Cimexomys

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Cimexomys is an extinct North American mammal that lived from the Late Cretaceous into the Paleocene, a time when dinosaurs were still around before dying out. It was part of the extinct order Multituberculata, a group of early mammals, and its exact position within that group is not fully settled. Some scientists have suggested it might belong to a subgroup called the Paracimexomys group, but this is still uncertain.

The genus Cimexomys, meaning “bug mouse,” was named by Sloan and Van Valen in 1965. The name comes from the Bug Creek area in Montana, where the first fossil remains were found. Most Cimexomys fossils are tiny teeth; only a few bones are known.

Size and appearance: Cimexomys was small, with body mass estimated from a few tens of grams up to about 130 g in some species. Much of what we know comes from the teeth, which are the main fossils.

Species: The genus includes several species. The type species is Cimexomys minor. Other named species include Cimexomys arapahoensis, Cimexomys gratus, and Cimexomys judithae. Some fossils once called Cimexomys are now considered unclear or placed in related groups, reflecting ongoing scientific discussion.

Fossil locations and age: Fossils have been found in western North America (places like Montana, Wyoming, Colorado, and Utah) and in Canada (Saskatchewan). Cimexomys lived from the Late Cretaceous (Santonian–Campanian) into the early Paleocene (Puercan).