A new Crossognathus (Actinopterygii, Teleostei) from the Lower Cretaceous of Romania with comments on Crossognathidae relationships Lionel CAVIN Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD (United Kingdom) [email protected] Dan GRIGORESCU University of Bucharest, Faculty of Geology and Geophysics, Laboratory of Paleontology, 1 Bacescu Blvd, 70111 Bucharest (Romania) [email protected] Cavin L. & Grigorescu D. 2005. — A new Crossognathus (Actinopterygii, Teleostei) from the Lower Cretaceous of Romania with comments on Crossognathidae relationships. Geodiversitas 27 (1) : 5-16. ABSTRACT Crossognathus danubiensis n. sp., known by a single specimen from the middle Albian of the vicinity of Giurgiu, south Romania, is described. The new species differs from other Crossognathus by the very elongated posterior infra- orbitals covering the vertical limb of the preopercle and part of the opercle KEY WORDS and by the bones of the opercular series with fine posterior radiating ridges. Actinopterygii, Some of its characters, such as the presence of numerous well developed bran- Teleostei, Crossognathus, chiostegal rays, are unusual for crossognathids and are discussed. We discuss Lower Cretaceous, the phylogenetic relationships of crossognathids and we point out several Romania, characters indicating possible relationships with the Late Jurassic Vara- basal teleosts, phylogeny, sichthyidae. This possible sister-group relationship is regarded as a working new species. hypothesis for further studies on basal teleosts phylogeny. GEODIVERSITAS • 2005 • 27 (1) © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. www.geodiversitas.com 5 Cavin L. & Grigorescu D. RÉSUMÉ Un nouveau Crossognathus (Actinopterygii, Teleostei) du Crétacé inférieur de Roumanie et remarques sur les relations des Crossognathidae. Crossognathus danubiensis n. sp. est décrit sur la base d’un unique exemplaire en provenance de l’Albien moyen des environs de Giurgiu dans le sud de la Roumanie. La nouvelle espèce se distingue des autres Crossognathus par des infraorbitaires postérieurs très allongés couvrant entièrement la branche verti- cale du préopercule et une partie de l’opercule, ainsi que par les ossifications MOTS CLÉS de la série operculaire portant de fines crêtes rayonnantes. Certains de ses Actinopterygii, caractères, telle la présence de rayons branchiostèges bien développés, sont Teleostei, Crossognathus, inhabituels chez les Crossognathidae et sont discutés. Les relations phylogéné- Crétacé inférieur, tiques des Crossognathidae sont abordées et nous soulignons plusieurs carac- Roumanie, tères indiquant de possibles relations avec les Varasichthyidae du Jurassique téléostéens basaux, phylogénie, supérieur. Ce résultat doit servir d’hypothèse de travail pour de futures études nouvelle espèce. sur la phylogénie des téléostéens basaux. INTRODUCTION assessing relationships among basal teleosts, and we discuss the possible sister-group relationship The Cretaceous actinopterygian fossil record of with Varasichthyidae as already proposed by Romania is poor. The only documented occur- Cavin (2001). The goal of the present paper, rence is Osmeroides dobrogensis Grigorescu & however, is not to provide a comprehensive Marin, 1971 from the Turonian of the Babadag analysis of the phylogenetic relationships of basal Basin (Grigorescu & Marin 1971). We describe teleosts. here a new species based on a single isolated spec- imen from the middle Albian found in the vicini- A NATOMICAL AND INSTITUTIONAL ABBREVIATIONS ty of Giurgiu, about 100 km south of Bucharest An angular; Axp axillary process; (Fig. 1). Bop branchiopercle; Rich Albian fish assemblages are known from br branchiostegal ray; various localities around the world, such as in Cl cleithrum; North America (Paluxy Formation in US, Tepexi Ddentary; Dpt dermopterotic; de Rodriguez in Mexico), South America Dsp dermosphenotic; (Santana Formation in Brazil), and Australia Ecpt ectopterygoid; (Toolebuc Formation). The only rich Albian fish Enpt entopterygoid; Ext extrascapular; fauna in Europe is from the British Gault. No ext.com extrascapular commissure; comparable fish assemblages are known in Fr frontal; Central Europe and Asia. Thus, every single dis- Ggular; Io infraorbital bone; covery outside the main fish localities is impor- md median depression; tant for our understanding of Early Cretaceous Mx maxilla; teleost distribution and phylogeny. Op opercle; The objective of this paper is to describe the new Pa parietal; Pal palatine; species and to discuss its possible relationships. Pop preopercle; We also comment some characters relevant to Psp parasphenoid; 6 GEODIVERSITAS • 2005 • 27 (1) A new Crossognathus from the Cretaceous of Romania ROMANIA 0 3 00 km Cluj-N apoca