Geology and lithology of the Tagay-1 section at Olkhon Island (Lake Baikal, Eastern Siberia), and description of Aplodontidae, Mylagaulidae and Sciuridae (Rodentia, Mammalia)

Abstract

Excavations along the Tagay-1 section shed light into the composition of small mammal assemblages of the Tagay site. The present paper focuses on the geology and geomorphology of Olkhon Island, the lithology and fossil evidence along the Tagay-1 section and descriptions of the aplodontid, mylagaulid and sciurid rodents. The described fossils are isolated teeth of four taxa, Ansomys sp. (Aplodontidae), Lamugaulus olkhonensis Tesakov and Lopatin, 2015 (Mylagaulidae), Sciuridae indet. and Spermophilinus debruijni nov. spec. (Sciuridae). The archaic tooth pattern of these rodents suggests an age around the Early/Middle Miocene transition.

Amphilagus plicadentis (Lagomorpha, Mammalia) from the Tagay locality (Olkhon Island, Baikal region, Eastern Siberia)

“…The lagomorph fossils were collected by screen washing of sediments from three fossiliferous horizons (7, 9, 10) of the Tagay section; locality and rodent fauna are discussed in Daxner-Höck et al (2022a, 2022b, 2022c, 2022d and Mörs et al (2022, this issue). The lagomorph collections are stored at the Dobretsov Geological Institute, Siberian Branch, Russian Academy of Sciences (GIN SB RAS), Ulan-Ude, Russia.…”

Palaeomagnetic data from the late Cenozoic Tagay section (Olkhon Island, Baikal region, Eastern Siberia)

“…Some genera appeared first in the late Oligocene (Ansomys, Lamugaulus, Amphilagus), others in the Early Miocene (Spermophilinus, Leptodontomys, Keramidomys and Democricetodon), only Gobicricetodon, hitherto only known from the Middle and Late Miocene, has its first appearance in Tagay. More precise biostratigraphic data derive from the species level of these genera (see Daxner-Höck et al 2022a, 2022b, 2022c, 2022dErbajeva et al 2022;Mörs et al 2022, all this issue). Almost all species from Tagay-1 show strong affinities with taxa from the Early Miocene (concerning primordial dental characters and/or size), and they differ considerably from younger (middle and late Miocene) species of the respective genera.…”