AVERIANOV, A. O. 1997. A rare find of a vomerine tooth plate of an elephant fish (Holocephali, Callorhynchidae) in the Upper Cretaceous of Russia. Paleontologicheskii Zhurnal, No. 1: 78-80.

Translated by Oleg Lebedev

Abstract
A vomerine tooth plate of an elephant fish Callorhinchus sp. from the Upper Santonian of the Penza Region [of Russia] is described.

Extant elephant fishes (Callorhinchus ) inhabit temperate and subpolar basins of the Southern Hemisphere. Extremely rare finds of Callorhinchus are known from the Upper Jurassic of England and Russia (WOODWARD, 1892; WARD & McNAMARA, 1977; AVERIANOV, 1992), Cretaceous of Russia (NESSOV et al., 1986) and New Zealand (NEWTON, 1876), Paleocene and Eocene of England (GURR, 1963; WARD, 1973) and Cenozoic of Argentina(WOODWARD & WHITE, 1930). Egg capsule imprints that probably belonged to the callorhynchids are described from the Upper Jurassic of Yakutia (OBRUCHEV, 1966). In Callorhynchidae, as in all other members of the Chimaeroidei, the dentition consists of two pairs of tooth plates (vomerine and palatine) in the upper jaw and a pair (mandibular) in the lower one (PATTERSON, 1965). Up to the latest times, only palatine and mandibular callorhynchid tooth plates were found as fossils. Two vomerine tooth plates ascribed to a new species were discovered recently by L. A. NESSOV in the Albian (Lower Cretaceous) of the Belgorod Region, Russia. A new find of a Callorhinchus tooth plate comes from the Upper Santonian (Upper Cretaceous) deposits of the Penza Region close to the village of Kikino; it was collected in 1995 by the author and A. V. PANTELYEV. This specimen is stored in the Zoological Institute of the Russian Academy of Sciences (ZIN PC). The author thanks A. V. PANTELYEV for sorting, etc....

The vomerine tooth plate, Callorhinchus sp., is comparatively very narrow; the maximum width/length ratio is 0.33 (Fig. 1). The symphyseal margin is almost straight, and the labial one bears a deep S-shaped notch. The anterior end of the plate forms a hook-shaped (in the parasagittal plane) "beak" that descends significantly lower than the ventral plane of the plate. A row of six longitudinally elongated narrow tritors of various lengths is situated on the ventral surface by the symphyseal margin. A long and thin lingual process directed posteriorly is situated in the posterior part.The symphyseal surface does not extend to the lingual process. A clearly marked descending lamina, parallel to the labial edge, is situated on the dorsal surface of the tooth plate. Medially, the latter bears characteristic ornamentation composed of longitudinally elongated crests and furrows. The distance between the "beak" tip and the posterior part of the lingual process is 19.1 mm.

In the fossil members of the genus Callorhinchus the vomerine tooth plates are known only in a new species from the Albian of the Belgorod Region. These tooth plates have no pronounced "beak", but possess a long lingual edge and longitudinal rows of tritors on the wear surface. In modern forms, the vomerine tooth plates are usually wide and bear a small "beak" or are devoid of it; often they have no long lingual process (BIGELOW & SCHROEDER, 1953, fig. 127B; GARMAN, 1904, Pl. 6, fig.1,8,9, Pl. 7, fig.7; DEAN, 1906, fig.95, 106; PATTERSON, 1992, fig.2,9A). The tooth plate described here is most similar to the vomerine tooth plates of C. capensis Dumeril, 1865 from the coastal basins of South Africa (GARMAN 1904, Pl. 6, fig.5; CASE & BRAUN, 1972, fig.2C) by its S-shaped labial edge, comparative narrowness and long lingual process. It is similar as well to theCallorhinchus sp. tooth plates illustrated by PICTET (1853-1857, p. 37, fig. 8,9) and C. antarcticus McCoy, 1886 (usually regarded as a synonym of C. milii Bory 1823; however, in this species vomerine tooth plates differ in construction) figured by JAEKEL (1901, Pl. 24, fig. 3a). At the same time, in C. capensis and C. antarcticus the "beak" is shorter, and in Callorhinchus sp. is longer than in C . sp. from Kikino Village.

