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Re: Mesozoic mountains?
Amtoine Grant wrote:
My take on the theory that spinosaurs are derived coelophysids.
Is this the same theory that Gregory S. Paul proposed in 1988, in _Predatory
Dinosaurs of the World_?
Also, the gracile build, relatively similiar body proportions, and kinked
snouts - unless the latter trait evolved again in these theropods, wouldn't
be the first time.
If by "kink" you mean the elevation of the premaxillary tooth row relative
to the maxillary tooth row, then this is present in _Baryonyx_ and
_Suchomimus_, but not in _Spinosaurus_ AFAIK. (Sereno et al.  show a
nice comparison of baryonychine and spinosaurine snouts.)
In coelophysoids, this "kink" is more of a diastema between the premaxillary
and maxillary tooth rows, also called a subnarial "gap" or "notch". I am
not at all certain the conditions in spinosaurs and coelophysoids are the
same. I would argue the "stepped" snout of some spinosaurs and the
subnarial gap of coelophysoids evolved independently. Also note the
position of the narial openings relative to the premaxilla-maxilla
articulation - it is very different in coelophysoids and spinosaurs.
If there indeed was a chain of periodic landmasses in the Atlantic Ocean,
this affinity with water lends reason to the piscivorous adaptations. It
would also explain the recently discussed purpose of the spinosaurs jaws
being suited for small(er) prey than more robust-jawed theropods such as
allosaurs, megalosaurs & tyrannosaurs.
Hmmm.... I was left with the distinct impression this discussion argued
AGAINST piscivorous adaptations in spinosaurs. Sure, they did catch fish
(as shown by the fish remains inside _Baryonyx_'s torso). But spinosaurs
fed on young iguanodonts and pterosaurs as well - these were also
We all [should] know that when animals take up residence on islands, they
tend to experience a reduction in body size,
Big animals can certainly get smaller (e.g., island-dwelling ungulates and
subungulates). But small animals can get bigger once they establish
themselves on islands that are free of predators. Birds tend to fall into
the latter category: moas (New Zealand), elephant birds (Madagascar), dodo
And no, I haven't taken into account Irritator from South America, but then
again none of know ALL the answers. Also, if I recall, spinosaurid sizes go
from smaller to larger starting in Europe with Baryonx, reaching their peak
with Spinosaurus in North Africa.
I believe that the type specimen of _Baryonyx_ is subadult, so the
individual was not fully-grown when it died.