Cambaytherium

from Wikipedia, the free encyclopedia
Cambaytherium
Temporal occurrence
Lower Eocene
54.5 million years
Locations
Systematics
Mammals (mammalia)
Higher mammals (Eutheria)
Laurasiatheria
Scrotifera
Cambaytheriidae
Cambaytherium
Scientific name
Cambaytherium
Bajpai , Kapur , Das , Tiwari , Saravanan & Sharma , 2005

Cambaytherium is an extinct genus in the Cambaytheriidae family. It livedon the Indian subcontinent nearly 55 million years agoduring the Lower Eocene . Finds of Cambaytherium so far come only from the Cambay Shale Formation in western India and include more than 200 objects with remains of skulls, teeth and the body skeleton. The first scientific description of the genus as well as the family took place in 2005. Initially, an allocation to the base of the odd ungulate was favored, with some scientists alsosuggestinga position close to the proboscis within the Tethytheria . The new studies on the systematic relationshipscarried out on the extensive materialnow allow an assignment no longer to the basis of the odd ungulate, but to a close relationship to them. Finding the genus on the subcontinent, which at that time was an island and drifting north towards the Asian mainland mass, enables insights into the origin and early development of the odd ungulate, which, according to considerations, arose in Asia.

features

Cambaytherium was a medium-sized animal that, according to reconstructions, weighed around 20 to 35 kg, the size of today's peccary . The skull showed characteristics of the early odd-toed ungulates. This includes the only small nasal cavity. The nasal bone did not reach into the frontal bone , so that the bone seam between them ran clearly transversely to the longitudinal direction of the skull and both bones had a rather straight end. The orbit was above the posterior molars, which is different from the Tethytheria with their eye windows located very far forward in the skull. The zygomatic arch was fully developed. A closed symphysis appeared on the lower jaw , it reached approximately to the second premolar . The articular branches rose steeply so that the joints were clearly above the teeth. The bit consisted of the complete tooth number of early higher mammals and thus read: . The incisors were relatively small and spatulate or rounded in shape. The canine protruded well beyond the front teeth. There was a short diastema to the posterior dentition , as well as between the first and second premolar. The premolars as a whole showed no signs of molarization, so they were only slightly similar to the rear molars. Characteristic of the molars was the bumpy ( bunodonte ) structure of the chewing surface, whereby the cusps were relatively large and thus had a conical high shape. Two of the humps formed a row. Due to the structure of the cusps, the typical lophodontic teeth of the odd- toed ungulate (with transverse enamel ridges) did not yet exist . There were two rows of cusps on the first two molars, and the last molar had an additional third. The size of the molars increased backwards. The first molar in the lower jaw reached a length of 1.1 to 1.3 cm, the third from 1.5 to 1.9 cm.

The body skeleton showed a relatively robust design. The vertebral arches of the lumbar vertebrae, which articulate strongly with one another, are striking . The humerus was robust, but had a narrow lower joint end. The ulna was characterized by a strong upper joint end ( olecranon ) and a slightly curved barrel in the lower area. The spoke was positioned completely in front of the ulna. The thighbone is not fully known, but had a third trochanter, typical of odd-toed ungulates, as a muscle attachment point on the shaft. The tibia and fibula were not fused together. Fore and hind legs each ended in five rays, which differs from the early odd-toed ungulates. The inner rays of the forefoot and hind foot (ray I) may have already been greatly reduced in length, but so far they have only been demonstrated using the joint facets. The central ray of the hands and feet (ray III) each had the greatest length, with which the feet already showed the typical mesaxonic expression of the odd ungulate. Overall, the metapodia turned out to be very robust and short. The design of the terminal phalanges of the fingers and toes also indicates the presence of hooves. As a further indication of a close relationship with the odd-toed ungulates, the ankle bone had the saddle-shaped depression of the lower joint end that is characteristic of this group.

Fossil finds

Finds of cambaytherium come so far only from the Cambay Shale Formation in the western Indian state of Gujarat . The Cambay Shale Formation is 75 to 1500 m thick and is a fossil-rich rock deposit that contains the oldest vertebrate remains of the Cenozoic era on the subcontinent . It is largely exposed in the coal mines of Vastan and Mangrol around 40 km northeast of Surat . The formation consists of slate , clay and sandstones in which two layers of coal are embedded. The vertebrate remains came to light in thin clayey silts 5 m long and 30 cm thick, which are located around 1 to 3 m above the lowest coal seam. These lenses were formed under conditions close to the coast; their age has been dated to over 54 million years with the help of dinoflagellates and isotope studies . This corresponds to the Lower Eocene and is about 1.5 to 1 million years after the Paleocene / Eocene temperature maximum . The finds can be assigned to numerous early mammals , such as primates , even ungulates or rodents , but also lines that are now extinct such as the Tillodontia . In addition to mammals, birds , reptiles , amphibians and fish have also been identified.

