Acta Palaeontologica Polonica No. 1 1981 [antikvár]

ACTAPALAEONTOLOGICAPOLONICAVol. 261 9 8 1No. 1ZOFIA KIELAN-JAWOROWSKA and BORIS A. TROFIMOVA NEW OCCURRENCE OF LATE CRETACEOUS EUTHERIAN MAMMAL ZALAMBDALESTESKIELAN-JAWOROWSKA, Z. and TROFIMOV, B. A.: A new occurrence of Late Cretaceous eutherian mammal Zalambdalestes. Acta Palaeont. Polonica, 26, 1, 37, October, 1981.Nearly complete left lower jaw of Zalambdalestes lechei is described, from Toog-reeg beds, locality of Toogreeg on the Gobi Desert. An occurrence of Z. lechei, (known so far only from the Djadokhta Fm.) in Toogreeg beds, gives support to an opinion that Toogreeg beds are a stratigraphie equivalent of the Djadokhta Fm., which is of ?late Santonion and/or ?early Campanian age.Key words: Mesozoic mammals, Zalambdalestes, Late Cretaceous, Gobi Desert. Zofia Klelan-Jaworowska, Zaklad Paleobiologii, Polska Akademia Nauk, 02-089 Warszawa, al. ?.wirki i Wigury 93, Poland; Boris A. Trofimov, Paleontologiczeskij Mu-ze) Akademii Nauk, Moskva W-71, Leninskij Prospekt 16, USSR. Received: Januarymo.The specialized Late Cretaceous eutherian mammal Zalambdalestes^ represented by a single species Z. lechei was known so far only from the locality of Bayn Dzak (formerly Shabarkh Usu) in the Gobi Desert, Mongolia (Gregory and Simpson 1926, Simpson 1928, Kielan-Jaworowska 1969, 1975, Szalay and McKenna 1971). The age of the Djadokhta Formation, which crops out at Bayn Dzak and yields Z. lechei has been estimated as ?late Santonian and/or ?early Campanian (Gradzihski et al, 1977).Ca. 30 km WNW of Bayn Dzak is the locality of Toogreeg, (Toogree-geen Shireh). The yellowish-gray sandstone, known as the Toogreeg beds, which crops out at Toogreeg and yields the same dinosaur species {Velo-ciraptor mongoliensis and Protoceratops andrewsi) as the sandstone of the Djadokhta Formation has been tentatively regarded as a stratigraphic equivalent of the Djadokhta Fm. (Gradzihski et al., 1977). So far only one mammalian species, has been described from the Toogreeg beds: an eucos-modontid multituberculate Tugrigbaatar saichanensis (Kielan-Jaworowska and Dashzeveg 1978).During the 1978 Soviet-Mongolian Palaeontological Expedition to the Gobi Desert, Mongolian technician Mr. Namsray, working under Dr. R. Barsbold, found a lower jaw of a eutherian mammal in Toogreeg; this is