Conservation of rib skeleton regionalization in the homoplastic evolution of the snake-like body form in squamates

Squamates have independently evolved an elongate, limb-reduced body form numerous times. This transition has been proposed to involve either changes to regulatory gene expression or downstream modification of target enhancers to produce a homogeneous, deregionalized axial skeleton. Analysis of vertebral morphology has suggested that regionalization is maintained in snake-like body forms, but morphological variation in the other primary component of the axial skeleton, the dorsal ribs, as not been previously examined. We quantified rib morphology along the anterior-posterior axis in limbed and limbless squamates to test different regionalization models. We find that the relative position of regional boundaries remains consistent across taxa of differing body types, including in the homoplastic evolution of snake-like body forms. The consistent retention of regional boundaries in this primaxial domain is uncorrelated with more plastic abaxial region markers. Rather than loss of regions, r..., , , # Conservation of rib skeleton regionalization in the homoplastic evolution of the snake-like body form in squamates

[https://doi.org/10.5061/dryad.1jwstqk46](https://doi.org/10.5061/dryad.1jwstqk46)

## Description of the data and file structure

These files provide the raw data that formed the basis for all analyses in this manuscript. Each file contains the 3D landmark data for a given sampled species. Landmarks were placed for geometric morphometric analysis. For more details on the landmark scheme, please refer to the manuscript and its associated electronic supplement, where the 3D landmarking scheme is figured and described in detail. 

### Files and variables

Each of these files contains the landmark coordinates before superimposition of all sampled ribs for each taxon sampled in our analysis. The experimental efforts involved collecting and analyzing whole-body computerized tomography (CT) scans from adult specimens of 56 species, covering all major squamate clades and *Sphe...