1 REVISION OF THE GENUS MARTINICHTHYS, MARINE FISH (TELESOSTEI, TSELFATIIFORMES) FROM THE LATE CRETACEOUS OF KANSAS (UNITED STATES) TAVERNE L., 2000. Revision of the genus Martinichthys, marine fish (Teleostei, Tselfatiiformes) from the Late Cretaceous of Kansas (United States). [Revision of the genus Martinichthys, marine fish (Teleostei, Tselfatiiformes) from the Late Cretaceous of Kansas (United States)]. GEOBIOS, 33, 2:211-222. Villeurbanne, 04/31/2000. ABSTRACT – The genus Martinichthys belongs to the order Tselfatiiformes and contains two valid species, M. brevis with a short rostrum and M. ziphoides with a long rostrum. The species M. acutus, M. alternatus, M. gracilis, M. intermedius and M. latus are junior synonyms of M. ziphoides. The genus is characterized by five autapomorphies: a snout lengthened in a rostrum, a narrow cranial roof, the premaxillae forming a secondary palate and hiding the vomer, the lack of anterior process on the maxilla, and the supraoccipital without a medial crest. Despite its specialized characters, Martinichthys also retains some primitive features for the order, such as the presence of an autogenous basisphenoid and the three lingual toothed plates. Within the Tselfatiiformes, Martinichthys appears especially close to the genera Plethodus and Thryptodus. KEYWORDS: TELEOSTEI, TSELFATIIFORMES, MARTINICHTHYS, MARINE LATE CRETACEOUS, KANSAS, OSTEOLOGY. INTRODUCTION The type species of the genus is Martinichthys brevis McClung, 1926, whose rostrum is The genus Martinichthys McClung, 1926 was moderately elongated. McClung (1926) also erected for large Teleostei from the describes a series of other species, where the Plethodidae family, characterized by a snout rostrum elongates in a more marked manner. elongated forming a rostrum (McClung, Martinichthys ziphoides (Cope, 1877), M. 1926). The strong erosion presented by the acutus McClung, 1926, M. alternatus end and the antero-ventral part of this McClung, 1926, M. gracilis McClung, 1926, rostrum, in all known specimens, probably M. intermedius McClung, 1926, and M. latus indicates that this fish used it to dig the sea McClung, 1926. These last six species only floor in search of preys. Martinichthys differ one from the other in minor changes in haunted the waters of Late Cretaceous North the shape of their respective rostra (McClung American Interior Sea. Its remains have been 1926: pl. 1). I have studied the concerned found in the Niobrara Formation of Kansas material. These slight morphological (United States) and are thus of a geologic age differences are due, in my opinion, to branching from the Coniacian to the Early individual, sexual, ontogenetic, or erosion Campanian (Schultze et al. 1982). Only variations and do not justify the erection of skulls, rostra and some vertebrae have been particular species. I subsequently propose to recovered. Almost nothing, then, is known of consider the five long rostrum species erected the postcranial skeleton. Judging by the size by McClung as junior synonyms of of the concerned parts, it can be estimated that Martinichthys ziphoides, a species clearly the whole specimens were nearing or even distinct from M. brevis. were bigger than one meter in length. 2 McClung (1926)’s osteologic description KUVP 499 (7.3cm long rostrum; holotype of remains very superficial and doesn’t allow a M. latus; Coniacian; Smoky Hill Chalk, clear comprehension of Martinichthys’s skull, member of the Niobrara Formation; Martin’s nor does it help envisage the relationships of Canyon, Gove County, Kansas). this fish with other Plethodidae genera. A KUVP 500 (4.2cm long rostrum; holotype of revision of Martinichthys was necessary. This M. alternatus; Coniacian; Smoky Hill Chalk, is the aim of the present work which also member of the Niobrara Formation; 1 ½ mile follows the series of publications that I south of Banner, Trego County, Kansas). dedicate to the study of Tselfatiiformes or KUVP 501 (5.2cm long rostrum; holotype of Bananogmiiformes (Taverne 1975, 1983, M. intermedius; Coniacian; Smoky Hill 1999 in press a, b), an order of large marine Chalk, member of the Niobrara Formation; 1 teleostei fish from the Cretaceous to which ½ mile south of Banner, Trego County, the Plethodidae family belongs (Patterson Kansas). 1993: 627; Nelson 1994: 90) et whose shape KUVP 502 (2.7cm long rostrum; holotype of reminds that of extant Scombridae and M. acutus; Coniacian; Smoky Hill Chalk, Coryphaenidae. member of the Niobrara Formation; Martin’s Canyon, Gove County, Kansas). For more information concerning the KUVP 503 (2.9cm long rostrum; paratype of Tselfatiiformes, as well as the discussion on M. acutus; Coniacian; Smoky Hill Chalk, their systematic position within the member of the Niobrara Formation; west side Clupeocephala, I recommend Taverne (in escarpments of sector 3. Trego County, press a). Kansas). KUVP 504 (5.5cm long rostrum; holotype of MATERIAL AND METHODS M. gracilis; Coniacian; Smoky Hill Chalk, member of the Niobrara Formation; Martin’s The material comes from the collections of Canyon, Gove County, Kansas). the