''Sikuomys'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of early

eutheria Eutheria (from Greek , 'good, right' and , 'beast'; ), also called Pan-Placentalia, is the clade consisting of Placentalia, placental mammals and all therian mammals that are more closely related to placentals than to marsupials. Eutherians ...

n mammals from the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

of Alaska. It is known from a few teeth and part of a jawbone in deposits of

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

age and, , is the only known

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

eutherian mammal to have lived north of the then location of the Arctic Circle. Estimated to have weighed between , it was also unusually small for the time, similar in size to a modern shrew. It was likely insectivorous and would probably have used burrows or nests to shelter during the Arctic winter, since it is thought to have been too small to have hibernated or migrated over significant distances.

References

{{Taxonbar, from=Q123985250 Late Cretaceous mammals of North America Leptictida Fossil taxa described in 2023 Prehistoric mammal genera Paleontology in Alaska