Stygimys

Stygimys is a mammal genus from the Upper Cretaceous and Paleocene of North America. It was a member of the extinct order of Multituberculata.
For those of a technical inclination, it's within the Suborder of Cimolodonta, and the family Eucosmodontidae.

Genus: Stygimys Sloan RE & Van Valen L, 1965
'Styx mouse' (Styx = river of hell)
Aka: Catopsalis (partly); Cimexomys (partly); Eucosmodon (partly); Parectypodus (partly)
Remarks: Remarks: Some skull material is known, but not much.
Reference: Sloan & Van Valen (1965), Cretaceous mammals from Montana. Science, 148, p.220-227.

Species: Stygimys camptorhiza Johnston PA & Fox RC, 1984
Place: Rav W-1, Saskatchewan
Country: Canada
Age: Puercan, Paleocene
Remarks: The holotype is in the University of Alberta collection.
Reference: Johnston & Fox (1984), Paleocene and Late Cretaceous mammals from Saskatchewan, Canada. Palaeontogr. Abt. A: Paläozool., Stratigr. 186, p.163-222.

Species: Stygimys cupressus Fox RC, 1989
Place: Long Fall Horizon
Country: Canada
Age: Puercan, Paleocene
Remarks:
Reference: Fox (1989), The Wounded Knee local fauna and mammalian evolution near the Cretaceous-Tertiary boundary, Saskatchewan, Canada. Palaeontogr. Abt. A: Paläozool., Stratigr. 208, p.11-59 + 6 plates.

Species: Stygimys jepseni (Simpson GG, 1935) Sloan & Van Valen, 1965
Aka: Eucosmodon sparsus Simpson, 1937a; E. jepseni; Parectypodus jepseni Simpson, 1935d
Place: Montana
Country: USA
Age: Torrejonian, Paleocene
Remarks: Has been cited as a descendant of S. kuszmauli. The animal weighed about 90g.
Reference:

Species: Stygimys kuszmauli Sloan RE & Van Valen L, 1965
Aka: Catopsalis foliates Cope, 1882; Cimexomys gratus (Jepsen GL, 1930); Eucosmodon gratus Jepson GL, 1930; Eucosmodon kuszmauli ; Stygimys gratus
Place: Polecat Bench Fm., Wyoming & Hell Creek Formation, Montana
Country: USA
Age: Maastrichtian, Upper Cretaceous - Puercan, Paleocene
Remarks: Some scraps of jaw are known. The most basal member of the genus, with a weight of 300g.
References: Sloan & Van Valen (1965), Cretaceous mammals from Montana. Science 148 (3367), p.220-227.
Jepson (1930), Stratigraphy and paleontology of the Paleocene of northeastern Park County, Wyoming. Proc. Am. Phil. Soc. 69(7), p.463-528.

Species: Stygimys teilhardi (Granger W & Simpson GG, 1929) Sloan RE & Van Valen, 1965
Aka: Eucosmodon teilhardi Granger W & Simpson GG, 1929
Place: San Juan Basin, New Mexico
Country: USA
Age: Torrejonian, Paleocene
Remarks: Has been cited as a possible descendant of S. kuszmauli.
Reference:

Page reference: Kielan-Jaworowska Z & Hurum JH (2001), Phylogeny and Systematics of multituberculate mammals. Paleontology 44, p.389-429.

(This information has been derived from [1] (http://home.arcor.de/ktdykes/taenio.htm) MESOZOIC MAMMALS; Eucosmodontidae, Microcosmodontidae and Taeniolabidoidea, an internet directory. As that's my webpage, there are no issues of copyright. Trevor Dykes)