Propterodon

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Propterodon
Lower jaw of Propterodon, holotype specimen of P. witteri

Lower jaw of Propterodon , holotype specimen of P. witteri

Temporal occurrence
Middle Eocene
47.8 to 38 million years
Locations
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Ferae
Hyaenodonta
Hyaenodontidae
Propterodon
Scientific name
Propterodon
Martin , 1906

Propterodon is a genus from the extinct group of Hyaenodonta . Finds have comedown to usfrom East and Southeast Asia as well as North America . These are largely fragmented bits of teeth. They date to the Middle Eocene or the transition to the Upper Eocene and are thought to be between 45 and 37 million years old. The animals were characterized by hypercarnivorous teeth, which indicates a predominantly meat-based diet. The genus was introduced in 1906, but a more detailed description was only given around twenty years later. Several species are distinguished within the genus.

features

Propterodon is a smaller representative of the Hyaenodonta, but is currently only known through remains of teeth. The lower jaw is incomplete, the anterior teeth are largely not preserved. The horizontal bony body was elongated and built straight. The symphysis between the anterior ends of the jaw reached back to the third premolar . A double mental foramen lay below the first and third premolars. On the ascending branch, a strong masseteric fossa was formed as a muscle attachment point, which digged deep into the bone and whose front end emerged as a sharp edge just behind the last molar . The front edge of the ascending branch rose at an obtuse angle of 120 to 130 ° relative to the plane of the tooth. The crown process was far above the occlusal plane and probably towered over the articular process. The latter was flush with the ascending branch and was not delimited by a neck or throat. The angular process at the posterior end of the lower jaw was not clearly extended. It pointed backwards and went up in a straight edge into the articular process. Only on the lower edge was there a slight indentation between the angular process and the horizontal bone body.

The posterior lower dentition consisted of four premolars and three molars. The molars were closed, while small gaps appeared between the premolar teeth. The premolars were defined by a high hump, the protoconid. The point of this was clearly oriented upwards and did not dip backwards. It grew larger towards the posterior premolars. Individual minor humps also appeared here. Three pointed humps dominated the molars (paraconid, protoconid, metaconid), which together formed the trigonid. This rose well above the talonid, a lower-lying area of ​​the occlusal surface. In Propterodon the trigonid was much more extensive than the talonid, which was increasingly developed from the foremost to the rearmost molar. In contrast to Hyaenodon , there was an extremely short talonid on the rear molar tooth. The protoconid towered over the paraconid and thus represented the largest hump. Both peaks were fused to each other about halfway up. In contrast to this, in Oxyaenoides both tips were separate. The metaconide, on the other hand, was greatly reduced in size in Propterodon and became smaller towards the posterior molar. It was partially connected to the protoconid and sometimes only acted as a small elevation on the edge of the protoconid. In the case of Furodon , the metaconide was much stronger and was not attached to the protoconid as high. In contrast to this, Oxyaenoides completely lacked the metaconide. The talonid, in turn, was dominated by a prominent but flat hypoconid. The teeth grew larger from front to back. The second molar was 11 mm long and 5.4 mm wide, while the third molar was 13.5 mm long and 6.2 mm wide. This feature is similar Propterodon about Furodon , but differs from some other Hyaenodonta as Pyrocyon or Tritemnodon from.

Fossil finds

The parts of the upper and lower jaw present from Propterodon are rather isolated and widely scattered. They came to light in both East and Southeast Asia and North America . The most extensive material at the moment comes from the Irdin Manha Formation in Inner Mongolia and the Hedi Formation in the Yuanqu Basin in the Chinese province of Shanxi . Both rock units belong to the Middle Eocene and were thus roughly formed in a period from 45 to 40 million years ago. The material found here consists of several remains of the upper and lower jaw, including parts of a juvenile, i.e. not fully grown, animal from the Irdin Manha formation. While only individual teeth are preserved in most parts of the dentition, the lower jaw from the Hedi formation still has the complete posterior teeth from the first premolar to the last molar. Apart from this find area, the Pondaung Formation in Myanmar hid a single branch of the lower jaw, the front part of which is largely missing. The Pondaung Formation is somewhat younger than the East Asian discovery areas. It was formed in the late Middle Eocene, and assumed age dates range from 40 to 37 million years ago. Again comparable to the age of Propterodon in East Asia is the only find from North America so far. It is a posterior remnant of the lower jaw from the Uinta formation in the US state of Utah .

