Primelephas
| Primelephas | ||||||||||||
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| Tortonium ( Upper Miocene ) to Zancleum ( Pliocene ) | ||||||||||||
| 7.246 to 3.6 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Primelephas | ||||||||||||
| Maglio , 1970 | ||||||||||||
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Primelephas is an extinct genus of the most original representatives in the evolutionary series of the modern, today's elephants (Elephantinae) from the Upper Miocene and the older Pliocene of Africa. These actual elephants include not only the fossil mammoths but also the ( recent ) elephants. The name "Primelephas" means something like "First Elephant". Only one species is known today, called Primelephas korotorensis , which has been largely proven through dental finds.
features
Primelephas was already very similar in appearance to today's elephants, but it may also have small, significantly reduced tusks in the lower jaw . The proboscis representative is largely only known through tooth finds and lower jaw fragments, finds of the upper skull are extremely rare, a partially traditional skull showed a bulging forehead area in front and side view, slightly diverging alveoli of the upper tusks with a diameter of 8 cm and a massive front section of the Zygomatic arches . The rostrum was very short overall, the eye windows were above the anterior molar and the base of the skull rose to well above the palatine bone . The lower jaw was strong, not elongated, and had only a short symphysis that did not extend as long as its older relative Stegotetrabelodon . He did not have alveoli for the mandibular tusks. The dental formula is therefore: . The molars of Primelephas already had the lamellar structure typical of modern elephants ( Elephantinae ). But they were very narrow, on average less than 10 cm wide, and extremely low-crowned ( brachyodont ). Their height was only half or three quarters of their width. It is primarily this low crown height of the molars that distinguishes Primelephas from all other genus of real elephants, which each have high-crowned ( hypsodontal ) teeth. The last molar was between 21 and 27 cm long and typically had seven to nine of these lamellar enamel folds , the front molars were correspondingly shorter and had only five or six enamel folds. In contrast to today's elephants, these tooth lamellae did not form a closed chewing surface, but were separated by deep, V-shaped crevices that reached to the base of the teeth and were only partially filled with dental cement . As a result, the individual slats themselves had a rather trapezoidal shape, in contrast to the rectangular shape of today's elephants. The tooth enamel that surrounded the respective tooth lamellae was about 3 to 6.5 mm wide, which is quite thick compared to today's trunk animals and underlines the primeval character of this elephant shape. In addition to the three molars (and the three milk premolars), which are also typical for the teeth of today's elephants, there were also two permanent premolars. These mostly had a small, round shape 3 to 4 cm in length and were made up of three lamellas.
Fossil sites
Finds of Primelephas are known from large parts of Central and East Africa and date to the Upper Miocene and Lower Pliocene from about 7.5 to 4 million years ago. The finds from the Djourab region in northern Chad are extensive, with sites such as Toros-Menalla, Kossom-Bougoudi, Koulà and Kollé. Toros-Menalla alone contained at least three lower jaws and individual upper jaw fragments, while largely isolated teeth were recovered in Kossom-Bougoudi and Koulà. Several mandibular fragments also come from the lower limb of the Nawata Formation at the important fossil site of Lothagam in Kenya . Very numerous, but largely only comprising isolated teeth, material has been reported from the Adu-Asa formation in the middle valley of the Awash in the Afar valley of Ethiopia , from which the important fossil remains of Ardipithecus come from the ancestral line of humans. In addition, many other, mostly isolated molars from Tanzania and Uganda are documented. A partially preserved upper skull was recovered from the Oluka formation in Uganda in the western section of the African Rift Valley .
Paleobiology
In some of the lower jaw remains from Lothagam in Kenya, which were used to establish the genus Primelephas , individual lateral openings appear, which were initially regarded as the alveoli of the tusks. The researchers interpreted this as a possible sexual dimorphism with missing lower jaw tusks in female animals. They also considered the interpretation as remnants of not fully grown individuals; the fragmented state of the find material did not permit any more precise statements. In contrast, the numerous new finds from northern Chad showed, interestingly, no evidence of tusks in the lower jaw. Subsequent analyzes showed that the suspected alveoli represent enlarged chambers of the mandible canal , so that Primelephas did not have any tusks in the lower jaw.
