Interspecific trends in skull allometry of marsupials: effects of phylogeny and body mass in allometric expression

FLORES, DAVID ALFREDO; GIANNINI; NORBERTO PEDRO; MORALES, MIRIAM MARIANA; ABDALA, FERNANDO

Punta del Este

Congreso; 9th International Congress of Vertebrate Morphology; 2010

International Society of Vertebrate Morphologists

We analyzed the allometric growth of the skull in representatives of three orders of basal marsupials varying in body size, as estimated from 14 linear measurements that describe skull shape. The species included are Didelphis albiventris, Lutreolina crassicaudata, Thylamys venustus, Metachirus nudicaudatus, Caluromys derbianus (Didelphimorphia), Dromiciops gliroides (Microbiotheria), and Dasyurus albopunctatus (Dasyuromorpha). The allometric trends of each ontogenetic series were assessed using bivariate and multivariate approaches. Each of the species for which an ontogenetic trajectory is available shows some level of speciesspecific variation, but all share allometric trends to a considerable extent. However, larger species tend to exhibit more allometric patterns, whereas small species are more isometric overall. In our interpretation, these marsupials share a general ontogenetic trajectory, with large-sized species expressing more allometry than small-sized species. For instance, the general morphology in young specimens of the small sized microbiotheriid Dromiciops gliroides is similar to that of adults, except for some structural details in the bullar morphology and zygomatic arches, and a similar condition is also evidenced in the mouse opossum Thylamys venustus. In turn, deviants from this pattern are specialized (more carnivorous) forms, Lutreolina and Dasyurus. Allometric variation is also structured phylogenetically, as shown by optimization of allometric coefficient in trees pruned to contain the species used while preserving their relationships. In this context, some species are indeed largely plesiomorphic; i.e., virtually none of the allometric trends are characteristically their own but they are instead inherited from common ancestors.