Click on the title to browse this book

The taxonomic revision of Isocetus depauwi Van Beneden, 1880 was carried out through the description of a number of specimens assigned to this species by Van Beneden and Abel in the last decades of the 19th and the early decades of the 20th centuries. After detailed comparisons with the published record of archaic mysticetes, the genus and species are considered valid despite the incompleteness and poor preservation of the material. Diagnostic features are found in the morphology of the mandibular condyle, the angular process of the dentary and the thoracic vertebrae. The new species Parietobalaena campiniana is established based on a partial skeleton, including most of the skull and ear bones, previously assigned to Isocetus depauwi by Abel. Parietobalaena campiniana is described and compared in detail, and its phylogenetic relationships are assessed by a new large-scale cladistic analysis of 246 morphological characters scored for 46 taxa. The results support a basal position of the genus Parietobalaena in the radiation of Miocene ‘cetotheres’, the monophyly of Balaenoidea (Neobalaenidae and Balaenidae), Balaenopteroidea (Eschrichtiidae and Balaenopteridae), and Cetotheriidae and the paraphyly of ‘cetotheres’s.l. The new superfamily Thalassotherii is established based on high bootstrap support and a number of morphological characters; Thalassotherii includes Balaenopteridae, Eschrichtiidae, Cetotheriidae and the basal ‘cetothere’ mysticetes with the exclusion of Balaenoidea, Eomysticetoidea and toothed mysticetes.

Secondary adaptation to aquatic life occurred independently in several amniote lineages, including reptiles during the Mesozoic and mammals during the Cenozoic. These evolutionary shifts to aquatic environments imply major morphological modifications, especially of the feeding apparatus. Mesozoic (250–65 Myr) marine reptiles, such as ichthyosaurs, plesiosaurs, mosasaurid squamates, crocodiles, and turtles, exhibit a wide range of adaptations to aquatic feeding and a broad overlap of their tooth morphospaces with those of Cenozoic marine mammals. However, despite these multiple feeding behavior convergences, suction feeding, though being a common feeding strategy in aquatic vertebrates and in marine mammals in particular, has been extremely rarely reported for Mesozoic marine reptiles. A relative of fossil protostegid and dermochelyoid sea turtles, Ocepechelon bouyai gen. et sp. nov. is a new giant chelonioid from the Late Maastrichtian (67 Myr) of Morocco exhibiting remarkable adaptations to marine life (among others, very dorsally and posteriorly located nostrils). The 70-cm-long skull of Ocepechelon not only makes it one of the largest marine turtles ever described, but also deviates significantly from typical turtle cranial morphology. It shares unique convergences with both syngnathid fishes (unique long tubular bony snout ending in a rounded and anteriorly directed mouth) and beaked whales (large size and elongated edentulous jaws). This striking anatomy suggests extreme adaptation for suction feeding unmatched among known turtles. The feeding apparatus of Ocepechelon, a bony pipette-like snout, is unique among tetrapods. This new taxon exemplifies the successful systematic and ecological diversification of chelonioid turtles during the Late Cretaceous. This new evidence for a unique trophic specialization in turtles, along with the abundant marine vertebrate faunas associated to Ocepechelon in the Late Maastrichtian phosphatic beds of Morocco, further supports the hypothesis that marine life was, at least locally, very diversified just prior to the Cretaceous/Palaeogene (K/Pg) biotic crisis.

Cynthiacetus peruvianus Martínez-Cáceres & Muizon, 2011 is a Dorudon-like basilosaurid (Cetacea, Basilosauridae), being one of the largest members of the family. The holotype of this species is a sub-complete skeleton, which comes from the late Eocene (Priabonian) of the Otuma Formation on the southern coast of Peru. A thorough description of this specimen is presented here. Cynthiacetus peruvianus differs from the other species of the genus (C. maxwelli) in having fewer accessory cusps on the distal and mesial edges of p3 and p4. Its skull shows the general pattern of the basilosaurid skull, which is relatively monotonous across the whole family, but it is much larger than those of Dorudon and Zygorhiza, and slightly smaller and distinctly more slender than that of Basilosaurus. The most characteristic features of C. peruvianus stand on the postcranial skeleton: it presents large vertebrarterial foramina on the cervical vertebrae; it lacks a ventral expansion of the transverse processes of C3-C5... RÉSUMÉ Anatomie et affinités phylogénétiques de Cynthiacetus peruvianus, un grand basilosauridé ressemblant à Dorudon (Cetacea, Mammalia) de l'Éocène supérieur du Pérou. Cynthiacetus peruvianus Martínez-Cáceres & Muizon, 2011 est un basilosauridé (Cetacea, Basilosauridae) présentant de grandes ressemblances avec le genre Dorudon et l'un des plus grands membres de la famille. L'holotype de cette espèce est un squelette sub-complet qui provient des couches de la Formation Otuma, d'âge Éocène supérieur (Priabonien), sur la côte sud du Pérou. Une description exhaustive de ce spécimen est présentée dans ce travail. Cynthiacetus peruvianus diffère de l'autre espèce du genre (C. maxwelli) par le nombre plus faible de cuspides accessoires sur les bords mésial et distal des p3-p4. Son crâne présente le patron général de celui des basilosauridés, lequel est relativement uniforme dans toute la famille, mais il est plus grand que ceux de Dorudon et Zygorhiza, légèrement plus petit et nettement plus gracile que celui ...