Palaeosyops

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Palaeosyops
Skeletal reconstruction of Palaeosyops at the Smithsonian Institute in Washington, DC

Skeletal reconstruction of Palaeosyops at the Smithsonian Institute in Washington, DC

Temporal occurrence
Middle Eocene ( Chadronian )
50.7 to 46.3 million years
Locations
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Hippomorpha
Brontotheriidae
Palaeosyops
Scientific name
Palaeosyops
Leidy , 1870

Palaeosyops is an ancient representative of the Brontotheriidae , an extinct family from the group of odd ungulates . The small animal the size of today's tapirs lived in the Middle Eocene 46 to 50 million years ago and is mainly known from North America, but individual fossil remains also come from South Asia. Finds of Palaeosyops are documented quite often, the polled Brontotherien representative inhabited reconstructions according to dense forests.

features

With a head-trunk length of 200 cm and a shoulder height of 100 cm, Palaeosyops is a small representative of the Brontotheriidae and reached about the size of today's tapir . Characteristic was its broad, compact skull with protruding zygomatic arches, which was 39 to 42 cm long and had a short and right-angled occipital bone . The nasal bone was sturdy and curved downwards. In contrast to the more modern Brontotheria of the late Eocene, it had no bony horn formations. The forehead line was still partly convex, the parietal bones formed a distinctive crest .

Skull and head reconstruction from Palaeosyops

In the dentition, Palaeosyops had the complete dentition of early mammals , the corresponding tooth formula was: The canine was comparatively very large, to the rear dentition there was a more or less large diastema that was much more pronounced in the lower jaw and could reach a maximum length of 8 mm. The premolars were hardly molarized and therefore did not resemble the molars . These were low-crowned ( brachyodont ) and had strongly folded enamel , which on the tongue side of the upper rear molars between the protruding points metastylid and parastylid had a W-like course typical of brontotheria. The largest tooth was the rearmost molar, up to 4.2 cm in length.

The postcranial skeleton is largely fully known, but apart from its slimmer structure, it differs only little from that of other Brontotheria. The humerus was 29 cm long, the radius was significantly shorter at 23 cm. A similar ratio existed between the femur and the shin , 36 by 29 cm. The forefeet ended in four rays ( metacarpus II to V), the hind feet in three rays ( metatarsus II to IV), a primitive feature of the odd ungulate , which today is only found in tapirs . As with most odd-toed ungulates, the focus was always on the third ray. In contrast to the more developed Brontotheria, however, the third metatarsal was 11 cm long and slightly more pronounced than the corresponding metacarpal bone, which was 10 cm long.

References

Finds of Palaeosyops are known from North America as well as from South Asia, but the largest part comes from the Bridger Formation in the US state of Wyoming . This formation comprises two separable rock units, the lying Blacks Fork Member and the Twin Buttes Member located in the hanging wall ; Both units can in turn be differentiated into a total of four sub-units ( Bridger A to D , two per unit). Numerous fossil material of this primeval Brontotheria representative comes from these two units, comprising a total of more than 40 individuals, including several, partly complete skulls. Other finds are known from the upper area of ​​the Huerfano Formation in Colorado , which is stratigraphically older, but also less well preserved than that from the Bridger Formation. Noteworthy are the teeth and dentition finds of Palaeosyops , which were found in the Margaret Formation on the west coast of Ellesmere Island in the far north of Canada and represent the northernmost finds of this genus. They show somewhat more modern developments than the finds from the mid-latitudes of the USA and probably immigrated from the south, possibly adapting to the conditions of polar night and polar day . All previously known finds in North America can be ascribed to the Middle Eocene from 46 to 50 million years ago (locally stratigraphically Bridgerium ). Outside North America, teeth and upper jaw finds from the Kuldana Formation near Ganda Kas in Pakistan were described in 2011 , which have been in the Munich Academy of Sciences since the first half of the 20th century and are also placed in the Middle Eocene.

Paleobiology

Palaeosyops possibly shows a sexual dimorphism in the skull structure . Male animals were characterized by a more robust skull with a clear and wider crest, which stood out at a sharp angle from the parietal bones. In contrast, those of female animals are more delicate, the crest is thinner and not so prominently set off from the parietal bones. There are also some individual variations in the structure of the molars, such as additional enamel folds, which were originally understood as expressing different genera. The molars also show typical cut patterns, which indicate a main diet of soft vegetable food ( browsing ), with leaves being dominant. A mixed vegetable diet could not be demonstrated. Palaeosyops lived in dense, partly rain-rich primeval forests.

Systematics

Internal systematics of the early Brontotheriidae according to Mihlbachler 2008 and Missiaen et al. 2011
  Brontotheriidae  

 Eotitanops


   

 Palaeosyops


   

 Balochititanops


   

 Bunobrontops


   

 Mesatirhinus


   

 younger Brontotheriidae







Template: Klade / Maintenance / Style

Palaeosyops is an extinct genus of the family of brontotheriidae , a primitive group of perissodactyls that in the vicinity of today due to the design of the molars horses will be provided. It turns palaeosyops is a fairly primitive form of Brontotherien and forms the Schwesterklade to all modern species of this family, only Eotitanops is as basaleres taxon classified. In his revision of the Brontotherien, Henry Fairfield Osborn placed Palaeosyops in the monotypical subfamily of the Palaeosyopinae in 1929 , this was rejected by Matthew C. Mihlbachler in 2008 , because possibly some unspecific fossils from Asia , previously only placed pro forma on Palaeosyops , would have to be included in this group . A revision by Bryn J. Mader from 2010 recognizes the subfamily as valid, however, without considering the Asian finds.

