MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
A new Colhuehuapian Caviomorph rodent from Patagonia and preliminary considerations on the early evolution of the superfamily Octodontoidea
Autor/es:
ARNAL, M.; KRAMARZ, A.; VUCETICH, M.G.
Lugar:
La Plata
Reunión:
Congreso; X Congreso Argentino de Paleontología y Bioestratigrafía y VII Congreso Latinoamericano de Paleontología; 2010
Institución organizadora:
FCNyM UNLP
Resumen:
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Octodontoidea
includes the most diverse superfamily of South American rodents in terms of morphology,
taxonomy and ecology. The morphological and taxonomic diversity are evident since
their earliest records (late Eocene? - early Oligocene). Nowadays there are two
major lineages, the Echimyidae (including Myocastor)
and the Octodontidae. Nevertheless, the phylogenetic relationships of these two
lineages with the most ancient members of the superfamily are not clear and
need to be revised. In this contribution a new octodontoid rodent from Colhuehuapian
levels (early Miocene) of the Trelew Member (Sarmiento Formation) at Gaiman,
Chubut Province, Argentina, is described. It is known through teeth and partially
preserved jaws. This new taxon is characterized by having braquiodont cheek teeth
and the retention of DP4/dp4; it shares with Caviocricetus (Colhuehuapian) the general morphology of the upper
cheek teeth and the terraced occlusal surfaces. The development of the metalophulid
II in the lower cheek teeth and the pentalophodont premolar morphology are
similar to that of Prospaniomys (Colhuehuapian).
A cladistic analysis was performed in order to evaluate the relationships of
the new taxon; we used 22 taxa and 39 dental and mandibular characters, since
they are the only ones that can be tested in the new taxon. The results indicate
this new specimen forms, with Caviocricetus
and Plesiacarechimys (Colloncuran,
middle Miocene), the stem group of a clade constituted by the acaremyids (+ Acarechimys), and by the fossils echimyids
traditionally included within the subfamily Adelphomyinae. Moreover, we
verified a variety of evolutionary lines within the superfamily that are not directly
related with modern octodontoids; some of these lineages would have diverged in
pre-Deseadan times (Oligocene) and persisted until the middle Miocene,
retaining a generalized dental morphology for the superfamily.