Teleoceras

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Teleoceras
Teleoceras in the National Museum of Natural History in Washington, DC

Teleoceras in the National Museum of Natural History in Washington, DC

Temporal occurrence
Miocene to early Pliocene
20 to 4.7 million years
Locations
  • North America
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Rhinocerotoidea
Rhinoceros (Rhinocerotidae)
Teleoceras
Scientific name
Teleoceras
Hatcher , 1894

Teleoceras is an extinct genus of rhinos thatlivedin North America in the Miocene 20 to almost 5 million years ago. She was characterized by a cylindrical body with very short legs and a small horn on the tip of the nose. The rhino genus is one of the most common fossil records in North America. Due to the well-preserved skeletal remains, the way of life of this rhinoceros representative can be reconstructed very precisely.

features

Live reconstruction of Teleoceras

Representatives of the genus Teleoceras included medium to large animals that were slightly larger than today's Sumatran rhinoceros . They reached a head-trunk length of 3 m with a shoulder height of 1.2 to 1.3 m. The weight is estimated at 0.6 to 2.3 t, depending on the species. The rather cylindrical body, which is calculated to be 2.8 m in circumference and therefore larger than that of today's Indian rhinoceros ( Rhinoceros unicornis ), and the very short limbs were striking . The skull reached a length of 54 to 65 cm and was shaped like a wedge with protruding cheekbones when viewed from above due to cuts in the facial area . The occiput was broad and slightly extended to almost right-angled. The nasal bone had a narrow shape with the long sides drawn downwards and was quite short. At the tip of some representatives there was a small roughened area that shows the position of the horn, which, however, was not very large. Individual other species, however, had no evidence of a nasal horn. The forehead line between the nasal and occiput was slightly saddled.

The lower jaw was up to 45 cm long and very massive. It had a strong and wide-spreading symphysis that reached to the end of the last premolar . The dental formula for adult animals was: . The outer front incisors in the lower jaw, each formed from the I2, were directed forward and had an elongated dagger-like shape with a length of up to 4 cm. The other incisors, on the other hand, were already severely receded. There was a diastema in each case to the posterior dental apparatus . The molars usually have very high crowns ( hypsodontal ), whereby the premolars are sometimes more strongly receded and appear small compared to the molars . The back molars were up to 7 cm high and had clearly folded enamel .

The postcranial skeleton of Teleoceras has survived in its entirety. The spine consisted of 7 cervical, 19 thoracic, 3 lumbar and 5 sacral vertebrae. The short but robust limbs were characteristic. In the naturally angled state, these reached a length of only 70 to 80 cm and were thus significantly shorter than z. B. the Indian rhinoceros living today, whose legs are each more than 1 m long. The humerus showed a length of almost 30 cm, while the radius was only 25 cm. The thigh bone could be 40 cm on average, the shin longer than 20 cm. The metapodia were also very short at around 10 cm.

References

Fund a teleoceras -Skelettes in Ashfall Fossil Beds State Historical Park in Nebraska

Teleoceras has been found in numerous places in North America, especially in the USA and Mexico , the species was very common in the Great Plains , where it was the dominant herbivore, especially in the late Miocene , and here also with the earliest representative, T. americanum happened. From the Phillips County Quarry quarry in Kansas alone, there are more than 16 skulls and 13 lower jaws that were found in the Loup Fork Beds of the Upper Miocene and include representatives of all ages and are assigned to the species T. fossiger . The finds were discovered in 1883 and were also used for the first skeleton reconstruction of this rhino genus. Outstanding are the fossils of the Ashfall Fossil Beds State Historical Park in Antelope County of northeastern Nebraska . Here in 1971 in the Ash Hollow Formation , which consists of up to 2 m thick layers of ash from a catastrophic volcanic eruption in the late Miocene , more than one hundred largely complete skeletons of the species T. major were found, along with skeletons of three-toed horses and long-necked camels and gomphotheries , which showed excellent conservation . The finds belong to the few records of group formation in fossil rhinos, similar to what is the case with today's representatives. The findings from the Ash Hollow State Historical Park in western Nebraska probably point to the same event , since the finds belong to the same geological formation. Other extensive skeletal material with up to several thousand bone fragments comes from the Mixson's Bone Bed and Love Bone Bed in the Alachua Formation in Florida . Finds of the younger species T. guymonense are largely found in the southern part of the USA ( Texas ) and in Mexico. The Gray Fossil Site in the Appalachians near Gray in Washington County of Tennessee , where at least six individuals of the species T. aepysoma were found during the construction of a road , including two almost complete skeletons , also proved to be significant . The very large, probably hornless representative lived in the beginning of the Pliocene around 4.9 to 4.5 million years ago. It is one of the few pieces of evidence from mountainous regions.

