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

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

ANATOMÍA COMPARADA DEL LABERINTO ÓSEO DE LOS MURCIÉLAGOS PLATALINA GENOVENSIUM (PHYLLOSTOMIDAE, LONCHOPHYLLINAE) Y TOMOPEAS RAVUS (MOLOSSIDAE, TOMOPEATINAE)

Th e bony labyrinth inside the temporal bone houses the inner ear, sensory organ of hearing and balance. Variations in the three components of the bony labyrinth (cochlea, vestibule, and semicircular canals) give insight into the physiology and evolution of the diff erent groups of mammals. Based on high resolution micro-Computed Tomography (μCT), we reconstructed the digital endocasts of the bony labyrinths of Platalina and Tomopeas. We found that both species exhibit unique characteristics among bats, that were mainly located in the cochlea, including the aspect ratio of the cochlear spiral, cochlear width rela tive to that of the basicranial region, number of cochlear spiral turns, among others. Finally we highlight the need of more morphological comparative studies of the bony labyrinth.El laberinto óseo dentro del hueso temporal protege el oído interno, órgano sensorial para la audición y balance. La variación en los tres componentes del laberinto óseo (cóclea, vestíbulo y canales semicirculares) ofrece un alcance sobre la fi siología y evolución de los diferentes grupos de mamíferos. Usando la tomografía micro-computarizada de alta resolución (μCT), reconstruimos los moldes digitales internos de los laberintos óseos de Platalina y Tomopeas. Encontramos que ambas especies presentan características únicas entre los murciélagos, que están principalmente localizadas en la cóclea, entre ellos la proporción del espiral de la cóclea, ancho de la cóclea con respecto al ancho de la región de la base del cráneo, número de espirales cocleares. Finalmente, resaltamos la necesidad de más estudios de morfología comparada del laberinto óseo

Lutrinae Bonaparte, 1838 (Carnivora, Mustelidae) du Plio-Pléistocène de la basse vallée de l’Omo, sud-ouest éthiopien : systématique et nouvelles données sur la paléoécologie et la paléobiogéographie des loutres du Turkana

International audienceWe describe otter remains (Lutrinae Bonaparte, 1838) from the Plio-Pleistocene of the Lower Omo Valley of southwestern Ethiopia. We report isolated lower and upper teeth of Torolutra sp. dated to c. 3.3 Ma, dental specimens and a femur of Enhydriodon Falconer, 1868, attributed to a new species, dated between c. 3.4 Ma and 2.5 Ma, as well as a humerus of Lutrinae indet. dated between c. 1.9 Ma and 1.8 Ma. The new species Enhydriodon omoensis n. sp. is the largest species of the genus discovered so far. It is even larger than its close relative E. dikikae Geraads, Alemseged, Bobe & Reed, 2011, a Pliocene lion-sized otter from the Afar region and potentially from eastern Turkana. Based on stable oxygen and carbon isotope analyses, we found that Enhydriodon from the Lower Omo Valley could have been terrestrial and fed on both aquatic and terrestrial prey, acquired by either hunting or scavenging. It filled a unique ecological niche in the past communities co-existing with australopithecines. Enhydriodon and Torolutra Petter, Pickford & Howell, 1991 went extinct in Africa around the Plio-Pleistocene transition, along with many large-sized and ecologically specialized carnivorans. This extinction event could be linked to the many geological, climate, and biotic changes occurring in the eastern African rift during this period, notably the incursion of early hominins into the carnivore guild.Nous décrivons des restes de loutres (Lutrinae Bonaparte, 1838) du Plio-Pléistocène de la basse vallée de l’Omo, au Sud-Ouest de l’Éthiopie. Nous rapportons des dents inférieures et supérieures isolées de Torolutra sp., datées de c. 3,3 Ma, des specimens dentaires et un femur d’Enhydriodon Falconer, 1868, attribués à une nouvelle espèce, datés entre c. 3,4 et 2,5 Ma, ainsi qu’un humérus de Lutrinae indet., daté entre c. 1,9 et 1,8 Ma. La nouvelle espèce Enhydriodon omoensis n. sp. est la plus grande espèce du genre découverte à ce jour. Elle est encore plus grande que son proche parent E. dikikae Geraads, Alemseged, Bobe & Reed, 2011, une loutre pliocène de la taille d’un lion provenant de la région de l’Afar et potentiellement de l’Est du Turkana. Elle remplissait une niche écologique singulière dans les communautés du passé coexistantes avec les australopithécines. À partir des analyses des isotopes stables de l’oxygène et du carbone, nous avons mis en evidence qu’Enhydriodon de la basse vallée de l’Omo devait être terrestre et se nourrir de proies aquatiques et terrestres, acquises par la chasse ou le charognage. Enhydriodon et Torolutra Petter, Pickford & Howell, 1991 se sont éteintes en Afrique aux environs de la transition Plio-Pléistocène, à la même période que de nombreux carnivores de grande taille et spécialisés d’un point de vue écologique. Cet évènement d’extinctions pourrait être lié aux nombreux changements géologiques, climatiques et biotiques associés au rift est-africain durant cette période, notamment à l’incursion des hominines anciens dans la guilde carnivore

