roostetus

Roostetus is a genus of small, extinct mammals that lived during the late Cretaceous period, approximately 72 to 66 million years ago. The genus is known from a single species, Roostetus crassus, which was discovered in the Hell Creek Formation of North Dakota, USA. Roostetus is notable for its small size, with adults estimated to have weighed around 100 grams, and its primitive features, such as a long, narrow snout and small, simple teeth.

Roostetus is classified within the order Multituberculata, a group of mammals that are characterized by their complex, tooth-bearing structures. However, Roostetus exhibits several primitive features that suggest it may be more closely related to other early mammals, such as the order Eutheria. This has led some researchers to propose that Roostetus represents a transitional form between early mammals and the more advanced multituberculates.

The fossil record of Roostetus is limited to a few isolated teeth and jaw fragments, which have provided valuable insights into the early evolution of mammals. The genus is named after the Roost family, who discovered the fossils in the 1970s, and the specific epithet crassus means "thick" in Latin, referring to the robust nature of the teeth.

Despite its small size and primitive features, Roostetus is an important fossil for understanding the early evolution of mammals. Its discovery has helped to fill in gaps in the fossil record and has provided new insights into the diversity and complexity of early mammalian evolution.