Barytherium
| Barytherium | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Late Eocene to early Oligocene | ||||||||||||
| 37 to 33 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Barytherium | ||||||||||||
| Andrews , 1901 | ||||||||||||
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Barytherium is an extinct genus of the proboscis ; it lived in the late Eocene and early Oligocene around 37 to 33 million years ago. It was mainly restricted to northern Africa and the Arabian Peninsula . Representatives of this genus were distinguished by the presence of a total of eight tusks. The term barytherium is made up of the Greek words βαρύς ( barýs , "heavy") and θηρίον ( thērion, "Animal") and refers to the significant increase in size and weight of the animals, which has been demonstrated for the first time in the proboscis evolution.
features
Barytherium is a relatively large proboscis. It reached a shoulder height of 2.5 to 3 m and weighed an estimated 3 to 4 tons. Thus it was considerably larger than the phylogenetically older, only tapirgroße Moeritherium . In general, it is characterized by an elephant-like physique and columnar limbs . The thigh ( femur ), however, showed lateral flattening. The skull was flat and only slightly arched, but like all later proboscis animals also had air-filled chambers in the skull, which significantly reduced the weight of the entire head. The nostril was large and highlighted on the side, which is interpreted as a point of attachment for the trunk. However, nothing is known about the size and appearance of the trunk.
The lower jaw was massive and had a very extensive symphysis that reached to the first molar . The teeth showed over the older Moeritherium the reduction of an incisor and the canine depending on pine bough and thus presented already a significant advancements is the dental formula for adult animals was.: . There was a large diastema behind the second incisor . The molars had a lophodontic structure, with the premolars having only singular transverse ridges. The molars, on the other hand, were characterized by two ridges each and thus showed a typical bilophodontic structure.
Most notable about barytherium , however, were the incisors, which were converted into tusks . The animals had two tusks per arch, making a total of eight. The upper tusks sat vertically in the jawbone. The outer tusk (I2) was significantly larger than the inner (I1). In contrast, the tusks of the lower jaw had a horizontal position. In addition, the inner tusk (I1) was made significantly larger than the outer (I2). The position and shape of the tusks created a kind of scissors between the inner surface of the upper second incisor and the outer surface of the lower first incisor.
Fossil finds
Finds of barytherium are relatively rare. The first finds come at the beginning of the 20th century in the Fayyum area in Egypt, where most of the finds come from. They camp there in the Qasr-el-Sagha Formation and the Gebel-Qatrani Formation , which date from the Obereocene to the Lower Oligocene. The finds from the Fayyum were the only known of Barytherium for almost 60 years . It was not until the 1960s and 1970s that several skeletons, some of them complete, came to light in Dor el-Talha in the Sirte Basin in Libya , another important site. Here it is detected in the evaporite unit and the idam unit. Other finds come from Aidum in the Dhofar Governorate in Oman .
Paleobiology
Barytherium was widespread during the Eocene - Oligocene transition across what is now North Africa and the Arabian Peninsula , which at that time was still connected to the African continent. The way of life of barytherium was unexplained for a long time. Isotope examinations on teeth from new finds from Egypt now made a reconstruction possible. Barytherium lived in hot, humid tropical rainforests on the banks of freshwater lakes . Interestingly, the tooth enamel had a relatively constant proportion of the heavy oxygen isotope 18 O, which varied more than that of marine mammals, but was significantly more balanced than that of land-dwelling mammals. As a rule, he had variances of today's semi-aquatic country dwellers. It is now assumed that barytherium had a relatively limited habitat and changed its location less often. It probably spent a large part of the day in the water of the surrounding lakes, feeding on the aquatic plants or near-shore phytoplankton .
