Stegotetrabelodon
| Stegotetrabelodon | ||||||||||||
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Lower jaw of Stegotetrabelodon syrticus |
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| Temporal occurrence | ||||||||||||
| Miocene to Pliocene | ||||||||||||
| 7.5 to 4.5 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Stegotetrabelodon | ||||||||||||
| Petrocchi , 1941 | ||||||||||||
Stegotetrabelodon is an extinct genus of proboscis thatlived in Europe (e.g. Italy), the Middle East and Africa fromthe late Miocene to the early Pliocene 7.5 to 4.5 million years ago. It is one of the earliest members ofthe Elephantidae family and is characterized by the presence of tusks in the upper and lower jaw.
features
Stegotetrabelodon represents a large representative of the proboscis, a previously single, crushed skull suggests an elephant-like shape. The animals had tusks in both the upper and lower rows of teeth. Those of the upper jaws were slightly curved upwards and up to 2 m long with undeveloped tooth enamel , those of the lower jaw stood close together and were also long, but straight, they protruded about halfway from the alveoli . In addition, they were laterally narrowed so that they had an oval cross section with a maximum of 7 and a minimum of 4 cm in diameter. The lower jaw was still relatively slender, but had a strong, extensive, downward-facing symphysis . The bit of Stegotetrabelodon had the following dental formula : . The molars already had the lamellar structure typical of real elephants, but the individual lamellae were still partly clearly divided into two parts, an inner and an outer enamel fold . They gave the chewing surface a bumpy ( bunodontes ) appearance that was somewhat reminiscent of that of the gomphotheria . In contrast to the related tetralophodon , however, there were already clear indications that these lamellar parts had grown together, which was particularly evident on the last molar. The width of the enamel folds was also very large. The molars also had a high proportion of dental cement . The first and second molars typically had four enamel folds and the last seven or more. With a length of up to 32 cm, this was also the largest molar in the dentition. In terms of body structure, the species was already very similar to today's elephants . In addition to the three molars of the permanent dentition, there were also two permanent premolars that were rectangular in shape and had two lamellae.
Fossil finds
Finds of Stegotetrabelodon are limited to Africa and western Eurasia . The oldest finds are known so far from Uganda from the Oluka formation . Extensive fossil material is available from Lothagam in Kenya . Old finds from Europe are occupied with a lower jaw Cessanity in Italy , it belongs to one of the northernmost representatives. In addition, fossils have also been described from the Arabian Peninsula , for example from the Baynunah Formation in Abu Dhabi .
Paleobiology
Despite the low-crowned molars, their lamellar structure indicates a predominantly grassy diet. This is congruent to a stronger seasonalization of the annual cycle combined with the drying out and expansion of open landscapes towards the end of the Miocene .
Systematics
With its typical laminated molars belongs Stegotetrabelodon the family of Elephantidae , in addition to the Stegodonten the phylogenetically youngest member of the superfamily Elephantoidea forms within the mammoths. However, an assignment within the superfamily Gomphotherioidea was originally considered. Among the elephants, due to its dental structure, it is a rather primitive representative and stands outside the subfamily Elephantinae , to which the elephants living today belong. Stegodibelodon is sometimes seen as the closest relative, but only a few finds are known. Others see Stegodibelodon more within the Elephantinae.
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Internal systematics of the Elephantoidea according to Cozzuol et al. 2012
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Only one species is recognized within Stegotetrabelodon today :
- S. syrticus Petrocchi 1941
Occasionally S. lybicus , also introduced by Carlo Petrocchi in 1943, is considered to be independent. The independence of S. orbus , which was established in 1970 by Vincent J. Maglio on the basis of a lower jaw from Lothagam in Kenya, is also under discussion, but it is often synonymous with S. syrticus . The shape shows only a few differences to S. syrticus , such as a smaller body size, shorter mandibular tusks and a slightly different symphysis. A possibly new species was found with S. sp. accepted from Uganda. Other originally described species such as S. lehmani or S. maluvalensis are now more closely related to Tetralophodon or Stegolophodon , while the proboscis described as "Mastodon" grandincisivum and partly related to Stegotetrabelodon is more closely related to Amebelodon . Likewise, the numerous alleged Stegotetrabelodon fossils described from China can also be attributed to older proboscis species.
The origin of Stegotetrabelodon is most likely in central Africa and dates to the late Miocene more than seven million years ago. Tetralophodon may be regarded as the predecessor form . The proboscis species was then also detected in Europe and western Asia almost seven million years ago. It last appeared in the early Pliocene around 4.5 million years ago in North Africa.
Web links
- The Paleobiology Database: Stegotetrabelodon
Individual evidence
- ↑ a b c d e William J. Sanders, Emmanuel Gheerbrant, John M. Harris, Haruo Saegusa and Cyrille Delmer: Proboscidea. In: Lars Werdelin and William Joseph Sanders (eds.): Cenozoic Mammals of Africa. University of California Press, Berkeley, London, New York, 2010, pp. 161-251
- ↑ a b c d e f Marco .P. Ferretti, Lorenzo Rook and Danilo Torre: Stegotetrabelodon (Proboscidea, Elephantidae) from the Late Miocene of Southern Italy. Journal of Vertebrate Paleontology 23 (3), 2003, pp. 659-666.
- ^ A b Jan van der Made: The evolution of the elephants and their relatives in the context of a changing climate and geography. In: Harald Meller (Hrsg.): Elefantenreich - Eine Fossilwelt in Europa. Halle / Saale, 2010, pp. 340-360.
- ^ A b Vincent J. Maglio: Four new species of Elephantidae from the Plio-Pleistocene of northwestern Kenya. Breviora 341, 1970, pp. 1-43
- ↑ a b c Marco P. Ferretti, Danilo Torre, Lorenzo Rook: The Stegotetrabelodon remains from Cessaniti (Calabria, Southern Italy) and their bearing on Late Miocene biogeography of the genus. In: G. Cavarretta et al. (Ed.): The World of Elephants - International Congress. Consiglio Nazionale delle Ricerche. Rome, 2001, pp. 633-636. ( pdf )
- ^ William J. Sanders: Horizontal tooth displacement and premolar occurrence in elephants and other elephantiform proboscideans. Historical Biology, 2018 doi: 10.1080 / 08912963.2017.1297436
- ↑ Mario A. Cozzuol, Dimila Mothé and Leonardo S. Avilla: A critical appraisal of the phylogenetic proposals for the South American Gomphotheriidae (Proboscidea: Mammalia). Quaternary International 255, 2012, pp. 36-41.
- ↑ Zhou Mingzhen and Zhang Yuping: Occurence of the proboscidean genus Stegoterabelodon in China. Vertebrata Palasiatica 1983, ( [1] ).
- ^ Georgi N. Markov: The Turolian proboscideans (Mammalia) of Europe: Preliminary observations. Historia naturalis bulgarica, 19, 2006, pp. 153-178.