Cuvieronius

Cuvieronius is an extinct New World genus of gomphothere which ranged from southern North America to western South America during the Pleistocene epoch. Among the last gomphotheres, it became extinct at the end of the Pleistocene, approximately 12,000 years ago, following the arrival of humans to the Americas.

Taxonomy
The species now known as Cuvieronius hyodon was among the first fossil animals from the New World to be studied. The first remains of this species were recovered from Ecuador by Alexander von Humboldt, at a location the local population referred to as the "Field of Giants". Humboldt recognized that, rather than being bones of giant humans as had been thought by the local population and previous Spanish colonists, they were similar to the giant elephants (Mastodon) being described from Ohio. Humboldt sent teeth that he had collected from Mexico, Ecuador, and Chile to French anatomist Georges Cuvier, who classified the teeth into two species, which he referred to as the "mastodonte des cordilières" and the "mastodonte humboldtien", in an 1806 paper. It was not until 1824 that Cuvier formally named the species. He referred both to the genus Mastodon, calling them M. andium and M. humboldtii.

Unknown to Cuvier, Fischer had, in 1814, already named the two species based on Cuvier's original description, in the new genus Mastotherium as M. hyodon and M. humboldtii. The idea of two distinct species continued to be accepted into the 20th century, usually using Cuvier's names, though Fischer's names were older. In 1923, Henry Fairfield Osborn recognized that these species were distinct from Mastodon, and assigned each to its own new genus, Cuvieronius humboldtii and Cordillerion andium, with the name Cuvieronius in honour of Cuvier. However, by the 1930s, general agreement had shifted to regard both forms as representing a single, geographically widespread species, with Cuvieronius humboldtii considered to be the correct name. During the 1950s, the nomenclature of this species became increasingly tangled, as various scientists regarded the type species of the genus Cuvieronius to be Fischer's first published name Mastotherium hyodon, rather than the originally designated Mastodon humboldtii. This situation went unaddressed until 2009, when Spencer Lucas petitioned the International Commission on Zoological Nomenclature to officially change the type species of Cuvieronius to M. hyodon as had been followed for over 50 years by that time, rather than abandoning the well-known Cuvieronius as a synonym. In 2011, Opinion 2276 of the ICZN ruled to conserve the names.

The species level taxonomy of Cuvieronius is confused. historically, several species were recognised, typically C. tropicus and C. hyodon for North and South American remains, respectively, but recent scholarship suggests that there is only a single valid species, C. hyodon.

Description
Alive, specimens typically stood about 2.3 m tall at the shoulder, and weighed about 3.5 t. The skull was relatively long and low-vaulted. The upper tusks were straight to slightly curved, and had a spiral shaped-enamel band, and reached considerable size, with tusks in the region of 2.2 m in length and weights in excess of 50 kg. The lower tusks present in more primitive gomphotheres were vestigial in Cuvieronius, being only present in young juveniles, and the lower jaw shortened (brevirostrine). The third molars typically had 4 to 4.5 lophs/lophids, with some specimens having 5 lophs/lophids, with relatively simple crowns.

Ecology
Cuvieronius is suggested to have been a generalist mixed feeder that consumed a wide range of plant resources, including grasses and browse. Costa Rican C. hyodon were specialised forest inhabitants that primarily fed on C3 plants. In 1982, Daniel H. Janzen and Paul Schultz Martin suggested that the diet of Cuvieronius probably included fruit, and that it was likely an important seed disperser of a variety of Neotropical plants with large fleshy fruits similar to those consumed by large animals in Africa, but which lack effective living native seed dispersers, which they described as "Pleistocene anachronisms".

Evolution
Cuvieronius initially evolved in North America. It is considered closely related to, if not derived from, Rhynchotherium, a North American gomphothere genus known from the Late Miocene and Pliocene. The oldest remains attributed to the genus from the Blancan are very fragmentary, and may belong to Rhynchotherium instead. The oldest unambiguous records of the genus in North America date to 1.4 million years ago (Ma). Cuvieronius was extirpated from its northern range in North America over the course of the Irvingtonian after the arrival of mammoths in North America around 1.3 Ma, presumably due to competitive exclusion by mammoths as well as mastodons, with its last records in Florida dating to around 500,000 years ago, but persisted in southern North America (including Mexico) and Central America until the very end of the Pleistocene. During the Great American Interchange, Cuvieronius and a relative, Notiomastodon, dispersed into South America. Cuvieronius apparently reached South America considerably later than Notiomastodon, with the oldest possible date being 760,000 ±30,000 years ago and the oldest confirmed date being 304,000 ±54,000 years ago, and had a much more restricted range, confined mostly to the Andes.

Distribution and habitat
In North America, Cuvieronius is known from the Southern United States, including Texas, Florida, Arizona, New Mexico and Oklahoma, as well as Mexico. It was also widespread across Central America.

According to a group of Brazilian mammalogists, many sites in South America referred to Cuvieronius actually refer to Notiomastodon, with many previous studies simply labeling fossils one or the other depending on location, with only localities definitely identified as Cuvieronius, the range now extends in the high Andes from Ecuador in the north, to Bolivia in the south, with the localities in the southern Andes in Chile and Argentina now thought to belong to Notiomastodon. The same group maintains that all the South American specimens represent the single species C. hyodon. By the end of the Pleistocene, the northern limit of the range of Cuvieronius was in Mexico and Central Texas. Remains found near the town of Hockley in Texas near Houston, which date to around 24,000 years Before Present (BP), are the most recent findings north of Mexico. Cuvieronius was extirpated from South America by the end of the Late Pleistocene, with its youngest dates on the continent being around 44,000 years ago, before the arrival of people.

Extinction
Curiveronius became extinct at the end of the Pleistocene, approximately 12,000 years ago as part of the Late Pleistocene megafauna extinctions, simultaneously alongside most other large animals across the Americas. The extinction of Cuvieronius and other megafauna postdates human arrival in the Americas, which occurred several thousand years prior. At the El Fin del Mundo kill site in Sonora, Mexico, remains of an individual of Cuvierionius and another indeterminate gomphothere were found associated with Clovis spear points, suggesting that hunting may have played a role in its extinction. The site was initially suggested to date to 13,390 years Before Present, however this date was later contested, and the site may be younger than this.