A unique feeding strategy of the extinct marine mammal Kolponomos: convergence on sabretooths and sea otters

Mammalian molluscivores feed mainly by shell-crushing or suction-feeding. The extinct marine arctoid, Kolponomos, has been interpreted as an otter-like shell-crusher based on similar dentitions. However, neither the masticatory biomechanics of the shell-crushing adaptation nor the way Kolponomos may have captured hard-shelled prey have been tested. Based on mandibular symphyseal morphology shared by Kolponomos and sabre-toothed carnivores, we hypothesize a sabretooth-like mechanism for Kolponomos prey-capture, whereby the mandible functioned as an anchor. Torque generated from jaw closure and head flexion was used to dislodge prey by prying, with prey then crushed using cheek teeth. We test this hypothesized feeding sequence using phylogenetically informed biomechanical simulations and shape analyses, and find a strongly supported, shared high mandibular stiffness in simulated prey-capture bites and mandibular shape in Kolponomos and the sabre-toothed cat Smilodon. These two distantly related taxa converged on using mandibles to anchor cranial torqueing forces when prying substrate-bound prey in the former and sabre-driving forces during prey-killing in the latter. Simulated prey-crushing bites indicate that Kolponomos and sea otters exhibit alternative structural stiffness-bite efficiency combinations in mandibular biomechanical adaptation for shell-crushing. This unique feeding system of Kolponomos exemplifies a mosaic of form-function convergence relative to other Carnivora

Tsengetal_PRSB_FE_models

Finite element models of all species analyzed in the study, with forces loaded. In Strand7 file format

Data from: A unique feeding strategy of the extinct marine mammal Kolponomos: convergence on sabretooths and sea otters

Mammalian molluscivores feed mainly by shell-crushing or suction-feeding. The extinct marine arctoid, Kolponomos, has been interpreted as an otter-like shell-crusher based on similar dentitions. However, neither the masticatory biomechanics of the shell-crushing adaptation, nor the way Kolponomos may have captured hard-shelled prey, have been tested. Based on mandibular symphyseal morphology shared by Kolponomos and sabretoothed carnivores, we hypothesize a sabretooth-like mechanism for Kolponomos prey-capture, whereby the mandible functioned as an anchor. Torque generated from jaw closure and head flexion was used to dislodge prey by prying, with prey then crushed using cheek teeth. We test this hypothesized feeding sequence using phylogenetically-informed biomechanical simulations and shape analyses, and find a strongly supported, shared high mandibular stiffness in simulated prey-capture bites and mandibular shape in Kolponomos and the sabretoothed cat Smilodon. These two distantly related taxa converged on using mandibles to anchor cranial torquing forces when prying substrate-bound prey in the former and sabre-driving forces during prey-killing in the latter. Simulated prey-crushing bites indicate that Kolponomos and sea otters exhibit alternative structural stiffness-bite efficiency combinations in mandibular biomechanical adaptation for shell-crushing. This unique feeding system of Kolponomos exemplifies a mosaic of form-function convergence relative to other Carnivora

The bony labyrinth of toothed whales reflects both phylogeny and habitat preferences

The inner ear of toothed whales (odontocetes) is known to have evolved particular shapes related to their abilities to echolocate and move under water. While the origin of these capacities is now more and more examined, thanks to new imaging techniques, little is still known about how informative inner ear shape could be to tackle phylogenetic issues or questions pertaining to the habitat preferences of extinct species. Here we show that the shape of the bony labyrinth of toothed whales provides key information both about phylogeny and habitat preferences (freshwater versus coastal and fully marine habitats). Our investigation of more than 20 species of extinct and modern odontocetes shows that the semi-circular canals are not very informative, in contrast to baleen whales, while the cochlea alone bears a strong signal. Inner ear shape thus provides a novel source of information to distinguish between morphologically convergent lineages (e.g. river dolphin

Investigation of the bony labyrinth shape variation in Carnivora: the case of Musteloidea

International audienc