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



2011/3/3 Don Ohmes <d_ohmes@yahoo.com>:
> Is the record complete enough to state w/ any confidence that sails are
> proportionally larger in large spinosaurid species as opposed to smaller
> species, thereby fulfilling the prediction that follows from a speculated
> heat radiator function for a sail?
>
As far as I know, sails are proportionally larger in the larger taxa
of some non therapsid synapsid groups (pelycosaurs), supporting your
viewpoint. There are, however, "pelycosaurs" without sails which are
much larger than the largest ones with sails. Among spinosaurs, they
are only present in two taxa, as far as I know: Spinosaurus and
Suchomimus. They are proportionally larger in the larger Spinosaurus,
also supporting the hypothesis. They are present in the relatively
large Acrocanthosaurus, but I am not sure if the sailed Ouranosaurus
is proportionally large as an ornithopod. The sails may also have to
do with particular environments where it is difficult to loss (or
gain) heat.

2011/3/3 David Marjanovic <david.marjanovic@gmx.at>:
>
> Great. Now I have the mental image of a 17-m-long *Spinosaurus* paddling
> around like a duck with a sail on its back and a mean, mean, mean grin...
> X-D

Heh, true... and advancing with a side as a crab when the wind blows...

> No, really, there's no evidence for a hump. There just happen not to be any
> mammals with a sail, and Bailey doesn't seem to have looked at squamates
> like *Hydrosaurus* very much.

According to this, and if not done yet, it would be nice for someone
with interest and time to search if there are more similarities
between the elongated spines of the dinosaurs and those of Hydrosaurus
than with those of mammals, or if the reverse was true (better if with
biologically significative features).

Truly, the spines in dinos seem much taller than in mammals, and if
full with fat would imply an incredible weight in larger animals,
which would require even proportionally thicker limbs than predicted
from elastic similarity (hey, may it be useful to check if the limb
bones are cross-sectionally larger than in similarly sized ornithopods
without sail?)