Brachydiastematherium
| Brachydiastematherium | ||||||||||||
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Lower jaw of Brachydiastematherium transylvanicum , holotype specimen |
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| Temporal occurrence | ||||||||||||
| Upper Eocene ( Priabonium ) | ||||||||||||
| 38 to 33.9 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Brachydiastematherium | ||||||||||||
| Böckh & Matyasovsky , 1876 | ||||||||||||
Brachydiastematherium is an extinct member of the Brontotherien that lived in the Upper Eocene 38 to 34 million years ago. It represents one of the very rare records of this odd ungulate group in Europe and was discovered in Transylvania in Romania . Very few finds have been discovered to date, so little is known about the animal's appearance. However, Brachydiastematherium is close to the modern and large Brontotheria of Eurasia.
features
Brachydiastematherium is a large representative of the Brontotheria , but it is known only from very few skull fragments. Based on the size of the finds, a shoulder height of around 2 m compared to related animals can be reconstructed. The most important find is an anterior mandibular fragment with fully preserved anterior teeth, while on the left branch of the jaw the row of teeth up to the first molar and on the right branch to the second premolar has been handed down. The symphysis of the lower jaw reached up to the fourth premolar and was so very extensive. The front teeth consisted of three incisors and the canine and formed only a slight arch. The two inner incisors were rather small and spatulate, the outer (I3) clearly larger and conical . The adjoining canine was only small in shape. There was no diastema between this and the first premolar, so the entire row of teeth was closed. The posterior set of teeth has only survived incompletely, but since the first premolar was formed, a complete row of teeth comprising seven molars (4 premolars, 3 molars) can be assumed. The anterior premolar was small at 2 cm in length and had only a single enamel cusp on the chewing surface. The back teeth increased in size, the rear premolars were clearly molarized. The first molar was 5.3 cm in length. Due to the lack of find material, it can only be speculated about the further appearance, whether the Brontotherien representative had a horn is unknown, but his closest relative Metatitan had such a bony formation, but it was rather small.
References
Only a few finds are known of Brachydiastematherium . The lower jaw comes from the red-colored sandstone deposits of the Valea-Nadăşului formation near Andrásháza near Radaia, just a few kilometers west of Cluj-Napoca in Transylvania . The formation dates to the Upper Eocene . The lower jaw was discovered in 1871 and published five years later. It represents the holotype of the genus and is part of the collection of the University of Cluj-Napoca, which also contains some unpublished postcranial skeletal parts of Brachydiastematherium that were found with it but have not been published . For more than a century, these finds were the only evidence of this genus of Brontotheria. More recent evidence comes from the same formation at Morlaca, also near Cluj-Napoca, and includes isolated teeth. These new fossils were found associated with Sharamynodon , a large member of the Amynodontidae of the rhinoceros, and with Eocricetodon , an early European hamster .
Systematics
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Internal systematics of the Embolotheriita according to Averianov et al. 2018
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The genus Brachydiastematherium belongs to the family of Brontotheriidae (originally Titanotheriidae). The Brontotherien represent an extinct group of mammals from the order of the odd-toed ungulate , which is related to today's horses due to the structure of the rear teeth . Within the Brontotheriidae, Brachydiastematherium is a member of the subfamily of the Brontotheriinae and the intermediate tribus of the Embolotheriita. The tribe Embolotheriita originally formed its own subfamily, the Embolotheriinae, which was introduced by Henry Fairfield Osborn in 1929 only for Embolotherium . However, Matthew C. Mihlbachler moved this to the level of the intermediate tribus in 2008. Today, in addition to Embolotherium, the Embolotheriita also include other genera, such as Aktautitan , Metatitan and Gnathotitan , which mostly had an Asian distribution. They face the sub-tribus of the Brontotheriita with Megacerops as a sister group.
Brachydiastematherium is one of the few Brontotheria that are proven in Europe , another form is known from Bulgaria . In part, the genus was equated with Protitanotherium , which was later synonymous with Diplacodon ; both names refer to Middle Eocene forms from North America . However, there are also similarities to Metatitan , the closest relative of which is Brachydiastematherium , the latter being distinguished by larger and clearly more spatula-shaped incisors. The genus was described in 1876 by Johann Böckh using the lower jaw fragment from Andrásháza in Transylvania. With Brachydiastematherium transylvanicum only one species is known. The generic name Brachydiastematherium is derived from the Greek words βραχύς ( brachýs "short"), διάστημα ( diástēma "space") and θηρίον ( thērion "animal") and refers to the non-existent distance between the canine and the first premolars. The species name transylvanicum is a reference to the find area.
Individual evidence
- ↑ a b Cristina Farcas: Study of the Upper Eocene-Lower Oligocene continental formations from north western side of Transylvanian Depression - Biostratigraphy, and palaeoenvironmental reconstructions based on land vertebrates. Babes Bolyai University, Cluj-Napoca, 2011
- ↑ a b c Matthew C. Mihlbachler: Species taxonomy, phylogeny, and biogeography of the Brontotheriidae (Mammalia: Perissodactyla). Bulletin of the American Museum of Natural History 311, 2008, ISSN 0003-0090 , pp. 1-475
- ↑ Vlad A. Codrea, O. Maridet, M. Venczel, Cristina Fărcaş and A. Solomon: New data on the terrestrial Eocene / Oligocene boundary in Transylvania (Romania). In: Alexandra van der Geer and Athanassios Athanassiou (eds.): European Association of Vertebrate Palaeontologists - 9th Annual Meeting Heraklion, Crete, Greece 14-19 June, 2011. Program and abstracts. Heraklion 2011, p. 19
- ↑ Alexander Averianov, Igor Danilov, Wen Chen and Jianhua Jin: A new brontothere from the Eocene of South China. Acta Palaeontologica Polonica 63. 2018 doi: 10.4202 / app.00431.2017
- ^ Henry Fairfield Osborn: Embolotherium, gen. Nov., Of the Ulan Gochu, Mongolia. , American Museum Novitates 353, 1929, pp. 1-20
- ^ Spencer George Lucas and Robert M. Schoch: European Brontotheres. In: Donald R. Prothero and Robert M. Schoch (Eds.): The evolution of perissodactyls. New York and London, 1989, pp. 485-489