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Re: Differences between *Vancleavea* and thalattosaurs
David Peters <email@example.com> wrote:
> Then remember, "the apple doesn't usually
> fall far from the tree" which is another way of saying
> evolution works in small incremental steps.
This is not always true. Developmental studies have taught us that certain
major changes can be sudden, rather than representing a culmination of "small
steps". Major morphological transformations can be determined by one or a few
key developmental genetic changes.
In other words, certain changes in evolution are likely to have occurred
rapidly, with few or no intermediate stages. For example, the addition of an
extra vertebra into the neck, or the switch from procoely to opisthocoely (both
seen in sauropod evolution) probably occurred in a single step.
The extreme elongation of the fingers of bats could have occurred by relatively
minor changes to a single developmental pathway (see work of Karen Sears &c).
The same might be true of pterosaurs.
Arthropods could gain or lose segments in a single step - with the process
governed by essentially the same mechanism by which sauropods gain or lose
All sorts of evolutionary jumps no doubt went on in the evolution of feathers.
And so on...