Leptolepis nevadensis, a New Cretaceous Fish Author(s): Lore David Source: Journal of Paleontology, Vol. 15, No. 3 (May, 1941), pp. 318-321 Published by: SEPM Society for Sedimentary Geology Stable URL: https://www.jstor.org/stable/1298900 Accessed: 09-08-2021 23:07 UTC

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This content downloaded from 131.215.71.167 on Mon, 09 Aug 2021 23:07:04 UTC All use subject to https://about.jstor.org/terms JOURNAL OF PALEONTOLOGY, VOL. 15, No. 3, PP. 318-321, 2 TEXT FIGS., MAY, 1941

LEPTOLEPIS NEVADENSIS, A NEW CRETACEOUS FISH

LORE DAVID California Institute of Technology

ABsTRACT-Leptolepis nevadensis n. sp., the first known species of the genus from North America, is described from the "Weber conglomerates" east of Eureka, Nevada. The advanced characters of the structure of the fish suggest Cretaceous age.

DR. S. A. BERTHIAUME while on field work Family LEPTOLEPIDAE in Nevada during the summer of 1939 LEPTOLEPIS NEVADENSIS David, n. sp. discovered a deposit containing fish and Figures 1, 2 plant fossils in the so-called "Weber con- Holotype.-A specimen 41 +9 =50 mm. in glomerates" east of Eureka. These beds length, no. 10138, California Institute of have not yielded fossil material heretofore. Technology Coll. Vertebrate Paleontology. They were originally mapped as Upper Car- Paratypes.-Ten specimens 33+ 7 =40 to boniferous, but this age seemed open to 48+ 10 =58 mm. in length and a number of question. Hence the present material, since more or less fragmentary specimens. All it can be identified, is of some significance from Cornell University locality 38C. in throwing light on the age of the formation Diagnosis.-Body 5.75-6.5 mm. in stand- in which it occurs. The fish material has ard length, head 3.6 mm., orbit a little more been kindly sent to us by Dr. C. W. Mer- than 3 in head; 49 to 50 vertebrae; D. = 14 to riam. Fortunately the specimens are for 15; the A. =9; V=8, below posterior part of most part well preserved. They indicate dorsal the fin base; P. =14; C.=38. Nine well-known genus Leptolepis Agassiz. Thehypurals, five below, four above median structural characters of the Nevadan species line; two epurals. suggest that the deposits in which it occurs Description.-Body elongate, depth 5 - are Lower Cretaceous in age. (6?) in standard length, caudal peduncle 2 I am indebted to Dr. Chester Stock of the greatest depth. Head 3 in standard length, California Institute of Technology for ad- elongate 1 as long as deep. Orbit large vice and for a critical reading of the manu- (possibly ovoid in shape), slightly more script. than 3 in head. The structure of the headbones, in general, DESCRIPTION OF MATERIAL does not differ apparently from that de- The material in the present collection scribed con-in detail by Rayner (1938). The sists of several complete specimens and parasphenoid is always distinct, rising up- numerous fragments. The species seems ward toward the front, and situated rather abundant in the region, since the different low in most specimens, cutting through the slabs now at hand indicate the presence of abasal part of the orbit. Maxillary with two number of additional specimens in part well-developed supramaxillaries; lower jaw visible on other bedding planes. The ma- typical for genus, with highly arched den- terial shows an excellent preservation of de- tary. No teeth can be seen. The ceratohyale tails especially in the fins and vertebral distinct in several specimens with 10 column. Most of the bones of the head can- branchiostegals. Opercular arch as in Lep- not be distinguished with satisfaction. The tolepis, opercular 1 as deep as long, with a proportions of the body of this small species pronounced diagonal lower border, lower have suffered slightly from distortion; theanterior corner sharply pointed. type shows best the normal proportions in Vertebrae 34 to 35+15 =49 to 50. Verte- this fish. Some of the syntypes have been brae pierced by notochord, which is covered lengthened in a post-mortem stage. The by a layer of dark ossified material. The material is preserved in a siliceous shale, vertebrae constricted in middle, where thinly laminated and of a buff to gray color. neural and haemal arches originate, the

