Hayet Khayati

Bio: Hayet Khayati is an academic researcher. The author has contributed to research in topics: Prorastomus & Afrotheria. The author has an hindex of 2, co-authored 2 publications receiving 57 citations.

Cranial Remain from Tunisia Provides New Clues for the Origin and Evolution of Sirenia (Mammalia, Afrotheria) in Africa

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 sea cows were likely restricted to fresh waters.

A new taxon of stem group Galliformes and the earliest record for stem group Cuculidae from the Eocene of Djebel Chambi, Tunisia

Abstract: A distal tarsometatarsus and a fragment of carpometacarpus of a small galliform, the size of a recent quail, have been found in the late Early or early Middle Eocene of Chambi, in Tunisia. Although a large number of stem group representatives of Galliformes are known from the Eocene of the Northern Hemisphere, and one from the middle Eocene of Namibia, the taxon from Chambi differs from them and is described as a new genus and species. A very small zygodactyl form, represented by three distal tarsometatarsi, is also present in the same locality. This form, described as a new genus and species, is a stem group representative of the recent family Cuculidae. It shows a plesiomorphic morphology compared to the recent members of the Cuculidae, but it is, however, more derived than the younger genus Eocuculus. It is the earliest Cuculidae known so far.

Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls

Abstract: Anthracobunidae is an Eocene family of large mammals from south Asia that is commonly considered to be part of the radiation that gave rise to elephants (proboscideans) and sea cows (sirenians). We describe a new collection of anthracobunid fossils from Middle Eocene rocks of Indo-Pakistan that more than doubles the number of known anthracobunid fossils and challenges their putative relationships, instead implying that they are stem perissodactyls. Cranial, dental, and postcranial elements allow a revision of species and the recognition of a new anthracobunid genus. Analyses of stable isotopes and long bone geometry together suggest that most anthracobunids fed on land, but spent a considerable amount of time near water. This new evidence expands our understanding of stem perissodactyl diversity and sheds new light on perissodactyl origins.

The origins of crown group birds: molecules and fossils

Abstract: Knowledge of the evolutionary history of crown group birds (Neornithes) has significantly improved through emerging congruence among phylogenetic hypotheses and the description of numerous new Palaeogene stem group representatives. However, controversies still persist about the precise interrelationships of many extant and fossil taxa and about the timing of the diversification of the neornithine crown group. Using the example of Phaethontiformes (tropicbirds) and Psittaciformes (parrots), it is shown how new sequence-based phylogenies may shed light on the relationships of fossils with an unexpected character mosaic, and how such fossils can improve our understanding of character evolution in morphologically disparate avian taxa. The earliest occurrences of neornithine birds are plotted on a current phylogeny. As noted by previous authors, an extensive diversification of neornithine birds before the latest Cretaceous is not supported by the fossil record, and the existence of essentially modern-type representatives of Telluraves (the clade including most arboreal birds) in the Cretaceous, such as suggested from molecular calibrations, is highly unlikely.