Moeritherium

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Moeritherium
Skeletal reconstruction of Moeritherium

Skeletal reconstruction of Moeritherium

Temporal occurrence
Eocene ( Bartonian and Priabonian ) to Oligocene ( Rupelian )
40 to 30 million years
Locations
Systematics
Higher mammals (Eutheria)
Afrotheria
Paenungulata
Tethytheria
Russell animals (Proboscidea)
Moeritherium
Scientific name
Moeritherium
Andrews , 1901

Moeritherium belongs beside eritherium , numidotherium and phosphatherium the oldest known species of mammoths (Proboscidea) making it one of the oldest ancestors of today's elephants . It was mainly found in northern Africa .

features

Moeritherium , depiction by Heinrich Harder (1912).
Skull of Moeritherium lyonsi in the Muséum national d'histoire naturelle in Paris.

Moeritherium , in German animal of the Moeri lake , lived about 40 to 30 million years ago in the Upper Eocene ( Bartonian and Priabonian ) and Lower Oligocene ( Rupelian ). It reached about the size of a tapir living today and had a shoulder height of 60, in extreme cases up to 100 cm. The body, however, was very elongated and, according to reconstructions, reached up to 350 cm head-torso length in larger specimens . The limbs were very strong and short, but sometimes also shortened at the sides. The animal should have weighed around 200 kg.

The skull had a clearly elongated shape with widely spreading cheekbones . The occiput was wide and had a distinct bulge as the starting point for massive neck muscles. The forehead was only slightly curved, but there were small, air-filled cavities in the upper skull to reduce the weight of the skull, with which Moeritherium anticipated the development of the later proboscis. The nasal bone ended just in front of the upper jaw , the nostrils were very high on the skull and were not laterally elevated as in the later proboscis, which speaks against the existence of a proboscis, but a more mobile upper lip was possibly developed. The eye sockets were located very far in front of the skull, roughly at the level of the anterior premolars . The ear region was much more developed than that of earlier elephants and corresponded to that of today's elephants .

The lower jaw was very strong and high with a massive but short symphysis . The Moeritherium set of teeth was more reduced than that of its ancestors due to the loss of a lower pair of incisors , the lower pair of canines and the upper and lower front pair of the premolars, making them much more modern than the teeth of older proboscis. The dental formula is: . The second pair of incisors ( I 2) in the upper and lower jaw was elongated, but did not yet form real tusks . In the case of the lower jaw, the extension of the second incisor is a unique feature of Moeritherium , since the tusks of all other proboscis are always formed from the first (I1). The molars generally had a bunodont structure, but had small ridges (bunolophodont) between the characteristic enamel cusps. The last premolar and the first two molars each had two of these ridges (bilophodont), while the rearmost molar also had a third ridge. Early representatives of Moeritherium had a clearly more lophodontic tooth structure.

Paleobiology

In terms of research history, it was discussed early on whether Moeritherium lived amphibiously in lakes and rivers and primarily fed on aquatic plants . The reasons for this were anatomical, such as the very short limbs, the elongated body and the eyes, which were clearly located in the front of the skull. Isotope tests on teeth of newly found skeletal material from Egypt , which were carried out together with remains of barytherium , confirmed this assumption. A relatively constant proportion of the heavy oxygen isotope 18 O compared to terrestrial mammals could be detected in the tooth enamel , but this still fluctuated more clearly than in purely aquatic mammals. This suggests that Moeritherium like Barytherium inhabited the bank areas of waters in the tropical rainforest of that time and spent a large part of the day in the water to take in food. However, a low consumption of terrestrial plants cannot be ruled out. However, due to the strongly differing values ​​of the 13 C carbon isotope of Moeritherium compared to Barytherium , both proboscis fed on different plants.