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FIG. 1-Leptolepis nevadensis David, n.sp. a, Holotype, no. 10138 Calif. Inst. Tech. Coll. Vert. Paleont.; b, no. 10137, X2. Fr., frontal; Dent., dentary, Mx., maxillary; Op., opercular; Par., parietal; pop., preopercular; psph., parasphenoid; smx., supramaxillary; so., supraorbital; sop., subopercular. anterior and posterior extremities(zygapoph- and ventrally. The haemal processes of the yses?) of the vertebrae projecting into point- last five vertebrae extend ventrally from the ed edges. Abdominal neural processes feeble centra for a distance of one-fifth their and short, very delicate intermuscular bones length and then only are directed poste- lying across; numerous arched and strong riorly at a sharp angle, forming enlarged, ribs extend to ventral border of body. dagger-shaped hypurals; the end of the ven- Structure of tail end of column clearly shown on a small tail fragment, no. 10131 California Inst. Technology Coll. Verte- brate Paleontology (fig. 1). Structure ap- proaches homocerque tail of modern clu- peids; only last six vertebrae taking part in structure of tail have prolonged and strong haemal and neural processes. Urostyle slender, pointed; nine hypurals, two more haemal arches prolonged into base of caudal rays; five hypurals below, four above me- FIG. 2-Leptolepis nevadensis David, n. sp. Tail end of vertebral column, X4. c, Last verte- dian line; two small epurals, a horizontal bral centrum; ep, epurals; hy, hypurals; snp, rod preceding first caudal fulcra dorsally specialized neural processes; ur, urostyle.

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tral extension forms a sharp projection in L. congolensis Arambourg and Schneegans pointed forward. (1935) from the bituminous schists of Dorsal rays 14-15: the first two Coccobeach or three in French Gabon, and evidently short and simple, following rays tobranched, that of the related species, L. formosus third or fourth ray longest, two-thirds Traquair, fromto the Wealden of Barnissart, three-fourths of head. Dorsal inserted in Belgium, and of L. neocomiensis Bassani middle of body or slightly nearer tip from of the Cenomanian and Albian, Island of snout. Ventral rays 8: the first strong Lesina, and Dalmatia. The Purbeckian species simple, fin three-fifths to two-thirds of L.head, brodiei Agassiz is said to be related to originating below posterior part of dorsalthese. Judging from the illustrations, how- base. Pelvic girdle short, its anterior point ever, the caudal structure of this species not reaching below origin of dorsal. Anal seems less specialized. Further evidence of rays 9: longest not longer than ventral, a analCretaceous stage of development of L. fin near to caudal base, distance of anal nevadensis is shown in the following char- origin to caudal base 1? in distance from acters: vertebrae of transitional type in de- origin of ventrals to origin of anal. Pectoral gree of perforation by the notochord; the with 14 rays, longest ray not longer than branchiostegals are reduced; the ganoine ventral, fin situated near ventral border of cover of the scales appears to have been body. Caudal rays 26+6 pair of fulcra, 38; thin; and the dorsal fin is situated over the two middle rays spaced from neighboring middle of the body. rays, prolonged above hypurals. Fin three- As to the immediate affinities of the new fourths of length of head, distinctly furcated, species nothing very close seems to be middle rays one-half of longest outer known. The small species with a relatively rays. large orbit may be immature. In its slender Body stained dark with an irregular scale- body and larger number of vertebrae it like pattern. No scales are evident. differs from any known species of Leptolepis Affinities of species.-The well-known (49 or 50). One fragmentary specimen is of genus Leptolepis Agassiz is widely dis- much larger size; it may or may not belong tributed in Europe and is known from to the same species. The structure of the Africa. The genus is first known from the vertebral column, although comparable in Jurassic (Upper Lias) and continues into the degree of transformation of the tail to that Cretaceous; it has not been reported from in L. congolensis Arambourg and Schnee- deposits younger than Mesocretaceous. gans, shows evident differences in details. Jurassic species of the genus represented by The last five haemal processes in L. congo- the group of L. coryphaenoides Bronn ( =L. lensis do not show the distinctive ventral bronni Agassiz), including L. sprattiformis, and anterior processes of L. nevadensis, the L. dubius Agassiz and numerous others, are structure and number of hypurals is differ- very different from Cretaceous species. The ent, and the first neural process is shortened. latter are related to L. brodiei Agassiz (see Both forms are evidently specialized in Arambourg 1935, p. 210). different directions. L. nevadensis, when There is no doubt that the Leptolepis from compared with the different types of caudal near Eureka, Nevada, belongs to the group fin-structure shown by the Clupeoidea represented in the Cretaceous. The char- (Hollister 1936, text figures 3-13), does not acter that distinguishes most clearly the show closer relationship to any of these but Cretaceous forms is the transformation of might be ancestral to them all. the tail end of the vertebral column. In the Reports of occurrences of the family Lep- Jurassic forms the caudal column is ste- tolepidae in the Americas are still scanty. goure, while in the Cretaceous forms a pro- A tail, possibly of the leptolepid genus gressive transformation takes place to the Thrissops, has been reported from the Cre- homocerque type of the living clupeids. taceous of Mexico (Felix, 1890). We can The caudal end of the vertebral column in find no reference to the occurrence of Lep- L. nevadensis is highly specialized for tolepisthe in the fossil record of North Amer- genus. It is comparable to the structure ica. seen

