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Re: Velociraptor profiles and a little background



> >_All_ dinosaurs couldn't swim? While almost all living vertebrates can?
> >Strange, strange...
> >
> Alright, name some swimming reptiles that do not have any specialized
> characters, therefore eliminating the Iguana's from the Galapagos-islands.

Get away from being fixed on "reptiles"... see below.

> but what you are implying is constant activity in the water.

I'm not. I imagine something hardly as semiaquatic as a crocodile. Do you
know what a dipper (*Cinclus*) is? A little songbird (the German name
translates as water blackbird) that hunts in small mountain rivers by flying
underwater. (OK, it is so light that it walks around much on the bottom,
holding itself with its perching feet, but such extreme pneumaticity can't
be presupposed for a basal... maniraptoriform or so.) It has _one_
adaptation to diving: it can close its nostrils with skin that won't
fossilize.

> >Why lift? With all these air sacs, the animal produces already more than
> >enough lift and has to care about how to stay down. Beating wings
> underwater produces thrust. Lots of living birds do this.
>
> Has this been proven by testing or do you just or everyone assume this is
> how it works?

Living birds commonly have densities around 0.8. Swim like corks. It is well
known, and I've seen it on TV tens of times, that cormorants let their wings
get wet to be heavier. Loons and hesperornithiforms reduce their
pneumaticity to stay down. I've seen lots of various birds fly underwater on
TV (Discovery Channel productions and such).

> >> From the point that an animal starts with swimming, look at whales
> >> and manatees,
> >
> >They aren't _starting_ to swim. They have become _exclusively aquatic_.
> Look >at otters. Oh, er, and penguins. :-)
>
> But before that they had to move trough a fase when they are learning to
> swim, it's not like in a magical evolutionary clap in the hands or three
> clicks with your red heels evolution moves.

Did I write so? ~:-|

> >You do know what otters do? You do know what _all birds I know of_ do,
even
> >those that never come close to water except rain? They impregnate their
> >body coverings with oily secretions. (Galliformes have reduced that gland
> on the
> >tail, but they still have it.)
>
> Of course I know what otters do, they swim on their backs, cracking shells
> open with rocks. :)

You are referring only to *Enhydra lutris*, which lives above the kelp
forests off California and in the Bering Sea. There are many other species,
like *Lutra lutra*, which lives (though endangered) in the Austrian alps
(and throughout Eurasia and northern Africa) or the giant (up to 1.5 m
without tail) *Pteronura brasiliensis* in South America; all of them hunt in
fresh water and come out to eat etc. and never use rocks.

> But you are saying that that oil secretion is what is
> helping those birds to swim, it had to have evolved.

Not necessarily at the same time as feathers. Anyway, we all produce grease
that makes our hair hydrophobic if we don't wash it often enough, so that
gland may just be an exaggeration of a normal feature.

> The current theory

wrong, hypothesis

> regarding the origin of feathers is that is was meant to trap body heat,
> since dinosaurs, at least the theropods were warm-blooded.

Irrelevant here (even though Reichholf's hypothesis of feathers as protein
dumps sounds better to me; once feathers were present, they isolated).

> It is not the current concensus feathers evolved to make the
> dinosaur swim (although it could be a speculative possibility),

I didn't say so. As I just repeated 1 1/4 h before your post: I think that
(underwater) flight evolved in a coelurosaur that was already fully
feathered and fully winged.

> so the feature had to evolve from
> ordinary feathers we all see in present day birds. Well, kinda at least...

(Hm. A consensus is not a proof. But here I'm arguing science theory, not
the evolution of bird flight.)

> Just imagine this for moment: a poor lonesome Sinornithosaurus, let's call
> it "Dave" for the time being, is checking out a small lake and sees all
> these fish in it. He's hungry as hell and willing to eat anything, he
> decides to go for it and plunges itself in the water. Poor "Dave" drowned
> since his feathers are not equiped with the oily secretion. Almost seems
> like Mesozoic "Jackass" :)

*Sinornithosaurus* didn't have very long feathers. If it didn't lie around
in water for hours, I can't see it drown because of the weight of wet
feathers... if it really didn't have some sort of grease for them.

> And again you are implying the oily secretion was immediatly present in
> theropod dinosaurs, which hardly seems possible. It takes time to evolve
> such a feature.

Throw a dog into water. Dogs don't have such a specialized gland. What
happens?