Gomphotherium

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Gomphotherium
Skeletal reconstruction of Gomphotherium

Skeletal reconstruction of Gomphotherium

Temporal occurrence
Upper Oligocene to Upper Pliocene
28.1 to 3.6 million years
Locations

Africa , Eurasia , North America

Systematics
Tethytheria
Russell animals (Proboscidea)
Elephantimorpha
Elephantida
Gomphotheria (Gomphotheriidae)
Gomphotherium
Scientific name
Gomphotherium
Burmeister , 1837

Gomphotherium is an extinct pachyderm genus of the family of gomphotheres (Gomphotheriidae). It wasspread over large parts of Eurasia and North America in the Miocene and Pliocene , but has its origins in the Oligocene in Africa . Fossil remains of this proboscis are often found, but as a rule they are single finds. The almost complete skeleton of Gweng near Mühldorf east of Munich , which isover 3 m high atthe withers, is significant. Most of the representatives remained well below. The overall elephant-like body structure shows peculiarities on the skull, which was significantly flatter and longer than that of today's proboscis and had four tusks. As a pronounced herbivore, the animal mainly fed on a mixed vegetable diet. In terms of research history, gomphotherium was usually placed among the " mastodons ", a group of primeval trunk animals that is no longer recognized today. In the current system of the proboscis, it forms part of the Gomphotheriidae family, agroup that precededthe modern elephants in terms of time and evolution. Overall, Gomphotherium was a very species- and shape-rich genus that appeared quite frequently. Due to the mostly fragmentary find material, there are still problems of delimitation between the individual species.

features

size

Gomphotherium was a large proboscis with an elongated but low skull, four tusks (two each in the upper and lower jaw) and a generally elephant-like body. In its dimensions it reached about the size of today's Asian elephants . A relatively complete skeleton from Gweng, east of Munich , which is one of the largest known of this genus, is reconstructed to a shoulder height of 3.05 m and a head-trunk length of around 5 m (each without soft tissue ). The weight of this representative of the proboscis is given as about 3.9 to 4.7 t.

Skull and dentition features

Skull of Gomphotherium

The skull of Gomphotherium was very large, but is usually only preserved in fragments. A characteristic feature was the longer stretching of the elephants compared to today's elephants, which was largely caused by the lower and less dome-like upper skull. The bones of the skull had air-filled chambers, which on the one hand reduced the weight of the entire head, on the other hand, due to the increased surface area, served as a starting point for a much stronger musculature. This was necessary to stabilize the enormous head with the four tusks. The occiput was short and vertical, when viewed from behind it had a trapezoidal cross-section and was up to 77 cm wide. The nasal bone sat relatively high on the front skull and had slightly raised bones on the nostril as attachment points for the trunk . The tooth sockets of the upper tusks had, unlike today's elephants, a clearly forward-facing position.

The characteristic and extremely massive lower jaw reached a length of up to 129 cm and was therefore much longer than that of today's elephants. The longitudinal stretching took place mainly through the formation of the lower tusks , whose tooth sockets attached to the side of the symphysis and were largely horizontal. The symphysis itself was extremely robust and up to 52 cm long and extended to the beginning of the posterior dentition. The lower jaw as a whole was narrow, the two branches met at an angle of 40 °. The height of the lower jaw body in the anterior area of ​​the molar was around 21.5 cm. Here the two branches gaped about 10 cm apart, the lower jaw reached the greatest width at the two transverse joint ends, which were 26 cm apart on the inner edges and 62 cm on the outer edges.

