Tooth morphology of Echimyidae (Rodentia, Caviomorpha): homology assessments, fossils and evolution

CANDELA AND RASIA

ZOOLOGICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2012 p. 451 - 480

0024-4082

ABSTRACT- Echimyidae constitute the most important radiation of caviomorph rodents in the Neotropical region, represented by 20 extant genera and several extinct species. Both in extant and fossil forms, this diversity is reflected by a significant morphological variation found in crown structures of the cheek teeth. Different hypotheses of primary homology have been proposed for these structures, which, in turn, support diverse dental evolutionary hypotheses. In this contribution we inspect the main structures (cusps and lophids) of the lower deciduous teeth and molars in extinct and extant Echimyidae and establish their topological correspondences. Comparisons with cusps and lophids of Erethizontidae are emphasized. We explore the testing of alternative primary hypotheses of lophid correspondences in a cladistic context. Following a “dynamic” approach, we select the hypothesis of primary homology according to that which produced the more parsimonious results, and evaluate the evolutionary transformations of the analyzed dental characters. In this context, the phylogenetic relationships of living Myocastor coypus with the extinct Tramyocastor and Paramyocastor are tested. Our results indicate that pentalophodonty is the derived condition for the lower molars in Echimyidae; that trilophodonty evolved independently at least three times during the evolutionary history of these rodents, and that tetralophodonty represents the plesiomorphic condition. This study shows that dental evolution in echimyids can be better understood when occlusal structures are expressed as characters reliably comparable, and when fossils are taken into account.