Harington Hippus

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Harington Hippus
Skull of Harington Hippus, the lower one represents the holotype

Skull of Haringtonhippus , the lower is the holotype is

Temporal occurrence
Middle to Upper Pleistocene
0.781 to 0.012 million years
Locations
  • North America
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Horses (Equidae)
Equinae
Harington Hippus
Scientific name
Harington Hippus
Heintzman , Zazula , MacPhee , Scott , Cahill , McHorse , Kapp , Stiller , Wooler , Orlando , Southon , Froese & Shapiro , 2017

Haringtonhippus is an extinct genus ofthe horse family . It wascommonin North America during the Pleistocene . They are lightly built horses that reached the size of the Asiatic donkey . Her long and slender foot was striking, which distinguishes her from the other, more broad-footed horses on the North American continent. Originally, the animals thatbelongto Haringtonhippus today wereincluded in the genus Equus and referred to the slender foot as stilt-legged horses . Scientists initially assumed a closer relationship to the Asiatic donkey, but genetic studies at the beginning of the 21st century then suggested a closer relationship with the wild horse - domestic horse line. Further genetic analyzes from 2017 then led to the establishment of an independent genus.

features

The genus Haringtonhippus was defined according to genetic data, a morphological - anatomical description was not given. It includes lightly built horses the size of the Asiatic donkey ( Equus hemionus ). Weight estimates range from 167 to 251 kg and 368 kg, respectively. In the holotype of the genus, the skull measured 43.8 cm in length, its width was 17.5 cm at the level of the orbit . The facial skull took up about three quarters of the total length. The nasal bone again extended about a quarter of the total length. The lower jaw was 38 cm high and around 7 cm in the area of ​​the first molar . The bit corresponded to that of today's horses, the upper row of molars reached a length of 13.5 cm, which corresponded to about 30.5% of the length of the skull. This is significantly shorter than the Asian donkey. The tortuous enamel pattern on the chewing surface of the molars was less complex. In terms of physique, Haringtonhippus corresponded to today's horses. As with these, the fore and hind feet each consisted of only one ray (ray III), but the toe rays II and IV, which were attached to the side, were still rudimentary as stylus legs . The metatarsal bone is characteristic , in Harington hippus it had lengths of 25.1 to 29.0 cm and a diameter of 2.2 to 3.0 cm, so it had an overall slender structure. Comparable to this is the metatarsus of the Asian donkey, whose lengths vary between 23.6 to 27.0 cm, the diameter is 2.4 to 3.1 cm. The extinct horse form Equus lambei has a much more robust metatarsal bone with lengths of 23.4 to 26.7 cm and a diameter of 2.7 to 3.5 cm. Even more massive is that of the also extinct Equus scotti , the corresponding values ​​are 27.3 to 31.1 cm in length and 2.9 to 3.8 cm in diameter.

Fossil finds

Haringtonhippus is only known from the Pleistocene of North America . There the genus could be detected from Texas in the south to the Yukon Territory in the north. These include the extensive fossil material from the Natural Trap Cave in Wyoming or the Gypsum Cave in Nevada or the Dry Cave in New Mexico . The northernmost finds so far come from the region of the Klondike River in the Yukon Territory. Horses with similarly designed narrow feet but uncertain allocation are also known from Fairbanks in Alaska . A problem is a tooth from the San Josecito cave in the Mexican state of Nuevo León , which genetically falls within the range of Harington hippus, but was morphologically assigned to the broad-footed species Equus conversidens , whether the find is due to a mixed material or shows a certain plasticity within the horse representatives is unclear. The consideration of the other finds would expand the geographic range of Haringtonhippus . With the exception of a partial skeleton from the Lissie Formation in southern Texas, which dates to the Middle Pleistocene , all other known finds come from the Upper Pleistocene . However, narrow-footed horses are already known in North America from the transition from the Pliocene to the Lower Pleistocene , but they often reached larger dimensions than the later forms. A safe position in the genus Haringtonhippus has not yet been given. The most recent finds from northern North America date radiometrically to around 14,400 years BP ( 14 C years), in southern North America the corresponding values ​​are 13,100 years BP.