Third molar of gomphotherium

Like today's elephants, Gomphotherium had a horizontal tooth change , which meant that there was usually only one functional molar per jaw arch, i.e. four in total. This also sets the animal apart from the older, large representatives of the proboscis such as Deinotherium , who still had a vertical change of teeth, which is common to most mammals today, and so all teeth were functional at the same time. When changing teeth horizontally, a new tooth only pushed out when the previous one was largely chewed off. The dental formula for adult individuals of Gomphotherium is including the tusks: . Premolars were formed in the primary dentition phase and comprised a total of three per mandibular arch (dP2-4). In addition, there were two permanent premolars per jaw arch, which protruded before (P3) and after (P4) the first molar. Gomphotherium was able to change teeth a total of seven times after the first molar erupted. In terms of their morphology, the premolars approached the later permanent molars and were characterized by a low crown ( brachyodont ) and bumpy tooth enamel humps on the chewing surface ( bunodont ). A pair of these bumps formed a ridge on the chewing surface. The first two molars each had three ridges ( trilophodont ), while the last molar had four or five ridges (four in the upper jaw, five in the lower jaw). The last two milk premolars were rectangular in shape and also had three ridges each, while the two permanent premolars were more rounded in shape and had only two ridges. The size of the molars increased continuously, while the last premolar was about 4 cm long, the last molar could reach up to 23 cm. The bunodonte structure of the molars is a striking difference to today's elephants with their typical teeth, which are built up by enamel lamellae and therefore appear rather flat. Other tribe-historically mostly older proboscis such as the Mammutidae and Deinotheriidae , stand out with a clearly lophodontic to zygodontic structure of the molars, that is, these animals had markedly raised ridges that gave the teeth a roof-like structure.

tusks

Skull of gomphotherium with the tusks, after a drawing by Charles William Andrews from 1908

Gomphotherium had a total of four tusks, one for each branch of the jaw. As with all proboscis, these were hypertrophied incisors that had not developed a root and grew for a lifetime. In contrast to the tusks of today's elephants, which consist largely only of dentin , Gomphotherium had a narrow band of enamel 1 to 3 mm thick, which ran along the lateral edges of the entire tooth. As in today's elephants, the upper tusks were formed from the second incisor (I2) and usually protruded slightly curved downwards. The cross-section was oval at the base, about 13 by 9 cm in size, but changed to a round shape towards the tip, and the teeth also tapered continuously. The length could be up to 1.5 m. The lower tusks, on the other hand, were formed from the first incisor (I1) - for a long time, analogous to the tusks of the upper row of teeth, the second incisor was also held as the starting tooth - and were much shorter and slimmer than the upper teeth. These too had an oval cross-section with a diameter of 6.6 to 4.8 cm at the base and were more or less straight, but they only narrowed at the foremost tip. Occasionally the ends of the mandibular tusks could overlap.

Body skeleton

The body skeleton is largely known in full. The spine was composed of 7 cervical, 20 thoracic, 4 lumbar, 3 sacrum and 21 tail vertebrae. The first cervical vertebra alone, the atlas, was 48 cm wide and 22 cm high. Overall, the spine showed a slightly arched course, so that the back line of Gomphotherium corresponded more to that of today's Asian elephant, the greatest height of the animal was above the front extremities. The very high spinous processes on the anterior thoracic vertebrae served as attachment points for the strong neck muscles. The limbs stood vertically under the body and looked like a column. The total length of the front extremity was 219 cm, of which the humerus took about 100 cm and the ulna 93 cm. The basin was massive and measured over 1.5 m in total width across both blades. The longest tubular bone was the thigh bone with 120 cm, the shin reached 73 cm. The ratio of the longer upper limbs to the shorter lower limbs shows Gomphotherium as an animal adapted to a slower and more cumbersome type of locomotion, which is typical of the proboscis. The fore and hind feet each ended in five rays, which were short and broad, the middle metacarpus (Mc III) measured 22 cm, the middle metatarsus (Mt III) 16 cm. The front feet, which are larger than the hind feet, indicate that the main burden of movement was on the front limbs. As with today's elephants, a “sixth toe” was formed on the forefoot and hindfoot, a structure actually made of cartilage , which supported the feet when standing and running and which could be identified on certain joint surfaces of the wrist and tarsal bones. This cartilage formation emerged evolutionarily with the extreme increase in size of the proboscis and has been detectable in various representatives of the proboscis since around the end of the Oligocene 30 million years ago.

