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Re: Velociraptor profiles and a little background



David wrote:

>Okay. Key ref: Ebel 1996. Modified, though: You already start out with a
>fully feathered and winged coelurosaur that decides to go fishing. For that
>it's pretty useful if it can swim. How would an animal of this shape swim?
>It can't wriggle its stiff, thin tail. It doesn't have webbed feet, so
using
>the long, thin legs isn't efficient either. But if tries to grasp a fish
>underwater, it gets forward -- it is developing underwater flight. It
>doesn't specialize in this, it breeds on dry land (shading as always its
>large clutch with its long, broad wings, unlike a penguin) and searches a
>considerable part of its food there. You get something like a dipper, sort
>of; *Archaeopteryx* is IMHO an example of such an animal. (Difference:
>Dippers can already fly.) How does such an animal get quickly out of the
>water when it needs to? By jumping out like a penguin -- by simply swimming
>upwards into the air. When beaten fast enough, the wings can, if they are
>large enough, carry the animal on (if it is small enough, but
>*Archaeopteryx* certainly was, and so was the even smaller *Microraptor*,
so
>a theropod in this size range is to be expected). Advantages that lead to
>the retention of this ability, rather than it being selected away for being
>too expensive? The ability to flee; today birds have double the life
>expectancy of mammals of the same size. Allows one to hunt much closer to
>the crocs :-) . The ability to rise high above the water and look for fish
>from above -- much more efficient than looking around in the murky depths
>themselves. And maybe the ability to show off -- sexual selection strikes
>again.
>        "Advantages" when tested against to the fossil record: It can
happen
>fast, I think (neat explanation for the lack of fossils). It can probably
>happen in e. g. mountain rivers (where today's dippers live) (another neat
>explanation for the lack of fossils). It can explain what the hell Archie
>was doing all day, and it can explain why the basal, erm, hm,
>maniraptoriforms look more like Archie than the derived ones, respectively
>why they all look so secondarily flightless to some. And it explains why
>nonavian theropods (except the aye-aye-analog... which may be very close to
>birds...) seem so ill-suited to climbing (can't even sprawl their legs),
>including the fact that during chicken ontogeny the first toes start high
up
>and short and later migrate to the level of the others. IMNSHO flight came
>first, arboreality second.
>        In short, hard positive evidence is totally lacking, but I do think
>it is much more plausible than all alternatives I've seen so far, including
>all versions of the arboreal _and_ the cursorial hypotheses (and >gargl<
the
>attempts at a compromise between those two). (Keep in mind that I haven't
>seen the stuff about vertical running yet... <meditating> W4tP... W4tP...
>W4tP...)
>
One of the first things a person learns when starting with dinosaurs is that
dinosaurs couldn't swim and now you are advocating that they could? It
hardly seems plausible, even if the feathers could make some lift in the
water. From the point that an animal starts with swimming, look at whales
and manatees, it were just these weird hair balls we call mammals, animals
that are easily seperated from other groups by the presence of hairs on the
body. It could have helped with staying warm but do you see hairs on whales?
No, or else I must have missed them in every Discovery program there was
covering these creatures. When you go into the water and when you are all
hairy, it is a major disadvantage, because hairs slow you down. And another
thing, when you have feathers and you venture into the water, it's practicly
suicide! When feathers get wet, they become heavy, making it almost
impossible to swim.

Rutger Jansma