Omanitherium
| Omanitherium | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Lower Oligocene | ||||||||||||
| 34 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Omanitherium | ||||||||||||
| Seiffert , Nasir , Al-Harthy , Groenke , Kraatz , Stevens & Al-Savigh , 2012 | ||||||||||||
| species | ||||||||||||
Omanitherium is an extinct representative of the proboscis animals and livedon the Arabian Peninsula 34 million years ago in theearly Oligocene . It isclosely relatedto barytherium , but which became much larger. So far, fossils are relatively rare. Possibly Omanitherium had a mediator function for the development of the Deinotherien .
features
Omanitherium is a smaller representative of the early proboscis , but is only known from a lower jaw and isolated teeth, which were found in Oman on the Arabian Peninsula and which come from a not fully grown animal. The size of the animal mediated between Numidotherium and Barytherium , its closest relative. The holotype (copy number SQU -290) has broken down into several parts, but includes both lower jaw branches and the long symphysis . The front teeth consist of the second incisors , which have not yet fully erupted. However, they have a typical tusk shape, with a straight course and slightly elliptical cross-section, the diameters being 24 and 29.8 mm. This distinguishes Omanitherium from other early proboscis with their more spatulate lower jaw tusks. The tooth crown is covered with a thin layer of tooth enamel . There is a gap between the two tusks, but the state of preservation of the fossil does not reveal whether the alveoli of the first incisors, which typically form the tusks of the lower jaw in proboscis, are preserved.
The right branch of the jaw has the two posterior premolars and the first two molars with a partially preserved posterior molar (P3 to M3), the left one the last premolars and all molars (P4 to M3), the last of which is currently in the breakthrough. In addition, the tooth socket of the second premolar is formed. The premolars are less molarized and rather small. The molars have two clear, transversely positioned enamel ridges ( bilophodont ) and a low crown ( brachyodont ). The rearmost molar was 61.7 mm long.
Fossil finds and find history
The finds were discovered in 2010 by an international research team consisting of US and Omani experts. They come from the Shizar strata of the Ashawq Formation , which belongs to the early Oligocene and is open near Al-Mughsayl and Rakhyut in the Dhofar Governorate on the southwest coast near the border with Yemen . They became aware of the site through some finds by a local resident. As early as 1986 and 1992, however, a French- Romanesque group of scientists observed three incisors and a premolar of proboscis in the same layer segment near the village of Thaytiniti and classified them as belonging to the Barytheria ("cf. Barytheriidae"). Since the incisors are the first in the lower jaw and these are rather flat, it is unclear whether the finds are related to Omanitherium .
Paleobiology
The Shizar strata of the Ashawq Formation is similar in structure to the deposits in which remains of Moeritherium and Barytherium were discovered in North Africa and formed at the edge of the Tethys Ocean . The morphology of the teeth also corresponds to that of barytherium . The researchers assume that Omanitherium also followed a semi-aquatic way of life that was comparable to the other early proboscis.
Systematics
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Abbreviated internal systematics of the early proboscis according to Tabuce et al. 2019
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Omanitherium is a genus of the order of Rüsseltiere (Proboscidea). The simultaneous use of all molars shows with the typical vertical change of teeth a very early position within the proboscis . The characteristic of today's elephants horizontal dentition evolved phylogenetically later and is eritreum first detected. The bilophodontic structure of the molars refers Omanitherium to the Plesielephantiformes , which represent the parent group of this mammal order. The strictly lophodontic molars suggest a closer relationship with barytherium , which is characterized by eight tusks. Therefore it was assigned to the family of Barytheriidae . Other closely related groups are Numidotherium and Arcanotherium .
The extremely long symphysis of the lower jaw could speak for a closer position to the deinotheria , as well as the strongly lophodontic molars. However, the molars are characterized by two transverse ridges in Omanitherium , while Deinotherium has three. However, the development to the deinotheria, which has not yet been clarified, could have taken place via the barytheria, while the more modern proboscis were formed from a trunk group with less lophodontic molars.
The only known species so far is Omanitherium dhofarensis . The generic name Omanitherium refers to Oman as a land of discovery and the Greek word θηρίον ( thērion , "animal"). The species name dhofarensis refers to the Dhofar governorate.
Individual evidence
- ↑ a b c d e f g Erik R. Seiffert, Sobhi Nasir, Abdulrahman Al-Harthy, Joseph R. Groenke, Brian P. Kraatz, Nancy J. Stevens and Abdul Razak Al-Sayigh: Diversity in the later Paleogene proboscidean radiation: a small barytheriid from the Oligocene of Dhofar Governorate, Sultanate of Oman. Natural Sciences 99, 2012, pp. 133–141
- ↑ 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, Robert C. Walter, Michael Abraha, soap Berhe, Pascal Tassy, William J. Sander, Gary H. Marchant, Yosief Libsekal, Tesfalidet Ghirmai and Dietmar Zinner: A proboscidean from the late Oligocene of Eritrea, a '' missing link '' between early Elephantiformes and Elephantimorpha, and biogeographic implications. PNAS 103 (46), 2006, pp. 17296-17301