Evolution of the turtle body plan by the folding and creation of new muscle connections.
The turtle shell offers a fascinating case study of vertebrate evolution, based on the modification of a common body plan. The carapace is formed from ribs, which encapsulate the scapula; this stands in contrast to the typical amniote body plan and serves as a key to understanding turtle evolution. Comparative analyses of musculoskeletal development between the Chinese soft-shelled turtle and other amniotes revealed that initial turtle development conforms to the amniote pattern; however, during embryogenesis, lateral rib growth results in a shift of elements. In addition, some limb muscles establish new turtle-specific attachments associated with carapace formation. We propose that the evolutionary origin of the turtle body plan results from heterotopy based on folding and novel connectivities.
Nagashima
Hiroshi
H
Laboratory for Evolutionary Morphology, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minami, Kobe 650-0047, Japan.
Sugahara
Fumiaki
F
Takechi
Masaki
M
Ericsson
Rolf
R
Kawashima-Ohya
Yoshie
Y
Narita
Yuichi
Y
Kuratani
Shigeru
S
D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning; D002642:Chick Embryo; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology; D047108:Embryonic Development; D051379:Mice; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000196:embryology*; D041641:Musculoskeletal Development; D012272:Ribs / Q000033:anatomy & histology / Q000196:embryology*; D012540:Scapula / Q000033:anatomy & histology / Q000196:embryology*; D014426:Turtles / Q000033:anatomy & histology* / Q000196:embryology*