Research history

Skull of Moeritherium andrewsi

In 1901, fossil remains were discovered in the Fayyum in Egypt in the Qasr-el-Sagha formation , which were first described by Charles William Andrews as Moeritherium lyonsi . Just one year later, another, somewhat smaller specimen was found nearby in a fluvio-marine formation and assigned to the taxon Moeritherium gracile by Andrews . In 1904 Andrews found the first Moeritherium trigodon fossils in the sediments of the Fayyum. Max Schlosser from Munich divided another taxon from Moeritherium lyonsi in 1911 , which he called Moeritherium andrewsi . The latter taxon was also quite large and came from a fluvio-marine formation. Not so long ago (2006) the remains of the taxon Moeritherium chehbeurameuri first came to light in Bir El Ater in Algeria .

Systematics

Abbreviated internal systematics of the early proboscis according to Tabuce et al. 2019
  Proboscidea  

 Eritherium


   

 Phosphatherium


   

 Daouitherium


   

 Numidotherium


   


 Barytherium


   

 Omanitherium



   

 Arcanotherium


   

 Saloumia


   

 Moeritherium


   

 younger Proboscidea (Elephantiformes)


   

 Deinotheriidae



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Moeritherium is a genus of the order of Rüsseltiere (Proboscidea). Within this it belongs to the very early proboscis, which first appeared in the Upper Paleocene of North Africa. The genus is possibly part of the subordination of the Plesielephantiformes , which are characterized by two ridges on the molars. The simultaneous use of all teeth in the dentition (vertical tooth change) also refers to the early proboscis, which had not yet developed the horizontal tooth change characteristic of the later forms and today's elephants.

Other features that support the position within the proboscis are above all the air-filled skull bones and the massive mandibular symphysis, but also the position of the orbit far forward in the skull above the anterior premolars. Due to the stronger bunodontic structure of the molars, Moeritherium and Arcanotherium are much closer to the later proboscis than to the early proboscis such as Barytherium and Numidotherium , which had significantly more lophodontic molars. However, the earliest Moeritherium representatives with their stronger lophodont teeth are seen as a link to these proboscis, which they converted into bunodonts in the course of their phylogenetic development.

The discussion about the position of Moeritherium within the proboscis has been going on for a long time. Some researchers saw him only as a relative of the proboscis, with a closer taxonomic position to Anthracobune from South Asia . Today Moeritherium is considered a clear member of the proboscis, which was, however, a highly specialized branch that went out in the early Oligocene without further descendants. Among the trunk animals following Moeritherium are the Deinotherien (tusk elephants ), Palaeomastodon and via Phiomia also the Gomphotherien and later the elephants with the mammoths and the elephant species living today.

In the course of the history of research a total of eight species have been described, but only three of them are recognized today:

  • Moeritherium chehbeurameuri Delmer , Mahboubi , Tabuce & Tassy , 2006
  • Moeritherium lyonsi Andrews , 1901 (synonyms: M. gracile , M. ancestrale , M. latidens , M. pharaoensis )
  • Moeritherium trigodon Andrews , 1904 (Synonym: M. andrewsi )

Locations

Finds of Moeritherium have so far been largely limited to northern Africa. The genus does not occur outside of Africa, as the continent was separated from what was then Eurasia by the Tethys Ocean and the corresponding land bridges were only built in the early Miocene around 22 million years ago. The most important sites include:

