All known species of Eucosmodon have been found in the
San Juan Basin of
New Mexico (United States).
Eucosmodon americanus is a species of which
Puercan (Paleocene)-age fossils have been found. Some, but not all, of this fossil material has been reclassified as E. primus. This animal, which probably weighed something like 750 g, has been cited as a possible descendant of that species.
Eucosmodon molestus is a species of
Torrejonian (Paleocene) age. It has been cited as a possible descendant of E. americanus.
Eucosmodon primus, also from the Puercan part of the Paleocene, have been found in the
Nacimiento Formation of the San Juan Basin. This species is based on fossils originally ascribed to E. americanus.
A possible fourth species, Eucosmodon kuszmauli, has also been named.
Fox, Richard C (1971). "Early Campanian Multituberculates (Mammalia: Allotheria) from the Upper Milk River Formation, Alberta". Canadian Journal of Earth Sciences. 8 (8): 916–38.
Bibcode:
1971CaJES...8..916F.
doi:
10.1139/e71-082.