Mastodon - Taxonomy and Evolution

Taxonomy and Evolution

Mammut is a genus 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" as an informal name.

The ancestors of Mammut 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.

The oldest Mammut fossil (Mammut sp.) was unearthed in the Democratic Republic of the Congo. The genus gives its name to the family Mammutidae, assigned to the order Proboscidea. They superficially resemble members of the proboscidean family Elephantidae, including mammoths; however, mastodons were browsers, while mammoths were grazers. Confusingly, several genera of proboscids from the gomphothere family have similar-sounding names (e.g., Stegomastodon), but are actually more closely related to elephants than to mastodons.