Comparative patterns of postcranial ontogeny in therian Mammals: An analysis of relative timing of ossification events

Abstract

Data on the relative sequence of ossification of postcranial elements for eight therian mammals (Myotis lucifugus, Homo sapiens, Rattus norvegicus, Mus musculus, Mesocricetus auratus, Cavia porcellus, Didelphis albiventris, and Sminthopsis macroura) and three outgroups (Chelydra serpentina, Alligator mississippiensis, and Lacerta vivipara) were taken from the literature. For each species, a matrix was constructed in which the relative timing of the onset of ossification in 24 elements was summarized. This resulted in 276 event pairs (characters) for each species. Thirty-three (33.3)% of the characters examined are uniform across all taxa, 16.3% are variable but uninformative in the phylogeny, and 50.4% potentially deliver diagnostic features for clades of two or more taxa. In all species examined, the clavicle is the first bone to appear. Placentalia is not unequivocally diagnosed by the state of any event pair, while Marsupialia has the largest amount of autapomorphies with 18. The acceleration in the timing of ossification of the scapula in relation to the hindlimb in marsupials is most probably causally correlated to movements after birth and during early phases of pre-weaning life. Marsupials are almost unique among amniotes in that the earliest onset of ossification of at least one element among carpals and among tarsals is simultaneous. Three parsimony analyses, each one with a different reptilian taxon as outgroup, were performed using event pairs as characters. In all cases, results were incongruent with the phylogeny of the studied taxa.

Skeletal development in the African elephant and ossification timing in placental mammals

“…Although they show similarities with other placentals [ [17][18][19][36][37][38], there are some non-artefactual differences in their developmental trajectory: a late ossification of the basioccipital, periotic and phalanges, and an early ossification of the ischium and metacarpals (figure 3).…”

Heterochrony in limb evolution: developmental mechanisms and natural selection

“…Such intraspecific heterochrony has been studied in relatively few cases (Mabee and Trendler, '96;Mabee et al, 2000;Irmler et al, 2004). It may even be legitimate to describe heterochrony in a single individual, as when serially homologous structures develop at different stages in one ontogeny.The parameters of developmental timing used to record heterochrony include chronological age, developmental stage, rate, and the order or sequence in which developmental events occur (Alberch, '85; Richardson, '95; Nunn and Smith, '98; Richardson et al, '98a,b;Smith, 2001;Jeffery et al, 2002;Sánchez-Villagra, 2002; Sánchez-Villagra et al, 2008a,b;Weisbecker et al, 2008). The ''developmental events'' whose time relations are altered in sequence heterochrony are essentially transformations between two developmental character states .…”

Morphogenesis in Bat Wings: Linking Development, Evolution and Ecology

“…The wings of bats are the result of morphological divergence from a 'standard issue' vertebrate limb via key developmental shifts (heterochrony) that led to evolutionary innovation on a grand scale [Smith, 2003]. The links between evolutionary change and induced epigenetic shifts during ontogeny are unequivocal [Jablonka and Lamb, 1998;Sanchez-Villagra, 2002;Minelli, 2003;but see Alberch, 1985, for cautionary note]. Thus, understanding the morphogenesis of specialized flight anatomy and behaviors is critical to uncovering questions concerning how the evolution of powered flight occurred, as has recently been portrayed nicely for birds [Dial et al, 2006].…”