Re: Scandinavian dinos!!!....aaaaand some spinosaur stuff....

["Jonathan R. Wagner" <znc14@ttacs1.ttu.edu>]

Chandler Gibbons writes:
>I'm not saying that sails were common to the group, however, it was probably
>a climactic factor, because a hadrosaur from the same Egyptian deposits as
>Spinosaurus had a sail similar to Spinosaurus's. [...]
>I think that if the sail was used for "climatic" reasons like in Spinosaurus,
>Ouranosaurus, and Rebbachisaurus other dinosaurs from Cretaceous Argentina
>would have had sails also.  [...]
        A "climatic factor" is not necessarily such an obvious conclusion,
and the degree of certainty you imply is probably not justified.
        As a counter-hypothesis, this could be a case of mimicry, in which
the herbivore has large-spines for inter- or intra-specific display, and the
predator has a large spine to allow it to get closer to the herbivores.
Maybe the herbivores benefit too, since smaller predators might avoid
animals with elongate dorsal "sails", thinking they are all spinosaurs.

>They do have similar jaw structures, but that's about it.
        That seems to be most of what there is that can be referred to
_Spinosaurus_ with certainty. The affinities of Stromer's "Spinosaurus B"
are in doubt, which leaves teeth, dorsal vertebrae, and a few other odds and
ends. Remember, it is derived similarity we are looking for, and we work
with what we have...

>I know!!  That's my point.  I don't think Baryonyx walkeri and Spinosaurus
>aegipticus are extremely similar!
        This is:
        a) true
        b) irrelevant
        "Similarity" is unimportant. If we wish to discover their
relationships vis a vis each other and other theropods, we must look to
*derived* similarity. Charig and Milner make a pretty convincing case that
these two form a clade outside of other dinosaurs (except _Irritator_ and
_Angataurama_)

>And I'm also not saying that Baryonyx and Spinosaurus weren't the slight bit
>related, because they were.
        Which hardly says anything. All animals are related to each other in
some way. The idea is that certain derived features of these two animals
suggest they are more closely related than either is to any other animal
(except the argentine ?spinosaurs).

Darryl  writes:
>Dimetrodon had a sail, but other spenacodonts did not.  The lack of a sail
>does not exclude members from this group.
        It is amusing that _Dimetrodon_ and _Edaphosaurus_ both had long
spines, but their relatives did not. It would be interesting to look up
information on their depositional environments (if I had time), and compare
it to the environment in which _Spinosaurus_ lived. Without the geological
information, environment-related morphological hyptheses tend to be
unconvincing, for me at least.

DinosØMP writes:
>Yeah, but the Spinosaurus lower jaw, is similar to many, many other 
>theropods jaws too!!
        Of course it is. My jaw is similar in many ways to the jaws of other
mammals. But how many of these "ways" it is similar represent evolutionary
novelty amongst mammals, and how many represent the retention of an
ancestral state?

>Material:
>Jaw, neck vertebra, back vertebra and spines, rib, piece of ilium, partly 
>femur, tail vertebra; has there been found anything more?
        Sereno (1996) refers some of the material ("Spinosaurus B") to
_Carcharodontosaurus_, while I believe Russell treated it as spinosuarian
(although I don't have the article, and I can't read French anyway...).
        More certainly has been found, and is in private collections.
Unfortunately, this material may not ever be published. :(

        Wagner



----------------------------------------------------------------------------
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
        "There's a fine line between stupid and clever."  -- Spinal Tap