Individual evidence

  1. ↑ Jehezekel Shoshani: Skeletal and basic anatomical features of elephants. In: Jeheskel Shoshani, Pascal Tassy (Ed.): The Proboscidea. Evolution and Palaeoecology of the Elephants and their Relatives. Oxford, New York, Tokyo, 1996, pp. 9-20
  2. ↑ a b c d e f g Jeheskel Shoshani, Robert M. West, Nicholas Court, Robert JG Savage, John M. Harris: The earliest proboscideans: general plan, taxonomy, and palaeoecology. In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and Palaeoecology of the Elephants and their Relatives. Oxford, New York, Tokyo, 1996, pp. 57-75.
  3. ↑ a b c 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.
  4. ↑ a b Alexander GSC Liu, Erik R. Seiffert, Elwyn L. Simons: Stable isotope evidence for an amphibious phase in early proboscidean evolution. PNAS 105, 2008, pp. 5786-5791 ( PDF ).
  5. ↑ a b c d e Cyrille Delmer, Mohamed Mahiboubi, Rudolphe Tabuce, Pascal Tassy: A new species of Moeritherium (Proboscidea, Mammalia) from the Eocene of Algeria: New perspectives on the ancestral morphotype of the genus. Palaeontology 49 (2), 2006, pp. 421-434.
  6. ↑ a b c Cyrille Delmer: Reassessment of the generic attribution of Numidotherium savagei and the homologies of lower incisors in proboscideans. Acta Palaeontologica Polonica 54 (4), 2009, pp. 561-580.
  7. ↑ Charles William Andrews: About the occurrence of proboscidians in sub-tertiary deposits of Egypt. Tageblatt of the V International Zoological Congress, Berlin 6, 1901, pp. 4–5
  8. ^ Charles William Andrews: Preliminary note on some recently discovered extinct vertebrates from Egypt. Geological Magazine 4, 1901, pp. 400–409 ( [1] )
  9. ↑ Charles William Andrews: About the occurrence of proboscidians in sub-tertiary deposits of Egypt. Negotiations of the 5th International Zoological Congress in Berlin, 12. – 16. August 1901, 1902, p. 528 ( [2] )
  10. ↑ Rodolphe Tabuce, Raphaël Sarr, Sylvain Adnet, Renaud Lebrun, Fabrice Lihoreau, Jeremy E. Martin, Bernard Sambou, Mustapha Thiam and Lionel Hautier: Filling a gap in the proboscidean fossil record: a new genus from the Lutetian of Senegal. Journal of Paleontology, 2019, doi: 10.1017 / jpa.2019.98
  11. ^ A b Emmanuel Gheerbrant: Paleocene emergence of elephant relatives and the rapid radiation of African ungulates . PNAS. 106 (6), 2009, pp. 10717-10721
  12. ↑ Jehezekel Shoshani, WJ Sanders and Pascal Tassy: Elephants and other Proboscideans: a summary of recent findings and new taxonomic suggestions. In: G. Cavarretta et al. (Eds.): The World of Elephants - International Congress. Consiglio Nazionale delle Ricerche. Rome, 2001, pp. 676-679
  13. ^ Daryl P. Domning, Clayton E. Ray and Malcolm C. McKenna: Two New Oligocene Desmostylians anci a Discussion of Tethytherian Systematics. Smithsonian Contribution to Palaeobiology 59, Washington, 1983 ( PDF )
  14. ^ Charles William Andrews: A Descriptive Catalog of the Tertiary Vertebrata of the Fayum, Egypt; Based on the Collection of the Egyptian Government in the Geological Museum, Cairo, and on the Collection in the British Museum (Natural History). London, 324 pages, 26 plates, 101 illustrations, 1906
  15. ↑ PE Coiffait, B. Coiffait, JJ Jaeger and Mohamed Mahboubi: Un nouveau gisement a Mammiferes fossiles d'age Eocene superieure sur le versant sud des Nementcha (Algerie orientale): decouverte des plus anciens Rongeurs d'Afrique. Comptes Rendus de l'Academie des Sciences series 2, 299 (13), 1984, pp. 893-898
  16. ↑ G. Schlesinger: Studies on the tribal history of the Proboscidians. Yearbook of the Imperial and Royal Geological Institute 62 (1), 1912, pp. 87–182
  17. ↑ C. Arambourg and P. Magnier: Gisements de Vertebres dans le bassin tertiaire de Syrte (Libye). Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences 252 (8), 1961, pp. 1181-1183
  18. ^ H. Tobien: The Structure of the Mastodont Molar (Proboscidea, Mammalia), Part 3: The Oligocene Mastodont Genera Palaeomastodon, Phiomia and the Eo / Oligocene Paenungulate Moeritherium. Mainzer Geoswissenschaftliche Mitteilungen 6, 1978, pp. 177–208

Web links

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