Pediomys is an extinct genus of pediomyid marsupial from the Late Cretaceous of North America.
Naming
Named in 1889 for a molar from the
Lance Formation by Othniel Charles Marsh, the type species
P. elegans referred to its small size relative to other mammals from the late
Maastrichtian formation. The species
Protolambda hatcheri was moved into
Pediomys by Simpson in 1927, who also named the subfamily
Pediomyinae to separate
Pediomys from other members of
Didelphidae. Pediomyinae was then expanded by the work of Clemmens in the 1960s, who elevated the subfamily to Pediomyidae and described the new species
P. cooki,
P. krejcii, and
P. florencae, all from the Lance Formation. The new pediomyid species
P. exiguus,
P. clemensi,
P. prokrejcii and the genus
Aquiladelphis were then named by Fox and Sahni in the 1970s, with
P. clemensi and
P. prokrejcii from the
Campanian Judith River Formation and suggested to be ancestral to
P. cooki and
P. krejcii respectively. The species
P. fassetti has also been named, from the Fruitland Formation.
Description and taxon
Pediomyidae and
Pediomys expanded to include such a diversity of species and genera that it began to be suspected to be an
polyphyletic group. A revision of pediomyids by Brian M. Davis in 2007 recognized that only the type species
P. elegans was within
Pediomys, and the remaining species had to be reassigned. For
P. exiguus, which was found to not be a member of Pediomyidae, Davis named the new genus
Apistodon in reference to its unstrustworthy classification. The superfamily
Pediomyoidea was named to include Pediomyidae,
Aquiladelphidae and
Glasbiidae, with Pediomyidae including a restricted
Pediomys, the new genus
Leptalestes, and
Protolambda.
P. hatcheri,
P. florencae and
P. clemensi were moved to
Protolambda, and
P. krejcii,
P. prokrejcii (including
P. fassetti),
P. cooki were moved into
Leptalestes. As a result,
Pediomys is restricted to only
P. elegans and an unnamed species from Prince Creek Formation, with its material including a large number of teeth from a variety of
Lancian formations.
Pediomys is an important taxon to the understanding of Late Cretaceous marsupials as it has been known for so long, and is possibly also the only one to have survived the
K-T Extinction, with a possible molar from the
Puercan Ravenscrag Formation. Material from the Dinosaur Park Formation is very similar to
P. elegans but also likely represents a new species.
