Homeotic effects, somitogenesis and the evolution of vertebral numbers in recent and fossil amniotes.

ABSTRACT: The development of distinct regions in the amniote vertebral column results from somite formation and Hox gene expression, with the adult morphology displaying remarkable variation among lineages. Mammalian regionalization is reportedly very conservative or even constrained, but there has been no study investigating vertebral count variation across Amniota as a whole, undermining attempts to understand the phylogenetic, ecological, and developmental factors affecting vertebral column variation. Here, we show that the mammalian (synapsid) and reptilian lineages show early in their evolutionary histories clear divergences in axial developmental plasticity, in terms of both regionalization and meristic change, with basal synapsids sharing the conserved axial configuration of crown mammals, an

SUBMITTER: Muller J 

PROVIDER: S-EPMC2836685 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature