科研之友
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摘要
Vestigial biological structures provide an important line of evidence for macroevolution. They abound in the appendicular skeletons of limbless and reduced-limbed members of the skink subfamily Scincinae, which includes a predominantly Asian clade and a predominantly African clade. Reduced appendicular skeletons in the predominantly African clade have receivedmuch recent attention, but for most species in the predominantly Asian clade the appendicular skeleton has yet to be described. Here we provide descriptions of the appendicular skeletons of the reduced-limbed skinks Brachymeles bonitae and Ophiomorus blandfordi, the externally limbless skink Ophiomorus punctatissimus, and, for comparison, the pentadactyl skinks Brachymeles gracilis and B. talinis. We used x-ray radiographs to examine the skeletons of these species and to note similarities and differences in the previously-described appendicular skeletal morphology of related species. We found that in B. bonitae the pectoral and pelvic girdles are unreduced, the proximal limb elements are reduced, and the distal limb elements are vestigial. In O. punctatissimus vestigial pectoral and pelvic girdles are present. In O. blanfordi the fifth metatarsal is vestigial. The phylogenetic distribution of morphological features related to appendicular reduction shows that multiple, parallel reduction events have taken place within each of these two genera. In addition, the anatomical distribution of element reduction and loss in these genera shows that the bones are reduced and lost in the same sequence in the predominantly Asian scincine clade as they are in other squamate clades. This suggests a common evolutionary mechanism for appendicular reduction and loss across the Squamata.
- 出版日期2016