Paleobiology

Above all, the numerous complete skeletal finds from the Ash Hollow Formation made it possible to reconstruct the paleobiology of Teleoceras . The representatives are characterized by a clear sexual dimorphism , which results in significantly larger and more powerfully built bulls compared to smaller and more graceful cows. Adult bulls had larger values ​​in all body dimensions, both in the skull and in the postcranial skeleton, which hardly overlapped with those of the cows. In bulls, the lower dagger-like incisors were also found to be considerably larger and the muscle attachment points to be significantly more massive, just as the entire nasal cavity in bulls was structured much more spacious.

Further investigations based on the findings from the Ash-Hollow Formation showed a predominance of females over males, which are also mainly represented by strong bulls. This led to the conclusion that the group structures were similar to those of the recent rhinos with dominant bulls, whose territories were surrounded by small family groups of cows and young animals. The numerous fossils from the Alachua Formation, which do not go back to such a catastrophic event as in the Ash Hollow Formation, also show that the mortality rate was highest among subadults and young bulls. In connection with numerous, partly also healed rib fractures and head injuries, this is attributed to a strong aggression in the dominance and territorial struggle among the bulls, which in turn shows parallels with today's rhinos. The dagger-like incisors of male animals also show distinctive grinding surfaces, as they also occur in today's Asian rhinos. According to this, in the intra-species fights in Teleoceras, the bulls used the incisors in particular, analogous to the recent rhinoceros species with functional anterior teeth.

In addition to the violent injuries in Teleoceras , isolated pathological changes have also been proven. Some, especially young, three to four-year-old calves, for example, have enamel hypoplasia on the milk premolars, which is attributed to certain stress factors . Some researchers associate such malformations with the chasing away of the calf by the mother in the course of an imminent new birth. The mother-calf separation at the age of around three years can also be observed in today's rhinos and this specific behavior may already have been developed in fossil rhinoceros.

Due to the hippopotamus-like habitus of Teleoceras with cylindrical bodies and short legs, a more semi-aquatic way of life was adopted as early as the late 19th century, a view that persisted for a very long time. However, the high-crowned molars and the general structure of the skull with a rather recessed position of the orbit contradict this . Analyzes of plant remains found on the hyoid bone of some fossils of the Ash Hollow Formation revealed a predominance of hard, grassy food, which shows the frequent occurrence of pollen from Barriochloa grasses. Characteristic grinding marks on the molars and isotope examinations that have been carried out also indicate such a food source containing silica . According to this, Teleoceras lived in open landscapes, whereby the special short structure of this rhino genus represents an extremely strong adaptation to this biotope .

Systematics

Internal systematics of the North American rhinos according to Prothero 2005
  Rhinocerotidae  

 Uintaceras


   

 Teletaceras


   

 Penetrigonias


   

 Trigonias


   

 Amphicaenopus


   

 Subhyracodon


   

 Diceratherium


   

 Skinneroceras


   

 Menoceras


   


 Floridaceras


   

 Aphelops


   

 Galushaceras


   

 Peraceras





   

 Teleoceras




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Teleoceras belongs within the family of rhinos to the subfamily Aceratheriinae , medium to large animals, which are characterized by the absence or the expression of a very small horn. Within the subfamily Aceratheriinae, Teleoceras is a member of the tribe Teleoceratini , which are noticeable compared to their more graceful sister clade, the Aceratheriini , because of their hippopotamus physique. Closely related genera are the sometimes huge Brachypotherium , which is also widespread in Eurasia , and the Diaceratherium, which also occurs in North America .

Numerous species have been described by Teleoceras , the following are now recognized:

The individual species of the genus Teleoceras show a higher variability in terms of horn expression, body shape and proportional limb length. There are also differences in skeletal detail, such as the shape of a fourth toe on the forefoot, which is greatly reduced in size (ray V; the more primitive four-toed rhinos of North America have been extinct since the end of the Oligocene ), the size of the interior of the nose and the relative length of the premolars. A revision of the genre is therefore called for.

Teleoceras was first described in 1894 in a short essay by the American paleontologist John Bell Hatcher . The determination was based on skull finds in the Loup Fork Beds in Sheridan County , Nebraska. The generic name is derived from the Greek words τῆλε ( téle "fern") and κέρας ( kéras "horn") and refers to the position of the horn directly on the tip of the nasal bone. The independence of the genus was recognized relatively late, as three Teleoceras species, Rhinoceros meridianum , Aphelops fossiger and Rhinoceros proteros, had previously been described and assigned to different rhino groups.

Tribal history

The earliest occurrence of Teleoceras in North America is in the early Miocene (locally stratigraphically Hemingfordian about 20.9 million years ago). One of the earliest species is T. americanum , originally assigned to Brachypotherium . At that time, there were two rhinoceros lines in North America that were characterized by different diets. The Aceratheriini , especially Aphelops , were largely specialized in soft plant foods ( browsing ), while the Teleoceratini with Teleoceras preferred hard plant foods ( grazing ). What is remarkable about Teleoceras is that the representatives of the genus increased in body size in the course of their tribal history , which culminated with T. fossiger at the beginning of the late Miocene around 10 million years ago. Some later species like T. guymonense were then much smaller again. Towards the end of the Miocene and the beginning of the Pliocene , Teleoceras died out as a result of climatic changes in the form of cooling. Isotope analyzes showed that the disappearance of the rhinoceros genus goes hand in hand with the replacement of the C 3 grass by C 4 grass , possibly associated with a shortening of the growth phase of the plants in the course of the climate cooling. In contrast to the horses appearing at the same time , Teleoceras was only able to adapt to the changed nutritional basis to a limited extent and was therefore subject to increasing environmental stress, especially since C 4 plants contain fewer nutrients and are more difficult to digest than C 3 plants.

