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Long before rhinos, giraffes, hippos, and antelopes roamed the African savannah, a group of large, highly specialized mammals known as the seaweed inhabited the continent. The best known is Arsinoitherium, an animal that looked a lot like a rhinoceros but was actually closer to elephants, sea cows and hyraxes. Now, the researchers report in Current Biology on June 28 offer a glimpse of this ancient past with the discovery of the oldest and oldest still described epithet.
The fossilized dental remains of about 55 million years old found in the early lower Eocene levels of the Ouled Abdoun phosphate basin in Morocco represent two new species of the genus Stylolophus , report the researchers. The first toothfish were already known from 48 million years old fossils collected in Africa and Turkey.
"The brackets were large and strange extinct mammals that belonged, with hyraxes and elephants, to the mammalian megaherbivorous fauna that inhabited the island of Africa, well before the arrival there were 23 million dinosaurs. Years of Eurasian ungulate lines such as artiodactyls, including giraffes, buffaloes, hippos and antelopes, and perissodactyls, including zebras and rhinos "explains Emmanuel Gheerbrant of the CNRS-MNHN in Paris , in France. "They belong to the old endemic African fauna."
Gheerbrant said that the origins of the brackets were uncertain, with two known coexisting families: one in Africa and the other in Turkey and Romania: The exact relationship of the hippodopods to cows and elephants is unclear
![Ancient Moroccan dental remnants elucidate the history of long-lost African fauna [19659002] The paleogeographic distribution of Embrithopods and the hypothesis of the African origin of Embrithopoda and Palaeoamasiidae supported by the discovery of Stylolophus. Credit: Gheerbrant et al.
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<p> The new phylogenetic study of the two species of Stylolophus found in Morocco confirms that they are basal hematopods. It also shows that the order of extinct embryos is old, preceding the divergence of cows and elephants. </p>
<p> "The comparative anatomy of new Moroccan species shows that highly specialized embryonic teeth derived from the ancestral dental morphology of all paenungulate, a clade comprising elephants, sea cows, and hyraxes , with the W-crested molars seen in some of the oldest hyracoids, "the group comprising hyraxes," says Gheerbrant. "The specialized design of the teeth with two transverse ridges, known in the most advanced forms such as Arsinoitherium, is a convergence of the brackets and the existing group of thethytheres, including manatees and elephants, towards the consumption of leaves, which has was favored by the ancient herbivorous niches available on the African island. "</p>
<p> The new species S. minor – which was unusually small about the size of a sheep – is also the first to show the presence in the embrithopods of widened incisors and inclined towards the front, in the form of nascent defenses, as seen in the early ancestors of the group including elephants. </p>
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