Systematics
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Abbreviated internal systematics of the early proboscis according to Tabuce et al. 2019
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Numidotherium is a genus of the order of Rüsseltiere (Proboscidea). Due to the bilophodontic structure of the anterior molars and the verifiable vertical change of teeth, it clearly belongs to the group of the primitive Plesielephantiformes , from which the more developed, higher elephantiformes differ by a higher number of enamel strips on the teeth and the horizontal tooth change. Within this, Barytherium is referred to the family of Barytheriidae , in which Omanitherium may also be incorporated. However, with the reduction of the outermost incisor and the canine, as well as the appearance of a large diastema , barytherium shows significant further developments compared to older forms of proboscis such as Numidotherium , Daouitherium or Moeritherium and is closely related to the deinotherium . However, it is not considered to be their immediate ancestor, as these have a more complex structure of the molars. Most likely it forms an outgroup of the Deinotherien together with the newly discovered Arcanotherium in the late 2010s .
The position of barytherium within the proboscidea was often controversial in the course of research history. Andrews himself created the taxon Barytheria, which he placed among the Amblypoda, supposedly early ungulates . It was not until 1906 that he assigned them to the trunk animals as the Barytheriidae family. The American paleontologist and proboscis expert Henry Fairfield Osborn (1857–1935) separated barytherium and placed it again in the taxon Barytheria, as did various other researchers. Today, barytherium is considered a definite member of the proboscis.
First described was barytherium based on findings from the Fayyum by Charles William Andrews in 1901. Based formed an upper and lower jaws as well as individual elements of the forelimbs. Andrews first gave the genus the name Bradytherium , but in the following year he renamed it Barytherium , as the name had already been given to an extinct representative of Malagasy primates ( Palaeopropithecus ). Barytherium grave is the elephant-sized type species described by Andrews. A possibly second species from the Upper Ocene site of Dor el-Talha in Libya was mentioned in 1969. This should be much smaller than Barytherium grave and only reach a shoulder height of 1 to 1.5 m and a body weight of around 200 kg. In 1995, Nicholas Court re-described these finds as Numidotherium savagei due to numerous deviations from barytherium . Again in 2009 morphological differences caused Cyrille Delmer to transfer the species to the genus Arcanotherium, which she created . An additional, not yet described species of Barytherium was discovered in the Fayyum area at the end of the 2010s and lies intermediate between the small Arcanotherium savagei and the large Barytherium grave . It comes from the earliest Upper Eocene.
Individual evidence
- ↑ a b c d e f g Jeheskel Shoshani, Robert M. West, Nicholas Court, Robert JG Savage and 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
- ↑ a b Pascal Tassy: Who is who among the Proboscidea? In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and palaeoecology of the Elephants and their relatives. Oxford, New York, Tokyo, 1996, pp. 40-48
- ↑ a b c d Alexander GSC Liu, Erik R. Seiffert and Elwyn L. Simons: Stable isotope evidence for an amphibious phase in early proboscidean evolution. PNAS 105, 2008; Pp. 5786-5791
- ↑ 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
- ↑ 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
- ↑ 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. (Ed.): The World of Elephants - International Congress. Consiglio Nazionale delle Ricerche. Rome, 2001, pp. 676-679
- ↑ Emmanuel Gheerbrant, Jean Sudre, Henri Cappetta, Mohamed Iarochène, Mbarek Kamaghzaz and Baâdi Bouya: A new large mammal from the Ypresian of Morocco: Evidence of surprising diversity of early proboscideans. Acta Palaeontologica Polonica 47 (3), 2002, pp. 493-506
- ^ Charles W. Andrews: Note on the Barypoda, an new order of ungulate mammals. Geological Magazine 5, 1904, pp. 481–482 ( [1] )
- ↑ 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
- ^ Charles William Andrews: Preliminary note on some recently discovered extinct vertebrates from Egypt. Geological Magazine 4, 1901, pp. 400–409 ( [2] )
- ↑ 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 ( [3] )
- ^ Charles W. Andrews: A descriptive catalog of the Tertiary Vertebrata of the Fayum, Egypt. London, 1906, pp. 1–324 (pp. 172–177)
- ↑ RJG Savage: Early Tertiary mammal locality in southern Libya. Proceedings of the Geological Society of London 1657, 1969, pp. 167-171 ( [4] )
- ↑ Nicholas Court: A new species of Numidotherium (Mammalia: Proboscidea) from the Eocene of Libya and the early phylogeny of the Proboscidea. Journal of Vertebrate Paleontology 15, 1995, pp. 650-671, doi: 10.1080 / 02724634.1995.10011254