Chalicotheria

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Chalicotheria
Skeleton of Moropus in the National Museum of Natural History in Washington, DC

Skeleton of Moropus in the National Museum of Natural History in Washington, DC

Temporal occurrence
Eocene to Old Pleistocene
55.8 to 1.7 million years
Locations
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Tapiromorpha
Ancylopoda
Chalicotheria
Scientific name
Chalicotheriidae
Gill , 1872

The Chalicotherien (Chalicotheriidae) are an extinct family of the odd ungulate (Perissodactyla). They lived from the Upper Eocene to the Pleistocene and have been recorded from Eurasia, North America and Africa. From today's point of view, the animals were characterized by a very strange physique, some of which included retractable claws on the hands and feet similar to today's cats. Two main lines can be distinguished within the Chalicotheri, the more original Schizotheriinae, whose bodies were equipped with limbs of equal length, and the more modern Chalicotheriinae with very long fore and short hind legs, which means that the gait of these animals must have resembled that of today's gorillas . The Chalicotherien lived largely in forests near the shore and ate a soft vegetable diet.

features

Habitus

Chalicotheria were a diverse group of odd ungulates, which today, due to some atypical features, have a very characteristic, sometimes also called "bizarre" habit . They reached sizes ranging from today's sheep to very large domestic horses and sometimes even beyond. The relatively large head, which sat on a rather long neck, was characteristic. The body was noticeably plump, the limbs strong. The oldest Chalicotherien were in their physique similar to the primitive odd-toed ungulates and thus resembled Hyrachyus , an ancestor of the tapirs , or Hyracotherium , an early equine species.

Basically, two different groups can be distinguished in habitus among the later Chalicotheria. The genealogically older line of the subfamily Schizotheriinae, which includes genera such as Schizotherium and Moropus , had, according to their ancestors, rather the same length of front and rear legs and an arched back. The later forms from the subfamily of Chalicotheriinae such as Chalicotherium or Anisodon, however, had significantly longer forelegs, so that the topline was markedly sloping. All limbs ended in three toes, but the forefoot of early representatives had an additional fourth toe. The most striking feature of both groups, however, were the powerful claws on the front and rear feet. This distinguishes them from all other odd-toed ungulates, which are characterized by crooked walking legs. Overall, chalicotheria showed a clear sexual dimorphism with smaller females compared to significantly larger males.

Skull and dentition features

Skull of Moropus

The skull of the Chalicotherien was usually elongated and built very low and looked quite large compared to the body. Younger forms of the Chalicotheriinae such as Kalimantsia also had a fairly high skull. In general, the skull was similar to that of horses . The occiput was not extended backwards and was rather rectangular. The nasal bone was short and ended well behind the median jawbone . Early Chalicotherien had a very extensive snout area, which was significantly reduced in later forms. A special feature of the skull structure had the North American genus Tylocephalonyx on whose apex legs up to 25 cm high dome-like bulged and to honeycombs were interspersed reminiscent, air-filled cavities in the bone interior.

The set of teeth was very variable. All chalicotheria, except for the earliest, were characterized by the reduction of the anterior premolar . It is noteworthy that most of the members of the Chalicotheriinae had a functional canine , which, however, could be reduced in the latest forms, as well as partially the anterior dentition. The older Schizotheriinae, on the other hand, had no canine teeth; here, too, some of the representatives of the Schizotheriinae had partially receded the front dentition. Another difference can be found in the molars, which were high-crowned ( hypsodont ) in the Schizotheriinae - here Ancylotherium had the highest crown of all known chalicotheria. In the later Chalicotheriinae, however, the molars were again equipped with lower crowns ( brachyodont ), analogous to the oldest representatives of the Chalicotheria. The upper molars also had strongly folded enamel , which was W-shaped on the inner, tongue-side side between two prominent protrusions ( metaconid and metastylid ).

