Protostega gigas and other sea turtles from the Campanian of Eastern Europe, Russia

The Campanian Beloe Ozero locality within the Rybushka Formation in Saratov Province, Russia, produces numerous isolated bones of sea turtles (clade Pan-Chelonioidea) identified as belonging to Protostega gigas, a giant protostegid, previously reliably known only from the Coniacian - Campanian of North America, and Pan-Chelonioidea indet. The Protostega gigas specimens described in this paper include bones of the skull (maxillae, jugal, ?quadratojugal, and squamosal), shell (neural, peripherals, and hypoplastron), and appendicular skeleton (scapula and humeri). The material of Pan-Chelonioidea indet. demonstrates similarity with different sea turtle taxa of North America and Western Europe: non-Protostega protostegids, Toxochelys spp., ctenochelyids, dermochelyids, and pan-cheloniids. The estimated size of the Protostega gigas specimens from the Beloe Ozero locality well corresponds to those of the largest specimens of this species from North America. Protostega gigas from the Beloe Ozero locality represents the first finding of this species outside North America and the first reliable evidence of its cosmopolitanism.