Mesodma

Mesodma is an extinct genus of mammal, a member of the extinct order Multituberculata within the suborder Cimolodonta, family Neoplagiaulacidae. It lived during the upper Cretaceous and Paleocene Periods of what is now North America. This genus has been the subject of much revision, and has also been known in part as Cimexomys, Cimolomys, Halodon, Parectypodus, and Ptilodon.

List of Species, location of discovery

• Mesodma hensleighi The holotypes for this species are in the collection of the University of Alberta.
  • Place: Hell Creek Formation in the U.S. and in Saskatchewan, Canada.
  • Age: Campanian (Upper Cretaceous).
  • Weight: around 15 g

• Mesodma ambigua, cited as a possible descendant of M. thompsoni.
  • Place: Mantua Lentil, Wyoming (USA)
  • Age: Maastrichtian-Puercan, Upper Cretaceous - Paleocene
  • Weight: about 55 g

• Mesodma formosa, also known as Cimolomys formosus; Cimolomys gracilis; Halodon formosus; M. formosus; and Ptilodon formosus
  • Place: Hell Creek and Frenchman Formation, USA & Canada. This species is possibly also known from Utah.
  • Age: Maastrichtian-Puercan (Upper Cretaceous to the Paleocene).
  • Weight: about 30 g

• Mesodma garfieldensis
  • Place: Hells Hollow of Montana.
  • Age: Puercan (Lower Paleocene)
  • Weight: around 40 g

• Mesodma primaeva, also known as Cimolomys primaevus; Parectypodus primaeva; Ptilodus primaevus
  • Place: Montana and Wyoming
  • Age: Campanian (Upper Cretaceous – Lower Paleocene)

• Mesodma pygmaea
  • Place: Gidley Quarry, Montana, as well as Wyoming and Alberta, Canada
  • Age: Torrejonian-Tiffanian (Middle Paleocene).
  • Weight: about 8 g

• Mesodma senecta, a University of Alberta holotype.
  • Age: Campanian (Upper Cretaceous)
  • Weight: about 50 g

• Mesodma thompsoni, also known as Cimolodon nitidus; Cimolomys gracilis; Cimolomys nitidus
  • Place: St Mary River Formation & Montana and Wyoming of the USA and Canada
  • Age: Maastrichtian-Puercan, Upper Cretaceous - Paleocene
  • Weight: about 55 g

References

• Osborn (1891); "A review of the Cretaceous Mammalia". Proc. Acad. Nat. Sci. Phila. 124 - 135.
• Simpson (1929), "American Mesozoic Mammalia". Mem. Peabody Mus. Nat. Hist. iii (i): p.1-235.
• Clemens (1963), "Fossil mammals of the type Lance formation Wyoming. Part I. Introduction and Multituberculata". Univ. Calif. Pub;. Geol. Sci. 48, p.1-105. (According to Peabody Museum database.)
• Marsh (1889), "Discovery of Cretaceous Mammalia". Am. J. Sci. (3) xxxviii, p.177-180.
• Archibald (1982), A study of Mammalia and geology across the Cretaceous-Tertiary boundary in Garfield County, Montana. Univ. of Calif. Publ. Geol. Sci. 122xvi+, 286pp.
• Jepsen (1940), "Paleocene faunas of the Polecat Bench formation, Park County, Wyoming". Pro. Amer. Philos. Soc 83, p.217-341, 21 figs., 5 pls.
• Kielan-Jaworowska Z & Hurum JH (2001), "Phylogeny and Systematics of multituberculate mammals". Paleontology 44, p.389-429.
• Mesozoic Mammals; Ptilodontoidea, an Internet directory.