Deinotheriidae
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Subfamily Chilgatheriinae: Subfamily Deinotheriinae: |
Deinotheriidae ("terrible beasts") are a family of prehistoric elephant-like proboscideans that lived during the Tertiary period, appearing in Africa, and then spreading across southern Asia (Indo-Pakistan), and Europe. During that time they changed very little, apart from growing much larger in size, until by the late Miocene they had become the largest land animals of their time. Their most distinctive feature were the downward curving tusks on the lower jaw.
Deinotheres were not a very diverse group; there are only three known genera, Chilgatherium, Prodeinotherium and Deinotherium. These form an evolutionary succession, with each new and more advanced genus replacing the preceding one.
Unlike the various mammoth and mastodont lineages, the deinotheres died out in the early Pleistocene, rather than continuing through the ice age.
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[edit] Description
As far as their body shape and proportions are concerned, deinotheres were very much like modern elephants. The legs were long, as in modern elephants, but the skull was rather flat, not high as in true elephants. The upper jaw lacked incisor and canine teeth, but possessed five low-crowned molars on each side, with the same number in the lower jaw. Harris 1976 has shown that deinitheres used their front teeth for crushing their food, and the back teeth for shearing (slicing), the plant material.
The front part of the lower jaw was turned downwards, and bore the two tusk-like incisors. These curved downwards and backwards in a sort of huge hook, and constituted the most distinct feature of this strange animal.
[edit] Ecology
Harris (1975) argues that deinotheres were "shearing browsers" adapted for feeding on plants above ground level. The way they chewed their food was probably similar to that of modern tapirs, with the front teeth being used to crush the food, while the second and third molars have a strong vertical shearing action, with little lateral (side to side) movement. This chewing action differs from both that of gomphotheres (lateral grinding) and elephants (horizontal shearing). Deinothere molars show little wear, indicating a diet of soft, nongritty, forest vegetation, with the down-turned lower tusks being used for stripping bark or other vegetation.
Deinotherium giganteum has a more elongate lower forelimb than early and middle Miocene Prodeinotherium, indicating a more efficient stride as an adaptation to the spread of savannas in Europe during the late Miocene. Deinotheres would probably migrate from forest to forest, traversing the wide and (to them) useless grasslands.
[edit] Relationships
The ancestry and evolutionary relationships of the deinotheres remain obscure. It has been suggested that they are related to the barytheres, due to similarities in the structure of the teeth. What is clear is that they diverged from the rest of the proboscideans at a very early date. In the 1970s several researchers placed them in a separate order to the Proboscidea, but this view is not followed nowadays.
[edit] Evolutionary history
The oldest known deinothere is Chilgatherium harrisi from the late Oligocene. Its fossil remains have been found in the district of Chilga in Ethiopia (hence the name). This indicates that, like other proboscideans, deinotheres evolved in Africa. Chilgatherium was quite small, about midway between a large pig and a small hippopotamus in size.
By the early Miocene, deinotheres had grown to the size of a small elephant, and had migrated to Eurasia. Several species are known, all belonging to the genus Prodeinotherium.
During the late middle Miocene these modest-seized proboscideans were replaced by much larger forms across Eurasia. In Europe, Prodeinotherium bavaricum appeared in the early Miocene mammal faunal zone MN 4, but were soon replaced by Deinotherium giganteum in the middle Miocene. In Asia likewise, Prodeinotherium is known from the early Miocene strata in the Bugti Hills, and continued into the middle Miocene Chinji Formation, where it is replaced by Deinotherium indicum.
While these Miocene deinotheres were dispersed widely and evolved to huge elephant size, they were not as common as the contemporary (but smaller) euelephantoidea. Fossil remains of this age are known from the France, Germany, Greece, Malta, and northern India and Pakistan. These consist chiefly of teeth and the bones of the skull.
After the extinction of the indricotheres at the end of the early Miocene, the deinotheres were (and remained) the largest animals walking the Earth.
The late Miocene was the heyday of the giant deinotheres. D. giganteum is common from Vallesian and Turolian localities in Europe. Prodeinotherium, which was reasonably well represented in the early Miocene of Africa, was succeeded by D. bozasi at the beginning of the late Miocene. And in Asia Deinotherium indicum was most common in the late Miocene Dhok Pathan Formation.
Fossil teeth of D. giganteum, from the late Miocene Sinap Formation at the Turkish site of Kayadibi are larger than those from older localities, such as Eppelsheim, Wissberg, and Montredon, indicating a tendency for increasing size of members of the species over time. These were the biggest animals of their day, protected from both predators and rival herbivores by virtue of their huge bulk. Not until the Pleistocene would the largest mammoths approach them in size.
With the end of the Miocene, deinothere fortunes declined. Deinotherium indicum died out about 7 Million years ago, possibly driven to extinction by the same process of cliamte change that had previously eliminated the even more enormous Indricotherium. While in Europe, Deinotherium giganteum continued, albeit with dwindling numbers, until the middle Pliocene; the most recent specimen is from Romania.
In its original African homeland, Deinotherium continued to flourish throughout the Pliocene, and fossils have been uncovered at several of the African sites where remains of hominids have also been found.
The last deinothere species to become extinct was Deinotherium bozasi. The youngest known specimens are from the Kanjera Formation, Kenya, about a million years ago (early Pleistocene). The causes of the extinction of such a successful and long-lived animal are not known, although a small number of other species of African megafauna also died out at this time.
[edit] In Cryptozoology
In several central African countries such as the Congo, there have been reports of hippopotamuses being mysteriously killed, and the native people of those areas claimed that they were not responsible for the hippos' deaths. Cryptozoologists believe that only a Deinotherium was capable of killing a hippo in this way.
[edit] References
- Carroll, R.L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.
- Colbert, E. H. (1969), Evolution of the Vertebrates, John Wiley & Sons Inc (2nd ed.)
- Gugliotta, Guy (2003) Six New Species of Prehistoric Mammals Discovered in Africa Find Proves Elephants Originated on Continent, Scientist Says, Washington Post, Thursday, December 4, 2003; Page A02
- Harris, J.M. (1975) Evolution of feeding mechanisms in the family Deinotheriidae (Mammalia: Proboscidea). Zool. J. Linn. Soc. 56: 331-362
- ----- (1978) Deinotherioidea and Barytherioidea. 315-332, in Maglio, V. J. & Cooke, H. B. S., (eds.) 1978: Evolution of African mammals, Harvard University Press, Cambridge & London
- ----- (1983), Family Deinotheriidae, in J. M. Harris, ed., Koobi Fora research project, Volume 2: The fossil ungulates: Proboscidea, Perissodactyla, and Suidae, Clarendon Press, Oxfordpp. 22-39.
- Sanders, W.J., 2003, chap 10, Proboscidea, in Mikael Fortelius (ed) Geology and paleontology of the Miocene Sinap Formation, Turkey, Columbia University Press, New York
- Sanders, W. J., Kappelman, J. & Rasmussen, D. T., 2004: New larg-bodied mammals from the late Oligocene site of Chilga, Ethiopia. Acta Palaeontologica Polonica Vol. 49, no.3, pp. 365-392 pdf
- "Dinotherium", 1911 Encyclopædia Britannica