Fossil finds

Reconstruction of the “ Gweng Gomphotherium ” in the Bavarian State Collection for Paleontology and Geology in Munich. This exhibit is Fossil of the Year 2013.
Lower jaw discovery of Gomphotherium

Gomphotheriums are known from wide areas of Africa , Eurasia and North America . Some of the most important fossils are from Central Europe , most of which come from the Molasse basin of the Alpine foothills. A nearly complete skeleton with more than 170 individual bones should be emphasized , which was found in 1971 in a 50 cm thick, gray-colored sand layer on the banks of the Inn near the village of Gweng, southwest of Mühldorf . It is around 10 million years old, but was no longer completely in the skeletal structure at the site where it was found. The animal is known as the "Mühldorfer Urelefant" after where it was found. The original skeleton is kept in the Bavarian State Collection for Paleontology and Geology in Munich , a cast is in the Senckenberg Museum . The find is a male individual who was around 50 years old. Pathological - anatomical changes in the right hind foot indicate a serious injury to the animal in its youth. The fossil was systematically classified as Gomphotherium aff. steinheimense posed. Due to the size of the reconstructed skeleton and the good state of preservation, the find is one of the most important of all. The finds from Sandelzhausen , 70 km north of Munich, are also significant . Over 200 skeletal remains, mainly teeth and tusks, but also some postcranial elements, were found here, but these were largely no longer in the skeletal structure. Most of the other finds in Central Europe are often unique pieces, such as from the area around Ulm , where several tooth finds and remains of tusks come from, but also a tusk from Mettmach in the Innviertel on the edge of the Kobernaußerwald .

There are also very numerous finds outside of Central Europe, but complete skeletal remains or skeletal elements that belong together are the exception; in the following only exemplary information can be given. Fossils from more than 125 sites have come down to us from the Iberian Peninsula alone . The age of the finds varies from around 17 to 11 million years, including a complete skull and lower jaw from Cerámica Mirasierra in Madrid . Finds from En Pejouan near Simorre in southwest France are outstanding , where 10 skulls and 18 lower jaws including their fragments of different ages and genders were found from the Middle Eocene and interpreted as belonging to one population . In Egypt since 1981, in several investigations in the Moghara Formation in Wadi Moghara in the north of the country, gomphotherium teeth have been found that include at least a dozen pieces. With an age of 17 to 18 million years these are to be placed in the Lower Miocene and belong possibly to the latest records of this genus on the African continent. Several good fossil remains have been documented in China , including a complete skull from Middle Eocene deposits from Lantian in the Shaanxi province and a lower jaw of about the same age with missing tusks from Nanyucun in the Gansu province . The most recent remains of Gomphotherium to date include dental finds from various quarries in central Florida in North America. They come from the upper sections of the Bone Valley Formation and date to the beginning of the Pliocene , so they should be around 5 million years old. In general, Gomphotherium was widespread in North America and was one of the most common proboscis of that time.

Paleobiology

The found fossils of Gomphotherium show a certain sexual dimorphism , which is more clearly worked out, especially in species such as G. angustidens , which are frequently found than in less common species. This is mainly reflected in the skull and lower jaw and shows stronger and more massive characteristics in males with longer tusks than in comparison to females. Such differences between the sexes can also be seen in the postcranial skeleton, which differ only slightly from those of today's elephants. Since the growth within the youth phase with a tooth eruption pattern hardly deviating from the African elephant was relatively similar, this proves that the general physique of the proboscis was determined evolutionarily very early in the development of this mammal group and the later changes mainly through variations in the skull - and dental construction took place.

The low-crowned molars with their typically humped ( bunodont ) chewing surface patterns indicate that the animal mainly nourished itself on soft vegetable foods ( browsing ). Isotope examinations on the molars showed a somewhat different pattern, however, that indicates a diet based on a mixed vegetable diet. However, there seem to have been certain regional dietary differences, as some of the individuals examined from today's Texas suggest a higher consumption of grasses . However, these variations are seen as differences in the food supply in the individual regions. This is concluded from the fact that all examined animals belong to different geological epochs from the Lower to the Upper Miocene . During this time there were serious changes in natural space towards more open landscapes with a drier to cooler and more seasonal climate , but none of the animals examined showed a general change in the preference for certain plants. Also, during the growth phase of the young animals there does not seem to have been a switch to certain food plants. However, these analyzes also suggest that Gomphotherium preferred to stay in open, sometimes dry grasslands and park forests and avoided dense, closed forests. However, investigations of phytolites on fossil finds from today's East Asia showed that at least individual representatives such as G. steinheimense ate almost exclusively grass as early as the Middle Miocene. These belong to the earliest records of proboscis with such a specialized diet, as they occurred around 10 million years before the first appearance of the elephants.