Musculoskeletal system

Anisodon foot bones with typically elongated fourth metatarsals

The structure of the limbs of the Chalicotheria was very striking, especially the hands and feet. The more original chalicotheria differ significantly from the later ones in that the rear and front legs are of the same length. The hind feet ended in three toes ( metatarsus II – IV), the front feet in four toes ( metacarpus II – V), of which the fifth ray was gradually reduced. The oldest forms, such as Litolophus , still had hooves on the end links of the hands and feet, more developed forms such as Grangeria possibly had short claws. The Schizotheriinae then each had long claws, the end links of the toes on the forefoot and rear foot also had a mechanism for retracting the claws, similar to today's cats , so that they could walk on their toes like other ungulates ( toe walkers ). In contrast to other unpaired ungulates, in some of these representatives the main axis of the hands and feet did not run through the central ray ( Metapodium III), in Moropus rays III and IV were rather the same size.

The more modern Chalicotheriinae developed very long front legs and shortened the hind legs. The main changes were a significant reduction in length of the tibia and metatarsal bones. The hands and feet, which are generally three-pronged, have also been reshaped, with the fourth jet significantly enlarged and thus longer than the central jet. In addition, the mechanism for retracting the claws was only designed on the hind feet, it was not present on the front feet, so that these representatives of the chalicotheria had to bend their long claws backwards when walking, similar to today's anteaters . This created a way of moving that, due to the long arms, was reminiscent of today's gorillas ( ankle gait ) and was most likely not designed for higher speeds. In addition, the long front legs and physique meant that a large part of the body weight had to be supported by the rear extremities and the pelvic girdle.

Fossil finds

Fossil remains of anisodon from Sansan in France

Finds of chalicotheria have so far been discovered in Eurasia , Africa and North America . As a rule, only a few remains are preserved at the individual sites, which rarely represent more than one animal. Nevertheless, there are occasional fossil sites where chalicotheria remains occur in large numbers. Significant in this context is the site of Devínska Nová Ves , a district of Bratislava in Slovakia , which can be assigned to the Middle Miocene , where more than 1,500 remains of Chalicotherium bones were found in a karst fissure . At least 60 individuals could be distinguished on the basis of the remains of the teeth. The Agate Fossil Beds National Monument in Nebraska is also outstanding, with the remains of up to 75 Moropus individuals from the early Miocene, including some complete skeletons. At the Askazansor site in the Betpak-Dala of Kazakhstan , also at the early Miocene site , numerous remains of Borissiakia have come down to us, although they are more fragmented. A nearly complete skeleton is still known from Anisodon and comes from Sansan in France .

Paleobiology

The vast majority of fossil finds come from sites that used to be near water and are thus embedded in sediments influenced by limnic or fluvial influences . The predominant vegetation is mostly alluvial forests or forests close to the banks in which the animals lived, but it is also possible to reconstruct partly open forest landscapes up to park landscapes such as Ancylotherium , which is often associated with numerous open land species. As a result, a predominantly leaf-eating diet was adopted early on, despite the different tooth structure of the individual Chalicotheria lines with higher-crowned molars in the Schizotheriinae and lower-crowned ones in the Chalicotheriinae. Traces of abrasion on the occlusal surfaces of the teeth in the form of hollow-like cavities confirm this and show that mainly soft plant foods such as leaves were consumed. Components with greater abrasion were bark , twigs or thick branches. Grasses only played a subordinate role. The Chalicotheriinae seem to have used more chewing food than the older Schizotheriinae. Since frequently at numerous sites a high number of Hackberry occurs -Fruchtkernen whose fruit could also have been a food source, whose seeds were then additionally common. The hard fiber plant food of the Chalicotheriinae also led to a more robust design of the lower jaw and its symphysis . The most original chalicotheria were more adapted to fruit nutrition.

It was often assumed that the Chalicotherien also dug roots and tubers or dug water holes. The anatomical structure of the forelimbs does not permit this conclusion, however, since the radius and ulna were firmly fused and lateral rotation movements were hardly possible. The use of the long claws, especially on the front feet, is therefore seen in the form of peeling the bark of trees. The construction of the pelvis and the hind legs made it possible for the animals to stand up and use their arms to pull up and break branches and twigs. As a result, the range to get to food was significantly increased. This facultative bipedia was developed in both the Schizotheriinae and the Chalicotheriinae. In addition, the claws can also have served to ward off enemies.

