Phylogenetic relationships of the extinct cardiomyines (Rodentia, Cavioidea, Hydrochoeridae)

PÉREZ, M. E.; VUCETICH, M. G.

SAN JUAN

Congreso; IV CONGRESO LATINOAMERICANO DE PALEONTOLOGÍA DE VERTEBRADOS; 2011

The crown group of Cavioidea s.s. (Patterson and Wood, 1982) comprises caviids [caviines and dolichotines] and hydrochoerids. The latter encompasses the gigantic semiacuatic capybaras, the small and rock dweller Mocos, and the extinct cardiomyines a group of large rodents that share with the hydrochoerines ever-growing cheek teeth with accessory fissures on lingual (lowers) and labial (uppers) walls, enlarged M3 and p4, and a broad palate. In spite of these similarities cardiomyines were classically classified as caviids. However, Pérez (2010), and Vucetich and Deschamps (in press) considered cardiomyines as more closely related to hydrochoerines. Cavioids also includes the extinct “eocardiids” which are the stem group of Cavioidea s.s., plus the extant dasyproctids and cuniculids. In order to test the phylogenetic position of the cardiomyines in the context of the cavioids, a cladistic analysis was performed. The matrix (modified of Pérez and Vucetich, 2011) includes 87 morphological characters and 28 taxa of Cavioidea. An equally weighted parsimony analysis was conducted using TNT 1.1 (Goloboff et al. 2008a, b), performing a heuristic search of 100 Wagner tree replicates followed by TBR and considering some multistate characters as additives. The parsimony analysis resulted in 105 most parsimonious trees of 270 steps (CI=0,474; RI=0,679). The strict consensus shows that Procardiomys martinoi Pascual, 1961, Cardiomys cavinus Ameghino 1885, and Caviodon Ameghino, 1885 form a polytomy with hydrochoerins. This node is supported by five unambiguous sinapomorphies: 1) Absent constriction of the apex in each lobe, 2) shape of the m1-m2, in oclussal view formed by triangular lobes with wide base, 3) mesopterigoid fosae at the level of posterior prisms of M3, 4) squamosal process curved, and 5) 6–7 lobes in M3. Mocos is the sister group of this clade. When the position of conflictive taxa was ignored, the reduced consensus show cardiomyines grouped as a monophyletic taxa, more closely related to the hydrochoerines than to the caviines. The clade of cardiomyines is supported by two unambiguous sinapomorphies: 1) length of the upper diastema shorter than molariform series, and 2) location of the notch for the insertion of the tendon of the m. masseter medialis pars infraorbitalis with respect to the toothrow, between p4-m1. As an additional result, the Mara placed in a more basal position than the clade formed by caviines + (Moco + (cardiomyines + hydrochoerines) in opposition to Rowe et al. (2010).