The fact that Gomphotherium lived at a time when the climate was changing dramatically could also be determined from the growth of the tusks. Since these increased in length over the entire life of an animal, certain growth rates appear in the form of darker and lighter deposits in the dentin , the width of which correlates directly with the food supply. The lighter areas mean phases of intense growth, the darker those of less intensive growth. Investigated tusk remnants from the Middle Miocene showed a rather irregular growth pattern, which shows that there were only various food shortages that were not seasonal. Late Miocene finds, on the other hand, had a very regular growth pattern with alternating broad light and narrow dark stripes. This is associated with stronger seasonal climatic fluctuations and the associated varying food resources.

Tribal history

The origin of Gomphotherium lies in Africa , the oldest finds are known from the Oligocene from the Chilga site in northern Ethiopia and are dated around 28 million years ago, but the finds only include individual teeth. The formation of four tusks is also known from the older Phiomia , as whose descendant he is sometimes regarded. In Eurasia the genus appeared for the first time in the Lower Miocene after the creation of a land bridge through the closure of the Tethys , the occurrence of proboscidos outside of Africa is also known as Proboscidea datum event . The oldest finds here come from the camlial formation of the Bugti Mountains on the Indian subcontinent and date more than 18.3 million years ago, in Europe Gomphotherium was first documented around 18 million years ago. At the latest in the middle Miocene 16.5 million years ago it also reached North America , but it did not advance to South America , which at that time was not yet connected to the northern continent via the Isthmus of Panama . The southernmost sites in America are in what is now Costa Rica .

In Eurasia, Gomphotherium was replaced in the late Middle and early Upper Miocene by more advanced proboscis such as Tetralophodon ; some researchers also see this proboscid form as the direct successor of Gomphotherium . The exchange process began about 11 to 12 million years ago. The most recent finds in Europe include those from Gweng near Munich, which are around 10 million years old. In North America the representative of the proboscis lasted until the Pliocene four million years ago.

Systematics

Internal systematics of the Gomphotheriidae according to Cozzuol et al. 2012
  Proboscidea  

 early proboscis


   

 Mammutidae


  Gomphotheriidae  
  Choerolophodontinae  

 Choerolophodon


   
  Amebelodontinae  


 Protanacus


   

 Archaeobelodon



   

 Serbelodon


   

 Amebelodon


   

 Platybelodon





   
  Gomphotheriinae  

 Gomphotherium


   

 Serridentinus



  Rhynchotheriinae  

 Eubelodon


   

 Rhynchotherium


   

 Stegomastodon


   

 Notiomastodon (including haplomastodon )


   

 Cuvieronius


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 Gnathabelodon


  Sinomastodontinae  

 Sinomastodon



   

 Elephantidae



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Gomphotherium is a genus of the order of Rüsseltiere (Proboscidea) and within this to the family of Gomphotheriidae provided, in turn, to the superfamily Gomphotherioidea belongs. The gomphotheries include developed proboscis, which, like today's elephants, had the feature of horizontal tooth change, in contrast to the earliest representatives of the order, which still had vertical tooth change typical of mammals. The horizontal change of teeth resulted from the enlargement of the molar teeth - in the course of the proboscis evolution an increase in the number of enamel ridges from two to six to seven per molar was recorded - with simultaneous shortening of the jaw, so that not all teeth could be found at the same time. It was first proven with the genus Eritrea around 28 million years ago. All proboscis with the characteristic of the horizontal change of teeth are placed in the subordination of the Elephantimorpha. Within the Gomphotheriidae an allocation to the subfamily of the Gomphotheriinae is common, the closest related genus is Serridentinus , which is relatively similar and was synonymous with Gomphotherium for a long time .

