A new genus and Zhestid mammal species have been identified from fossilized remains found in the Bayanshiree training In the Gobi desert of Mongolia.
Reconstruction of the life of Ravjaa Ishiii (foreground), illustrated at the foot of the Hadrosauride dinosauride Gobihadros. Image credit: Kohei Futaka.
Appointed Ravjaa IshiiiThe new species traveled the earth during the Cretaceous period, about 90 million years ago.
The old mammal was the size of a mouse and belonged to ZhelestidaeA family of widely distributed Eutherian mammals from Eurasia in North America in the upper Cretaceous.
“Many extremely preserved mammals fossils unearthed by the late strata of the Cretaceous in the Gobi desert of Mongolia played a key role in understanding the evolution of mesozoic mammals,” said the doctorate of the University of Okayama Tsukasa Okoshi and his colleagues.
“These splendid fossils of mammals were mainly given training for Baruungoyot and Djadokhta, but only two fragmentary remains of mammals were collected in the underlying formation of Bayanshiree.”
The New Zhestid Fossil was found in 2019 in the locality of Bayan Shiree of the Bayanshiree formation.
The sample is a partial lower jaw, 1 cm long with the distal part of an ultimate premolar and the first in the third molars.
“Finding an so tiny fossil in the vast expanse of the Gobi desert resembles a gift from the Gobi desert. It is nothing less than miraculous,” said Professor Mototaka Saneyoshi of the Okayama University of Sciences.
“Its unusually high molars and its distinctive jaw shape differ from known parents, so we have erected a new genre and a new genre,” said paleontologists.
“The robust nature of the molars resembles those of mammals of seeds and fruit, providing an intriguing overview that the first Eutherians already exploited resources created by flower plants.”
According to the team, Ravjaa Ishiii is the first Zhelestid of the Bayanshiree formation and in fact the first discovered in Mongolia.
“”Ravjaa Ishiii Potentially represents the oldest member among the Zhelestides or as old as the oldest Zhestids currently known in Uzbekistan, suggesting that the emergence of this group has occurred around the early / late border of the Cretaceous in the upper Cretaceous, “said researchers.
Their paper was published online in the journal Acta Palaeontologica Polonica.
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Tsukasa okoshi and al. 2025. The new mammal of the Zhestid of the upper Cretaceous of the formation of Bayanshiree, Mongolia. Acta Palaeontologica Polonica 70 (1): 193-203; DOI: 10.4202 / app. 01213.2024