Previously, Late Cretaceous callorhynchid remains were known only from the Cenomanian of the Saratov Region (E. V. POPOV, pers. comm.) and the Cenomanian of New Zealand (NEWTON, 1876).

Apart from Callorhinchus sp., a mandibular tooth plate of the chimaeroid Elasmodus sp., shark teeth of Acrodus sp., Ptychodus mammilaris Ag. 1843, Synechodus sp. cf. S. lerichei Herman 1977, S. sp. cf. S. hesbayensis Casier 1943, Hexanchus sp., Heterodontus sp., ?Cretorectolobus sp., Squatina sp., Eostriatolamia sp., Cretolamna appendiculata (Ag. 1843), Cretoxyrhina mantelli (Ag. 1843), Paracorax sp., andSqualicorax sp., cf. S. santonicus (Glickman & Zhelezko 1979), and teleost fish remains, including Enchodontidae teeth are known from the Kikino Village locality.

Bibliography
AVERIANOV, A. O. 1992. New Jurassic chimaeras from Russia. Palaeont. J. No.3:57- 62.

BIGELOW, H. B. and W. C. SCHRODER. 1953. Fishes of the Western North Atlantic, Pt.2. Sears Found. Mar. Res., 561 p.

CASE, G. R. and M. K. BRAUN. 1972. Capture of a chimaera in False Bay, South Africa. Underwater Nat., 7(3):28-30,48.

DEAN, B. 1906. Chimaeroid fishes and their development. Publ. Carnegie Inst. Wash., No.32, p. 1-195.

GARMAN, S. 1904. The chimaeroids (Chismopnea Raf. 1815, Holocephala Mull. 1834), especially Rhinochimaera and its allies. Bull. Mus. Comp. Zool., 41(2):245-272.

GURR, P. R. 1963. A new fish fauna from the Woolwich Bottom Bed (Sparnacian) of Herne Bay, Kent. Proc. Geol. Assoc., 73(4):419-447.

JAEKEL, O. 1901. Über jurassischeZähne und Eier von Chimaeriden. Neues Jahrb. mineral., geol., paläontol. B. 14, S. 540-564.

NEWTON, E. T. 1876. On two chimaeroid jaws from the Lower Greensand of New Zealand. Quart. J. Geol. Soc. 32:326-331.

OBRUCHEV, D. V. 1966. Fossil chimaera egg capsules. Paleont. J. No. 3:117-124.

PATTERSON, C. 1965. The phylogeny of the chimaeroids. Phil. Trans. Roy. Soc. London, Ser. B. 249:101-219.

PATTERSON, C. 1992. Interpretation of the tooth plates of chimaeroid fishes. Zool. J. Linn. Soc., 106(1):33-61.

PICTET, F. J. 1853-1857. Traité de Paleontologie ou histoire naturelle des animaux fossiles considerés dans leurs rapports zoologiques et geologiques. Paris. Atlas, 110 pl.

WARD, D. J. 1973. The English Paleogene chimaeroid fishes. Proc. Geol. Assoc., 84(3):315-330.

WARD, D. J. and K. J. McNAMARA. 1977. Associated dentition of the chimaeroid fish Brachymylus altidens from the Oxford Clay. Palaeontol., 20(3):589-594.

WOODWARD, A. S. 1892. On some teeth of new chimaeroid fishes from the Oxford and Kimmeridge Clays of England. Ann. Mag. Nat. Hist., Ser. 6, 10:13-16.

WOODWARD, A. S. and E. I. WHITE. 1930. On some new chimaeroid fishes from Tertiary formations. Ann. Mag. Nat. Hist., Ser. 10, 6:577-582.

Figure Caption
Fig. 1. Left vomerine tooth plate of Callorhinchus sp., ZIN PC, N 7/11; a, anterior; b, ventral; c, lateral; d, dorsal; e, medial. Penza Region, Kamenka District, the left bank of the Kevda River in the vicinity of Kikino Village; Cretaceous (Upper Santonian).
Key:B_, descending lamina; K, "beak", _O, lingual process; T, tritors. (The "_" takes the place of letters not available on the Western keyboard.)