Developmental pathways
From EvoWiki
Suboptimal design > Developmental pathways
One of the most striking patterns observed in amniote ontogeny is the presence of highly conserved developmental pathways across lineages, except for a few glaring exceptions. Take for instance digital reduction in the manus. Morse's Law models the stereotypical, symmetrical reduction of manual digits via the loss of digits I and digits V. Certain lepidosaurs and theropod dinosaurs mark the only known exceptions to this conserved pattern, in that in these groups digit IV is lost after serving as the organizational axis for the development of the digital arch, while digit I is retained and digit V reduced as usual. This produces a highly specialized asymmetrical postaxial reduction pattern in the manus. Such a seemingly inexplicable anomaly is readily accommodated by evolutionary biology, but it is a significant problem for the ID model. If lizards and dinosaurs were created by the same designer at the same time, why should they display so bizarre a pattern of digital reduction in the manus vis-a-vis all other amniotes?
