A new mammal species discovered in Mongolia reveals surprising insights into ancient inland ecosystems and the dietary habits of early mammals.
A collaborative research team from Okayama University of Science (OUS) and the Institute of Paleontology and Geology, Mongolian Academy of Sciences (IPMAS) has discovered the fossil of a previously unknown genus and species of mammal in the Late Cretaceous strata (dating from 100 to 66 million years ago) of Mongolia’s Gobi Desert. The newly identified, mouse-sized species has been named Ravjaa ishiii. The discovery was officially announced on April 4th during a press conference held by OUS.
The species name honors two individuals: Dulduityn Danzanravjaa, a revered 19th-century Mongolian Buddhist monk, and the late Kenichi Ishii, former director of the Hayashibara Museum of Natural Sciences, who played a key role in establishing the Mongolia-OUS research collaboration.
During the joint expedition in 2019 at the Baynshire Formation, the fossil-bearing deposit in the Gobi Desert, Mongolia, the team found a one-centimeter partial lower jaw. Analysis suggested the specimen is a member of Zhelestidae, a Cretaceous mammal family. Yet, its unusually tall molars and distinctive jaw shape differ from known relatives, and therefore the study erected a new genus and species. The discovery marks the first record of a zhelestid in Mongolia, showing the group also thrived far inland, not only along ancient coastlines as was previously inferred.
Link Between Flowering Plants and Early Mammals
The suggested age of the Baynshire Formation corresponds to the early spread of angiosperms (flowering plants) in terrestrial ecosystems. The robust nature of the molars resembles those of seed and fruit-eating mammals, providing an intriguing insight that early eutherians were already exploiting resources created by flowering plants.
Tsukasa Okoshi (lead author, OUS doctoral candidate) said, “Due to the COVID-19 pandemic, the publication process took longer than expected, but we were finally able to establish the scientific importance of this specimen. We hope this research will serve as a starting point for further taxonomic studies of other small vertebrate fossils from the same site and era and will ultimately help uncover the rich biodiversity — including dinosaurs — that once inhabited the Gobi Desert during the age of dinosaurs.”
Professor Mototaka Saneyoshi (OUS) added, “Finding such a tiny fossil in the vast expanse of the Gobi Desert feels like a gift from the Gobi Desert. It’s nothing short of miraculous.”
Reference: “New Late Cretaceous zhelestid mammal from the Bayanshiree Formation, Mongolia” by Tsukasa Okoshi, Ryuji Takasaki, Kentaro Chiba, Masahito Natori, Mototaka Saneyoshi, Akio Takahashi, Shota Kodaira, Shoji Hayashi, Shinobu Ishigaki, Buuvei Mainbayar and Khishigjav Tsogtbaatar, 2025, Acta Palaeontologica Polonica.
DOI: 10.4202/app.01213.2024
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