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Re: What ever happened to Deinodon?

Saurischia@aol.com wrote:

>I'm not a professional - I'm just grown up childhood dinosaur enthusiast
>with a failing memory.  I was wondering if someone could summarize for me
>what criteria caused reclassification of Tyrannosaurus and his kin over

    Boy, you've missed a bunch.

>the years.  Why were the Theropod infraorders Coelurosauria and
>Carnosauria dropped - was the line drawn between them too ambiguous?

        No, Coelurosauria exists as a monophyletic (all of it's members
come from one common ancestor) taxon (generic group) which is defined as
"all critters more closely related to birds than to Allosaurus".  This
includes troodontids, ornithomimmids, dromaeosaurs, birds, oviraptors, and
tyrannosaurs (yes, tyrannosaurs!).  For a somewhat technical explanation,
read Holtz's 1994 artical in the Journal of Paleontology, and his more
recent (May, 1996) article in JP.
          Carnosauria has been redefined a few times, and is currently
defined as "all animals more closely related to Allosaurus than to birds"
(Tom Holtz: could you supply a ref. on this, so I don't end up putting my
foot in my someday professional mouth? :) ).  What this taxon contains has
been the subject of an highly esoteric discourse on this mailing list for
several months.  Sereno's 1996 Carcharodontosaurus paper (Science, May
17th) has a reasonable idea of what is currenlty in the Carnosauria, but he
ignores many basal species, and you may not recognize the ones he lists.

>I've noticed the Ornithosuchidae were extracted from Carnosauria and
>given a suborder to replace the Pseudosuchian Thecodonts.  Is this
>Ornithosuchia suborder now believed the common ancestor between
>Saurischia and Ornithoschia?

        I'm not too good on this, but here goes:  Saurischia (which some
regard as an unnatural group, but I have yet to see a good analysis of the
data which support Bakker's Phytodinosauria (Ornithiscia+Sauropodamorpha))
is the "sister taxon" of Ornithiscia, meaning that they are more closely
related to each other than either is to any other group.  Their union in
the Dinosauria (the name for the node which includes both taxa, aka "the
common ancestor of Iguanodon and Megalosaurus and all of it's descendants")
has been one of the many recent reversals in dinosaurological thought
(others include warmbloodedness and avain ancestry).
        This excludes the Ornithosuchidae, and all other groups which are
not part of the Dinosauria as described above.  the idea of seperate origin
of the two "dinosaurian orders" is not well supported by modern study.  If
I'm not mistaken, the origin of the Dinosauria is thought to have occurred
within the Ornithosuchidae, or the two may be sister taxa.

>And I remember Tyrannosauridae was once
>also referred to as Deinodontidae, and Gorgosaurus as Deinodon.  (Am I
>right in assuming Gorgosaurus and Deinodon are now both synonymous with
>Albertosaurus?  At one point Albertosaurus and Gorgosaurus were
>considered different animals.)  As I'm not current in paleontology, I
>find myself getting confused, especially since my library is outdated.

        Check out Gregory Paul's _Predatory Dinjosaurs of the World_ (may
be hard to find, but lots of libraries have it).  It's out of date (it was
written in 1988, gasp! :) ), but it is a wonderful introduction to modern
theories about dinosaurs.  All I know about this question comes from there.
As it stands, I believe that Deinodon is synonymous with Tyrannosaurus,
and I think someone bent the rules a little to ressurect Tyrannosauridae,
but I'm not certain.

>Why do new genus names sometimes replace older ones?  I always liked the
>name Brontosaurus better than Apatosaurus.  (I remember there was an
>issue over a missing Brontosaurus skull - was that a factor?)  I always

        To prevent wholesale confusion, such as what is happening with
Coelophysis right now.  The idea is that a genus is based on a "type
specimen", and all judgements about what is in that genus is based on that
type specimen.  If, either by reexamination of the type or of new,
demonstrably referrable material, a genus turns out to referrable to
another, we then have a problem, "what do we call the genus?"  The
solution, according to the Rules of Zoological Nomenclature, set and
maintained by the International Committe on Zoological Nomenclature (ICZN),
whose rules are applicable to all biological sciences, is to use the first
name applied, by year, month, date, and order in a sentence iff necessary.
It is more complicated than this, but the upshot is, it was later
determined that Brontosaurus was referrable to Apatosaurus.  And it *is* a
darned shame.

>liked the name Trachodon too, perhaps only due to childhood familiarity.
>That's a name I NEVER see anymore.  I thought Trachodon was renamed
>Anatosaurus but I have one *old* book that lists them as two separate
>specimens, and a newer book that doesn't list Trachodon at all.  And at

        I am unfamiliar with the case, but it sounds like they later
decided that Trachodon was referrable to Anatosaurus, which, btw, was then
referred to Anatotitan.

>some point in the past I thought Antrodemus was going to replace
>Allosaurus, but I'm glad to see that it hasn't.

        Yet another case...  Although, I think someone may have mentioned
somewhere that Antrodemus may have priority.  I hope not...
        As an aside, several genera are sunk into Allosaurus, including
Antrodemus, Creosaurus, and possibly the family value-sized Epanterias,
Saurophagus and Saurophaginax.

>--Christopher Sirmons Haviland

        Nice to meet you,
        Jonathan R. Wagner