Paleobiology

The only short talonid and the greatly reduced metaconid distinguish the teeth of Propterodon as hypercarnivorous. It has thus largely lost its perforating (Metaconid) or breaking (Talonid) function and is mainly suitable for cutting. As a rule, hypercarnivorous dentition indicates an increased consumption of carnal food based on vertebrates .

Systematics

Internal systematics of the Hyaenodontidae according to Solé & Mennecart 2019
  Hyaenodontoidea  
  Hyaenodontidae  



 Preregidens


   

 Leonhardtina



   


 Matthodon


   

 Oxyaenoides


   


 Thereutherium


   

 Prionogalidae



  Hyaenodontinae  

 Propterodon


   

 Hyaenodon






   


 Prodissopsalis


   

 Cartierodon



   

 Eurotherium





   
  " Cynohyaenodon clade"  


 Paracynohyaenodon


   

 Quercytherium



   

 Cynohyaenodon



   

 Boritia




   

 Proviverrinae



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Propterodon is a genus from the extinct order of Hyaenodonta . Originally, the Hyaenodonta were placed in the group of Creodonta , which in German carry the sometimes somewhat misleading trivial designation "primal predators". The Creodonta were once considered to be the sister group of today's carnivores within the parent taxon of the Ferae . However, several consistent phylogenetic studies led to the view that the Creodonta are not a self-contained group. They were therefore split into the Hyaenodonta and the Oxyaenodonta . As a characteristic of both groups, a crushing shear that is shifted further back in the teeth compared to the predators can be emphasized. In the hyaenodonts, this mostly consists of the second upper and third lower molars. The hyaenodonts appeared in fossils as early as the Middle Paleocene around 60 million years ago, while recent specimens point to the Middle Miocene around 9 to 10 million years ago.

The genus Propterodon was first scientifically described in 1906 by Rudolf Martin in a survey of the paleogenic Creodonts in Europe . He was referring to the elaborations by Ludwig Rütimeyer on the mammal fauna of the Upper Ocene site of Egerkingen from 1892, in which he presented a lower jaw and assigned it to Pterodon , but without referring to a specific species. Martin then recognized significant differences to Pterodon , on the one hand with regard to the general size, since the Egerking lower jaw is markedly smaller than other Pterodon finds , on the other hand also in the special tooth structure. Therefore, Martin suggested the name Propterodon . Analogous to Rütimeyer, however, Martin failed to define a type species . Due to the lack of reference to a species, the genus Propterodon had the status of a noun nudum (the lower jaw discussed by Rütimeyer was later referred to as Prodissopsalis ). A formal definition was only given in 1925 by William Diller Matthew and Walter W. Granger , when both authors evaluated finds from the Irdin Manha Formation in Inner Mongolia , which were collected during the “Third Asiatic Expedition” of the American Museum of Natural History had been.

In their redefinition of the genus Propterodon in 1925, Matthew and Granger established the species P. irdinensis on the basis of several jaw fragments (specimen number AMNH 20128). According to the regulations of the zoological nomenclature , this would therefore be regarded as the first named species within the genus Propterodon as its type form. The problem with this, however, is that Matthew and Granger had already defined Paracynohyaenodon morrisi a year earlier, a species based on a lower jaw of a non-adult individual (specimen number AMNH 19160) also from the Irdin Manha formation. After investigations by Leigh Van Valen around 40 years later, this species then turned out to be identical to P. irdinensis . According to the priority rule, according to which the first given species name is also the valid one, P. morrisi is to be regarded as the recognized type form of Propterodon . P. tongi , introduced in 2002 by Liu Liping and Huang Xueshi via a lower jaw from the Hedi formation , is smaller compared to P. morrisi and has more hypercarnivorous dentition. The species P. panganensis from the Pondaung formation by Louis de Bonis and colleagues presented in 2018 on the basis of a lower jaw is also characterized by a clearly hypercarnivorous dentition, but the teeth have individual special features that make a comparison with other Propterodon representatives currently complicate. With P. witteri there is also a North American form. It was described in 2019 by Shawn P. Zack from the Uinta formation . Due to the dimensions of the preserved fossil, it is the largest known species of the genus to date.

