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On Ichthyosaur Remains from the Cretaceous of the Voronezh Region
A new ichthyosaur, Platypterygius ochevi sp. nov., from the Albian–Cenomanian of the Voronezh Region is described based on a partial forefin. It differs from congeners in the very large facet for the lageniformis on the humerus. INTRODUCTION Remains of the globally distributed ichthyosaur genus Platypterygius occur in the Cretaceous of Russia and adjacent countries. They are usually confined to condensation horizons (phosphoritic horizons) of the Albian and Cenomanian stages and represented by isolated extremely rolled vertebral centers, fragmentary ribs and jaws, and, less frequently, by tooth crowns (Pervushov et al., 1999). The fragmentary nature of the material complicates exact identification and morphological examination. Relatively complete skeletal specimens of representatives of this genus have been recorded outside Russia (Broili, 1907; Kuhn, 1946; Romer, 1968; McGowan, 1972; Wade, 1984, 1990; Bardet, 1992; Fernandez and Aguirre-Urreta, 2005; Kear, 2005), but the Russian Cretaceous beds have yielded only three relatively complete specimens; Platypterygius birjukovi (Ochev et Efimov, 1985) and P. bedengensis (Efimov, 1997) from the Barremian and Hauterivian of the Ulyanovsk Region, respectively, and P. bannovkensis Arkhangelsky, 1998 from the Cenomanian of the Saratov Region (Ochev and Efimov, 1985; Efimov, 1997; Arkhangelsky, 1998). P. kiprianoffi (Romer, 1968) from the Albian–Cenomanian of the Belgorod and Kursk regions is represented only by fragmentary cranial and postcranial bones, and has not yet been thoroughly described (Kiprianoff, 1881; Romer, 1968). Therefore, even incomplete specimens of Platypterygius deserve special attention. In this connection, an incomplete ichthyosaur skeleton found in the spring of 1984 during educational field work for students of the Geological Faculty of Voronezh State University (VGU) is of significant interest (Koval’ and Sirotin, 2001). The bones were found by employees of the Department of General and Historical Geology of VGU in a sand quarry (Semiluki locality) in the valley of the right bank of the Veduga River (close to the Voronezh– Semiluki highway), 4 km north of the town of Semiluki of the Voronezh Region. Many bones were in situ, with slight displacement relative to their natural positions in the skeleton. Some specimens were collected in debris.