In total, more than 75 different species of Gomphotherium have been described in the course of the history of research , most of which, however, represent synonyms of on the one hand other types of Gomphotherium , on the other hand of other genera of proboscis , others are considered nomina nuda . The exact number of species cannot currently be determined, as the African and East Asian representatives in particular have not yet been subject to a more detailed revision. Only those species that can be safely identified as Gomphotherium are listed here :

Internal systematics of the genus Gomphotherium according to Wang et al. 2017
  Gomphotherium  

 Gomphotherium sp.? (Mwiti)


  G. annectens group  

 G. hannibali


   

 G. annectens


   

 G. cooperi


   

 G. sylvaticum


   

 G. lybicum


   

 G. pygmaeus



   
  G. angustidens group  

 G. inopinatum


   

 G. mongoliense


   

 G: connexum


   

 G. angustidens





  "Developed" gomphotheries  


 G. subtapiroideum


   

 G. tassyi



   

 G. wimani


   

 G. browni


   

 G. Steinheimense


   

 G. productum


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Within Gomphotherium , two larger form circles were distinguished. The G. annectens group comprises morphologically archaic forms such as the eponymous species or G. cooperi from South Asia and is predominantly placed in the Lower Miocene. These usually have simple bunodontic teeth with only a small fourth ridge on the rearmost molar. Rather modern forms are summarized in the G. angustidens group , which occurs mainly in Eurasia and is mostly dated to a younger age. Overall, due to the lack of revisions of the species, but also due to the fact that the finds are often only very fragmented, there are still many difficulties in distinguishing between the individual species and between genera that are closely related. This can also be seen in numerous synonymous generic names, such as Genomastodon , Ocalientinus , Tetrabelodon , Trilophodon , Trobelodon , Tatabelodon or Hemilophodon .

Research history

Hermann Burmeister in 1856

The first fossils presented today at Gomphotherium were called Mastodon angustidens by Georges Cuvier in 1817 , but he had already coined the term mastodonte à dents étroites in 1806 . Hermann Burmeister introduced the generic name Gomphotherium in 1837, whereby he in his brief description "had tusks in both jaws of the also submerged Gatt. Gomphotherium." This clearly stood out from the "mastodons", which he also gave the name "Ohiothier" ( This meant the American mastodon with today's scientific name Mammut americanum ). The name "Mastodon" later served as the name for a whole group of elephants that differed from today's elephants due to their more primitive morphology. Henry Fairfield Osborn (1857-1935) assigned these older forms in 1921 as "Mastodontoidea" to the status of a superfamily. This superfamily, usually referred to as " mastodonts ", includes several families, such as the mammutids (originally referred to as "real mastodons"), the gomphotheria and the stegodonts . Due to differing tooth structures, a distinction was made as a rule between the "bunodont" (gomphotheria) and the "zygodont mastodont" (mammutid), whereby within the bunodont forms a development from a trilophodont (the actual gomphotheria) to a tetralophodont group (genera such as Anancus or Tetralophodon , today placed among the Elephantoidea) was recognized. The terms referred to the number of pairs of enamel cusps on the first two molars. However, the superfamily "Mastodontoidea" turned out to be polyphyletic on the one hand - the mammutids most likely come from Palaeomastodon , but the Gomphotherien and their successors from Phiomia - on the other hand, the term "Mastodon" was increasingly seen as synonymous with the genus Mammut , which was already Johann Friedrich Blumenbach in 1799 based on North American fossils as Mammut ohioticum (now called Mammut americanum , the American mastodon). The tri- and tetralophodont gomphotheria and the stegodonts were therefore incorporated into the more modern superfamily of the Elephantoidea in the 1980s and 1990s, to which today's proboscis also belong, while the mammutids belong to the superfamily of the Mammutoidea. The term “mastodon” is no longer used today, except as part of a generic name or colloquially for the American mastodon. It was not until after 2000 that the trilophodonts and thus the actual gomphotheria including gomphotherium received a place in the superfamily Gomphotherioidea, which was established by Oliver Perry Hay in 1922 , but was only rarely used as an organizational group.

