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Re: Carniadactylus paper and pterosaur ontogeny
David Peters wrote:
None of the embryos discovered are geometrically similar to the
Not true. Trace and reconstruct the bones. Then get back to me.
We'll compare notes.
I've done one better: measuring the original specimens, there are
notable deviations from isometry. For example, the small
Santanadactylus at the AMNH is not geometrically similar to larger
ones, though it's close in some dimensions. Same for Quetz. Also
true of Anurognathus.
It's also worth noting that for pterosaurs to be flighted at small
size and retain flight ability through growth, they cannot grow
1. Only Unwin said they were flighted at hatching.
2.Your statement is not backed up by the literature. Please share.
It just comes from basic biomechanics (which I have checked against
bone strength calculations, using my own dimensions data and those
from the literature) - if you scale the hatchlings up isometrically
you end up with a wing spar that cannot handle flight loads. Same
pattern appears with making comparisons among species - as body size
increases, there is an allometric change in wing spar dimensions. In
both cases, the trend is not at all unexpected, because the small
species and/or juveniles would need to be exceptionally "overbuilt"
for isometric growth to result in a viable adult. As it is, they
appear to have flown at a higher safety factor than the adults, but
not by the margin that would exist under isometric growth.
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205