The early mammals that were present in this region during the time of Avimimus were the placental mammals Asioryctes nemegetensis and Barunlestes butleri, the amphibian Gobiates khermeentsavi, the multituberculate mammals Catopsbaatar catopsaloides, Chulsanbaatar vulgaris and Nemegtbaatar gobiensis, and the marsupial mammal Asiatherium reshetovi and Deltatheridium pretrituberculare.
The early mammals that were present in this region during the time of Conchoraptor were the placental mammals Asioryctes nemegetensis and Barunlestes butleri, the amphibian Gobiates khermeentsavi, the multituberculate mammals Catopsbaatar catopsaloides, Chulsanbaatar vulgaris and Nemegtbaatar gobiensis, and the marsupial mammal Asiatherium reshetovi and Deltatheridium pretrituberculare.
A few even received the locality name, like the Dinheirosaurus lourinhanensis and Jurassic mammals like Portopinheirodon asymmetricus and the multituberculates family Pinheirodontidae.
Animals that may have shared the same habitat with Tsaagan include Protoceratops, Shuvuuia, the small mammal Zalambdalestes, the multituberculate mammal Kryptobaatar, as well as several lizards and two yet-undescribed species of troodontid and dromaeosaurid.
These include the gondwanathere Lavanify, an indeterminate multituberculate, and a few other indeterminate teeth, as well as a nearly complete skeleton representing an otherwise unknown mammalian lineage.