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The Evolution of Limb Reduction in Teiid Lizard Genus Bachia





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The reduction pattern of limbs in the teiid lizard genus Bachia is described and discussed. The pattern which has emerged for Bachia is as follows: Reduction of the limb and girdles can be correlated with the length of the limb and the terminal structures of the appendage; the reduction is greater in the hindlimbs than the forelimbs. with the complete loss of hindlimb externally. The forelimbs are greatly reduced (down to 2-3 mm in length), but are not lost externally. Comparison of the limbs of the species of Bachia suggests that the pattern of limb formation is a result of paedomorphic development. Comparison of the limb structure with other genera of limb-reduced or limbless forms results in the construction of two possible models: 1) the loss of hindlimbs first with reduction or loss of forelimbs and 2) loss of the forelimbs with reduction, loss or modifications of the hindlimbs. The first model may represent the stages leading to the amphisbaenians, whereas, the second model probably represents the mode of limb loss in the ancestry of snakes.