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Re: Spinosaurs show semi-aquatic oxygen isotopes

This abstract generates many questions (to me, at least, with certain
Does the observed isotopic composition mean that the animal was most
of its time within a water body as a crocodile, hyppopotamus or
freshwater turtle?
Or just that it ate things living in the water body like a heron?
Do you need a very specialized postcranium to live most of your time
in the water like a hyppopotamus or crocodile?
Does the hyppopotamus show many functional differences in its
locomotor apparatus compared with other large terrestrial ungulates?
Is there any evidence of greater "bone density" (which may mean, a
thicker cortex) in the bones of spinosaurids when compared to other
theropods, or even supposedly terrestrial dinosaurs?

I do not see a cursorial-looking animal going so bad in the water.
After all, primarily cursorial dogs dig and primarily cursorial cats
can climb. Hyppos also seem to have mostly cursorial limbs (in the
sense of being digitigrade, fore-and aft limited). Many cursorial
animals can swim more or less well... If its neck moved fast enough to
catch something, it seems it may not have great trouble...

2010/2/5  <bh480@scn.org>:
> From: Ben Creisler bh480@scn.org
> In case this ref has not been mentioned yet:
> Oxygen isotope evidence for semi-aquatic habits among
> spinosaurid theropods.
> Romain Amiot, Eric Buffetaut, Christophe Lécuyer, Xu Wang,
> Larbi Boudad, Zhongli Ding, François Fourel, Steven Hutt,
> François Martineau, Manuel Alfredo Medeiros, Jinyou Mo,
> Laurent Simon, Varavudh Suteethorn, Steven Sweetman,
> Haiyan Tong, Fusong Zhang, and Zhonghe Zhou
> Geology 38: 139-142 (February 2010)
> Abstract:
> Spinosaurs were large theropod dinosaurs showing peculiar
> specializations, including somewhat crocodile-like
> elongate jaws and conical teeth. Their biology has been
> much discussed, and a piscivorous diet has been suggested
> on the basis of jaw as well as tooth morphology and
> stomach contents. Although fish eating has been considered
> plausible, an aquatic or semiaquatic lifestyle has seldom
> been suggested because of the apparent lack of
> corresponding adaptations in the postcranial skeleton of
> spinosaurs, which on the whole is reminiscent of that of
> other large terrestrial theropods. On the basis of the
> oxygen isotopic composition of their phosphatic remains
> compared with those of coexisting terrestrial theropod
> dinosaurs and semiaquatic crocodilians and turtles, we
> conclude that spinosaurs had semiaquatic lifestyles, i.e.,
> they spent a large part of their daily time in water, like
> extant crocodilians or hippopotamuses. This result sheds
> light on niche partitioning between large predatory
> dinosaurs, since spinosaurs coexisted with other large
> theropods such as carcharodontosaurids or tyrannosaurids.
> The likely ichthyophagy and aquatic habits of spinosaurids
> may have allowed them to coexist with other large
> theropods by reducing competition for food and territory.