The occasional massive occurrence of Chalicotherien sometimes suggested a way of life in large herds. Although they are a regularly occurring faunal element in the majority of the sites, they usually only have a few skeletal remains. However, the pronounced sexual dimorphism may speak in favor of small group formations with a dominant male animal. This may also lead to rival fights, the characteristically dome-shaped skull of Tylocephalonyx could speak for shock fights among the competing males.

Systematics

Internal systematics of the perissodactyla according to Holbrook and Lapergola 2011
  Perissodactyla 
  Tapiromorpha 

 Isectolophidae (†)


   
  Ancylopoda 

 Lophiodontidae (†)


   

 Chalicotheriidae (†)



  Ceratomorpha 
  Tapiroidea 

 Helaletidae (†)


   

 Tapiridae



  Rhinocerotoidea 

 Amynodontidae (†)


   

 Hyracodontidae (†)


   

 Rhinocerotidae







  Hippomorpha 
  Equoidea 

 Palaeotheriidae (†)


   

 Equidae



  Brontotherioidea 

 Lambdotheriidae (†)


   

 Brontotheriidae (†)





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The Chalicotherien are an extinct family of the odd ungulate , within this they belong to the superfamily Chalicotherioidea . This is traditionally assigned to the Eomoropidae family , which includes important genera such as Eomoropus or Litolophus from the Eocene and early Oligocene . However, this family is of paraphyletic origin, as some members may be basal forms of the Brontotheriidae family . More recently, therefore, Litolophus , Eomoropus and Grangeria are regarded as the original representatives of the Chalicotheria (parent group). Another family within the Chalicotherioidea are the Lophiodontidae .

Originally, experts saw the Chalicotherioidea in the closer relationship of today's Equidae and the also extinct Brontotheriidae and so assigned them to the suborder Hippomorpha , which traditionally stand opposite the Ceratomorpha with the tapirs and rhinos in the odd- toed systematics . Due to the mixed characteristics of both groups of odd ungulates, Leonard Radinsky introduced a third, equivalent rank for the Chalicotherioidea in the 1960s, which he named Ancylopoda . In order to clarify the closer position of the Chalicotherien to the Ceratomorpha, which was worked out in the 1980s, a new intermediate order was introduced with Tapiromorpha (originally called Moropomorpha), which includes the Ceratomorpha and Ancylopoda.

Internal systematics of the Chalicotheriidae according to Bai et al. 2010, Coombs 2009 and Anquetin et al. 2007
  Chalicotheriidae 

 Litolophus


   

 Eomoropus


   

 Grangeria


   
  Schizotheriinae 

 Schizotherium


   

 Borissiakia


   

 Moropus


   

 Tylocephalonyx


   

 Metaschizotherium


   

 Chemositia


   

 Phyllotillon


   

 Ancylotherium


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  Chalicotheriinae 

 Butleria


   

 Chalicotherium


   

 Anisodon


   

 Nestoritherium









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A distinction is made between two clearly different subfamilies of the Chalicotheriidae, the Schizotherinae and the Chalicotherinae , which, however, did not take place until very late in research history, in the 1930s. The former differ from the latter in the more modern structure of the teeth and the more original design of the musculoskeletal system. The following structure of the Chalicotheriidae is valid today:

  • Chalicotheriidae Gill , 1872
Theodore Nicholas Gill (1837-1914)

Another genus that was originally assigned to the Chalicotheria is Olsenia , which William Diller Matthew and Walter W. Granger introduced in 1925. According to recent studies, it belongs to the Olseniidae family and thus to the Mesonychia due to its four-pointed foot . The position of Huanghotherium and Gansuodon is also problematic ; both were only named on the basis of a few tooth finds. While Gansuodon continues to be used as a synonym for Ancylotherium , Huanghotherium may represent an independent genus, according to some experts.

