Xyronomys

Xyronomys is a small mammal from the Paleocene of North America. A second species is awaiting publication. It was a genus within the extinct order of Multituberculata.
For those of a technical inclination, it's within the Suborder of Cimolodonta, family Neoplagiaulacidae.

Genus: Xyronomys Rigby JK, 1980
Aka: Xironomys
Remarks: Material has also been reported from Rav W-1, Saskatchewan. The genus may belong to Eucosmodontidae. However, according to more recent research, it doesn't seem to.

Species: Xyronomys swainae Rigby JK, 1980
Place: Swain Quarry, Wyoming
Country: USA
Age: Torrejonian, Paleocene
Remarks: Represented by a couple of teeth, this genus was originally assigned to Eucosmodontidae. Kielan-Jaworowska and Hurum (2001, p.406) refer it to Neoplagiaulacidae, on the basis of its possession of microprismatic enamel; ie. the tooth enamel's built up from small prisms.
Reference: Rigby (1980), Swain Quarry of the Fort Union Formation, Middle Paleocene (Torrejonian), Carbon County, Wyoming: geologic setting and mammalian fauna. Evolutionary Monographs, 3, vi+179pp.

Species: Xyronomys robinsoni (Unpublished)
Place: Colorado
Country: USA
Age: Puercan, Lower Paleocene
Remarks:
Reference: Not as yet.

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/ptilodon.htm) MESOZOIC MAMMALS; Ptilodontoidea, an internet directory. As that's my webpage, there are no issues of copyright. Trevor Dykes)