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Temporal range: Late Cretaceous
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Superorder: Ameridelphia
Order: Didelphimorphia
Family: Alphadontidae
Genus: Alphadon
  • A. marshi (type)
    Simpson, 1927
  • A. wilsoni
    Lillegraven, 1969
  • A. halleyi
    Sahni, 1972
  • A. attaragos
    Lillegraven & McKenna, 1986
  • A. sahnii
    Lillegraven & McKenna, 1986
  • A. clemensi
    Eaton, 1993
  • A. lillegraveni
    Eaton, 1993
  • A. perexiguus
    Cifelli, 1994
  • A. eatoni
    Cifelli & Muizon, 1998

Alphadon (meaning “first tooth”)[2] was a genus of small, primitive mammal that was a member of the metatherians, a group of mammals that includes modern-day marsupials. Its fossils were first discovered and named by George Gaylord Simpson in 1929.

Not much is known of its appearance as it is only known from teeth. It probably grew to about 12 in (30 cm) and may have resembled a modern opossum. Judging from its teeth, it was likely an omnivore, feeding on fruits, invertebrates and possibly small vertebrates.[2]

Alphadon lived during the end of the late Cretaceous period, alongside dinosaurs such as Tyrannosaurus and Triceratops. Its fossils have been found across North America, ranging from as far north as Alberta, Canada, to as far south as New Mexico in the United States.[2]

The type species is A. marshi.[2]

The species Nortedelphys jasoni was originally described as a species of the genus Alphadon by Storer (1991); however, it was subsequently transferred to the herpetotheriid genus Nortedelphys.[3]

The number of marsupial species in North America plummeted at the end of the Cretaceous, and Alphadon represent the only surviving lineage together with its Paleocene successor Peradectes.[4]


  1. ^ Mikko's 2003
  2. ^ a b c d Enchanted Learning 2010
  3. ^ Thomas E. Williamson, Stephen L. Brusatte, Thomas D. Carr, Anne Weil and Barbara R. Standhardt (2012). "The phylogeny and evolution of Cretaceous–Palaeogene metatherians: cladistic analysis and description of new early Palaeocene specimens from the Nacimiento Formation, New Mexico". Journal of Systematic Palaeontology 10 (4): 625–651. doi:10.1080/14772019.2011.631592. 
  4. ^ Jehle 2005