A New Extinct Genus of Cavioidea (Rodentia,Hystricognathi) from the Miocene of Patagonia (Argentina) and the Evolution of Cavioid Mandibular Morphology |
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Authors: | María Encarnación Pérez María Guiomar Vucetich |
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Institution: | 1.Museo Paleontológico Egidio Feruglio,Trelew,Argentina;2.Departamento Científico Paleontología de Vertebrados,Museo de La Plata,La Plata,Argentina |
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Abstract: | The family Caviidae is represented in modern faunas by cavies and maras, whereas the family Hydrochoeridae is represented
by capybaras. The evolutionary origin of these families has been related to a diversity of plesiomorphic fossil forms (recorded
from the late Oligocene up to the middle Miocene) traditionally grouped in the family “Eocardiidae”. These fossil forms were
included, together with Caviidae and Hydrochoeridae, within the Cavioidea s.s. (sensu stricto), because they share high crowned
cheek teeth, double-hearted occlusal surface, short lower incisors, and moderate hystricognathy. Within Cavioidea s.s., caviids
and hydrochoerids were interpreted as forming its crown group, because they have unique craniomandibular and dental features.
In this contribution, a new taxon of Cavioidea s.s. from the middle Miocene of central Patagonia, Argentina, is described,
and its phylogenetic position is determined on the basis of a morphological cladistic analysis in which “eocardiids” were
included. The study permits the understanding of the sequence of appearance of characters that originated the highly divergent
morphology of crown-group cavioids. The analysis of the sequence of appearance of the characters that traditionally diagnosed
the crown group indicates that these changes did not occur at the same time. On the contrary, many of these features seem
to have appeared at different nodes of the evolutionary history of Cavioidea s.s. The remarkably derived morphology of modern
cavioids is the result of a stepwise appearance of a mosaic of evolutionary innovations that originated gradually along the
history of Cavioidea during the late-middle Miocene. |
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