The first known finds of chalicothere date from the early 19th century and were greeted by Georges Cuvier recognized in 1822 as the phalanges (ie, finger and toe bones) of a large animal, which he called a pangolin gigantesque ( "giant pangolin ") belonging addressed. Johann Jakob Kaup submitted further finds in 1833, which were teeth that came from the Dinotheriensands of Eppelsheim . The name Chalicotherium goes back to this publication . The name is made up of the Greek words. χαλιξ ( khalix "gravel" or "lime") and θηρίον ( thērion "animal") together; however, Kaup did not state what the name refers to. As early as 1832, however, Kaup had also mentioned phalanges from the same site that he referred to the Edentata (today's tooth arms ). Also Édouard Lartet described in 1837 tooth finds from Sansan (France) as Anoplotherium with similarities to Kaups Chalicotherium also discovered postcranial skeletal remains but when Macrotherium which were to ask his opinion also on the Edentata. The mixture of characteristics of the chalicotheria, consisting of dentition typical of herbivores and predator-like claws, initially made the early researchers doubt whether the finds belonged to only one animal species or whether they were mixed finds. Only around 70 years later this contradiction in the consideration of skull and postcranial remains was resolved when a complete skeleton uncovered in Sansan was published by Henry Filhol in 1890 and clearly demonstrated that these skeletal elements, which supposedly represent different animal groups, belong together. This find is exhibited today in the Muséum national d'Histoire naturelle in Paris . The family name Chalicotheriidae had already been introduced in 1872 by Theodore Nicholas Gill .

Tribal history

Adaptive radiation

General evolutionary trends within chalicotheria are increase in size, reduction in the anterior skull area and remodeling of the anterior dentition. The mixture of characteristics between primitive and derived characteristics in the two subfamilies speaks for a very early separation in the development of this odd ungulate family. Possibly this already happened within the core group, since these largely still had a trained canine tooth, while this was missing in most of the members of the Schizotheriinae. These retained their conservative physique, but developed a retraction mechanism on the toe and finger phalanges for the claws. In addition, there was a significant increase in the heights of the crowns of the molars. The Chalicotheriinae, on the other hand, strongly regressed their hind legs by reducing the length of the tibia and the metatarsals. Here a mechanism for pulling back the claws formed only on the hind feet.

Origins

The Chalicotherioidea formed one of the main lines of the odd ungulate. Representatives of the Lophiodontidae were among the earliest forms. The oldest finds of Chalicotheria, which are still very similar to the other primitive odd-toed ungulates, such as the ancient horse Hyracotherium , come from the Upper Eocene. Two of these early genera from this period are Eomoropus and Litolophus . From the latter, a tapir-sized animal with an average body weight of 150 kg, excellent finds come from the Erlian Basin in the Chinese autonomous region of Inner Mongolia , where over 1,250 bone fragments from a total of 25 individuals were found in an area of ​​12 m², which were probably during a catastrophic flood had died. The fact that some genera, such as Eomoropus and Grangeria, were found both in North America and in Asia (China) shows that the two continents were connected by land bridges at that time. The first Chalicotheria to be assigned to the subfamily Schizotheriinae appeared with Schizotherium as early as the Oligocene in Eurasia . This represented a significantly larger animal weighing up to 620 kg. At around the same time, Moropus was also detected in North America, early findings in the form of isolated teeth with an age of over 25 million years are from the John Day Formation in Oregon occupied.

Miocene

In the Miocene the Chalicotherien reached their maximum species abundance. The most important development in the Miocene was the emergence of the more modern group of Chalicotheriinae, but the representatives of the Schizotheriinae also existed and continued to develop. In Asia, in the early Miocene, mainly smaller schizotheria forms such as Borissiakia and Phyllotillon were represented, but were later replaced by Ancylotherium , an animal weighing up to 1.2 t. As early as the early Miocene, the more modern Chalicotherium appeared, which, with a weight of up to 1.7 t, was one of the largest representatives and dominated until the end of the Miocene. In Europe, on the other hand, Metaschizotherium from the subfamily of Schizotheriinae occurred frequently in the early Miocene , which is rarely found in Asia. It replaced the Oligocene schizotherium here. Metaschizotherium was in turn largely displaced in Europe by the Chalicotheriinae, mainly Chalicotherium , during the Middle Miocene around 15 million years ago . Remains of this more modern representative are known from about 10 million year old deposits of the Ur-Rhine ( Dinotheriensande ) in Rheinhessen. Later the even more modern forms anisodon and the high-skulled Kalimantsia were added. Ancylotherium occurs about 8 million years ago , after schizotherium has not been detectable in Europe for four million years.

