Evolution of Scapula Size and Shape in Didelphid Marsupials (Didelphimorphia: Didelphidae)

Abstract

The New World family Didelphidae, the basal lineage within marsupials, is commonly viewed as morphologically conservative, yet includes aquatic, terrestrial, scansorial, and arboreal species. Here, I quantitatively estimated the existing variability in size and shape of the Didelphidae scapula (1076 specimens from 56 species) using geometric morphometrics, and compared size and shape differences to evolutionary and ecologic distances. I found considerable variation in the scapula morphology, most of it related to size differences between species. This results in morphologic divergence between different locomotor habits in larger species (resulting from increased mechanical loads), but most smaller species present similarly shaped scapulae. The only exceptions are the water opossum and the short-tailed opossums, and the functional explanations for these differences remain unclear. Scapula size and shape were mapped onto a molecular phylogeny for 32 selected taxa and ancestral size and shapes were reconstructed using squared-changed parsimony. Results indicate that the Didelphidae evolved from a medium-to small-sized ancestor with a generalized scapula, slightly more similar to arboreal ones, but strikingly different from big-bodied present arboreal species, suggesting that the ancestral Didelphidae was a small scansorial animal with no particular adaptations for arboreal or terrestrial habits, and these specializations evolved only in larger-bodied clades.K E Y W O R D S : Locomotion, marsupials, morphological evolution, shoulder girdle.

Taxonomic identification using geometric morphometric approach and limited data: an example using the upper molars of two sympatric species of Calomys (Cricetidae: Rodentia)

“…The overlap areas in morphometric cranial analyses using orthogonal matrix transformation techniques as PCA, irrespective of whether traditional or geometric, have also been identified in other species of other genera and in Calomys (Cordeiro-Estrela et al 2006, Astúa 2009, Bonvicino et al 2010, Martínez and Di Cola 2011. Furthermore, the results obtained in the present study for M1 shape are in agreement with those reported in other studies that showed a divergence in the shape of Calomys skull, but with small areas of intersection (Cordeiro-Estrela et al 2006.…”

Structure of Parasite Component Communities of Didelphid Marsupials: Insights From a Comparative Study

“…In Los Tuxtlas, the similarity between communities in P. opossum compared with D. marsupialis and D. virginiana dropped to approximately 50% (55 and 42%, respectively). The different diet composition of the 2 species of Didelphis relative to the gray four-eyed opossum may account for this difference (McManus, 1974;Castro-Arellano et al, 2000;Astú a, 2009).…”

“…This evolutionary event resulted in the diversification of some anatomical features that enabled marsupials to specialize in aquatic, terrestrial, scansorial, and arboreal lifestyles (Astú a, 2009). This allowed habitat segregation and the use of different dietary resources even in species occurring in sympatry (JulienLaferrière, 1991;Cá ceres et al, 2002;Cunha and Vieira, 2002;Gentile et al, 2004).…”

Ecomorphological determinations in the absence of living analogues: the predatory behavior of the marsupial lion (Thylacoleo carnifex) as revealed by elbow joint morphology

“…McArdle and Rodrigo 1994;Martins and Hansen 1997;Garland et al 1999;Polly 2001;Rohlf 2001;Finarelli and Flynn 2006;Astúa 2009;Figueirido et al 2010;Almécija et al 2013;Figueirido et al 2013;Martín-Serra et al 2014a,b) using the square-changed parsimony method of Maddison (1991) with MorphoJ (Klingenberg 2011). We used this approach to specifically compare the elbow of Thylacoleo with the ancestral states of other mammalian groups and with other tips of the phylogeny.…”