Eucosmodontidae is a poorly preserved family of fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 mammals within the extinct order Multituberculata

Multituberculata

The Multituberculata were a group of rodent-like mammals that existed for approximately one hundred and twenty million years—the longest fossil history of any mammal lineage—but were eventually outcompeted by rodents, becoming extinct during the early Oligocene. At least 200 species are...

. Representatives are known from strata

Stratum

In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

 dating from the Upper Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 through the Lower Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, as well as the Paleocene

Paleocene

The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...

 to Eocene of Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

. The family is part of the suborder of Cimolodonta

Cimolodonta

The Cimolodonta are a taxon of extinct mammals that lived from the Cretaceous to the Eocene. They were some of the more derived members of the extinct order Multituberculata. They probably lived something of a rodent-like existence until their ecological niche was assumed by true rodents...

. They might be related with the Djadochtatherioidea

Djadochtatherioidea

Djadochtatherioidea is a group of extinct mammals known from the upper Cretaceous of Central Asia. They were members of an also extinct order called Multituberculata. These were generally small, somewhat rodent-like creatures, who scurried around during the "age of the dinosaurs". Unusually for...

 but without further finds, this remains unclear. Other than a partial snout, fossil evidence is presently limited to teeth.

The taxonomic name Eucosmodontidae was given by Jepsen in 1940. Some authors interpret this version of Eucomsmodontidae and Microcosmodontidae

Microcosmodontidae

Microcosmodontidae is a poorly preserved family of fossil mammals within the extinct order Multituberculata. Representatives are known from the Upper Cretaceous though the Lower Paleocene of North America. The family is part of the suborder Cimolodonta...

as being subfamilies rather than families.