Africa was first reached in the early Miocene with the creation of a land bridge to Eurasia through the closure of the Tethys by the more modern Butleria (originally described as Chalicotherium ), a rather small, long-snouted animal; the oldest evidence is around 19 million years old and comes from eastern Africa. Significant finds came to light in the Wayando Formation in Kenya and include several upper jaw fragments, and postcranial skeletal elements have also been described from the Kiahera Formation , which is about the same age . However, the genus died out in Africa at the beginning of the Middle Miocene. It was not until the end of the late Miocene that two representatives of the schizotheria, Ancylotherium and Chemositia, were found again. Remains of the more modern representatives of the Chalicotheriinae have not yet been found in North America.The Schizotheriinae first reached the continent in the transition from the late Oligocene to the early Miocene around 23 million years ago, but died out again at the beginning of the late Miocene around 11 million years ago. The most important and most common representative was Moropus , which has only been recorded in western Eurasia in the early Miocene and weighed up to 1.1 t. A characteristic independent line of the North American schizotheria is the domskullige Tylocephalonyx . As early as the early Miocene, the chalicotheria in present-day Panama reached their southernmost point of spread on the American double continent, as evidenced by a tooth find from the Las Cascadas formation near the Panama Canal . Due to the size of the tooth, it is probably a rather small representative.

Plio and Pleistocene

In Europe the last representatives of the Schizotheriinae died out in the Pliocene , here the latest representatives of the genus Ancylotherium can be assigned. Chalicotheria persisted in Africa and East Asia until the early Pleistocene . The last species, Ancylotherium hennigi , disappeared in Africa around 1.7 million years ago. Some of the most recent fossil remains were found in the Omo Valley in Ethiopia and in the Olduvai Gorge in Tanzania . The last Asian finds fall in a similar period and are represented by Nestoritherium . Very late Asian sites are known with Longdan in the Chinese province of Gansu , Huangjiwan near Zhen'an in the province of Shaanxi and the Gigantopithecus cave of Liucheng in the autonomous region of Guangxi . The finds are mostly assigned to the late form Hesperotherium , which is reconstructed to a body weight of up to 580 kg and had a characteristically short snout.

literature

  • TS Kemp: The Origin and Evolution of Mammals. Oxford University Press, Oxford et al. 2005, ISBN 0-19-850761-5 .
  • Arno Hermann Müller : Textbook of paleozoology. Volume 3: Vertebrates. Part 3: Mammalia. 2nd, revised and expanded edition. Gustav Fischer Verlag, 1989, ISBN 3-334-00223-3 .

