SMALL VERTEBRATES FROM THE LATE CRETACEOUS AND EARLY TERTIARY OF THE NORTHEASTERN ARAL SEA REGION, KAZAKHSTAN

Abstract

Field work conducted in the northeastern Aral Sea Region, southwestern Kazakhstan has produced a large number of vertebrates from late Cretaceous and early Tertiary sediments. Included among these vertebrates are sharks, bony fishes, amphibians, turtles, lizards, crocodiles, and dinosaurs. This fauna comes from three formations, the Turonian-Coniacian Zhirkindek, the Santonian-Campanian Bostobe, and the early Tertiary Akzhar formations. In this paper we describe the microvertebrate fauna. The Akzhar fauna consists only of marine sharks, one hexanchiform species (Notidanodon cf. loozi) and four lamniform species (Carcharias teretidens, Striatolamia striata, Otodus obliquus var. minor, and Palaeocarcharodon orientalis). These suggest a Paleocene age, most likely Selandian or earliest Thanetian. In addition to previously described components, the Bostobe fauna now includes a discoglossid frog and the lizard Slavoia cf. darevskii. This is the first Mesozoic record of each in Kazakhstan and the latest record anywhere of the latter. The Zhirkindek fauna is now known to include a varanid lizard.