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Re: Spinosaurs ate pterosaurs
----- Original Message -----
From: "Jaime A. Headden" <email@example.com>
Sent: Sunday, July 04, 2004 2:52 AM
> David Marjanovic (firstname.lastname@example.org) 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.
> 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
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
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_.