More than a dozen species have been described by Palaeosyops , the following are generally valid today:

Other species that were valid just a few years ago were described as P. laticeps and M. laevidens , the former was synonymous with P. robustus in 2010 , the latter with P. paludosus . P. dayi was originally placed near Eotitanops , but new assessments of the find material in 2011 revealed a closer relationship to Palaeosyops .

The first known finds of Palaeosyops comprised four individual mandibular and maxillary molars, which came to light at Church Buttes near Fort Bridger at the confluence of the Big Sandy River into the Green River in Wyoming together with other vertebrate fossils and can be assigned to the Bridger Formation. Joseph Leidy described this in 1870 and recognized similarities to Palaeotherium , an early equine, but also to Chalicotherium , an extinct odd-toed ungulate, closely related to the tapirs and rhinos , and to Titanotherium , a representative of Brontotherium, which is now equivalent to Megacerops . A skull presented by Othniel Charles Marsh in 1872 , which he assigned to the genus Limnohyus , is also identical to Palaeosyops , as is the term Limnohyops , which he coined in 1890 . In 1929, Osborn determined a lectotype that includes a second mandibular molar (specimen number USNM 759) based on the first material found . Also synonymous with Palaeosyops is the genus Eometarhinus established by Osborn in 1919 on the basis of a poorly preserved skull , which was originally seen as the ancestor of Metarhinus , but is now assigned to Palaeosyops .

literature

Individual evidence

  1. ^ Arthur Smith Woodward: Outlines of vertebrate palaeontology, for students of zoology. Cambridge, University Press, 1898, pp. 1-470 (332)
  2. ↑ a b c d e f g Bryn R. Mader: A species-level revision of the North American brontotheres Eotitanops and Palaeosyops (Mammalia, Perissodactyla). Zootaxa 2339, 2010, pp. 1-43
  3. ↑ a b c d e Bryn J. Mader: Brontotheriidae: A systematic revision and preliminary phylogeny of North American genera. In: Donald R. Prothero and Robert M. Schoch (Eds.): The evolution of perissodactyls. New York and London, 1989, pp. 458-484
  4. ↑ Matthew C. Mihlbachler, Spencer George Lucas, Robert J. Emry and Bolat Bayshashov: A New Brontothere (Brontotheriidae, Perissodactyla, Mammalia) from the Eocene of the Ily Basin of Kazakstan and a Phylogeny of Asian `` Horned '' Brontotheres. American Museum Novitates 3439, 2004, pp. 1-43
  5. ^ A b Peter Robinson: Fossil Mammalia of the Huerfano formation, Eocene, of Colorado. Bulletin of the Peabody Museum of Natural History 21, 1966, pp. 1-95
  6. ↑ Jaelyn J. Eberle: Early Eocene Brontotheriidae (Perissodactyla) from the Eureka Sound Group, Ellesmere Island, Canadian High Arctic - Implications for Brontothere origins and high latitude dispersal. Journal of Vertebrate Paleontology, 26 (2), 2006, pp. 381-386
  7. ↑ a b Jaelyn J. Eberle and David R. Greenwood: Life at the top of the Eocene greenhouse world - A review of the Eocene fl ora and fauna vertebrate from Canada's High Arctic. Geological Society of America Bulletin; January / February 124 (1/2), 2012, pp. 3–23
  8. ↑ Jaelyn J. Eberle and David A. Eberth: Additions to the Eocene Perissodactyla of the Margaret Formation, Eureka Sound Group, Ellesmere Island, Arctic Canada. Canadian Journal of Earth Sciences 52, 2015, pp. 123-133
  9. ↑ a b c d Pieter Missiaen, Gregg F. Gunnell and Philip D. Gringerich: New Brontotheridae (Mammalia, Perissodactyla) from the Early and Middle Eocene of Pakistan with implications for Mammalian palaeobiogeography. Journal of Paleontology 85 (4), 2011, pp. 665-677
  10. ^ Matthew C., Mihlbachler: Body size, dental microwear, and Brontotheres diets through the Eocene. Journal of Vertebrate Paleontology 22 (suppl.), 2002, p. 88A
  11. ^ A b 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
  12. ↑ Bryn J. Mader: Brontotheriidae In: Christine M Janus, Kathleen M Scott and Louis L Jacobs (eds.): Evolution of Tertiary mammals from North America, Vol. 1. Cambridge 1998, pp. 525-536
  13. ↑ Joseph Leidy: (On fossils of Church Buttes, Wyoming Territory). Proceedings of the Academy of Natural Sciences of Philadelphia 22, 1870, pp. 113-114

Web links

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