Individual evidence

  1. ↑ a b c d e f g h i j k Ursula B. Göhlich: Elephantoidea (Proboscidea, Mammalia) from the Middle and Upper Miocene of the Upper Freshwater Molasse of Southern Germany: Odontology and Osteology. Munich Geoscientific Treatises Series A 36, Munich, 1998
  2. ^ A b Eva-Maria Natzer: Fossil of the year 2013: Gomphotherium von Gweng ( [1] ) on the website of the Bavarian State Collection for Paleontology and Geology in Munich; also Gertrud Rößner: Fossil of the year 2013: Gomphotherium von Gweng ( [2] ) on the website of the Faculty of Geosciences of the Ludwig Maximilians University in Munich; both last accessed on April 14, 2019
  3. ↑ Per Christiansen: Body size in proboscideans, with notes on elephant metabolism. Zoological Journal of the Linnean Society 140, 2004, pp. 523-549
  4. ^ William J. Sanders: Horizontal tooth displacement and premolar occurrence in elephants and other elephantiform proboscideans. Historical Biology, 2018 doi: 10.1080 / 08912963.2017.1297436
  5. ↑ a b c Jan van der Made: The evolution of the elephants and their relatives in the context of a changing climate and geography. In: Harald Meller (Hrsg.): Elefantenreich - Eine Fossilwelt in Europa. Halle / Saale, 2010, pp. 340-360
  6. ^ A b David L. Fox: Growth increments in Gomphotherium tusks and implications for late Miocene climate change in North America. Palaeogeography, Palaeoclimatology, Palaeoecology 156, 2000, pp. 327-348
  7. ^ Cyrille Delmer: Reassessment of the generic attribution of Numidotherium savagei and the homologies of lower incisors in proboscideans. Acta Palaeontologica Polonica 54 (4), 2009, pp. 561-580
  8. ↑ John R. Hutchinson, Cyrille Delmer, Charlotte E. Miller, Thomas Hildebrandt, Andrew A. Pitsillides and Alan Boyde: From Flat Foot to Fat Foot: Structure, Ontogeny, Function, and Evolution of Elephant “Sixth Toes”. Science 234, 2011, pp. 1699-1703
  9. ↑ Ursula B. Göhlich: The Proboscidea (Mammalia) from the Miocene of Sandelzhausen (southern Germany). Paläontologische Zeitschrift 84, 2010, pp. 163–204
  10. ↑ Volker J. Sach and Elmar PJ Heizmann: Stratigraphy and mammalian faunas of the brackish water molasses in the area around Ulm (southwest Germany). Stuttgart Contributions to Natural History Series B 310, 2001, pp. 1–95
  11. ^ AV Mazo and Jan Van der Made: Iberian mastodonts: Geographic and stratigraphic distribution. Quaternary International 255, 2012, pp. 239-256
  12. ^ A b Pascal Tassy: Growth and sexual dimorhism among Miocene elephantoids: the example of Gomphotherium angustidens. In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and palaeoecology of the Elephants and their relatives. Oxford, New York, Tokyo, 1996, pp. 92-100
  13. ^ A b William J. Sanders and Ellen R. Miller: New Proboscideans from the Early Miocene of Wadi Moghara, Egypt. Journal of Vertebrate Paleontology 22 (2), 2002, pp. 388-404
  14. ↑ a b c d Wang Shi-Qi, Liu Shan-Pin, Xie Guang-Pu, Liu Jia, Peng Ting-Jiang and Hou Su-Kuan: Gomphotherium wimani from Wushan County, China, and its implications for the Miocene stratigraphy of the Tianshui area. Vertebrata Palasiatica 51 (1), 2013, pp. 71-84
  15. ^ S. David Webb, Richard C. Hulburt, Jr., Gary S. Morgan, and Helen F. Evans: Terrestrial mammals of the Palmetto Fauna (early Pliocene, latest Hemphillian) from the Central Florida Phosphate District. Science Series 41, 2008, pp. 293-312
  16. ^ W. David Lambert: The biogeography of gomphotheriid proboscidean of North America. In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and palaeoecology of the Elephants and their relatives. Oxford, New York, Tokyo, 1996, pp. 143-148
  17. ↑ David L. Fox and Daniel C. Fisher: Dietary reconstruction of Miocene Gomphotherium (Mammalia, Proboscidea) from the Great Plains region, USA, based on the carbon isotope composition of tusk and molar enamel. Palaeogeography, Palaeoclimatology, Palaeoecology 206, 2004, pp. 311-335
