The neurocranium of Ekweeconfractus amorui gen. et sp. nov. (Hyaenodonta, Mammalia) and the evolution of the brain in some hyaenodontan carnivores

This project forms part of the NSF-funded Research on East African Catarrhine and Hominoid Evolution (REACHE) Project and is REACHE Paper #16. Fieldwork by The West Turkana Miocene Project was funded by NSF award BCS 1241817 to JBR, the Natural Sciences and Engineering Research Council of Canada, and the University of Calgary.</p

Craniofacial Morphology of <i>Vintana Sertichi</i> (Mammalia, Gondwanatheria) from the Late Cretaceous of Madagascar

<div><p>ABSTRACT</p><p>The Gondwanatheria are an enigmatic clade of Cretaceous and Paleogene mammals known from South America, Africa, Madagascar, India, and the Antarctic Peninsula. The eight valid species—each belonging to a monotypic genus and the first of which was described only 30 years ago—are represented almost exclusively by isolated teeth, in addition to fragmentary dentaries attributed to <i>Sudamerica</i>, <i>Gondwanatherium</i>, <i>Ferugliotherium</i>, and an unnamed taxon from Tanzania. No cranial (skull exclusive of lower jaw) or postcranial material has heretofore been assigned to the Gondwanatheria, a severe limitation that has precluded a comprehensive assessment of phylogenetic affinities. Here we describe, in detail, the first cranial specimen of a gondwanatherian mammal. This material consists of a complete and well-preserved cranium of the sudamericid <i>Vintana sertichi</i>, recovered from the Upper Cretaceous (Maastrichtian) Maevarano Formation in the Mahajanga Basin of northwestern Madagascar. Salient features of the cranium include elongate, scimitar-like jugal flanges, huge orbits, strong klinorhynchy, and a vaulted nuchal region. Micro-computed tomography greatly facilitated the delineation of sutures and the description of internal morphology. The cranial features of <i>Vintana</i> are compared with those of a broad range of synapsids, with particular concentration on other Mesozoic mammaliaforms. The cranium of <i>Vintana</i> exhibits a mosaic of extremely primitive and extremely derived features. It is the second largest known for a Mesozoic mammaliaform, superseded only by that of the eutriconodontan <i>Repenomamus giganticus</i> from the Early Cretaceous of China. <i>Vintana</i> is the largest known Late Cretaceous mammaliaform; it is also the largest known Mesozoic mammaliaform from Gondwana.</p><p>SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP</p></div

Skeleton of a Cretaceous mammal from Madagascar reflects long-term insularity

Fig. 2 | Cranium, lower jaw and dentition of A. hui holotype (UA 9030). a–d, Reconstructed cranium in dorsal (a), ventral (b), right lateral (c) and anterior (d) views.e–g, Reconstructed right lower jaw in lateral (e), dorsal (= occlusal) (f) and medial (g) views.h–k, Micro-computed tomography (ΜCT) digital renderings of right upper dentition,showing the postcanine teeth (h), distal incisor (i) and mesial incisor (j) in buccal views,and the postcanine teeth in occlusal view (k). l–n, ΜCT digital renderings of right lower dentition, showing the postcanine teeth (l) and incisor (m) in buccal views,and the postcanine teeth in occlusal view (n). Scale bars,2 cm (a–g; scale bar above e and f applies to a–g), 5 mm (h–n). PC,upper postcanine tooth; pc,lower postcanine tooth.Published as part of Krause, David W., Hoffmann, Simone, Hu, Yaoming, Wible, John R., Rougier, Guillermo W., Kirk, E. Christopher, Groenke, Joseph R., Rogers, Raymond R., Rossie, James B., Schultz, Julia A., Koenigswald, Wighart von & Rahantarisoa, Lydia J., 2020, Skeleton of a Cretaceous mammal from Madagascar reflects long-term insularity, pp. 1-21 in Nature 580 (7805) on page 3, DOI: 10.1038/s41586-020-2234-8, http://zenodo.org/record/378415

Primitive Old World monkey from the earliest Miocene of Kenya and the evolution of cercopithecoid bilophodonty

Old World monkeys (Cercopithecoidea) are a highly successful primate radiation, with more than 130 living species and the broadest geographic range of any extant group except humans. Although cercopithecoids are highly variable in habitat use, social behavior, and diet, a signature dental feature unites all of its extant members: bilophodonty (bi: two, loph: crest, dont: tooth), or the presence of two cross-lophs on the molars. This feature offers an adaptable Bauplan that, with small changes to its individual components, permits its members to process vastly different kinds of food. Old World monkeys diverged from apes perhaps 30 million years ago (Ma) according to molecular estimates, and the molar lophs are sometimes incompletely developed in fossil species, suggesting a mosaic origin for this key adaptation. However, critical aspects of the group's earliest evolution remain unknown because the cercopithecoid fossil record before ∼18 Ma consists of only two isolated teeth, one from Uganda and one from Tanzania. Here we describe a primitive Old World monkey from Nakwai, Kenya, dated at ∼22 Ma, that offers direct evidence for the initial key steps in the evolution of the cercopithecoid dentition. The simple dentition and absence of bilophodonty in the Nakwai monkey indicate that the initial radiation of Old World monkeys was first characterized by a reorganization of basic molar morphology, and a reliance on cusps rather than lophs suggests frugivorous diets and perhaps hard object feeding. Bilophodonty evolved later, likely in response to the inclusion of leaves in the diet