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American Mastodon

This article is about the animal. For other uses, see Mastodon (disambiguation).
"Mammut" redirects here. For other uses, see Mammut (disambiguation).
Mastodon
Temporal range: Late Miocene - Late Pleistocene, 5.3–0.011Ma
Mounted M. americanum skeleton, AMNH
Type species
Elephas americanus
Kerr, 1792
Species
  • M. americanum (Kerr, 1792)
  • M. matthewi Osborn, 1921
  • M. raki Frick, 1933
  • M. cosoensis Schultz, 1937
Synonyms
  • Mastodon Cuvier, 1817
  • Tetracaulodon Godman, 1830
  • Missourium Koch, 1840
  • Leviathan Koch, 1841 (Emend. Koch, 1843)
  • Pliomastodon Osborn, 1926

Mastodons (Greek: μαστός "breast" and ὀδούς, "tooth") are an extinct group of mammal species related to elephants, that inhabited North and Central America during the late Miocene or late Pliocene up to their extinction at the end of the Pleistocene 10,000 to 11,000 years ago.[1] Their genus name is Mammut, and they are members of the order Proboscidea. They lived in herds and were predominantly forest dwelling animals that fed on a mixed diet of browsing and grazing with a seasonal preference for browsing, in contrast to living elephants that are mostly grazing animals.

The American mastodon is the most recent and best-known species of the genus. They disappeared from North America as part of a mass extinction of most of the Pleistocene megafauna, widely presumed to have been a result of rapid climate change in North America, as well as the sophistication of stone tool weaponry used by the Clovis hunters which may have caused a gradual attrition of the mastodon population.

Etymology

The name Mastodon (or mastodont) means nipple tooth (Greek: μαστός "nipple" and ὀδούς, "tooth"),[2][3] and was assigned by the French anatomist George Cuvier, derived from the cone-shaped cusps of their tooth which resembles the shape of nipples. Mastodon as a genus name is obsolete;[4] the valid name is Mammut, a name that preceded Cuvier's description, making Mastodon a junior synonym. The change was met with resistance, and authors sometimes applied "Mastodon" as an informal name so it became the common term for members of the genus.

Description

Mastodons were similar in appearance to elephants and mammoths, though not closely related. Compared to mammoths, mastodons had shorter legs, a longer body and were more heavily muscled,[5] a build similar to that of the current Asian elephants. The average body size of the species M. americanum was around 2.3 m (7 ft 7 in) in height at the shoulders, corresponding to a large female or a small male, but large males could grow up to 2.8 m (9 ft 2 in)[6] in height and weigh as much as 4.5 tonnes (5 short tons).[7] Like modern elephants, the females were smaller than the males. They had a low and long skull with long curved tusks,[8] with those of the males being more massive and more strongly curved.[6] Mastodons had cusp-shaped teeth, different from mammoth and elephant teeth (which have a series of enamel plates), well-suited for chewing leaves and branches of trees and shrubs.[7]

Discovery

The first remains of Mammut were found in the village of Claverack, New York, in 1705, a tooth some 2.2 kilograms (5 lb) in weight, which became known as the “incognitum”. Some time later, similar remains were found in South Carolina, which according to the slaves, looked remarkably similar to those of African elephants, soon followed discoveries of complete bones and tusks in Ohio, and people started referring to the "incognitum" as a mammoth, like the ones that were being dug out in Siberia. Anatomists noted that the teeth of mammoth and elephants were different from those of incognitum, which possessed rows of large conical cusps, indicating that they were dealing with a distinct species.[9]

Classification and species

Mammut is a genus of the extinct family Mammutidae, related to the proboscidean family Elephantidae (mammoths and elephants) from which it originally diverged approximately 27 million years ago.[10] The following cladogram shows the placement of the American mastodon among other proboscideans, based on hyoid characteristics:[11]




Mammut americanum (American mastodon)




Gomphotherium sp.




Stegodon zdanskyi




Loxodonta africana (African elephant)




Elephas maximus (Asian elephant)



Mammuthus columbi (Columbian mammoth)








Over the years, several fossils from localities in North America, Africa and Asia have been attributed to Mammut, but only the North American remains have been named and described, one of them being M. furlongi, named from remains found in the Juntura Formation of Oregon, dating from the late Miocene.[12] However, it is no longer considered valid,[13] leaving only 4 valid species left.

M. matthewi: Found in the Snake Creek Formation of Nebraska, dating from the late Hemphillian. Some authors consider it practically undistinguishable from M. americanum.[14]

M. raki: Its remains were found in the Palomas Formation, nearby Truth or Consequences, New Mexico, dating from the early-middle Pliocene, between 4.5-3.6 Ma.[15] It coexisted with Equus simplicidens and Gigantocamelus and differs from M. americanum in having a relatively longer and narrower third molar,[14] similar to the description of the defunct genus Pliomastodon which supports its arrangement as an early species of Mammut.[16] However, like M. matthewi, some authors don't consider it sufficiently distinct from M. americaum to warrant its own species.