Systematics

Internal systematics of modern horses according to Heintzman et al. 2017
  Equini  

  Equus  
  non-caballines  




 Equus kiang (Kiang)


   

 Equus hemionus (Asian donkey)



   

 Equus asinus (African donkey)



   


 Equus quagga (plains zebra)


   

 Equus grevyi (Grevy's zebra)



   

 Equus zebra (mountain zebra)




   

 Equus ovodovi † ( Sussemiones )



  caballines  

 Equus caballus (domestic / wild horse)



   

 Haringtonhippus † ( New World stilt-legged horses )



   

 Hippidion †



Template: Klade / Maintenance / Style

Haringtonhippus is an extinct genus of the family of Equidae (horses). Within this, it is placed in the more modern subfamily Equinae , whose members are characterized by better adaptation to grass food and thus developed high-crowned ( hypsodontal ) teeth. Here again the genus belongs to the tribe of the Equini and the sub- tribus of the Pliohippina . The Pliohippina are composed of the modern, single-hoofed horses, a characteristic that all modern representatives of the genus Equus have. Opposite them are the Protohippina , which are a bit more primitive and still have three toes and differ in individual skull and tooth features. The representatives of the genus Equus are considered to be the closest relatives of Harington hippus , although this is based on both morphological and molecular genetic data. It should be noted that there is no genetic material for other very closely related species of horses such as Dinohippus . According to the genetic data, Harington hippus separated from the Equus line in the transition from the Miocene to the Pliocene 5.7 to 4.1 million years ago . Today's horses diversified into a caballine (wild / domestic horse) and a non-caballine line (donkey / zebra) between 4.5 and 4.0 million years ago. Even before 7.66 to 5.15 million years ago, the predominantly had South America derived hippidion from the common ancestor with Haringtonhippus and Equus split.

The generic name Haringtonhippus was introduced in 2017 by Peter D. Heintzman and fellow researchers. It is based on the genetic knowledge that the narrow-footed horses of North America, often referred to as stilt-legged horses , do not belong to the genus Equus , but rather form the sister group to it. The name Haringtonhippus was chosen in honor of Charles Richard Harington , who in 1973 first described narrow-footed horses from the eastern part of the Beringia , but then associated them with the Kiang . The only recognized species is Harington hippus francisci . It goes back to Equus francisci by Oliver Perry Hay from 1915. Hays Art is based on a full skull and partial skeleton from the Lissie Formation in Wharton County , Texas . The specimen described by Hay now forms the holotype of the new genus (specimen number TMM 34-2518). The holotype was not genetically determined to belong to Harington hippus, its assignment is based on morphological aspects. According to morphological considerations, some authors see Haringtonhippus embedded within the genus Equus and thus classify both as synonymous with each other.

To the New World stilt-legged horses

Metatarsal bones of different horse forms: above: Haringtonhippus francisci , middle: Equus lambei , below: Equus scotti , scale 5 cm

The origin of modern horses lies in North America, where numerous forms emerged in the transition from the Miocene to the Pliocene . The first representatives of the genus Equus can be detected in the course of the Pliocene, for example from the Ringold Formation in the US state of Washington or the Hagerman local fauna of Idaho , both sites originating around 3.5 million years ago. In the period from the late 19th century to the second half of the 20th century, numerous species of extinct horses were described for the North American continent; their number rose to almost 60 by the 1980s. In 1970, Ernest L. Lundelius and Margaret S. Stevens recognized that the horses of Pleistocene North America can be divided into two groups of shapes based on the structure of the foot. Accordingly, one group consists of horses with short and broad, the other of horses with long and narrow metatarsal bones . In the latter corresponding to the metatarsal in its dimensions and proportions of the Asian donkey ( Equus hemionus ) or the Kiangs ( Equus Kiang ). Lundelius and Stevens referred to the narrow-footed horses as stilt-legged horses (for example, " stilt-legged horses ") and established Equus francisci as the type form . The shape goes back to Oliver Perry Hay , who introduced it in 1915 using a complete skull and partial skeleton from the Lissie Formation in Wharton County , Texas . The finds, which belong to the Middle Pleistocene , had been excavated two years earlier by a farmer and shortly afterwards secured by Mark Francis, a professor at the Agricultural and Mechanical College of Texas (Hay named his species after him). Hay presented a comprehensive description of the material and made numerous comparisons with today's horses, but he reconstructed the foot incorrectly, which Lundelius and Stevens only corrected about half a century later.

