other species. All four of these sharks are poorly understood. We these species are now placed in a new genus, must instead recognize "ctenacanths" to be Amelacanthus. Agassiz (1837) listed (but did a non-monophyletic group containing mem- not describe) another Ctenacanthus species, bers of various lineages, the interrelation- C. heterogyrus, which was later described ships of which will hopefully become better by McCoy (1855). This species is now placed known. within the genus Eunemacanthus. The finspines of Amelacanthus and Eunemacan- thus have thick enameloid layers and most LITERATURE CITED have a concave posterior wall, features that Agassiz, L. suggest affinity with neoselachians. 1833-1844. Recherches sur les poissons fos- Whereas some taxa previously included in siles. Neuchatel, 5 vols., 1420 pp. Ctenacanthus can be assigned elsewhere, Branson, E. B. another distinct 1916. The lower Embar of Wyoming and its previously Agassizian ge- fauna. Jour. Geol., vol. 24, pp. 639-664. nus, Sphenacanthus, has become unde- Davis, J. W. servedly reduced to a synonym of Cten- 1879a. Notes on Pleurodus affinis Agassiz, and acanthus. Finspines of Sphenacanthus differ descriptions of three spines of cestra- from those of Ctenacanthus, however, and cionts from the lower Coal Measures. a revised diagnosis of Sphenacanthus (based Quart. Jour. Geol. Soc., vol. 35, pp. on its finspines) is proposed. Similarities 181-188. 1982 MAISEY: CTENACANTHUS AGASSIZ 23

1879b. Description of a new species of fossil taxa. Amer. Mus. Novitates, no. 2718, fish spine, Ctenacanthus minor, from pp. 1-26, figs. 1-10. the Lower Coal-measures of Yorkshire. McCoy, F. Geol. Mag., N.S. Dec. 2, vol. 6, pp. 1855. Descriptions of the British Palaeozoic 531-532. fossils in the Geological Museum of the 1883. On the fossil fishes of the Carboniferous University of Cambridge, Cambridge Limestone Series of Great Britain. Univ. Press, 661 pp. Trans. Roy. Soc. Dublin, vol. 1, pp. Moy-Thomas, J. A. 327-548. 1936. The structure and affinities of the fossil De Koninck, L. G. elasmobranch fishes from the Lower 1878. Faune du Calcaire Carbonifitre de la Carboniferous rocks of Glencartholme, Belgique. Ann. Mus. Roy. d'Hist. Nat. Eskdale. Proc. Zool. Soc. London de Belgique, vol. 2, pp. 1-150. (1936), pp. 761-788. Dick, J. R. F. 1978. On the Carboniferous shark Tristychius Miinster, G. arcuatus Agassiz from Scotland. Trans. 1840. Ueber einige Placoiden um Kupfer- Roy. Soc. Edinburgh, vol. 70, pp. 63- schiefer zu Richelsdorf. Beitriige zur 109. Petrefactenkunde, vol. 3, pp. 122-126, Eastman, C. R. Bayreuth. 1902. Some Carboniferous cestraciont and 1843. Nachtrag zu der Beschreibung einiger acanthodian sharks. Bull. Mus. Comp. merkwiirdigen Fische aus den Kupfer- Zool., vol. 39, pp. 55-99. schiefern in V. Heft.-Beitraige zur Pe- Egerton, P. M. G. trefactenkunde, vol. 6, pp. 47-52. Bay- 1853. On two new species of placoid fishes reuth. (Ctenacanthus hybodoides and Ct. no- Newberry, J. S. dosus) from the Coal Measures. Quart. 1873. Description of fossil fishes. Ohio Geol. Jour. Geol. Soc., vol. 9, pp. 280-282. Surv. I., part 2, pp. 245-255. Khabakob, A. V. Newberry, J. S., and A. H. Worthen 1928. Description of new species of ichthyo- 1866. Description of vertebrates. Geol. Surv. dorulites of the genus Ctenacanthus Illinois, vol. 2, Palaeontology, pp. 9- Ag. from Carboniferous deposits in the 141. USSR. Izvestiya Geol. Komiteta, vol. Pageau, Y. 47, pp. 23-31 (in Russian with English 1969. Nouvelle faune ichthyologique du De- summary). vonien moyen dans le gres de Gaspe Leidy, J. (Quebec), II. Morphologie et systema- 1873. Contributions to the extinct vertebrate tique, Premi&re Section. A. Eurypter- fauna of the western territories. First ides, B. Ostracodermes, C. Acantho- Ann. Rept., U.S. Geol. Sur. Terr., 1867 diens et Selachiens. Nat. Can., vol. 96, (1873), pp. 1-358. pp. 399-478. Maisey, J. G. Romer, A. S. 1975. The interrelationships of phalacanthous 1942. Notes on certain American Paleozoic selachians. Neues Jahrb. Geol. Pa- fishes. Amer. Jour. Sci., vol. 240, pp. lIont., vol. 9, pp. 553-567. 216-228. 1977. The fossil selachian fishes Palaeospinax Schaumberg, G. Egerton, 1872 and Nemacanthus Agas- 1977. Der Richelsdorfer Kupferschiefer und siz, 1837. Zool. Jour. Linn. Soc., vol. seine Fossilien. III. Die tierischen Fos- 60, pp. 259-273. silien des Kupferschiefers. 2. Vertebra- 1978. Growth and form of finspines in hybo- ten. Aufschluss, vol. 28, pp. 297-352. dont sharks. Palaeontology, vol. 21, pp. St. John, O., and A. H. Worthen 657-666. 1875. Description of fossil fishes. Geol. Surv. 1981. Studies on the Paleozoic selachian ge- Illinois, Geol. Paleont., vol. 6, pp. 245- nus Ctenacanthus Agassiz: No. 1. His- 488. torical review and revised diagnosis of 1883. Description of fossil fishes. Ibid., vol. Ctenacanthus, with a list of referred 7, pp. 55-264. 24 AMERICAN MUSEUM NOVITATES NO. 2722

Thomson, J. Woodward, A. S. 1869. On teeth and dermal structures associ- 1889. Catalogue of the fossil fishes in the Brit- ated with Ctenacanthus. Rept. Brit. ish Museum (Natural History), Part 1, Assoc. Adv. Sci., 39th meeting, 1869, London, Brit. Mus. (Nat. Hist.), xlvii + pp. 102-103. 474 pp. Traquair, R. H. 1891. Catalogue of the fossil fishes in the Brit- 1884. Description of a fossil shark (Ctenacan- ish Museum (Natural History), Part II, thus costellatus) from the lower Car- London, Brit. Mus. (Nat. Hist.), xliv + boniferous rocks of Eskdale, Dumfries- 567 pp. shire. Geol. Mag., vol. 1, pp. 3-8.