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There are two references to occurrences of REFERENCES Leptolepis in South America. D'Erasmo ARAMBOURG, CAMILLE, 1935, Contribution a (1934) calls attention to a fragment ofl'etude a des poissons du Lias superieur: Annales head of Leptolepis from the Neocomian ofde Palgontologie, vol. 24, p. 1. Patagonia. The same author (1938) describes ARAMBOURG, C. and SCHNEEGANS, D., 1935, Pois- an otolith of a member of the Leptolepidae sons fossiles du bassin sedimentaire du Gabon: from the Cretaceous of Brazil. He believes idem. p. 139. CABRERA, A., 1927, Sobre un pez f6sil del lago that Haplospondylus clupeoides Cabrera San Martin: Mus. La Plata, Rev., vol. 30, p. from the Lower Cretaceous Leptoceras strata 317. of Santa Cruz Province, Patagonia, is nearly D'ERAsMO, G., 1934, Sopra alcuni avanzi fossili related to or synonymous with Leptolepis. della Patagonica: (R.) Accad. Sci. fis. e nat. Because of presence of genera associated (Soc. R.) Napoli), Atti. ser. 2, vol. 20, no. 8. --, 1938, Ittioliti cretacei del Brasili: idem. (3), with Leptolepis congolensis in Coccobeach, 1, no. 3. which however may have survived Lepto- FELIX, J., 1890, Versteinerungen aus der mexi- lepis, Arambourg and Schneegans are able canischen Jura und Kreideformation: Palaeon- to correlate the Gabon fauna with one of tographica, Band 37, p. 140. middle or even late Cretaceous age from HOLLISTER, GLORIA, 1936, Caudal skeleton of Bermuda shallow-water fishes: Zoologica, vol. Bata in Spanish Guinea (Eastman 1912, 21, no. 4. Weiler 1922). Corresponding Cretaceous JORDAN, D. S., 1911, Description of a collection faunas have been described from South of fossil fishes from the bituminous shales at America-from Bahia, Brazil (Cope 1868, Riacho Doce, State Alagaos, Brazil: Carnegie Woodward and Mawson, and Woodward, Mus., Ann., vol. 7. RAYNER, D. H., 1938, On Leptolepis bronni 1907) and from Riacho Doce in Algaos Agassiz: Annals and Mag. Nat. History, ser. 10, (Jordan 1910). The age of these South vol. 19, p. 46. American faunas is not yet assured; they WEILER, W., 1922, Die Fischreste aus den may be Lower or Upper Cretaceous. None bitum6sen Schiefern von Ibando bei Bata of them includes Leptolepid fishes. (Spanisch Guinea): Palaeont. Zeitschr., Band 2. WOODWARD, A. S., 1916-1919, The fossil fishes of Judging from the relationships of L. the English Wealden and Purbeck formations: nevadensis to European and African forms, Palaeontogr. Soc., Mon., pt. 3 (1919), p. 121. we seem to be justified in regarding the - , 1908, On some fossil fishes discovered by formation near Eureka, whence the speci- Prof. Enues de Souza in the Cretaceous forma- mens came, as of Lower Cretaceous or pos- tion of Ilheos (State of Bahia) Brazil: Geol. Soc. London, Quart. Jour., vol. 64, p. 358. sibly younger.

MANUSCRIPT RECEIVED BY THE EDITOR SEPTEMBER 30, 1940.

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