American Mastodon - Taxonomy and Evolution

Taxonomy and Evolution

M. americanum is a species of the extinct family Mammutidae, related to the proboscidean family Elephantidae (mammoths and elephants). The common name "Mastodon" derives from a genus named to describe various extinct members of proboscideans, Mastodon (Cuvier) is not currently used. The assignment of the taxon to Mammut, a name that preceded Cuvier's description, met with resistance, and authors sometimes applied "Mastodon americanus" as an informal name. Common names for the species have sometimes been "ludicrous and misleading ... The Great American Incognitum. The Leviathan Missourium, The Carnivorous Elephant, Ohio Incognitum, Elephas americanus, a Behemoth, The Pseudelephant, Le Grande Mastodonte, Mastodon giganteus and many others".

The ancestors of M. americanum diverged from the Elephantidae clade approximately 26.8 million years ago. In 2007 the complete mitochondrial genome of M. americanum was published using an Alaskan fossil tooth dated between 50,000 and 130,000 years old. Working from the previously established date of divergence and utilizing this new sequence as an outgroup to the Elephantidae line, the researchers inferred that the ancestors of the African elephant (Loxodonta sp.) diverged from the line that led to Asian elephants (Elephas maximus) and mammoths approximately 7.6 million years ago, and that the Asian elephant and mammoth lines diverged approximately 6.7 million years ago. This further confirmed another study which, utilizing a fully sequenced wooly mammoth mitochondrial genome showed that the wooly mammoth was more closely related to Asian elephants than African elephants. Furthermore, it demonstrated that M. americanum could be used as an effective outgroup to the Elephantidae clade, representing a preferable alternative to the dugong (Dugong dugon) and hyrax (order Hyracoidea), which had been used previously due to their being the closest living relatives of elephants.