The following species can therefore be assigned to the genus Propterodon :

Another species was created by Demberelyin Dashzeveg with P. rechetovi in 1985. He was referring to two parts of the upper jaw from the Kaichin formation in Mongolia , which roughly corresponds to the Irdin Manha formation. The species was later transferred to the new genus Neoparapterodon , but Michael Morlo and Jörg Habersetzer noted in 1990 that the structure of the maxillary teeth is identical to P. morrisi and that both forms are therefore synonymous . P. pishigouensis also comes from East Asia and was named in 1986. The lower jaw fragment with two teeth from the Hetaoyuan Formation in the Chinese province of Henan shows only a few matches with the genus Propterodon in particular and the Hyaenodonta in general; the species was moved to Apataelurus within the Oxyaenodonta in 2019 .

Originally Propterodon was placed in the subfamily of the Proviverrinae . The prominent metaconid on the molars of the lower jaw and the separation of the metaconus from the paraconus on those of the upper jaw can be cited as special characteristics of the Proviverrinen. Until the 1990s, the Proviverrinen combined a larger part of the forms of the Lower and Middle Eocene and held the status of a generalized group. However, in the first phylogenetic studies they turned out to be paraphyletic and showed a more complex relationship. Therefore, in the following period, several authors tried to find a coherent structure of the Proviverrinae. Floreal Solé and colleagues separated out individual kin groups such as the Arfiinae, Sinopinae and Indohyaenodontinae in 2013 and 2014. The Proviverrinae restricted them to an original, more European strain. In the case of Propterodon , the lower molars lack the metaconide, which is to be regarded as an expression of the hypercarnivorous dentition. The genus was then moved to the Hyaenodontinae and placed on the side of Hyaenodon . Later phylogenetic studies could confirm this. In principle, there is a certain similarity in dental construction to Matthodon , which is documented from the Middle Eocene of the Geiseltal and thus the European area. But these are probably adaptations to similar ways of life.

literature

  • Liu Liping and Huang Xueshi: Propterodon (Hyaenodontidae, Creodonta, Mammalia) from the middle Eocene of Yuanqu Basin, Shanxi, China. Vertebrata PalAsiatica 40, 2002, pp. 133-138
  • William Diller Matthew and Walter Granger: New mammals from the Irdin Manha Eocene of Mongolia. American Museum Novitates 198, 1925, pp. 1-10
  • Shawn P. Zack: The first North American Propterodon (Hyaenodonta: Hyaenodontidae), a new species from the late Uintan of Utah. PeerJ 7, 2019, p. E8136, doi: 10.7717 / peerj.8136