Cambaytherium is relatively numerous within the vertebrate community . A total of over 120 jaw and tooth remains, including the skull of an adult and juvenile animal, and around 100 parts of the body skeleton, such as vertebrae and limb elements, have been found. The first discoveries of the genus largely comprised remains of dentition and isolated teeth and were made shortly after the first evidence of fossil-bearing layers. This was done at the beginning of the third millennium and resulted in intensive field research. On the basis of these on-site investigations, more extensive material could be discovered, which thus enables more precise statements on the systematic allocation.

Paleobiology

The entire body structure of Cambaytherium appears to be relatively robust and less adapted to fast- moving ( cursorial ) locomotion compared to the early odd-toed ungulates. The bumpy structure of the molars, on the other hand, generally speaks in favor of a more omnivorous diet. Analyzes of the teeth provided some details about the diet. Larger individuals of Cambaytherium , which belong to the species C. thewissi , show a high level of stress on the chewing surfaces, which began in the early individual development. In these, the cusps of the anterior molar teeth were already clearly chewed when the rearmost molar had reached its full height. In addition, according to the signs of wear, vertical chewing movements dominated over horizontal ones. It is therefore assumed that C. thewissi probably consumed tougher plant parts such as hard fruits or nuts . In the average smaller animals of the species C. gracilis these features are not as pronounced and the teeth are generally less robust. Here, softer plants predominated in the food spectrum.

Systematics

Systematic position of the Cambaytheriidae according to Rose et al. 2014


 Artiodactyla


   



 Phenacolophidae


   

 Phenacodontidae


   

 Radinskya




   

 Afrotheria ?



   
  Cambaytheriidae  

 Cambaytherium


   

 Nakusia



   

 Perissodactyla





Template: Klade / Maintenance / Style

Cambaytherium is a genus of the extinct family of Cambaytheriidae . Genus and family were first scientifically described together in 2005 by Sunil Bajpai and research colleagues . The basis for the initial description was formed by several lower and upper jaws as well as individual teeth from the Cambay Shale formation in the Indian state of Gujarat . The holotype (copy number IITR / SB / VLM 505) comprises a lower jaw on which the teeth from the last premolar to the last molar have been preserved on both the right and left. The name Cambaytherium is composed of the name for the Cambay Shale Formation, which in turn is named after the city of Khambhat (Cambay) and the Gulf of Khambhat , and the Greek word θηρίον ( thēríon "animal"). Today further genera are distinguished within the Cambaytheria. These include Kalitherium , which was described in 2006 based on a relatively complete skull also from the Cambay Shale Formation, as well as the basis of an upper jaw of Baluchistan in 1999 named Nakusia . Another genus, Indobune , was based on some parts of the upper jaw from the Cambay Shale Formation and was introduced in 2006, but according to recent studies it is to be regarded as identical to Cambaytherium .

Today two types of Cambaytherium are recognized:

C. gracilis is about 10 to 20% smaller in length than C. thewissi . Certain features of the anterior dentition and the mandibular symphysis rule out a sexual dimorphism as an explanation for the size differences, so that both types can be viewed as independent. In the first description of Cambaytherium , two other species, C. bidens and C. minor , were listed in addition to C. thewissi , but these are now assigned to C. thewissi . The species name thewissi honors JGM Thewissen for its work on fossil mammals from Indo-Pakistan. (The species name should correctly be thewisseni .)

In the first description, the Cambaytherium and the Cambaytheria were considered to be the original phylogenetic representatives of the odd ungulate , which are characterized by a bunodont chewing surface pattern of the molars. In addition to the high age of the formation, which dates back to the Lower Eocene , the fact that early odd-toed ungulates such as Cardiolophus or Hallensia also had teeth constructed in this way , however, Cambaytherium showed the most simply designed teeth within this group. The assignment was initially criticized by pointing out that the Anthracobunidae , which have largely only survived from Asia, had a similar chewing surface pattern, just as they had a third pair of cusps on the last molars. At that time the Anthracobunidae were only known through individual teeth and were actually considered to be more closely related to the proboscis . For this reason, the Indobune, originally seen as an independent, was described as a member of the Anthracobunidae. Another agent who with cambaytherium related close Nakusia already received above a position in the same group of mammals.

