Short communicationAquatic adaptations in the four limbs of the snake-like reptile Tetrapodophis from the Lower Cretaceous of Brazil
Section snippets
Materials and methods
We expanded a multivariate morphometric analysis of lepidosaurs (lizards, snakes, tuataras) of known ecology (Wiens et al., 2006, Müller et al., 2011) by adding Tetrapodophis and fossil marine squamates (pleurosaurs, dolichosaurs, mosasauroids). The original habitat divisions were reduced by combining three overlapping categories (cryptic, saxicolous, terrestrial) into one category (terrestrial); a new category (fully aquatic) was added to accommodate the additional taxa included, leading to 5
Results and discussion
The PCA analysis (data scaled to SEL; Fig. 1, File 1) revealed that most (82%) of the variance was captured by the first 2 principal components, with loadings suggesting that PC1 represents shape change associated with body elongation, and PC2 relative tail length. The bivariate plot of the first 2 PCs confirms that Tetrapodophis falls near fossorial forms, close to long-bodied but tetrapodal skinks that burrow through loose sediments and leaf litter, such as Sepsina angolensis and Chalcides (
Conclusions
The results of our multivariate morphometric analyses (PCA, LDA) intriguingly suggest that Tetrapodophis has a body shape similar to that of modern burrowers as well as surface-active but cryptozoic lizards (e.g. the diploglossid Celestus). The burrowers most similar to Tetrapodophis are relatively generalised forms that move through loose soil or leaf litter, so if Tetrapodophis is accepted as a stem snake, it would suggest that snake ancestors were not heavily specialised fossors. An
Acknowledgements
MC and RR thank Martin Röper (Museum Solnhofen) for access to Tetrapodophis during late 2015. MJ thanks Oliver Rauhut (LMU Munich) for access to specimens of Pleurosaurus. AP and MC thank Giorgio Teruzzi and Cristiano dal Sasso (Museo Civico di Storia Naturale di Milano) for access to a specimen of Pontosaurus. AP thanks Alan Resetar and Kathleen Kelly (Field Museum of Natural History) for access to specimens of Chalcides. We thank Johannes Müller, Christy Hipsley, for discussion, and Michel
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