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Re: What did Spinosaurus eat? New species of Lepidotes found



2011/3/3 Don Ohmes <d_ohmes@yahoo.com>:
> Yes. Adopting temporarily the assumption that sails served to dump heat, I
> would expect a lifestyle wherein the main body was usually immersed in warm
> water and size was an advantage. The thermal conductance of water being much
> higher than air, a vascularized flat plate sticking up in the breeze to take
> advantage of evaporative cooling would allow for a larger body w/out
> overheating.
> I am a little skeptical of the "sail as heat absorber" btw, just because in
> my experience flat plates w/out insulation make crappy solar collectors
> (even with liquid tubes), especially when wet, only working well on hot days
>
Great idea... Although the Spinosaurus more likely did not transpired
the way us mammals do, being an aquatic animal it may have submerged
wetting the sail for the evaporation to relieve warmth. Is there
something written about sails as bad solar collectors?

Some further toughts on Spinosaurus

-Lenght of the skull and neck may have also permitted a reach
advantage, relative to body size, over short-necked crocodiles or
short-snouted theropods, good to increase the feeding area with less
locomotor energy expanditure.

-From the figures I was able to see, it seems that the expansions of
the snout and irregularities of the mouth borders may be simply
results of the enlargement of a small numer of relatively spaced
teeth. The transverse, ghara-like expansions of the snout of
spinosaurids may be mostly a consequence of the simple expansion of
the alveoli that harbor the teeth with a greater diameter. The
irregular shape of the oral border in lateral view has to do with the
dorsoventral expansion of the alveoli allowing the longer teeth, for
the longer the teeth, if the root is not deepened, the more easily the
tooth would be dislodged by the action of external forces. The longest
teeth are apparently those with greater transversal diameter, surely
because the increase in width may enhance resistance to breakage,
surely to compensate the greater risk of breakage implied by their
increase in length. These tooth dimensional factors may thus explain
the coincidence in the snout of the points of greater transversal
width with those of greater dorsoventral height.

-The mentioned spacing of the large tooth may be useful to put more
pressure into each large tooth. Regarding the size variation on the
teeth, it seems the large tooth are more useful to grab a relatively
large fish, and the small tooth located opposite them are better to
grasp smaller fishes, perhaps to exploit more resources (a larger
range of sizes). This may mean that the relatively larger and thicker
the conical teeth of an ichthyophagous vertebrate, the proportionally
larger the prey it hunted?

-Alternatively, or additionally, although I hypothesized Spinosaurus
to be worst than baryonychines in tearing, the irregular oral border
in lateral view may help with the overbite, tearing effect Jaime
hypothesized, but in a greater degree than in gulls and
procellariiforms (and perhaps even baryonychines), because not only
the premaxillary “hook” would form an overbite relative to the
dentary, but also the dentary rostral expansion may form an “overbite”
with respect to the maxillary expansion, so perhaps “two hooks” would
be present, not only helping at a greater degree in prey retention,
but also alleviating the stresses on each hook both at prey retention
and tearing.

-What about the possibility of Spinosaurus being able to project a
mostly cranially directed narrow shadow, by getting the sun from
behind and slightly from a side, close to the range of motion of the
skull and neck?