Exceptional skull of huayqueriana (mammalia, litopterna, macraucheniidae) from the late miocene of Argentina: Anatomy, systematics, and peleobiological implications

The Huayquerías Formation (Late Miocene, Huayquerian SALMA) is broadly exposed in westcentral Argentina (Mendoza). The target of several major paleontological expeditions in the first half of the 20th century, the Mendozan Huayquerías (badlands) have recently yielded a significant number of new fossil finds. In this contribution we describe a complete skull (IANIGLA-PV 29) and place it systematically as Huayqueriana cf. H. cristata (Rovereto, 1914) (Litopterna, Macraucheniidae). The specimen shares some nonexclusive features with H. cristata (similar size, rostral border of the orbit almost level with distal border of M3, convergence of maxillary bones at the level of the P3/P4 embrasure, flat snout, very protruding orbits, round outline of premaxillary area in palatal view, and small diastemata between I3/C and C/P1). Other differences (e.g., lack of sagittal crest) may or may not represent intraspecific variation. In addition to other features described here, endocast reconstruction utilizing computer tomography (CT) revealed the presence of a derived position of the orbitotemporal canal running below the rhinal fissure along the lateroventral aspect of the piriform lobe. CT scanning also established that the maxillary nerve (CN V2) leaves the skull through the sphenoorbital fissure, as in all other litopterns, a point previously contested for macraucheniids. The angle between the lateral semicircular canal and the plane of the base of the skull is about 26°, indicating that in life the head was oriented much as in modern horses. Depending on the variables used, estimates of the body mass of IANIGLA-PV 29 produced somewhat conflicting results. Our preferred body mass estimate is 250 kg, based on the centroid size of 36 3D cranial landmarks and accompanying low prediction error. The advanced degree of tooth wear in IANIGLA-PV 29 implies that the individual died well into old age. However, a count of cementum lines on the sectioned left M2 is consistent with an age at death of 10 or 11 years, younger than expected given its body mass. This suggests that the animal had a very abrasive diet. Phylogenetic analysis failed to resolve the position of IANIGLA-PV 29 satisfactorily, a result possibly influenced by intraspecific variation. There is no decisive evidence for the proposition that Huayqueriana, or any other litoptern, were foregut fermenters.Fil: Forasiepi, Analia Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: MacPhee, Ross D. E.. American Museum Of Natural History; Estados UnidosFil: Hernández del Pino, Santiago Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Schmidt, Gabriela Ines. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Amson, Eli. Universitat Zurich; SuizaFil: Grohé, Camille. American Museum Of Natural History; Estados Unido

The internal carotid artery in early eutherians

Although evidence from comparative anatomy and embryology shows that only one internal carotid artery is present among extant eutherians, numerous early eutherians have two vascular-like grooves on the petrosal suggesting the presence of two separate internal carotids. It is argued here that the most acceptable model for the interpretation of this morphology places the single internal carotid in the lateral groove and a venous channel (inferior petrosal sinus) in the medial one. This lateral course for the internal carotid artery is not necessarily primitive for Eutheria, only widespread among early groups. The earliest known eutherian basicrania have only a medial groove and therefore, a medial course to the internal carotid. However, based on ontogenetic research, this medial course in the earliest known eutherians was most likely not identical with the medial course in non-eutherian mammals

Pangolins : science, society and conservation

This chapter provides an authoritative account of the phylogeny and taxonomy of fossil and extant pangolins. Historical discrepancies around the taxonomy of pangolins are discussed, notably in terms of infraordinal classification, while the respective merits of morphological and molecular analyses to solve the phylogenetic relationships among pangolins are addressed. Additionally, the contribution of DNA-based phylogeographic analyses in revealing cryptic diversity within wide-ranging species is reviewed, and a biogeographic scenario for the diversification of extant pangolins is proposed. Finally, the chapter presents an updated, synthetic classification of extant pangolins

Pangolins : science, society and conservation

Pangolins'evolutionary history is poorly known, with historically uncertain relationships to other placental mammals, and weak representation in the fossil record. Their closest relatives are extinct Palaeanodonta and extant Carnivora. The oldest fossil pangolins come from the European Eocene, with early records confined to Laurasia, and a modern range established in the Plio-Pleistocene. Extant pangolins are characterized by many distinctive anatomical features, including an external armor of epidermal scales, along with traits associated with myrmecophagous, fossorial, and arboreal habits. Their skull is edentulous and narrow. The postcranial skeleton is marked by powerful digging claws and forelimbs, and a prehensile tail in some forms. The tongue is attached to an elongated xiphisternum. Food is masticated in a stomach containing horny denticles. Females have axillary nipples and a bicornuate uterus; males lack a scrotum. The vascular system includes several retia mirabilia, and the carnivoran-like brain has a low encephalization quotient