How the Turtle Got Its Shell (4 of 5) (IMAGE)
Caption
This is a comparison of muscles connecting the trunk and shoulder girdle/forelimb. Deep (as, serratus anterior; lsr, levator scapulae and rhomboid complex) and superficial (ld, latissimus dorsi; p, pectoralis) muscles are shown in transverse view (A and D) and lateral view (B, C, E and F). (B and E) The muscles in the inner layer, connecting the shoulder girdle and trunk, and (C and F) the superficial muscles connecting the upper arm and the trunk are illustrated. All of the muscles are inside of the carapace in turtles and outside of the ribs in the chicken. The latissimus dorsi of turtles spreads anterior to the shoulder joint (F), not posterior as in the chicken (C). The turtle pectoral muscle attaches inside the plastron (F), not outside the sternum as in the chicken (C). This image relates to an article that appeared in the July 10, 2009, issue of Science, published by AAAS. The study, by Dr. Hiroshi Nagashima of RIKEN Center for Developmental Biology and colleagues was titled, "Evolution of the Turtle Body Plan by the Folding and Creation of New Muscle Connections."
Credit
[Image courtesy of Shigeru Kuratani and Hiroshi Nagashima]
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