The extensive fossil material that has come to light since its first description and also contains postcranial skeletal elements now allows a more precise assessment of the systematic position of Cambaytherium and Cambaytheria. Accordingly, they represent close relatives of the odd ungulates, which can be recognized, among other things, by the indentation of the navicular joint at the lower end of the ankle bone , one of the defining characteristics of the odd ungulates, as well as the existing mesaxonic design of the hands and feet with a strong and elongated central ray. Individual connecting characteristics also occur on the skull, such as the transverse bone seam between the nasal and frontal bones . Other features, on the other hand, are original in the phylogenetic history and no longer occur in the odd-toed ungulates, such as the generally five-pointed hands and feet. The earliest odd-toed ungulates, on the other hand, had four rays in front and three rays in the back (analogous to today's tapirs ). Only Sifrhippus , the earliest known representative of the horse , still had a severely stunted outer beam on the hind foot. They refer to a descent from older lines of development that are to be found in the heterogeneous group of the " condylarthra ". Furthermore, there are no beginnings of transverse ridges on the chewing surfaces of the molars, which give them a bilophodontic character; the latter in turn is generally typical for odd ungulates. For this reason, the Cambaytheria and thus also Cambaytherium are seen today as a sister group of the odd-toed ungulates, and the Anthracobunidae are also in a very close relationship to the odd-toed ungulates. An almost similar relationship diagnosis was found in an almost simultaneous study based on material from the skull and mandible. Here, too, the Cambaytheriidae are closely related to the odd-toed ungulates and are regarded as "regular ungulates". According to this study, the semi-aquatic Desmostylia , to which a close relationship to the proboscis and thus to the Tethytheria are generally ascribed, should belong to the immediate family circle in addition to the Anthracobunidae .

The unpaired ungulates represented one of the most diverse groups of the higher mammals in their phylogenetic past . They appeared relatively suddenly at the beginning of the Lower Eocene around 56 million years ago in present-day North America as well as in Eurasia . An origin from the Asian area was often advocated. The finds of close relatives of the odd ungulates in the Cambay Shale Formation could support this view and limit the region of origin to South Asia . During the Lower Eocene, the Indian subcontinent was an island that moved north towards Asia after separating from Madagascar , the collision occurring 50 million years ago or later. A possible island bridge could have connected the island with the Afro-Arab land mass through which the ancestors of the odd-toed ungulates reached the Indian subcontinent. This would also explain the presence of some more original European forms, such as early primates or rodents , in the Cambay Shale Formation. At about the same time as these finds, early odd-toed ungulates appear in the Ghazij formation in Baluchistan , some of which still resemble Cambaytherium , but also include more developed forms of the early Tapiromorpha and Hippomorpha . Today's Balochistan is seen as an independent island, separated from the Indian subcontinent by a sea road. In order to examine and test these considerations more closely, however, fossil remains from the Paleocene are missing in both regions .