Individual evidence

  1. ^ A b c Donald R. Prothero and Robert M. Schoch: Horns, tusks, and flippers. The evolution of hoofed mammals. Johns Hopkins Univ. Pr., Baltimore 2003, ISBN 0-8018-7135-2 , pp. 248-252.
  2. ↑ a b c d e Kurt Heissig: Family Chalicotheriidae. In: Gertrud E. Rössner and Kurt Heissig: The Miocene land mammals of Europe. Munich, 1999, pp. 189-192.
  3. ↑ a b Denis Geraads, Nikolai Spassov and Dimitar Kovachev: New Chalicotheriidae (Mammalia) from Bulgaria. Journal of Vertebrate Palaeontology, Northbrook, 21 (3), 2001, pp. 596-606.
  4. ^ A b Luke T. Holbrook: Comparative osteology of early Tertiary tapiromorphs (Mammalia, Perissodactyla). Zoological Journal of the Linnean Society 132, 2001, pp. 1-54.
  5. ^ A b c Qiu Zhan-Xiang: Hesperotherium - a new genus of the last Chalicotheres. Vertebrata Palasiatica 40 (4), 2002, pp. 317-325.
  6. ^ A b Robert M. Hunt Jr .: An Early Miocene Dome-Skulled Chalicothere from the “Arikaree” Conglomerates of Darton: Calibrating the Ages of High Plains Paleovalleys Against Rocky Mountain Tectonism. American Museum Novitates, Number 3486, 2005, pp. 1-45.
  7. ↑ a b c d e f g h i j Margery C. Coombs: Interrelationships and diversity in the Chalicotheriidae. In: Donald R. Prothero and RM Schoch (Eds.): The evolution of the Perissodactyls. New-York, 1989, pp. 438-457.
  8. ↑ a b Bin Bai, Yuanqing Wang, and Jin Meng: Early Eocene Chalicothere Litolophus with Hoof-Like Unguals. Journal of Vertebrate Paleontology, 31 (6), 2011, pp. 1387-1391.
  9. ↑ a b c Spencer George Lucas and Robert M. Schoch: Taxonomy and biochronology of Eomoropus and Grangeria, Eocene Chalicotheres from the Western United States and China. In: Donald R. Prothero and RM Schoch (Eds.): The evolution of the Perissodactyls. New-York 1989, pp. 422-437.
  10. ↑ a b c Helmuth Zapfe: Ancylotherium in the Upper Miocene of the Vienna Basin. Annals of the Natural History Museum Vienna 71, 1967, pp. 401–411.
  11. ^ John Graham: Agate Fossil Beds National Monument - Geologic Resources Inventory Report. US Department of the Interior ( PDF ).
  12. ↑ a b c Jérémy Anquetin, Pierre-Olivier Antoine and Pascal Tassy: Middle Miocene Chalicotheriinae (Mammalia, Perissodactyla) from France, with a discussion on chalicotheriine phylogeny. Zoological Journal of the Linnean Society 151, 2007, pp. 577-608.
  13. ↑ Ellen Schulz, Julia M. Fahlke, Gildas Merceron and Thomas M. Kaiser: Feeding ecology of the Chalicotheriidae (Mammalia, Perissodactyla, Ancylopoda). Results from dental micro- and mesowear analyzes: Negotiations of the Natural Science Association Hamburg NF 43, 2007, pp. 5–31.
  14. ↑ Ellen Schulz and Julia M. Fahlke: The diet of Metaschizotherium bavaricum (Chalicotheriidae, Mammalia) from the MN 5 of Sandelzhausen (Germany) implied by the mesowear method. Paläontologische Zeitschrift 83, 2009, pp. 175–181.
  15. ↑ a b Gina M. Semprebon, Paul J. Sise and Margery C. Coombs: Potential Bark and Fruit Browsing as Revealed by Stereomicrowear Analysis of the Peculiar Clawed Herbivores Known as Chalicotheres (Perissodactyla, Chalicotherioidea). Journal of Mammal Evolution 18, 2011, pp. 33-55.
  16. ^ Luke T. Holbrook and Joshua Lapergola: A new genus of Perissodactyl (Mammalia) from the Bridgerian of Wyoming, with comments on basal Perissodactyl phylogeny. Journal of Vertebrate Paleontology 31 (4), 2011, pp. 895-901
  17. ↑ a b c Bin Bai, Yuanqing Wang and Jin Meng: New Craniodental Materials of Litolophus gobiensis (Perissodactyla, `` Eomoropidae '') from Inner Mongolia, China, and Phylogenetic Analyzes of Eocene Chalicotheres. American Museum Novitates 3688, 2010, pp. 1-27.
  18. ↑ a b J. J. Hooker and D. Dashzeveg: The origin of chalicotheres (Perissodactyla, Mammalia). Palaeontology 47 (6), 2004, pp. 1363-1386.
