A New Finding of a Docodontan (Mammaliaformes, Docodonta) in the Lower Cretaceous of Western Siberia
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A New Finding of a Docodontan (Mammaliaformes, Docodonta) in the Lower Cretaceous of Western Siberia Academician A. V. Lopatina,b,*, A. O. Averianovc,d, I. T. Kuzmine, E. A. Boitsovae, P. G. Saburove,
S. V. Ivantsovf, and P. P. Skutschase Received December 20, 2019; revised June 30, 2020; accepted July 1, 2020
Abstract—The first finding of the docodontan (a lower molar of Sibirotherium sp.) from the Bol’shoi Kemchug 3 locality (Ilek Formation, Lower Cretaceous) in Krasnoyarsk Territory is described. Sibirotherium rossicum, one of the youngest docodontans in the geological record, is known from the Ilek Formation of the Shestakovo 1 locality (Kemerovo Region). Previously, only indeterminable remains of docodontans had been found in the localities of the Ilek Formation (Bol’shoi Terekhtyul’ 2 and Bol’shoi Ilek) on Krasnoyarsk Territory. Keywords: mammals, docodontans, Early Cretaceous, Ilek Formation, Western Siberia, Russia DOI: 10.1134/S1028334X20090123
Docodontans are a diverse group of Mesozoic mammaliaforms (archaic mammals unrelated to modern taxa), including terrestrial, burrowing, arboreal, and semiaquatic ecomorphs [1–4]. They were characterized by the presence of pseudotribosphenic molars with a large inner protrusion on the upper teeth and an opposing depression on the lower ones. This feature is significant for effective food processing when chewing. Owing to this feature, docodontans became one of the dominant groups in the communities of small vertebrates during the Middle–Late Jurassic in the Northern Hemisphere. In Russia, a vertebrate assemblage with dominant and very diverse docodontan mammaliaforms is known from the Middle Jurassic deposits of Krasnoyarsk Territory (Berezovsk coal mine) [5]. Furthermore, the latest docodontans in the geological record are known in Russia: Sibirotherium from the Early Cretaceous of the Kemerovo Region (Shestakovo 1 locality) and Khorotherium from the Early Cretaceous of Yakutia (Teete locality) [6–8]. aBorissiak Paleontological Institute, Russian Academy of Sciences, Moscow, 117647 Russia bMoscow State University, Moscow, 119991 Russia cZoological Institute, Russian Academy of Sciences, St. Petersburg, 199034 Russia dKazan Federal University, Kazan, 420008 Russia eSaint Petersburg State University, St. Petersburg, 199034 Russia fTomsk State University, Tomsk, 634050 Russia *e-mail: [email protected]
In recent years, remains of indeterminable docodontans have been found in the deposits of the Ilek Formation (Lower Cretaceous, Barremian–Aptian) in Krasnoyarsk Territory (Bol’shoi Terekhtyul’ 2 and Bol’shoi Ilek localities) [9, 10]. Here we report a new find of docodontans in Russia, a lower molar from the Bol’shoi Kemchug 3 locality in Krasnoyarsk Territory. This locality is also confined to the Ilek Formation and contains a rich assemblage of mammals [11]. However, no docodontans were previously found here. The studied material is stored in the collection of the Laboratory of Mesozoic and Cenozoic Continental Ecosystems (LMCCE) of Tomsk State University. The stud
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