Individual evidence

  1. ↑ a b c d Sunil Bajpai, Vivesh Kapur, Debasis P. Das, BN Tiwari, N. Saravanan and Ritu Sharma: Early Eocene land mammals from Vastan Lignite Mine, District Surat (Gujarat), western India. Journal of the Palaeontological Society of India 50 (1), 2005, pp. 101-113
  2. ↑ a b c d e f g h i j Kenneth D. Rose, Luke T. Holbrook, Rajendra S. Rana, Kishor Kumar, Katrina E. Jones, Heather E. Ahrens, Pieter Missiaen, Ashok Sahni and Thierry Smith: Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications 5 (5570), 2014 doi : 10.1038 / ncomms6570
  3. ^ A b Kenneth D. Rose, Luke T. Holbrook, Rajendra S. Rana, Kishor Kumar, Katrina E. Jones, Heather E. Ahrens, Pieter Missiaen, Ashok Sahni and Thierry Smith: Early Eocene fossils suggest that the mammalian order Perissodactyla originated in India. Nature Communications 5 (5570), 2014 (suppl.)
  4. ↑ a b c d Kenneth D. Rose, Thierry Smith, Rajendra S. Rana, Ashok Sahni, H. Singh, Pieter Missiaen and A. Folie: Early Eocene (Ypresian) continental vertebrate assemblage from India, with description of a new anthracobunid ( Mammalia, Tethytheria). Journal of Vertebrate Paleontology 26 (1), 2006, pp. 219-225
  5. ↑ Rahul Garg, Khowaja-Ateequzzaman, Vandana Prasad, SKM Tripathi, IB Singh, AK Jauhri and S. Bajpai: Age-diagnostic dinoflagellate cysts from lignite-bearing sediments of the Vastan lignite mine, Surat District, Gujarat, western India. Journal of the Palaeontological Society of India 53 (1), 2008, pp. 99-105
  6. ↑ Mark Clementz, S. Bajpai, V. Ravikant, JGM Thewissen, N. Saravanan, IB Singh and V. Prasad: Early Eocene warming events and the timing of terrestrial faunal exchange between India and Asia. Geology 39 (1), 2011, pp. 15-18
  7. ↑ Kenneth D. Rose, Rajendra S. Rana, Ashok Sahni, Kishor Kumar, Pieter Missiaen, Lachham Singh and Thierry Smith: Early Eocene Primates from Gujarat, India. Journal of Human Evolution 56, 2009, pp. 366-404
  8. ↑ Kishor Kumar, Kenneth D. Rose, Rajendra S. Rana, Lachham Singh, Thierry Smith and Ashok Sahni: Early Eocene Artiodactyls (Mammalia) from Western India. Journal of Vertebrate Paleontology 30 (4), 2010, pp. 1245-1274
  9. ↑ Rajendra S. Rana, Kishor Kumar, Gilles Escarguel, Ashok Sahni, Kenneth D. Rose, Thierry Smith, Hukam Singh and Lachham Singh: An Ailuravine Rodent from the Lower Eocene Cambay Formation at Vastan, Western India, and Its Palaeobiogeographic Implications. Acta Palaeontologica Polonica 53 (1), 2008, pp. 1-14
  10. ↑ Kenneth D. Rose, Kishor Kumar, Rajendra S. Rana, Ashok Sahni and Thierry Smith: New Hypsodont Tillodont (Mammalia, Tillodontia) from the Early Eocene of India. Journal of Paleontology 87 (5), 2013, pp. 842-853
  11. ↑ a b c d Thierry Smith, Kishor Kumar, Rajendra S. Rana, Annelise Folie, Floréal Solé, Corentin Noiret, Thomas Steeman, Ashok Sahni and Kenneth D. Rose: New early Eocene vertebrate assemblage from western India reveals a mixed fauna of European and Gondwana affinities. Geoscience Frontiers, 2016 doi: 10.1016 / j.gsf.2016.05.001
  12. ^ A b Sunil Bajpai, Vivesh Kapur, JGM Thewissen, Debasis P. Das and BN Tiwari: New Early Eocene cambaythere (Perissodactyla, Mammalia) from the Vastan Lignite Mine (Gujarat, India) and an evaluation of cambaythere relationships. Journal of the Palaeontological Society of India 51 (1), 2006, pp. 101-110
  13. ↑ a b c Pieter Missiaen, Kenneth Rose, Heather Ahrens, Kishor Kumar and Thierry Smith: Revision of Indobune and Cambaytherium from the early Eocene of Vastan (India), and their affinities with anthracobunid and perissodactyl mammals. Journal of Vertebrate Paleontology 31 (suppl.), 2011, p. 159
  14. ↑ Wighart von Koenigswald, Kenneth D. Rose, Luke T. Holbrook, Kishor Kumar, Rajendra S. Rana and Thierry Smith: Mastication and enamel microstructure in Cambaytherium, a perissodactyl-like ungulate from the early Eocene of India. Paleontological Journal, 2018 doi: 10.1007 / s12542-018-0422-8
  15. ↑ a b Léonard Ginsburg, Khadim Hussain Durrani, Akhtar Mohammad Kassi and Jean-Loup Welcomme: Discovery of a new Anthracobunidae (Tethytheria, Mammalia) from the Lower Eocene lignite of the Kach-Harnai area in Baluchistan (Pakistan). Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science 328 (3), 1999, pp. 209-213
  16. ↑ a b Kishor Kumar: Comments on 'Early Eocene land mammals from Vastan Lignite Mine, District Surat (Gujarat), western India' by Bajpai, S. et al. published in Journal of the Palaeontological Society of India 50, 1: 101-113, 2005. Palarch 1 (2), 2006, pp. 7-13
  17. ↑ Lisa Noelle Cooper, Erik R. Seiffert, Mark Clementz, Sandra I. Madar, Sunil Bajpai, S. Taseer Hussain and JGM Thewissen: Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls. PlosONE 9 (10), 2014, p. E109232
  18. ↑ Pieter Missiaen and Philip D. Gingerich: New Early Eocene Tapiromorph Perissodactyls from the Ghazij Formation of Pakistan, with Implications for Mammalian Biochronology in Asia. Acta Palaeontologica Polonica 57 (1), 2012, pp. 21-34
  19. ^ Pieter Missiaen and Philip D. Gingerich: New basal Perissodactyla (Mammalia) from the Lower Eocene Ghazij Formation of Pakistan. Contributions from the Museum of Paleontology, University of Michigan 32 (9), 2014, pp. 139-160