Individual evidence

  1. ^ A b c d e Henry Fairfield Osborn: A complete skeleton of Teleoceras fossiger. Notes on growth and sexual characters of this species. Bulletin American Museum of Natural History 10, 1898, pp. 51-59
  2. ↑ a b c d Michael R. Voorhies, Joseph R. Thomasson: Fossil grass anthoecia within miocene rhinoceros skeletons: diet in an extinct species. Science 206 (Oct 19), 1979, pp. 331-333
  3. ↑ a b c d e Rachel A. Short, Steven C. Wallace and Laura G. Emmert: A new species of Teleoceras (Mammalia, Rhinocerotidae) from the late Hemphillian of Tennessee. Bulletin of the Florida Museum of Natural History 56 (5), 2019, pp. 183–260 ( [1] )
  4. ↑ Harold J. Cook: A new rhinoceros of the genus Teleoceras from Colorado. Proceedings of the Denver Museum of Natural History 7 (1), 1927, pp. 1-5
  5. ^ A b Spencer George Lucas: The rhinoceras Teleoceras from the miocene of Jalisco, Mexico. New Mexico Museum of Natural History and Science Bulletin 44, 2008, pp. 65-70
  6. ^ Lloyd G. Tanner: Stratigraphic occurrences of Teleoceras with a new kimballian species from Nebraska. Bulletin University Nebraska State Museum (10) 1 (Feb), 1975, pp. 23-33
  7. ↑ Ashfall Fossil Beds State Historical Park. Designated a national natural landmark. ( PDF )
  8. ↑ Robert Diffendal, Jr., Roger K. Pabian and JR Thomasson: Geologic History of Ash Hollow State Historical Park, Nebraska. University of Nebraska, Lincoln, 1996 ( [2] )
  9. ↑ a b c d e Donald R. Prothero: The evolution of North American rhinoceroses. Cambridge University Press, 2005, pp. 1-219
  10. ^ A b c d Alfred J. Mead: Sexual dimorphism and paleoecology in Teleoceras, a North American Miocene rhinoceros. Paleobiology, 26 (4), 2000, pp. 689-706
  11. ^ A b c Matthew C. Mihlbachler: Linking sexual dimorphism and sociality in rhinoceroses: insights from Teleoceras proterum and Aphelops malacorhinus from the late miocene of Florida. Bulletin of the Florida Museum of Natural History 45 (4), 2005, pp. 495-520
  12. ^ Matthew C. Mihlbachler: Demography of late Miocene rhinoceroses (Teleoceras proterum and Aphelops malacorhinus) from Florida: linking mortality and sociality in fossil assemblages. Paleobiology, 29 (3), 2003, pp. 412-428
  13. ^ Alfred J. Mead: Enamel hypoplasia in Miocene Rhinoceroses (Teleoceras) from Nebraska: Evidence of severe physiological stress. Journal of Vertebrate Paleontology 19 (2), 1999, pp. 391-397
  14. ↑ Kurt Heissig and Oldřich Fejfar: The fossil rhinos (Mammalia, Rhinocerotidae) from the Lower Miocene of Tuchorice in northwestern Bohemia. Sborník Národního Muzea v Praze - Acta Musei Nationalis Pragae (series B, Natural History) 63 (1), 2007, pp. 19-64
  15. ↑ Kurt Heissig: Family Rhinocerotidae. In: Gertrud E. Rössner and Kurt Heissig: The Miocene land mammals of Europe. Munich, 1999, pp. 175-188
  16. ^ John Bell Hatcher: A median horned rhinoceros from the Loup fork beds of Nebraska. The American Geologist 13 (3) (March), 1894, pp. 149-150
  17. ↑ Esperanza Cerdeño: Diversity and evolutionary trends of the the family Rhinocerotidae (Perissodactyla). Palaeo 141, 1998, pp. 13-34
  18. ^ Donald R. Prothero, Claude Guérin and Earl Manning: The history of Rhinocerotoidea. In: Donald R. Prothero and RM Schoch (Eds.): The evolution of the Perissodactyls. New-York, 1989, pp. 321-340
  19. ↑ Bian Wang and Ross Secord: Paleoecology of Aphelopsand Teleoceras (Rhinocerotidae) through an interval of changing climate and vegetation in the Neogene of the Great Plains, central United States. Palaeogeography, Palaeoclimatology, Palaeoecology, 2019, doi: 10.1016 / j.palaeo.2019.109411

Web links

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