Individual evidence

  1. ↑ a b c d Liu Liping and Huang Xueshi: Propterodon (Hyaenodontidae, Creodonta, Mammalia) from the middle Eocene of Yuanqu Basin, Shanxi, China. Vertebrata PalAsiatica 40, 2002, pp. 133-138
  2. ↑ a b c d Louis de Bonis, Floreal Solé, Yaowalak Chaimanee, Aung Naing Soe, Chit Sein, Vincent Lazzari, Olivier Chavasseau and Jean-Jacques Jaeger: New hyaenodonta (Mammalia) from the middle Eocene of Myanmar. Comptes Rendus Palevol 17 (6), 2018, pp. 357-365
  3. ↑ a b c d e f Shawn P. Zack: The first North American Propterodon (Hyaenodonta: Hyaenodontidae), a new species from the late Uintan of Utah. PeerJ 7, 2019, p. E8136, doi: 10.7717 / peerj.8136
  4. ^ A b William Diller Matthew and Walter Granger: New Carnivora from the Tertiary of Mongolia. American Museum Novitates 104, 1924, pp. 1-9
  5. ^ A b c William Diller Matthew and Walter Granger: New mammals from the Irdin Manha Eocene of Mongolia. American Museum Novitates 198, 1925, pp. 1-10
  6. ↑ a b c d Floréal Solé, Jocelyn Falconnet and Laurent Yves: New proviverrines (Hyaenodontida) from the early Eocene of Europe; phylogeny and ecological evolution of the Proviverrinae. Zoological Journal of the Linnean Society 171, 2014, pp. 878-917
  7. ↑ a b Floréal Solé and Bastien Mennecart: A large hyaenodont from the Lutetian of Switzerland expands the body mass range of the European mammalian predators during the Eocene. Acta Palaeontologica Polonica 64, 2019, doi: 10.4202 / app.00581.2018
  8. ↑ Kenneth D. Rose: The beginning of the age of mammals. Johns Hopkins University Press, Baltimore, 2006, pp. 1–431 (pp. 122–126)
  9. ↑ Michael Morlo, Gregg Gunnell, and P. David Polly: What, if not nothing, is a creodont? Phylogeny and classification of Hyaenodontida and other former creodonts. Journal of Vertebrate Paleontology 29 (3 suppl), 2009, p. 152A
  10. ↑ a b c Floréal Solé: New proviverrine genus from the Early Eocene of Europe and the first phylogeny of Late Paleocene-Middle Eocene hyaenodontidans (Mammalia). Journal of Systematic Paleontology 11, 2013, pp. 375-398
  11. ↑ Floréal Solé, Eli Amson, Matthew Borths, Dominique Vidalenc, Michael Morlo and Katharina Bastl: A new large hyainailourinae from the Bartonian of Europe and its bearings on the evolution and ecology of massive hyaenodonts (Mammalia). PLoS ONE 10 (9), 2015, p. E0135698, doi: 10.1371 / journal.pone.0135698
  12. ↑ a b Matthew R. Borths, Patricia A. Holroyd and Erik R. Seiffert: Hyainailourine and teratodontine cranial material from the late Eocene of Egypt and the application of parsimony and Bayesian methods to the phylogeny and biogeography of Hyaenodonta (Placentalia, Mammalia). PeerJ 4, 2016, p. E2639 doi: 10.7717 / peerj.2639
  13. ↑ Rudolf Martin: Revision of the upper and lower oligocene Creodonts of Europe. Revue Suisse de Zoologie 14, 1906, pp. 405–500 (p. 455) ( [1] )
  14. ^ A b c Leigh Van Valen: Some European Proviverrini (Mammalia, Deltatheridia). Palaeontology 8 (4), 1965, pp. 638-665, here: pp. 653-658.
  15. ^ A b Paul David Polly and Brigitte Lange-Badré: A new genus Eurotherium (Mammalia, Creodonta) in reference to taxonomic problems with some Eocene hyaenodontids of Eurasia. Comptes Rendus de l'Académie des Sciences Paris Série 2 317, 1993, pp. 991-996
  16. ↑ a b c Michael Morlo and Jörg Habersetzer: The Hyaenodontidae (Creodonta, Mammalia) from the Lower Eocene (MP 11) of Messel (Germany) with special remarks on new x-ray methods. Courier Forschungsinstitut Senckenberg 216, 1999, pp. 31–73
  17. ↑ Tong Yongsheng and Lei Yizhen: Fossil creodonts and carnivores (Mammalia) from the Eocene of Hetaoyuan Henan. Vertebrata PalAsiatica 24, 1986, pp. 210-221
  18. ^ A b Rajendra S. Rana, Kishor Kumar, Shawn P. Zack, Floreal Solé, Kenneth D. Rose, Pieter Missiaen, Lachham Singh, Ashok Sahni and Thierry Smith: Craniodental and Postcranial Morphology of Indohyaenodon raoi from the Early Eocene of India, and Its Implications for Ecology, Phylogeny, and Biogeography of Hyaenodontid Mammals. Journal of Vertebrate Paleontology 35 (5), 2015, p. E965308, doi: 10.1080 / 02724634.2015.965308

Web links

Commons : Propterodon  - collection of images, videos and audio files