Moeritherium
Skeletal reconstruction of Moeritherium
Moeritherium heard next Eritherium, Numidotherium and Phosphatherium the oldest known species of Proboscidea ( Proboscidea ), making it one of the oldest ancestors of today's elephants. It was mainly found in northern Africa.
Features
Moeritherium to the German animal Moeri Lake, ( Bartonium and Priabonium ) and lower Oligocene lived about 40-30 million years ago in the Upper Eocene ( Rupelium ). 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 was, however, very elongated and reached reconstructions According larger specimen to 350 cm head-body length. The limbs were very strong and short, but partly also shortened the side. The animal is likely to have weighed about 200 kg.
The skull had a significantly elongated shape with wide overhanging cheekbones. The occiput was wide and had a distinct bead as a starting point for a massive neck muscles. The face showed only a slight curvature in the upper skull but were small, air-filled cavities to reduce the weight of the skull, which Moeritherium anticipated the development of later Russell animals. The nose leg ended just before the upper jaw, the nostrils were very high on the skull and were not increased laterally as in the later proboscidean, which argues against the existence of a proboscis, but possibly a more mobile upper lip was formed. The eye sockets were located very far forward in the skull, approximately at the level of the anterior premolars. The ear region was much more developed than in previous proboscis animals and corresponded to that of today's elephants.
The lower jaw had a very strong and high building with a massive but short symphysis. The dentition of Moeritherium was compared with that of his ancestors reduced more by the loss of a lower incisor, the lower Eckzahnpaars and the upper and lower front pair of premolars and thus more modern than the older teeth mammoths. The dental formula is:. In each case, the second pair of incisors (I2 ) in the maxilla and the mandible was prolonged, but made no real tusks. In the case of the lower jaw, the extension of the second incisor is a singular feature in Moeritherium, as with all other proboscidean the tusks are always formed from the first ( I1). The molars generally had a bunodonten construction, but possessed between the characteristic enamel cusps small strips ( bunolophodont ). Here, the last premolar and the first two molars each had two of these lists ( bilophodont ), while additionally was the approach of a third bar at the rearmost molar. But early representatives of Moeritherium had a significantly lophodonteren Zahnbau.
Paleobiology
Research History was discussed early on whether Moeritherium amphibian lived in lakes and rivers and is primarily fed on aquatic plants. This was due to anatomical reasons, such as the very short limbs, the elongated body and the eyes significantly lower in the anterior cranial area. Isotope studies of teeth of newly aufgefundenem skeletal material from Egypt, which took place together with the remains of Barytherium, confirmed this assumption. Here, a over terrestrial mammals relatively constant proportion of the heavy oxygen isotope 18O was detected in the enamel, but still clearly swayed than purely aquatic mammals. This suggests that Moeritherium as Barytherium in what was then Tropical rainforest inhabited areas at the banks of water bodies and a large part of the day spent in the water to take food. However, with him not also exclude a low intake of terrestrial plants. Due to the strongly differing values of the also examined carbon isotope 13C of Moeritherium compared to Barytherium both mammoths have but fed on different plants.
History of Research
In 1901, fossil remains were discovered in the Qasr el- Sagha lineup in the Fayyum oasis in Egypt, as Moeritherium lyonsi by Charles William Andrews were first described. Just a year later a nearby another, slightly smaller specimen was found in a fluvio - marine formation and assigned gracile from Andrews to the taxon Moeritherium. 1904 Andrews was the first Moeritherium trigodon fossils in sediments of the Fayyum oasis. Max Schlosser of Munich announced in 1911 by Moeritherium lyonsi from another taxon which he described as Moeritherium andrewsi. The latter taxon was also quite large and came from a fluvio - marine formation. Not too long ago (2006 ) Remains of the taxon Moeritherium chehbeurameuri came in Bir El Ater in Algeria for the first time revealed.
System
Moeritherium belongs to very early proboscidean, which first appeared in the Upper Paleocene of North Africa. Possibly the species is part of the order Plesielephantiformes, which are characterized by two strips on the molars. The simultaneous use of all teeth in the dentition (vertical tooth replacement) also refers to the early Russell animals that had not yet late for the forms and today's elephants trained characteristic horizontal tooth replacement.
Other features that support the position within the Proboscidea, are mainly the air-filled skull bone and the mandibular solidly formed but also the position of the orbit far forward in the skull above the front premolars. Due to the stronger bunodonten construction of the molars Moeritherium is much closer than the simultaneously occurring early proboscidean as Barytherium and Numidotherium, which had significantly lophodontere molars together with Arcanotherium later proboscidean. As a link to this proboscidean but the earliest Moeritherium representatives with their also more lophodonten teeth are seen, they but in the course of their phylogenetic development conversions to more bunodonten.
The discussion about the position of Moeritherium within the mammoths was out long. Some researchers looked at him only as a relative of the mammoths, with a closer taxonomic position to Anthracobune from South Asia. Today Moeritherium is considered as a unique member of the Russell animals, however, this was a highly specialized side branch that became extinct in the early Oligocene without further descendants. Among the on Moeritherium following proboscidean to find the Deinotherien ( elephant tusks ), Palaeomastodon and Phiomia the gomphotheres and later the elephant with the mammoth and the elephant species living today.
Throughout the history of research a total of eight species have been described, of which only three are recognized but 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 largely confined to northern Africa. Outside Africa, the species does not occur, since at that time the continent by the Tethys Ocean from Eurasia was then separated and corresponding land bridges were developed only in the early Miocene epoch, about 22 million years ago. Among the most important archaeological sites include:
- Egypt - Fayyum oasis - Upper Eocene, Oligocene
- Algeria - Bir el Ater ( Nementcha mountains ) - Intermediate to Upper Eocene and Khenchela - Eocene
- Libya - Dor el Talha ( Sirte Basin) - Upper Eocene, Lower Oligocene
- Mali - Tafidet in Gao
- Senegal - M'Bodione Dadere - lutetium Questionable Moeritheride
- Sudan