During amphibian somitogenesis, presumptive myotome cells change shape from round or polygonal to elongated and aligned parallel to the notochord (for reviews see Radice, et al., 1989; Keller, 2000). Although the final orientation of myotomal cells is always axial, the movements that achieve this final arrangement can differ greatly between species. The simplest movement is that seen in Bombina variegata, Pelobates fuscus, and Bufo bufo (Brustis et al., 1976; Brustis, 1979; Kielbowna, 1981 ). In these anurans, after segmentation myotomal cells simply elongate along the embryo’s anteroposterior axis. The urodeles Ambystoma mexicanum and Pleurodeles waltl have a very different pattern; cells of the unsegmented mesoderm first elongate dorsoventrally then at segmentation become wedge-shaped and form a rosette surrounding a central myocoele. Subsequetly, these cells reorient again and elongate, becoming parallel to the long axis of the embryo (Youn and Malacinski, 198lb).

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Copyright © 2001 Society for the Study of Amphibians and Reptiles. This article first appeared in Journal of Herpetology 35, no. 1 (March 2001): 114-16. doi:10.2307/1566031.

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