Re: Spinosaurs ate pterosaurs

["Jaime A. Headden" <qilongia@yahoo.com>]

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? Animals already
volant? There are several non-flying insectivores that prey on insects
that can fly, but while being few, they do exist. As for "ornithophages,"
there are few animals indeed that specialize in eating birds, so much so
that making statements of "more costly" without a basis for comparison may
not be wise. 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.

  Why do dolphins waste so much energy with barrel-rolls and leaping when
swimming in pods? What is the energetics expenditure versus animals that
swim in pods that DO NOT display this behavior? This doesn't seem to
prevent the dolphins from being so "costly" in energetics. As noted,
*Epidendrosaurus* seems adapted for catching or hunting insects,
displaying features akin to anurognathids, anurans, and various
caprimulgiforms, highly adapted insect eaters. 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
process.

  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. As will most hunters. Indeed, apart from a sifaka leaping from a
tree, increase of a drag-inducing structure would _reduce_ energetic
expenditure for a habitual performance. Cats display numerous adaptations
in their wrists, shoulder, tendons of the legs, and their tail that appear
to relate to the dynamics of adaptability, leaping, running, climbing, and
a variety of means of holding, catching, and subduing prey, that many
other open-field or jungle predators tend to lack. So it is no surprise
that servals are adapted for, it seems, leaping after avian prey "on the
wing," as it were.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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