Equus francisci was synonymous with Equus conversidens in 1965 by Walter W. Dalquest and Jack T. Hughes with reference to a similar dental structure . Richard Owen had already established the species in 1869 with the help of a skull fragment from the valley of Mexico , but it has a short and wide metatarsus , as Lundelius and Stevens worked out when correcting the foot of Equus francisci . At the same time, they also recognized differences in the structure of the teeth during their examinations. In Equus francisci , the enamel band on the lower posterior molar between the metaconid and metastylid has a narrow V -shape (which is often associated with zebras and donkeys), while in Equus conversidens it is openly U-shaped (often as Characteristic of caballiner horses interpreted). The two authors assigned other narrow-footed forms from North America such as Equus quinni (Dallas, Texas) and Onager zoyatalis (Mexico) to the stilt-legged horses , which they regarded as synonyms for Equus francisci . In the following period, individual scientists took over the opinion and confirmed the occurrence of a broad-footed and a narrow-footed species in North America. However, there were different views on the naming of the stilt-legged horses , as Equus calobatus by Edward L. Troxell in 1915 or Equus tau by Owen in 1869, among others , were preferred. In most cases, however, it was a question of taxa that were based on inadequate descriptions or less informative finds, or whose type material had been lost. In subsequent studies, Equus francisci turned out to be the oldest available name. In 1989 Melissa C. Winans summarized all stilt-legged horses in the " Equus francisci group" in a comprehensive analysis of the modern horses of North America . This combined forms such as Equus altidens , Equus arellanoi , Equus calobatus , Equus quinni and Equus zoyatalis . As a definition, she gave a length-to-width ratio of the metacarpal bone of 5: 1 and the metatarsal bone of 6: 1.

In their work, Lundelius and Stevens saw the stilt-legged-horses as a group of horses limited to southern North America. Only a little later, similar narrow-footed horses could also be described from the northern part of North America, for example from Gold Run Creek south of Dawson in the Yukon Territory , so that the distribution area expanded to the largest part of the North American land mass. Most scientists of that time brought the stilt-legged-horses in connection with the Asian donkeys, which was partly expressed through the use of the subgenus Hemionus , and viewed them as immigrants from the Asian region. Genetic studies on fossil material combined with the analysis of recent species, however, showed a different picture at the beginning of the 21st century. It turned out that the stilt-legged horses form a monophyletic group that is opposed to the caballine horses as a sister group . There was no connection to the Asian donkey or other recent non-caballine horse species of Eurasia, so the stilt-legged horses obviously had not crossed the Bering Bridge . Furthermore, the investigations did not reveal a closer relationship to various extinct horses of Eurasia and North America, as these fell directly into the range of variation of the caballine horses. For this reason, the narrow-footed horses of North America were seen as an endemic group of the continent and clearly referred to as New World stilt-legged horses (NWSL). Subsequently, this could be confirmed with several further genetic investigations, among other things, a closer relationship with the extinct South American equus representatives (often belonging to the Amerhippus subgenus ) could not be proven, since these also belong to the caballine horses. The analyzes were mostly based on incomplete DNA sequences. Studies of complete gene sequences carried out in 2017 revealed a position of the stilt-legged horses as a sister group of the horse / zebra / donkey clade, which is why they were moved to the new genus Haringtonhippus . According to this, Harington Hippus and Equus seem to have been present in North America up to the end of the Pleistocene , similar to what is shown for South America with Hippidion and Equus . The morphological similarities with some representatives of the genus Equus , such as the long, narrow legs of the Asian donkey, have thus developed independently of one another.

