Arctotherium angustidensGervais and Ameghino, 1880 (the South American giant short-faced bear) is known for being the earliest (Ensenadan Age, early to middle Pleistocene) and largest (body mass over 1 ton) of five describedArctotheriumspecies endemic to South America. Here we assess the diet of this bear from multiple proxies: morphology, biomechanics, dental pathology, stable isotopes and a previous study using geometric morphometric methodology. Results favor the idea of animal matter consumption, probably from large vertebrates in addition to vegetable matter consumption. Most probably, active hunting was not the unique strategy of this bear for feeding, since its large size and great power may have allowed him to fight for the prey hunted by other Pleistocene carnivores. However, scavenging over mega mammal carcasses was probably another frequent way of feeding. South American short-faced bears adjusted their size and modified their diet through Pleistocene times, probably as a response to the diversification of the carnivore guild (from the few precursory taxa that crossed the Panamanian Isthmus during the Great American Biotic Interchange).
In Antarctica, crabeater seals tend to strand as immature animals with disorientation, due to their inexperience, given as the probable cause. In 2012 and 2013, we examined a group of 80 mummified crabeater seals on Seymour Island (Marambio). The age and gender of 28 seals was determined, and virology and stomach content analyses were performed in order to determine the cause of stranding. Around 82% of the seals examined were adults and 79% were females, some of which were pregnant. All of the seals sampled tested negative for Morbillivirus, suggesting that the stranding was not related to the mass mortality event reported in the 1950s in the region. Most seals had empty stomachs and thin blubber suggesting that they died from starvation. The state of the carcasses suggests multiple stranding events. Most of the seals were located along an ice-covered stream, suggesting that this may act as a ‘natural trap’, isolating the seals from the open ocean. This is exceptional as it is the first report of mostly adult female seals to strand in Antarctica and refutes the theory that only young animals are prone to stranding.
The aim of the present study was to examine the catecholaminergic neurones located within the midbrain of the coypu, a South American hystricomorph rodent. The neuronal distribution of the catecholaminergic systems and morphological parameters of the immunostained cell bodies and fibres were investigated, using an immunohistochemical method. The brains of five coypu were fixed, immersed in gelatine-glycerol and cut in 40-micron slices using a freezing microtome. Samples were processed with ultrasound-based antigen retrieval and stained with labelled antityrosine hydroxylase monoclonal antibody. An image analyser was used to measure the neuronal bodies. The catecholaminergic neurones of the tuberoinfundibular system were mainly observed in the arcuate and periventricular nuclei with their axons projecting towards to the median eminence; they represented 28% of the global population of tyrosine hydroxylase-immunoreactive cells observed. Significant morphological differences were observed in comparison with the other two studied systems. Fifty per cent of total catecholaminergic neurones were detected in the nigrostriatal system distributed in the reticular and compact substance nigra. Most neuronal bodies had a fusiform aspect. The immunoreactive neurones of the mesolimbic system represented 22% of the total population. They were distributed around the interpeduncular nucleus. Two types of morphologically different catecholaminergic systems of the brain were established: hypothalamic neurones located in the periventricular and arcuate nuclei and mesencephalic neurones located in the substance nigra and interpeduncular nuclei. These systems showed morphological and probably physiological-pharmacological differences.
El objetivo de este trabajo de tesis fue identificar enfermedades osteoarticulares y dentarias en los caballos fósiles de la Argentina, Hippidion y Equus (Amerhippus), y analizar implicancias paleoambientales, paleoecológicas, evolutivas y analogías con los equinos actuales, Equus caballus. No existen antecedentes en relación a estudios paleopatológicos en los taxones objeto del presente estudio. El relevamiento del material se realizó sobre un número de 1.216 piezas, de las cuales 611 fueron molares aislados o grupos de molares implantados, 41 fueron incisivos aislados o grupos de incisivos implantados, y 564 fueron piezas óseas. Se logró distinguir signos de enfermedades reconocibles en los caballos actuales diferenciándolos de los cambios producidos por fenómenos tafonómicos y diagenéticos. Las modificaciones se corresponden con procesos morbosos que suceden en los seguimientos en vivo de los caballos actuales. En cada caso se ha diagnosticado la enfermedad, dando detalles de su evolución, y se han hecho inferencias sobre la paleoecología y paleobiología de cada individuo a partir de su situación patológica. En los taxones estudiados no se encontraron algunos signos de enfermedades que desarrollan con frecuencia los caballos actuales. Se propone la formación de un equipo interdisciplinario capacitado que desarrolle líneas de investigación en relación a esta disciplina y la realización de cursos formales en el ámbito de la Universidad Nacional de La Plata. Se propone la creación de Paleopatología Animal como materia optativa para la carrera de Ciencias Veterinarias y Paleontología de la Universidad Nacional de La Plata.
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