English: At stage 16/17, a turtle embryo in the egg is developing its shell. In cross-section, the ribs are seen to be growing sideways into the carapace bud, unique to the group, rather than downwards, so as to support the shell.
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ကိုယ်ပိုင်ဖန်တီးမှု. Redrawn from micrograph in Cebra-Thomas, Judith, et al (2005). "How the turtle forms its shell: a paracrine hypothesis of carapace formation". Journal of Experimental Zoology Part B: Molecular and Developmental Evolution304B (6): 558–569. DOI:10.1002/jez.b.21059. ISSN1552-5007.