Snout and orbit of Cretaceous Asian multitiuberculates studied by serial sections

The orbital wall in Nemegtbaatar gohiensis and Chulsanbaatar vulgaris, from the Late Cretaceous of the Gobi Desert, Mongolia, comprises a small lacrimal anteriorly, large orbital process of the frontal dorsally, orbitosphenoid posteriorly and maxilla ventrally. Nemegtbaatar also posesses an orbital process of the palatine ventrally, not recognized in Chulsanbaatar. Large frontal sinuses of both taxa are interpreted as related to lack of the sagittal crest. Other anatomical characters found in this study, such as orbital process of the frontal, ossified turbinals, ossified ethmoid and vomer, frontal, sphenoidal and maxillary sinuses, and the presence of the orbital process of palatine in Nemegtbaatar suggest a close relationship of multituberculates to monotremes and therian mammals. By the new data obtained from the serial sections the diagnostic character: orbital process of the palatine absent in Multituberculata, is no longer valid. Ossified ethmoid and maxillary turbinals, characteristic for Monotremata, Vincelestes, Marsupialia and Placentalia, are also present in Multituberculata. The precence of a cribiform plate and the precence of an ossified plate of ethmoid in Multituberculata is shared with Monotremata, Vincelestes, Marsupialia and Placentalia.

W artykule przedstawiono interpretację seryjnych skrawków, uzyskanych przy pomocy mikrotomu Junga, z przednich części czaszek dwu gatunków multituberkulatów z poźnej kredy pustyni Gobi. Okazało się, że u Nemegtbaatar gobiensis występuje oczodolny wyrostek kości podniebiennej. Jego brak nie może być więc dalej uważany za diagnostyczną cechę multituberkulatów.