Re: Spinosaurs ate pterosaurs

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

David Marjanovic (david.marjanovic@gmx.at) wrote:

<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.>

  Nonetheless, there are animals that do this, contrary to this
"neccessary" statement of comparitive energetics. The flying squirrel,
though not a typical predator species, like the aye-aye, does expend much
energy foraging, as do bees, without much succor in attaining a full belly
by the time it's back at "home." For a given mass, indeed, a prey species
seem to exert MUCH more effort to escape than the predator expends to
catch it, with some notable exceptions. Including _cheetahs_. When you are
adapted to catch fast prey, it becomes the _predator_, not the _prey_,
that is the more costly animal. This has led to various adaptations of the
feline form in some species to adapt to catching food. All a serval has to
do is crouch and stalk before the prey species "bursts" from the
underbrush, expending massive amounts of calories in the effort to not
being killed, then leap out and snatch it from the air, then back to
ground. This is, relative to it's massive, very little expenditure than
the bird's.

<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.>

  I mentioned that flying squirrels really did do this in the attempts to
catch food if it was prey, but then again, flying squirrels are not a
predator species, being herbivores for the most part and grub-eaters at
least. But a leaping predator does exists in the same general ecology,
including flying snakes, who do this to gain vantage point and access to
prey, colugos who get to feeding sites, etc. Cats will also climb after
food, including nests of birds, in a much more energy-intensive moment
than it takes the chick to chirp and squak.

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

  This is also contradicting a statement, and the reason I brought them
up. They will expend an _unneccessary_ amount of energy for the sake of
something unrelated to catching food. Why should a flying squirrel NOT
have the same consideration? Porpoises and dolphins still hunt food at
least as fast as they are; their _primary_ advantage is the pod: they have
the numbers to surround prey, and not be solitary as in most cats. Which
ALSO are efficient enough hunters.

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

  Would you mind demonstrating the U-shaped jaws in a juvenile of a
non-insectivore that did not, as a juvenile, eat insects? Though others
have also brought the large head/large eye "evidence" up for juvenile
*Epidendrosaurus,* the nearly identically-sized *Scansoriopteryx* shows
similar proportions with slight differences, a huge head and orbit, and
fused neurocentral sutures with developed epipophyses of limb bones,
indications of maturity. This would suggest that *Epidendrosaurus* could
very well be subadult at the most, rather than a super-young juvenile.

<Yep. It starves.>

  Cats and otters and seals and polar bears repeat their process as
neccessary ... they will lose 5 times out of 6 for most species. This does
not make them starve. Many of these abortive attempts may even be
neccessary for the feeding of young, yet still they will fail. Increasing
the number of predators in a group, through a pride of lionesses, a pack
of wolves or hunting dogs, or a pod of dolphin or whales, increases the
chances for ONE target, and minimizes energy over a period. So, typically,
these will chase prey for four times longer than a single animal can
afford to. They do not starve, they eventually get the prey, or get
better.

<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.>

  The cost of plunging into water includes the swimming underwater, the
struggle to subdue prey under water, the struggle to get BACK to the
surface and pull the prey up with you, and possibility to defend your
kill, and the neccessity of drying one's fur off. The same effort is
performed in anhingas for similarly-sized prey to themselves. They will do
this 3-5 or so times a day, and exert a great deal of energy for a single
moment, and then spend more time and energy _fixing_ themselves. This will


<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.>

  Quite on the contrary: servals have physical adaptations for the purpose
of hunting through tall grass and high-speed running, catching extremely
fast and tiny animals, and leaping, including the observed bird-snatching.
They will jump up for the sole purpose to pounce _down_, surprising prey.
The long legs, large auditory bullae, flexible, cheetah-like spine, and
small head are adaptations that relate to these ecological requirements.
Similarly, they have a short tail, a feature that does not serve an animal
used to making quick turns, but in short, fast bursts. This is
particularly adaptable to leaping up. Servals, like caracals and the
possibly conspecific servaline cat, have developed features for the sake
of catching prey that can move in any direction. They often catch food on
the wing thet they themselves have flushed, so the idea that they just
spot a low-flying bird is ridiculous: the birds of the area have an easy
choice here -- don't fly low. 

<The suggestion was that *Epidendrosaurus* jumped down from trees _for a
living_.>

  As noted before, the elongated arm and finger seem similar to
pterosaurs, and could relate to a parachuting structure. *Scansoriopteryx*
has integument arrayed along the arm that has been described as sifaka
like, and *Epidendosaurus* has been inferred as having similar integument.
If the animal were arboreal, then perhaps like sifaka they would have lept
to and fro. If so, then unlike such "leapin' monkeys," their large heads
would serve a dietary function. The only arboreal animals with similar
heads are flying insectivores, yet clearly these animals were not volant.
This implies then that such physical features may be related, but they
need not be. IF, however, they were, this would imply leaping _onto_ prey;
it is unlikely they, as in large-mouthed non-volant predators (being
anurans and gape-suction--feeding fish), waited for food to come by and
either create a vacuum to suck the food in, or used a likely absent
expulsive tongue apparatus to _snare_ the prey. Such a tongue requires a
sternomandibular complex of musculature that, apparently, is absent or
not-inferrable given the lack of any adapted hyoids or sternal complex.
The hyoids known, while large, are unlike those of chameleons and anurans,
and resemble those of other juvenile theropods, as in *Scipionyx.* This
suggests that active predation, and not "sit and wait" passive predation,
was the role. This leads to leaping down on prey as a possible mechanism
for employing all features at once; the aye-aye does not have a huge skull
with tiny teeth at the subadult level with a U-shaped jaw, nor does it
require this to eat grubs, so the use of the finger and the skull appear
mechanically unsuitable if they were for aye-aye--like predation together
(otherwise, why have such a huge subadult cranium with insectivore
features?). I already illustrated a wood-pecker--like posture on the
Dinosauricon, and another flying squirrel-style, clinging four-leggedly
and vertically to a branch. Both imply an arboreal, and non-fixed habitus.
What other possible ecology might also utilize a huge, rounded, wide head,
long third finger, relatively short leg, and long stiffened tail?

  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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