literature

  • Peter D. Heintzman, Grant D. Zazula, Ross DE MacPhee, Eric Scott, James A. Cahill, Brianna K. McHorse, Joshua D. Kapp, Mathias Stiller, Matthew J. Wooller, Ludovic Orlando, John Southon, Duane G. Froese and Beth Shapiro: A new genus of horse from Pleistocene North America. eLife 6, 2017, p. e29944 doi: 10.7554 / eLife.29944

Individual evidence

  1. ↑ Eduardo Jiménez-Hidalgo, Gerardo Carbot-Chanona, Rosalía Guerrero-Arenas, Victor Manuel Bravo-Cuevas, Genevieve Safi Holdridge and Isabel Israde-Alcántara: Species Diversity and Paleoecology of Late Pleistocene Horses From Southern Mexico. Frontiers in Ecology and Evolution 7, 2019, p. 394, doi: 10.3389 / fevo.2019.00394
  2. ^ Maria Teresa Alberdi, José L. Prado and Edgardo Ortiz-Jaureguizar: Patterns of body size changes in fossil and living Equini (Perissodactyla). Biological Journal of the Linnean Society 54, 1995, pp. 349-370
  3. ↑ a b Oliver P. Hay: Contributions to the knowledge of the mammals of the Pleistocene of North America. Proceedings of the United States National Museum 48, 1915, pp. 515-575 ( [1] )
  4. ↑ a b c d e f g Peter D. Heintzman, Grant D. Zazula, Ross DE MacPhee, Eric Scott, James A. Cahill, Brianna K. McHorse, Joshua D. Kapp, Mathias Stiller, Matthew J. Wooller, Ludovic Orlando , John Southon, Duane G. Froese, and Beth Shapiro: A new genus of horse from Pleistocene North America. eLife 6, 2017, p. e29944, doi: 10.7554 / eLife.29944
  5. ↑ Christina I. Barrón-Ortiz, Antonia T. Rodrigues, Jessica M. Theodor, Bryan P. Kooyman, Dongya Yang and Camilla F. Speller: Cheek tooth morphology and ancient mitochondrial DNA of late Pleistocene horses from the western interior of North America: Implications for the taxonomy of North American Late Pleistocene Equus. PLoS ONE 12 (8), 2017, p. E0183045, doi: 10.1371 / journal.pone.0183045
  6. ^ Matthew C. Mihlbachler, Florent Rivals, Nikos Solounias and Gina M. Semperbon: Dietary Change and Evolution of Horses in North America. Science 331, 2011, pp. 1178-1181
  7. ^ José L. Prado and María T. Alberdi: A cladistic analysis of the horses of the tribe Equini. Journal of Palaeontology 39 (3), 1996, pp. 663-680
  8. ^ José Luis Prado and María Teresa Alberdi: Fossil Horses of South America: Phylogeny, Systemics and Ecology. Springer, 2017, pp. 1–149
  9. ^ A b C. R. Harington and FV Clulow: Pleistocene Mammals from Gold Run Creek, Yukon Territory. Canadian Journal of Earth Sciences 10 (5), 1973, pp. 697-759
  10. ↑ Christina I. Barrón-Ortiz, Leonardo S. Avilla, Christopher N. Jass, Victor M. Bravo-Cuevas, Helena Machado and Dimila Mothé: What Is Equus? Reconciling Taxonomy and Phylogenetic Analyzes. Frontiers in Ecology and Evolution 7, 2019, p. 343, doi: 10.3389 / fevo.2019.00343
  11. ^ Eric Paul Gustafson: The Vertebrate Faunas of the Pliocene Ringold Formation, South-Central Washington. Bulletin of the Museum of Natural History University of Oregon 23, 1978, pp. 1-62
  12. ^ Lewis Gazin: A study of the fossil horse remains from the Upper Pliocene of Idaho. Proceedings of the United States National Museum 83 (2985), 1936, pp. 281-320
  13. ^ H. Gregory McDonalds: More than just horses Hagerman Fossil Beds. Rocks and Minerals 68, 1993, pp. 322-326
