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Benoit, Julien; Adnet, Sylvain; El Mabrouk, Essid; Khayati, Hayet; Ben Haj Ali, Mustapha; Marivaux, Laurent; Merzeraud, Gilles; Merigeaud, Samuel; Vianey-Liaud, Monique; Tabuce, Rodolphe
(detail)
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2013 |
Cranial remain from Tunisia provides new clues for the origin and evolution of Sirenia (Mammalia, Afrotheria) in Africa.
PLoS ONE 8(1): e54307. 9 pp. 1 tab. 6 figs. + 4 files of Supporting Information. doi:10.1371/journal.pone.0054307 Jan. 16, 2013.
–ABSTRACT: Sea cows (manatees, dugongs) are the only living marine mammals to feed solely on aquatic plants. Unlike whales or dolphins (Cetacea), the earliest evolutionary history of sirenians is poorly documented, and limited to a few fossils including skulls and skeletons of two genera composing the stem family of Prorastomidae (Prorastomus and Pezosiren). Surprisingly, these fossils come from the Eocene of Jamaica, while stem Hyracoidea and Proboscidea - the putative sister-groups to Sirenia - are recorded in Africa as early as the Late Paleocene. So far, the historical biogeography of early Sirenia has remained obscure given this paradox between phylogeny and fossil record. Here we use X-ray microtomography to investigate a newly discovered sirenian petrosal from the Eocene of Tunisia. This fossil represents the oldest occurrence of sirenians in Africa. The morphology of this petrosal is more primitive than the Jamaican prorastomids' one, which emphasizes the basal position of this new African taxon within the Sirenia clade. This discovery testifies to the great antiquity of Sirenia in Africa, and therefore supports their African origin. While isotopic analyses previously suggested sirenians had adapted directly to the marine environment, new paleoenvironmental evidence suggests that basal-most seacows were likely restricted to fresh waters.
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Benoit, Julien; Crumpton, Nick; Mérigeaud, Samuel; Tabuce, Rodolphe
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2013 |
A memory already like an elephant's? The advanced brain morphology of the last common ancestor of Afrotheria (Mammalia).
Brain Behav. Evol. 16 pp. 3 tabs. 5 figs. DOI: 10.1159/000348481 Publ. online March 21, 2013.
–ABSTRACT: Virtually reconstructed and natural endocranial casts are used in the study of brain evolution through geological time. We here present work investigating the paleoneurological evolution of afrotherian mammals. Using microCT-generated endocasts we show that, with the exception of the subfamilies Macroscelidinae and Tenrecoidea, most Afroinsectiphilia display a more or less gyrencephalic and ventrally expanded neopallium, two derived features that are unexpected for these insectivore-grade afrotherians. This implies that the endocranial cast morphology at the root of the afrotherian clade may have been more advanced than previously thought. The reconstructed endocranial morphology of the Afrotheria's last common ancestor reaches the level of complexity of some early Cenozoic archaic ungulates. Our result gives support to the hypothesis of an ungulate-like ancestral body plan for Afrotheria. It also implies that the a priori 'primitive' suite of traits evident in the brain of Afroinsectivora, especially in the tenrecs, may have been secondarily acquired. Implications on the overestimation of the divergence age of Afrotheria are discussed.
Provides a CT reconstruction of the endocranial cast of Prorastomus sirenoides, and a cladogram based on endocranial morphology including 8 fossil and Recent sir. taxa. Also comments briefly on Desmostylus.
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Bibliography and Index of the Sirenia and Desmostylia 