Developmental, genetic, and genomic insights into the evolutionary loss of limbs in snakes

  title={Developmental, genetic, and genomic insights into the evolutionary loss of limbs in snakes},
  author={Francisca Leal and Martin J. Cohn},
The evolution of snakes involved dramatic modifications to the ancestral lizard body plan. Limb loss and elongation of the trunk are hallmarks of snakes, although convergent evolution of limb‐reduced and trunk‐elongated forms occurred multiple times in snake‐like lizards. Advanced snakes are completely limbless, but intermediate and basal snakes have retained rudiments of hindlimbs and pelvic girdles. Moreover, the snake fossil record indicates that complete legs were re‐acquired at least once… 

A farewell to arms and legs: a review of limb reduction in squamates

A comprehensive review on limb reduction is presented, in which the importance of investigating and comparing the internal morphology of limb‐reduced lizards in contrast to external morphology is emphasised, which will be the first step in gaining a deeper insight into body‐shape variation.

Snake-like limb loss in a Carboniferous amniote

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The convergent evolution of snake‐like forms by divergent evolutionary pathways in squamate reptiles *

An important role of historical contingency as opposed to determinism is suggested in the convergent evolution of snake‐like body shapes in six clades of lizards, which showed that clades followed different evolutionary pathways.

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Loss and Re-emergence of Legs in Snakes by Modular Evolution of Sonic hedgehog and HOXD Enhancers

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Progressive Loss of Function in a Limb Enhancer during Snake Evolution


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The results show that vertebrate morphological evolution likely involved extensive reorganisation at Hox loci, yet within a generally conserved regulatory framework, and show that snake and mouse orthologous enhancer sequences can display distinct expression specificities.

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It is demonstrated that morphometric regional boundaries correspond to mapped gene expression domains in snakes, suggesting that their primaxial domain is patterned by a normally functional Hox code.

Developmental basis of evolutionary digit loss in the Australian lizard Hemiergis.

A comparative analysis of expression of MSX and Distal-less proteins among embryos from different populations suggests an early role for SHH in specification of digit identity and later importance in maintaining cell proliferation and survival in Hemiergis.

A Cretaceous terrestrial snake with robust hindlimbs and a sacrum

The new fossil from the Upper Cretaceous period of Patagonia fills an important gap in the evolutionary progression towards limblessness and retains several features associated with a subterranean or surface dwelling life that are also present in primitive extant snake lineages, supporting the hypothesis of a terrestrial rather than marine origin of snakes.

Axial patterning in snakes and caecilians: evidence for an alternative interpretation of the Hox code.