Re: Spinosaurs ate pterosaurs

[David Marjanovic <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Jaime A. Headden" <qilongia@yahoo.com>
Sent: Sunday, July 04, 2004 2:52 AM

> David Marjanovic (david.marjanovic@gmx.at) wrote:
>
> <Jumping up from the ground to catch flying insects would be too costly in
> comparison. So would parachuting from a tree to do the same be -- not the
> parachuting itself, but the need to climb back up the tree after each
> insect caught that way.>
>
>   Pardon ... in comparison with what other insectivores?

No, no -- the prey must provide more energy than the efforts to get it, and
I can't imagine this would be the case in an animal that would live off
climbing up a tree over and over again.

> There are several non-flying insectivores that prey on insects
> that can fly, but while being few, they do exist.

Yep. And they use _far_ more efficient methods!

> On the other hand, parachuters do precisely what David seems
> to imply they _don't_ by qualifying their energetics: when flying
> squirrels and snakes move from tree to tree, they do so in stages, leaping
> out, gliding or parachuting down, then climbing back up to a height higher
> than their target, and repeat. Sifakas and lemurs do the same thing with
> leaping from tree to tree.

Yep. But they do so in order to get from one entire feeding ground to the
next. They don't jump down a tree and climb back up to catch one fly.

>   Why do dolphins waste so much energy with barrel-rolls and leaping when
> swimming in pods?

Because they can afford it. They are efficient enough hunters.

> As noted, *Epidendrosaurus* seems adapted for
> catching or hunting insects, displaying features akin to anurognathids,
> anurans, and various caprimulgiforms, highly adapted insect eaters.

I'm still not convinced that the short skull isn't merely a juvenile feature
of this very young specimen.

> It, like the anurans, lacks flying adaptations.

Really? :-)

> It is doubtful it could fly particularly well, and if
> you're parachuting after food, and it flies out sideways or up from your
> landing spot, the animal isn't going to be getting food. So ... repeat the
> process.

Yep. It starves.

>   Polar bears display similar "needless" energetics when they plunge into
> the water to catch a departing seal, and they will do this time and time
> again.

Totally incomparable. Firstly, seal is much, much bigger compared to a polar
bear than most insects to the type specimen of *Epidendrosaurus*. Secondly,
plunging into water costs _nothing_ compared to the costs for a rather tiny
animal to climb up tens of meters tens of times per day.

> So it is no surprise that servals are adapted for,
> it seems, leaping after avian prey "on the wing," as it were.

They aren't dependent on this. They're just capable of taking advantage of
the rather rare situation that a bird flies by closely enough and slowly
enough. The suggestion was that *Epidendrosaurus* jumped down from trees
_for a living_.