Stegomastodon

Stegomastodon ('roof breast tooth') is an extinct genus of gomphotheres, a family of proboscideans. It is not to be confused with the genus Mammut from a different proboscidean family, whose members are commonly called 'mastodons', nor with the genus Stegodon, from yet another proboscidean subfamily, whose members are commonly called 'stegodonts'. The Stegomastodon was one of the smaller species through the genus. It ranged through North and possibly South America. The following definite species have been described: S. waringi is considered synonymous with S. platensis. A dispute now exists over whether S. platensis should remain within the North and Central American genus Stegomastodon or should be moved over to the exclusively South American genus Notiomastodon. The genus Haplomastodon is regarded as synonymous with the South American Stegomastodon species. The South American Stegomastodon fossils could be reassigned to Notiomastodon. Still, in paleontological literature, the genus and species name are used, until in 2016. Stegomastodon mirificus is known from NMNH 10707, a roughly 30-year-old male, of which most of the skeleton has been found. Alive, it stood about 2.6 m (8.5 ft) tall, with a weight around 4.7 tonnes (4.6 long tons; 5.2 short tons). Like modern elephants, but unlike most of its closer relatives, it had just two tusks, which curved upward and were about 3.5 m (11.5 ft) long. Stegomastodon's molars were covered in enamel and had a complex pattern of ridges and knobbly protrusions on them, giving the creature a large chewing surface that enabled it to eat grass. Its brain weighed about 11 lb (5 kg). The genus lived in North America from the Zanclean of the Pliocene to the Late Pleistocene. The most recent specimens in the fossil record originate from Jalisco, Mexico, and date to 28,000 BP. Revised taxonomy of Stegomastodon and other trilophodont gomphotheres according to Mothé et al., 2016: