The skeletal morphology and phylogenetic position of Adocus amtgai, an adocid turtle from the Late Cretaceous of Mongolia

• The almost complete skeleton of representative of Adocus is described in details.
• The described material of A. amtgai allows us to emend the diagnoses of the species.
• Most of skull and shell characters indicate A. amtgai is most similar to A. aksary.
• The result of our study confirms the assignment of A. amtgai to the genus Adocus.

This paper presents the description of the skeletal morphology of Adocus amtgai, an adocid turtle from the Late Cretaceous of Mongolia, based on an almost complete skeleton from the upper part of the Bainshire Formation (late Turonian–Santonian) of the Bayshin Tsav locality. Examination of this specimen, which is the best preserved among Asian Adocus species, reveals some previously unknown and misunderstood characters of A. amtgai and expands our understanding about variation within Adocus. The phylogenetic analysis of Adocusia (Adocidae + Nanhsiungchelyidae) places A. amtgai within the Adocus clade as a sister taxon to A. aksary from the Late Cretaceous of Uzbekistan.