IANIGLA   20881
INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Paleobiology of Huayqueriana, a late Miocene Litoptern from western Argentina: Interpreting conflicting signals from morphological attributes
Autor/es:
A. M. FORASIEPI, R. D. E. MACPHEE, S. HERNANDEZ DEL PINO, G.I. SCHMIDT, E. AMSON Y C. GROHE
Lugar:
Salt Lake City
Reunión:
Congreso; 76th Annual Meeting of the Society of Vertebrate Paleontology, Utah, USA; 2016
Institución organizadora:
Society fo Vertebrate Paleontology
Resumen:
IANIGLA-PV 29, a well preserved skull of the macraucheniine litopternHuayqueriana from the Huayquerías Formation (late Miocene), presents severalmorphological and paleobiological puzzles. Nasal apparatus: The highly derived dorsal positioning of the macraucheniineexternal nares has provoked discussion for more than a century. MicroCT scanning ofIANIGLA-PV 29 reveals simplified turbinate architecture and an air passageway orientedperpendicular to, rather than aligned with, the palate as in most mammals (includingelephants). The primitive nasal vestibule is present, but only as a blind diverticulumwithin the rostrum. To a degree these innovations recall conditions in cetaceans and someother aquatically adapted taxa, but macraucheniine limb skeletons lack obviousadaptations for aquatic life. Orientation of the lateral semicircular canal relative to theskull base is ~26°, indicating that in life the head was habitually oriented much as inmodern horses. If there was a proboscis, it would have been positioned frontally, notdorsally as in many reconstructions.  Endocast: Although the identity of the pathways of certain cranial nerves inlitopterns have been disputed, conditions in Huayqueriana conform to those in otherplacentals. The orbitotemporal canal runs well below the rhinal fissure, along thelateroventral aspect of the piriform lobe instead of more dorsally. No functionalconsequences for this rearrangement are evident. Body mass: Making size estimates for fossil taxa, especially those having no closeliving relatives, presents many difficulties. For IANIGLA-PV 29, conventionalestimators, especially those employing dental measurements, yielded highly conflictingresults (mean 400 kg; range 154?721 kg, prediction error >25%). Our preferred estimateof ~250 kg (prediction error ~6%) is based on an alternative approach utilizing centroidsize of 36 3D cranial landmarks. Longevity and diet: Advanced tooth wear implies that IANIGLA-PV 29 was senileat death. However, cementum line counts on a sectioned M2 are consistent with a 10?11year lifespan, much shorter than its body mass would suggest. The late Miocene flora ofwestern Argentina was dominated by xerophytic plants with thick foliar cuticles andhard-shelled fruits to combat desiccation, and perhaps excessive wear reflects a veryabrasive diet. Oddly, unlike the vast majority of Neogene South American nativeungulate lineages, litopterns did not develop euhypsodonty. There is no decisive evidencefor the proposition that Huayqueriana (or any other litoptern) was a foregut fermenter. 
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