  14. ^ Bruce M. MacFadden: Fossil horses. Systematics, paleobiology, and evolution of the family Equidae. Cambridge University Press, 1992 (p. 113)
  15. ^ A b Ernest L. Lundelius and Margaret S. Stevens: Equus francisci Hay, a small stilt-legged horse, middle Pleistocene of Texas. Journal of Palaeontology 44, 1970, pp. 148-153
  16. ↑ Walter W. Dalquest and Jack T. Hughes: The Pleistocene Horse, Equus conversidens. The American Midland Naturalist 74 (2), 1965, pp. 408-417
  17. ^ A b Morris F. Skinner and Claude W. Hibbard: Early Pleistocene pre-glacial and glacial rocks and faunas of North-Central Nebraska. Bulletin of the American Museum of Natural History 148, 1972, pp. 1–148 (p. 124)
  18. ↑ Walter W. Dalquest: The Little Horses (genus Equus) of the Pleistocene of North America. The American Midland Naturalist 101 (1), 1979, pp. 241-244
  19. ^ Melissa C. Winans: A quantitative study of North American fossil species of the genus Equus. In: Donald R. Prothero and R. Schoch (Eds.): The evolution of Perissodactyls. New York, Oxford University Press, 1989, pp. 262-297
  20. ↑ Walter W. Dalquest: Phylogeny of American horses of Blancan and Pleistocene age. Annales Zoologici Fennici 15, 1978, pp. 191-199
  21. ↑ Jaco Weinstock, Eske Willerslev, Andrei Sher, Wenfei Tong, Simon YW Ho, Dan Rubenstein, John Storer, James Burns, Larry Martin, Claudio Bravi, Alfredo Prieto, Duane Froese, Eric Scott, Lai Xulong and Alan Cooper: Evolution, Systematics , and Phylogeography of Pleistocene Horses in the New World: A Molecular Perspective. PLoS Biology 3 (8), 2005, p. E241, doi: 10.1371 / journal.pbio.0030241
  22. ↑ Ludovic Orlando, Dean Male, Maria Teresa Alberdi, Jose Luis Prado, Alfredo Prieto, Alan Cooper and Catherine Hänni: Ancient DNA Clarifies the Evolutionary History of American Late Pleistocene Equids. Journal of Molecular Evolution 66, 2009, pp. 533-538
  23. ↑ Ludovic Orlando, Jessica L. Metcalf, Maria T. Alberdi, Miguel Telles-Antunes, Dominique Bonjean, Marcel Otte, Fabiana Martin, Véra Eisenmann, Marjan Mashkour, Flavia Morello, Jose L. Prado, Rodolfo Salas-Gismondi, Bruce J. Shockey, Patrick J. Wrinn, Sergei K. Vasil'ev, Nikolai D. Ovodov, Michael I. Cherry, Blair Hopwood, Dean Maleb, Jeremy J. Austin, Catherine Hänni and Alan Cooper: Revising the recent evolutionary history of equids using ancient DNA. PNAS 106 (51), 2009, pp. 21754-21759
  24. ↑ Julia T. Vilstrup, Andaine Seguin-Orlando, Mathias Stiller, Aurelien Ginolhac, Maanasa Raghavan, Sandra CA Nielsen, Jacobo Weinstock, Duane Froese, Sergei K. Vasiliev, Nikolai D. Ovodov, Joel Clary, Kristofer M. Helgen, Robert C. Fleischer, Alan Cooper, Beth Shapiro, and Ludovic Orlando: Mitochondrial Phylogenomics of Modern and Ancient Equids. PLoS ONE 8 (2), 2013, p. E55950, doi: 10.1371 / journal.pone.0055950
  25. ↑ Clio Der Sarkissian, Julia T. Vilstrup, Mikkel Schubert, Andaine Seguin-Orlando, David Eme, Jacobo Weinstock, Maria Teresa Alberdi, Fabiana Martin, Patricio M. Lopez, Jose L. Prado, Alfredo Prieto, Christophe J. Douady, Tom W. Stafford, Eske Willerslev, and Ludovic Orlando: Mitochondrial genomes reveal the extinct Hippidion as an outgroup to all living equids. Biology Letters 11, 2015, p. 20141058, doi: 10.1098 / rsbl.2014.1058

Web links

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