The species
Microcosmodon arcuatus was named by P.A. Johnston and R.C. Fox in 1984.
Fossil remains have been found in the Puercan (Paleocene)-age
strata Rav W-1 of
Saskatchewan, Canada. The
holotype is in the
University of Alberta collection. When alive, the creature weighed about the same as a well-fed mouse (about 30 g). The
type species Microcosmodon conus was named by
G.L. Jepsen in 1930. Remains have been found in the Tiffanian (Paleocene)-age strata of the Polecat Bench Formation of
Wyoming (United States) and Saskatchewan, Canada. This species would have weighed around 15 g. The species
Microcosmodon harleyi was named by A. Weil in 1998. Remains have been found in the Puercan (Paleocene)-age strata of the Tullock Formation in
Montana (USA). "The presence of the new species suggests that microcosmodontine species richness in the Western Interior was as high at the beginning of the Paleocene as at its end," (Weil, 1998). The species would have weighed about 20 g. The species
Microcosmodon rosei was named by D.W. Krause in 1980. Remains have been found in the Clarforkian (Paleocene)-age strata of the Willwood Formation of Wyoming. This species weighed a fairly standard mouse-sized 25 g+. The species
Microcosmodon woodi was named by R.C. Holtzman and D.L. Wolberg in 1977. It is also known as
Eucosmodontid woodi (Weil 1998). Remains have been found in the Middle Paleocene-age strata of Montana and
North Dakota (USA) and
Alberta, Canada. However, Weil A. (1998) found that this material "does not belong to this genus or subfamily." == References ==