The low-crowned molars of Primelephas speak in favor of a diet based largely on a soft vegetable diet. On the other hand, isotope analyzes showed a predominance of grasses in the food spectrum.
Systematics
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Internal systematics of the Elephantoidea according to Cozzuol et al. 2012
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The typical laminated molars refer the genus primelephas the family of Elephantidae , in addition to the Stegodonten the phylogenetically youngest member of the superfamily Elephantoidea forms within the mammoths. Within the family, the genus represents the basal form of the subfamily Elephantinae , to which the elephants still alive today and the extinct Mammuthus can be assigned. Stegotetrabelodon is a possible predecessor form , but the fossil material known to date allows only few conclusions.
Only one species is recognized within Primelephas :
- P. korotorensis ( Coppens , 1965)
The first scientific description of Primelephas was in 1970 by Vincent J. Maglio , based on the fossil material from Lothagam. He presented with P. gomphotheroides in a new way, but closed another way, P. korotorensis with one. This had already been defined by Yves Coppens in 1965 as Stegodon korotorensis based on a molar fragment from Koulà in northern Chad. Because new find material took place in 2008, a revision of the genus, which P. gomphotheroides with P. korotorensis synonymised was, the latter is now the only recognized way primelephas thus represents a monotypic genus. The holotype (copy number KNM-LT comprises 351) the Corresponding posterior, left and right maxillary molars, a last mandibular molar and parts of the palatine bone . Further associated material is a mandibular fragment with a symphysis and the two first and second right molars. The finds belong to the extensive fossil material from the Lothagam site. Also included in Primelephas is part of the finds that Pascal Tassy described in 2003 as "Elephas" nawataensis using a lower jaw from Lothagam. The species was considered to be the earliest evidence of the Palaeoloxodon line in Africa. However, comparisons with Primelephas and with Stegotetrabelodon showed only a few differences, so that the remains assigned to “Elephas” nawataensis were divided between these two genera.
The Upper Miocene and Lower Pliocene and the emergence of the genus Primelephas coincide with the third and last radiation of the proboscis, which began in Africa . At that time there were numerous, now extinct, early forms of elephants, such as Stegotetrabelodon and Stegodibelodon , but also the ancestors of today's representatives of Elephas as well as Loxodonta and the extinct Mammuthus . Since most of the known fossil material of the proboscis of that geological epoch is very fragmentary, there may still be individual difficulties in distinguishing between the various early elephants.
Individual evidence
- ↑ a b c d e f 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 Vincent J. Maglio: Four new species of Elephantidae from the Plio-Pleistocene of northwestern Kenya. Breviora 341, 1970, pp. 1-43
- ↑ a b c d e Hassane Taïsso Mackaye, Yves Coppens, Patrick Vignaud, Fabrice Lihoreau and Michel Brunet: De nouveaux restes de Primelephas dans le Mio-Pliocène du Nord du Tchad et révision du genre Primelephas. Comptes Rendus Palevol 7, 2008, pp. 227-236
- ^ William J. Sanders: Horizontal tooth displacement and premolar occurrence in elephants and other elephantiform proboscideans. Historical Biology, 2018 doi: 10.1080 / 08912963.2017.1297436
- ↑ Jon E. Kalb and DJ Fröehlich: Interrelationships of Late Neogene Elephantoids: new evidence from the Middle Awash Valley, Afar, Ethiopia. Geobios 28 (6), 1995, pp. 727-736
- ↑ Haruo Saegusa and Yohannes Haile-Selassie: Proboscidea. In: Yohannes Haile-Selassie and Giday WoldeGabriel (eds.): Ardipithecus kadabba. Late Miocene Evidence from the Middle Awash, Ethiopia. University of California Press, Berkeley, 2009, pp. 469-516
- ↑ Thure E. Cerling, John M. Harris and Meave G. Leakey: Browsing and grazing in elephants: the isotope record of modern and fossil proboscideans. Oecologia 120, 1999, pp. 364-374
- ↑ 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
- ^ 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 c William J. Sanders and Yohannes Haile-Selassie: A New Assemblage of Mid-Pliocene Proboscideans from the Woranso-Mille Area, Afar Region, Ethiopia: Taxonomic, Evolutionary, and Paleoecological Considerations. Journal of Mammal Evolution 19, 2012, pp. 105-128
Web links
- The Paleobiology Database: Primelephas