>
> >Susan Brassfield:
> >dolphins do not superficiallly resemble sharks--certainly not to a
> >biologist.
> >
> >My comments:
> >Of course they do, or do you deny convergent evolution?
>
> of course not. But dolphins and sharks don't resemble each other at
all--not
> to a biologist (or to a 6 year old in the aquatic park either)
>
Actually Susan, they do resemble one another, and both together resemble
ichthyosaurs. In fact as a group sharks, dolphins and ichthyosaurs have
traditionally served as an example of convergence. All three have the same
torpedoe-shaped body style for quick movement through the water; all three
have large pectoral fins or flippers for stearing; all three have a powerful
caudal tail for rapid locomotion; and all three have a prominant dorsal fin.
Of course, the resemblance is only superficial; their differences far
outweight their similarities. But the idea still is that they have a common
body design because they adapted for similar lifestyles in similar habitats.
Kevin L. O'Brien