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Megistotherium is an extinct genus of Hyaenodonta belonging to the family Hyainailouridae that lived in Africa and possibly Asia as well. It first appeared in Early Miocene to late Middle Miocene from 22.5 to 12.0 million years ago, existing for .
The name of species Megistotherium osteothlastes comes and (with -es being an agent noun: 'bone-crusher').
The family Hyainailouridae comprised a diverse group of hyaenodont predators that were most successful during the Eocene before being possibly ecologically displaced by the order Carnivora during the late Oligocene. Megistotherium emerged in the Miocene towards the end of the hyaenodonts' flourishing; it was a part of a radiation of African hyaenodontids that occurred at that time. Hyainailouros is very closely related to Megistotherium, extremely similar in size, structure and ratios - with a long tail, short limbs and robust body.Ginsburg, L. (1980.) " Hyainailouros sulzeri, mammifère créodonte du Miocène d’Europe." Ann. Paléont., 66, 19-73 Other authorities Morales, J. and Pickford, M. (2005.) "Carnivores from the Middle Miocene Ngorora Formation (13-12 Ma) Kenya." Estudios Geol., 61, 271-284 have suggested that Megistotherium is actually a junior synonym of Hyainailouros sulzeri, which is known by an almost complete skeleton, among other remains, and has been found in Europe, Asia and Namibia,J. Morales, M. Pickford, S. Fraile, M. J. Salesa and D. Soria (2003.) "Creodonta and Carnivora from Arrisdrift, early Middle Miocene of southern Namibia" Mem. Geol. Surv. Namibia 19 177–194. and therefore comes from the same localities.
The extinction of Megistotherium and other Hyainailouroidea was thought to correlate with increasing aridity in Africa, as they were more adapted for forested environments. The youngest known remains were found in the Ngorora Formation and dated to the late Middle Miocene around 12.5 to 12 year.
Description
Megistotherium osteothlastes is the only known species from this genus, and it was a large Hyainailouridae that lived during the Early and Middle Miocene. Its remains have been found in the Ngorora and Muruyur Formations of Kenya, Egypt,Morlo, M., Miller, E.R., and El-Barkooky, A.N. 2007. Creodonta and Carnivora from Wadi Moghra, Egypt. Journal of Vertebrate Paleontology 27: 145–159. Namibia, UgandaMorales, J. and M. Pickford. (2008). "Creodonts and carnivores from the Middle Miocene Muruyur Formation at Kipsaraman and Cheparawa, Baringo District, Kenya." Comptes Rendus Palevol 7 (8): 487-497 and Libya. Named by Robert Savage in 1973, Megistotherium is one of the largest known hyaenodonts. Like the other hyaenodonts, it had an enormous skull relative to its body; up to in length and a body mass estimated at . The carnassial teeth of Megistotherium (like those of other hyaenodonts) were the upper first molars, and overlapped with their lower molar counterparts like scissors to form a formidable and powerful shearing action.
Paleoecology
The land that is now the Sahara desert was much more fertile in the Miocene. A considerable amount of it was grassland and rainfall was plentiful. Lakes and ponds provided water for large fauna, which provided Megistotherium and other predators with an ample supply of prey. Large hyaenodontids like this one could have originally evolved as specialized predators or of large African herbivores. Gomphothere bones have been found with its fossils, indicating that Megistotherium may have hunted them for food.
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