Mammal remains from the Lower Cretaceous Bolʹshoi Terekhtyulʹ locality in West Siberia, Russia

Four mammalian taxa have been identified based on upper molariform tooth and edentulous dentary fragments from the Bolʹshoi Terekhtyulʹ locality of the Lower Cretaceous Ilek Formation (Krasnoyarsk Territory, Russia): Docodonta indet., Amphidontidae indet., Zhangheotheria indet. sp. A and sp. B. The docodontan from Bolʹshoi Terekhtyul is smaller than Sibirotherium rossicum from the Ilek Formation at Shestakovo 1 locality (Kemerovo Province, Russia) and may belong to a distinct taxon. It is one of the younger docodontans in the fossil record. The mammal assemblage from the Bolʹshoi Terekhtyulʹ locality is drastically different from the mammal assemblage of nearby localities of the Ilek Formation along Bolʹshoi Kemchug River, which consists of Gobiconodontidae and Amphilestidae. The reason for this faunal discrepancy is unclear for the moment.