  19. ^ A b Donald R. Prothero and Robert M. Schoch: Classification of the Perissodactyla. In: Donald R. Prothero and RM Schoch (Eds.): The evolution of the Perissodactyls. New-York 1989, pp. 530-537.
  20. ↑ Magery C. Coombs: The chalicothere Metaschizotherium bavaricum (Perissodactyla, Chalicotheriidae, Schizotheriinae) from the Miocene (MN5) Lagerstätte of Sandelzhausen (Germany): description, comparison, and paleoecological significance. Paläontologische Zeitschrift 83, 2009, pp. 85–129.
  21. ^ A b Qiu Zhangxiang, Wang Banyue, Deng Tao, Ni Xijun and Wang Xiaoming: Notes on the Mammal Fauna from the bottom of the Loess deposits at Longdan, Dongxiang County, Gansu Province. Quaternary Sciences 22 (1), 2002, pp. 33-38.
  22. ↑ a b c Louis de Bonis, Geniève Bouvrain, Georges Koufos and Pascal Tassy: Un crane de Chalicothere (Mammalia, Perissodactyla) du Miocene Superieur de Macedoine (Grece): Remarques sur la phylogenie des Chalicotheriinae. Palaeovertebrata 24 (1-2), 1995, pp. 135-176.
  23. ↑ Yan Liu and Zhaoqun Zhang: New materials of Chalicotherium brevirostris (Perissodactyla, Chalicotheriidae) from the Tunggur Formation, Inner Mongolia. Geobios 45, 2012, pp. 369-376.
  24. ^ Jörg Erfurt and Alexander Averianov: Enigmatic ungulate-like mammals from the Eocene of Central Asia. Natural Sciences 92, 2005, pp. 182-187.
  25. ↑ Chen Shaokun: A review on Chinese Neogene Chalicotheres. In: Dong Wei (Ed.): Proceedings of the Eleventh Annual Meeting of the Chinese Society of Vertebrate Paleontology. Beijing, Ocean Press, 2008, pp. 31-41.
  26. ↑ magery C. Coombs: Moropus merriami in the Early Barstovian Lower Snake Creek fauna of Nebraska, with Comments on Biogeography of North American Chalicotheres. Bulletin American Museum of Natural History 285, 2004, pp. 191-208.
  27. ↑ a b Bin Bai, Yuangqing Wang, Jin Meng, Xun Jin, Qian Li and Ping Li: Taphonomic analyzes of an Early Eocene Litolophus (Perissodactyla, Chalicotherioidea) assemplage from the Erlian Basin, Inner Mongolia, China. Palaios 26 (4), 2011, pp. 187-196.
  28. ↑ a b c d e Tao Deng: Late Cenozoic environmental changes in the Linxia basin (Gansu, China) as indicated by cenograms of fossil Mammals. Vertebrate Palasiatica 47 (4), 2009, pp. 282-298.
  29. ^ Margery C. Coombs, Robert M. Hunt Jr., Ellen Stepleton, L. Barry Albright III and Theodore J. Fremds: Stratigraphy, chronology, biogeography, and taxonomy of early MIocene small chalicotheres in North America. Journal of Vertebrate Paleontology 21 (3), 2001, pp. 607-620.
  30. ^ A b Margery C. Coombs and Susanne M. Cote: Chalicotheriidae. In: Lars Werdelin and William Joseph Sanders (eds.): Cenozoic Mammals of Africa. University of California Press, Berkeley, Los Angeles, London, 2010, pp. 659-667.
  31. ^ A b Claude Guérin and Martin Pickford: Ancylotherium cheboitense nov. sp., nouveau Chalicotheriidae (Mammalia, Perissodactyla) du Miocène supérieur des Tugen Hills. Comptes Rendus Palevol 4, 2005, pp. 225-234.
  32. ^ Aaron R. Wood and Nicole M. Ridgwell, The First Central American Chalicothere (Mammalia, Perissodactyla) and the Paleobiogeographic Implications for Small-Bodied Schizotheriines. Journal of Vertebrate Paleontology 35 (3), 2015, p. E923893.
  33. ^ Li Xiao Chen and Deng Kai: Early Pleistocene Chalicothere fossils from Huangjiwan, Zhen'an, Shaanxi, China. Vertebrata Palasiatica 41 (4), 2003, pp. 332-336.
  34. ↑ Tong Haowen and Claude Guérin: Early Pleistocene Dicerorhinus sumatrensis remains from the Liucheng Gigantopithecus Cave, Guangxi, China. Geobios 42, 2009, pp. 525-539.

Web links

Commons : Chalicotheriidae  - Collection of images, videos, and audio files