Department of Palaeontology, University KUVP 506 (10cm long rostrum; Senonian; of Kansas, Lawrence (KUVP) and the Smoky Hill Chalk, member of the Niobrara American Museum of Natural History of New Formation; West of Kansas). York (AMNH). KUVP 507 (9.5cm long rostrum; Coniacian; Smoky Hill Chalk, member of the Niobrara Martinichthys brevis: Formation; 1 ½ mile south of Banner, Trego KUVP 497 (holotype; 14cm long skull and County, Kansas). some vertebrae; Senonian; Smoky Hill Chalk, member of the Niobrara Formation; south This material has been studied with the use of side of the Smoky Hill, Gove County, a stereomicroscope Wild M5, achieved by the Kansas). author in a clear chamber (camera lucida). KUVP 40015 (16cm long neurocranium from which the rostrum end is missing, some STUDY OF THE MATERIAL vertebrae and some bone fragments; Senonian; Niobrara Formation, Gove County, THE SKULL (Fig. 1-9) Kansas). The neurocranium is elongated in Martinichthys ziphoides: Martinichthys brevis and even more elongated AMNH 2131 (holotype; 10cm long rostrum; in M. ziphoides. In the first, the maximum Senonian; Niobrara Formation; Gove County, height of the neurocranium represents 42% of Kansas). its length, whereas it is no more than 25% in KUVP 498 (20cm long nearly complete the second. This neurocranium is also neurocranium and 23 vertebrae; Coniacian; laterally compressed. This compression is Smoky Hill Chalk, member of Niobrara highly reinforced by the lateral compression Formation; ¾ mile from Neuenschwander that the three discovered skulls have endured ranch, Trego County; Kansas). during fossilization. 3 The rostrum, rounded at its proximal end, is premaxillaries is ornamented by tiny facets formed by the vomeroethmoidian region and and wrinkles. This ornamentation is more by the very large premaxillaries which pronounced in M. brevis than in M. ziphoides. recover it with a truly ossified capuchon. This In M. brevis, one can observe a pair of lateral rostrum is clearly longer and thinner in M. ethmoids, just behind the mesethmoid and ziphoides than in M. brevis. The rostrum stuck between the frontals and the length (measured to the distal end of the parasphenoid. In M. ziphoides specimens, the mesethmoid) equals 158% of its maximum lateral ethmoid region is not preserved. height in M. brevis (skull KUVP 497), whereas it is 327% in M. ziphoides (skull A large part of the left nasal is present on KUVP 498). The mesethmoid is elongated, skull KUVP 497 (M. brevis). It is a small thick, very massive and made of a single part, bone, wide but not very elongated, flat and without it being possible to distinguish a which articulates with the frontal lateral edge dermethmoid and a supraethmoid. It is in a notch situated just above the lateral literally encapsulated in the premaxillaries ethmoid. The nasal is not preserved in M. which nonetheless let a part of it visible ziphoides specimens. laterally and dorsally, but totally recover and hide it ventrally. Laterally, near the posterior The skull roof is formed by the frontals, the edge of the mesethmoid, it can be observed a parietals, the pterotics, the epiotics and the short and narrow groove used for the supraoccipital. It is only well preserved in M. articulation of the anteromedial edge of the brevis, whereas only parts of the frontals are nasal. The mesethmoid and the premaxillaries visible in M. ziphoides. This skull roof is are fused together. This fusion is less elongated and narrow, even in the parieto- pronounced in M. brevis than in M. ziphoides. occipital region, and seems to have been The sutures are still clearly visible between relatively flat. However, the lateral crushing the two premaxillaries and between these and endured during fossilization has created an the mesethmoid on skull KUVP 497 (M. angle between the two frontals and the two brevis), whereas the fusion between the three parietals which, on skull KUVP497, are bones is more advanced in skull 40015 of the pushed on each side in a more oblique plan. same species. In M. ziphoides, on the In M. brevis, the frontals are long, moderately contrary, the two premaxillaries are intimately wide, but not a lot more distally than fused one to the other, without any visible proximally. The distal end of the frontal is suture persisting between them, and the suture situated at the level of the posterior edge of with the mesethmoid is more clearly blurred the orbit, just above the sphenotic. A little although still visible in the form of a pad . In groove can be observed along the medial part the two species, the two premaxillaries join of the frontal lateral edge; it is used to ventrally on the medial skull line, thus articulate with the supraorbital. The parietals forming a kind of false palate covering and are large, nearly quadrangular, a little longer entirely hiding the vomer region. More than wide and in medial contact, thus distally on this false palate, the premaxillaries determining a medioparietal skull. In the remain separated one from the other by a deep middle of the skull roof, the two parietals notch.