''Alphadon'' (meaning "first tooth") is an extinct genus of small, primitive

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

that was a member of the

metatheria Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as w ...

ns, a group of mammals that includes modern-day

marsupials Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

. Its fossils were first discovered and named by

George Gaylord Simpson George Gaylord Simpson (June 16, 1902 – October 6, 1984) was an American paleontologist. Simpson was perhaps the most influential paleontologist of the twentieth century, and a major participant in the modern synthesis, contributing '' Tempo ...

in 1929.

Description

Not much is known about the appearance of ''Alphadon'', as it is only known from teeth, a lower jaw and skull fragments. It probably grew to about and may have resembled a modern

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered No ...

. Judging from its teeth, it was likely an

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nu ...

, feeding on fruits, invertebrates and possibly small vertebrates. ''Alphadon'' had a very good sense of smell and sight to track down its food, both during the day and night. Its possible whiskers could have also aided in its search for food.

Taxonomy and classification

The type species is ''Alphadon marshi''. Eight other species are known. The species ''Alphadon jasoni'' was originally described by Storer (1991); it was subsequently transferred to the herpetotheriid genus '' Nortedelphys''. Recent phylogenetic studies group it with other northern non-marsupial metatherians such as ''

Albertatherium ''Albertatherium'' (meaning "beast of Alberta") is an extinct genus of alphadontid metatherians that lived during the Late Cretaceous of North America. The genus contains two species, ''Albertatherium primus'' (the type species), and ''Albertathe ...

'' and '' Turgidodon''.S. Bi, X. Jin, S. Li and T. Du. 2015. A new Cretaceous metatherian mammal from Henan, China. PeerJ 3:e896 A 2016 phylogenetic analysis is shown below.

References

{{Taxonbar, from=Q3768782 Prehistoric metatherians Late Cretaceous mammals of North America Hell Creek fauna Milk River Formation Fossil taxa described in 1927