M. cosoensis: Found in the Coso Formation of California, dating from the late Pliocene, originally a species of Pliomastodon[17] it was later assigned to Mammut.[18]

M. americanum: The American mastodon, the most known and the last species of Mammut, its earliest occurrences date from the early-middle Pliocene (early Blancan stage). It had a continent wide distribution, specially during the Pleistocene epoch,[14] known from fossil sites ranging from present-day Alaska and New England in the north, to Florida, southern California, and as far south as Honduras.[19] The American mastodon resembled a woolly mammoth in appearance, with a thick coat of shaggy hair.[20] It had tusks that sometimes exceeded five meters in length; they curved upwards, but less dramatically than those of the woolly mammoth.[21] Its main habitat was cold spruce woodlands, and it is believed to have browsed in herds.[20] It became extinct at the end of the Pleistocene approximately 11,000 years ago.\

A complete mtDNA sequence has been obtained from the tooth of an M. americanum skeleton found in permafrost in northern Alaska.[22] The remains are thought to be 50 to 130 Ma old. This sequence has been used as an outgroup to refine divergence dates in the evolution of the Elephantidae.[22] The rate of mtDNA sequence change in proboscideans was found to be significantly lower than in primates.

Paleobiology

Social behavior

Based on the characteristics of mastodon bonesites we can infer that, like in modern proboscideans, the Mastodon social group consisted of adult females and young, living in bounded groups called mixed herds. The males abandoned the mixed herds once reaching sexual maturity and lived either alone or in male bond groupings. Unlike modern elephants, the evidence suggest that there probably was no seasonal synchrony of mating activity, with both males and females seeking out each other for mating when sexually active.[23]

Range and habitat

The range of most species of Mammut is unknown as their occurrences are restricted to few localities, the exception being the American mastodon (M. americanum), which is one of the most widely distributed Pleistocene proboscideans in North America, ranging in age from the faunal stages of Blancan to Rancholabrean and with fossil sites from as north as Alaska, as east as Florida and as south as the state of Puebla in central Mexico,[19] however there is an isolated record from Honduras, probably reflecting the results of the maximum expansion achieved by the American mastodon during the Late Pleistocene. There is strong evidence to support that the members of Mammut were forest dwelling proboscideans, predominating in woodlands and forests,[23] feeding in sylvan vegetation.[8] They apparently did not disperse southward to South America, it is speculated this was because of a dietary specialization on a particular type of vegetation.[24]

Diet

Mastodons have been characterized as predominantly browsing animals, most accounts of gut contents have identified coniferous twigs as the dominant element in their diet, in other accounts (Burning tree mastodon) have found no coniferous content and suggest selective feeding on low, herbaceous vegetation, implying a mixed browsing and grazing diet,[25] evidence supported by studies of isotopic bone chemistry but displaying a seasonal preference for browsing.[26]

Extinction

They are generally reported as having disappeared from North America about 10,500 years ago[1] as part of a mass extinction of most of the Pleistocene megafauna, widely presumed to have been as a result of human hunting pressure.[27][28] The latest Paleo-Indians entered the American continent and expanded to relatively large numbers 13,000 years ago,[29] and their hunting may have caused a gradual attrition of the mastodon population.[30][31] Analysis of tusks of mastodons from the American Great Lakes region over a span of several thousand years prior to their extinction in the area shows a trend of declining age at maturation; this is contrary to what one would expect if they were experiencing stresses from an unfavorable environment, but is consistent with a reduction in intraspecific competition that would result from a population being reduced by human hunting.[31]

See also

Paleontology portal

References

External links

  • The Rochester Museum of Science - Expedition Earth Glaciers & Giants
  • Illinois State Museum - Mastodon
  • Calvin College Mastodon Page
  • American Museum of Natural History - Warren Mastodon
  • BBC Science and Nature:Animals - American mastodon Mammut americanum
  • BBC News - Greek mastodon find 'spectacular'
  • Paleontological Research Institute - The Mastodon Project
  • Missouri State Parks and Histroric Sites - Mastodon State Historic Site
  • Saint Louis Front Page - Mastodon State Historic Site
  • The Florida Museum of Natural History Virtual Exhibit - The Aucilla River Prehistory Project:When The First Floridians Met The Last Mastodons
  • Worlds longest tusks
  • Western Center for Archaeology & Paleontology, home of the largest mastodon ever found in the Western United States
  • Smithsonian Magazine Features Mammoths and Mastodons
  • 360 View of Mastodon Skull from Indiana State Museumar:الصناجة
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