  18. ↑ Ivan Calandra, Ursula B. Göhlich and Gildas Merceron: Feeding preferences of Gomphotherium subtapiroideum (Proboscidea, Mammalia) from the Miocene of Sandelzhausen (Northern Alpine Foreland Basin, southern Germany) through life and geological time: evidence from dental microwear analysis. Paläontologische Zeitschrift 84, 2010, pp. 205–215
  19. ^ Mark T. Clementz. New insight from old bones: stable isotope analysis of fossil mammals. Journal of Mammalogy, 93 (2), 2012, pp. 368-380
  20. ↑ Yan Wu, Tao Deng, Yaowu Hu, Jiao Ma, Xinying Zhou, Limi Mao, Hanweng Zhang, Jie Ye and Shi-Qi Wang: A grazing gomphothere in the Middle Miocene Central Asia, 10 million years prior to the origin of Elephantidae. Scientific Reports 8, 2018, p. 7640, doi: 10.1038 / s41598-018-25909
  21. ^ William Sanders, John Kappelmann and D. Tab Rassmussen: New large-bodied mammals from the late Oligocene site of Chilga, Ethiopia. Acta Palaeontologica Polonica 49 (3), 2004, pp. 365-392
  22. ↑ a b Pascal Tassy: The earliest Gomphotheres. In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and palaeoecology of the Elephants and their relatives. Oxford, New York, Tokyo, 1996, pp. 89-91
  23. ^ Spencer Georges Lucas and Guillermo E. Alvarado: Fossil Proboscidea from the Upper Cenozoic of Central America: taxonomy, evolutionary and palaeobiogeographic significance. Revista Geológica de America Central 42, 2010, pp. 9-42
  24. ↑ Mario A. Cozzuol, Dimila Mothé and Leonardo S. Avilla: A critical appraisal of the phylogenetic proposals for the South American Gomphotheriidae (Proboscidea: Mammalia). Quaternary International 255, 2012, pp. 36-41
  25. ↑ a b Jeheskel Shoshani, Robert C. Walter, Michael Abraha, Seife Berhe, Pascal Tassy, ​​William J. Sander, Gary H. Marchant, Yosief Libsekal, Tesfalidet Ghirmai and Dietmar Zinner: A proboscidean from the late Oligocene of Eritrea, a ' 'missing link' 'between early Elephantiformes and Elephantimorpha, and biogeographic implications. PNAS 103 (46), 2006, pp. 17296-17301
  26. ↑ a b Jeheskel Shoshani and Pascal Tassy: Advances in proboscidean taxonomy & classification, anatomy & physiology, and ecology & behavior. Quaternary International 126-128, 2005, pp. 5-20
  27. ^ William J. Sanders, Emmanuel Gheerbrant, John M. Harris, Haruo Saegusa and Cyrille Delmer: Proboscidea. In: Lars Werdelin and William Joseph Sanders (eds.): Cenozoic Mammals of Africa. University of California Press, Berkeley, London, New York, 2010, pp. 161-251
  28. ↑ a b Shi-Qi Wang, Yu Li, Jaroon Duangkrayom, Xiang-Wen Yang, Wen He and Shan-Qin Chen: A new species of Gomphotherium (Proboscidea, Mammalia) from China and the evolution of Gomphotherium in Eurasia. Journal of Vertebrate Paleontology, 2017, p. E1318284 doi: 10.1080 / 02724634.2017.1318284
  29. ^ Hermann Burmeister: Handbook of natural history. For use during lectures. Berlin, Enslin, 1837, pp. 1–858 (p. 795)
  30. ^ Henry Fairfield Osborn: The Evolution, Phylogeny, and Classification of the Mastodontoidea. Bulletin of the Geological Society of America 32 (3), 1921, pp. 327-332
  31. ^ Henry Fairfield Osborn: Adaptive radiation and classification of the Proboscidea. PNAS 7, 1921, pp. 231-234
  32. ↑ Jeffrey J. Saunders: North American Mammutidae. In: In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and palaeoecology of the Elephants and their relatives. Oxford, New York, Tokyo, 1996, pp. 271-279
  33. ^ Johann Friedrich Blumenbach: Handbook of natural history. Göttingen, 1799 (pp. 697–698)
  34. ↑ Jehezekel Shoshani: Understanding proboscidean evolution: a formidable task. Tree 13, 1998, pp. 480-487
  35. ^ Pascal Tassy: Who is who among the Proboscidea? In: Jeheskel Shoshani and Pascal Tassy (eds.): The Proboscidea. Evolution and palaeoecology of the Elephants and their relatives. Oxford, New York, Tokyo, 1996, pp. 40-48

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