Tim isoar a B r a s o v B U C A RES T C r a i o v a G i u r g i u EUROPE F IG. 1. — Location map of Romania showing the position of the type locality (★ ). Ptt posttemporal; For more than 40 years the specimen was kept in Qquadrate; a private collection, without being described. It Scl supracleithrum; Smx supramaxilla; eventually reached Prof. Theodor Neagu from Sob supraorbital; the Laboratory of Paleontology of the University Sop subopercle; of Bucharest, who gave it for study to the second sr sclerotic ring; BMNH The Natural History Museum, London; author of this paper. FGGUB Faculty of Geology and Geophysics, The circumstances of the discovery – acci- University of Bucharest. dentally, by a non-specialist – did not leave information on the depth and consequently, on the precise stratigraphic level of the speci- GEOLOGICAL SETTING men. According to Prof. T. Neagu who studied the ammonites and foraminifera from the The fossil was found on the Romanian bank of drillings near Giurgiu (Neagu 1959), the marl the Danube in a shallow drill core made in the deposits that yielded the specimen is middle 1950’s during the building of a railway and road Albian in age with the ammonite Hoplites den- bridge crossing the Danube from Giurgiu in tatus (Sowerby, 1821) and the belemnite Romania to Russe in Bulgaria. The locality is Neohibolites minimus (Miller, 1826) as index- now flooded by the Danube waters. The rock in species. which the bridge pillars were embedded and which provided the fossil fish specimen is a fine gray marl with glauconite, that filled the body MATERIAL EXAMINED after the death and bury. The matrix, visible in the posterodorsal part of the specimen where the Apsopelix (= “ Syllaemus”) anglicus (Dixon, 1850): squamation is eroded, resembles the British BMNH P.611, holotype (Lower Chalk), BMNH Gault. The gray marls represent the uppermost P.49055 (Lower Chalk), BMNH P.9890 (youngest) deposit that outcrops at the lowest (Gault), BMNH P.9053 (Gault), BMNH level of the river under the Quaternary terraces. P.47196 (Gault). Wenz (1965: 21) suggested The place of the discovery belongs to the that the specimens from the Gault and from the Moesian Platform, the geotectonic unit that sepa- Chalk show different body ratios and constitute rates the Southern Carpathians from the Stara two groups. But she did not create a new taxon Planina Mountains in northern Bulgaria. for the Gault specimens. GEODIVERSITAS • 2005 • 27 (1) 7 Cavin L. & Grigorescu D. Osmeroides lewesiensis (Mantell, 1822): BMNH tapered ventrally at the level of the mandibles, P.4296 (Chalk). but broadens posteriorly at the levels of the oper- Osmeroides levis Woodward, 1901: BMNH cular apparatus. P.1854 (Chalk). Crossognathus danubiensis n. sp.: FGGUB.V.210. Skull roof Only the posterior part of the skull roof is pre- served. The anterior tips of both frontals (Fr) are SYSTEMATICS missing. The preserved posterior parts show that the frontal is broader posteriorly than anteriorly, Subclass ACTINOPTERYGII Cope, 1887 giving a roughly triangular outline in dorsal view. Division TELEOSTEI The surface of both frontals is not well preserved, sensu Patterson & Rosen, 1977 but ridges and weak reticulated networks of Family CROSSOGNATHIDAE ridges radiate from each centre of ossification. A Patterson & Rosen, 1977 stronger ridge runs posteromedially from each centre of ossification and meets its counterpart in Genus Crossognathus Pictet, 1858 the midline, defining the posterior margin of a median shallow depression (md). Such a median T YPE SPECIES. — Crossognathus sabaudianus Pictet, depression is present in crossognathids (Taverne 1858: 18-28, pls 2, 4, figs 1-6. 1989) and pachyrhizodontids (Forey 1977) among other teleosts. The suture between frontals is smooth and forms a sigmoid line in the half of Crossognathus danubiensis n. sp. the length of preserved bones. Most of the poste- H OLOTYPE AND ONLY KNOWN SPECIMEN. — rior part of the skull roof is covered by the hyper- FGGUB.V.210. trophied extrascapulars (Ext) and only reduced surfaces of both parietals (Pa) are visible. They T YPE LOCALITY. — On the bank of the Danube, vicin- ity of Giurgiu, Romania. contact the frontals with interdigitate sutures. Because of the size of extrascapulars, we cannot T YPE LEVEL. — Middle Albian. determine if both parietals are in contact in the E TYMOLOGY. — From the Latin Danubius, the name midline (the medioparietal condition versus the of the Danube River. lateroparietal condition). Posterolaterally to the D IAGNOSIS. — Crossognathus with elongated posterior frontals and laterally to the parietals is a pair of infraorbitals covering the vertical limb of the preoper- cle and part of the opercle, opercular bones with fine badly preserved ossifications,