Cimolestes

Nyssodon Simpson, 1927

Cimolestes ("Bug Thief") is a genus of basal, non-placental eutherians. Fossils have been found in North America, where they first appeared during the Late Cretaceous; they died out at the start of the Paleocene.

They were once considered to be marsupials, then primitive placental mammals, but now are considered to be members of the order Cimolesta (which was named after the genus), outside of placental mammals proper. Before they were determined to be non-placental eutherians, the cimolestids were once considered the common ancestral group of the clades Carnivora and the extinct Creodonta.

Cimolestes in particular follows as the direct outgroup to Taeniodonta, indicating that the latter evolved from forms similar to it.

Three nominal species of Cimolestes, C. magnus, C. cerberoides, and C. propalaeoryctes, have been reassigned to their own genera, Altacreodus, Ambilestes, and Scollardius, respectively.