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Bakker and Paleo Splitting



>BAKKER AND MOROSAURUS
>
>Who was it that told me about Olshevsky and Bakker oversplitting genera? Bakker
>(I don't yet have the Olshevsky material) includes Epanterias, Morosaurus and
>Creosaurus amongst his 'famous Morrison dinosaurs'. In Hunteria vol. 2 no. 6,
>_Epanterias_ is diagnosed as 'giant allosaur... with a maximum skeletal size
>20% greater than that of any other allosaur sample'. Kirkland and Stephenson
>have discovered a third locality yielding 'Epanterias' - I wonder if they think
>it deserves generic distinction?

        It was me who told you that, Darren!  8-)  And it's true, too:
Bakker is a notorious splitter.  For example, his genera of _Drinker_ and
_Edmarka_... what tiny tidbits of _Drinker_ have been described don't
convince me that it's a separate genus from, perhaps, _Dryosaurus_ or a
hypsilophodont such as _Othnielia_.  And, from what I recall about
_Edmarka_ (my ref is all packed away right now...), it's nice that he
wanted to describe it, but I think it's too fragmentary to base a species
on.  I am highly skeptical of anyone naming new genera on scrappy material
except in special circumstances.  It could well be a large _Allosaurus_,
and so could _Epanterias_.  Though it's debatable, based on the current
base of material, _Epanterias_ is best considered a species of, if not
conspecific with, _Allosaurus_.

>In the same paper, Bakker mentions three Stegosaurus species alien to me:
>_sulcatus_, _armatus_ and _duplex_. A while ago he wanted S. ?stenops to be a
>separate genus, _Diracodon_ (or was it _S._ laticeps_?). I'm not really
>questioning Bakker's allocations here, but it now seems that Stegosaurus is
>quite a multispecies genus. If you're a successful genus, certainly makes sense
>to evolve multiple species... Multispecies genera, like Stegosaurus, make for
>exciting faunas because sympatric species have to evolve different feeding and
>behavioral adaptations - there would be a plethora of plate colour designs and
>arrangements (I'm not implying that all these species lived in the same place
>at the same time - they didn't). It has even been hypothesised that stegosaurs
>evolved 'better' techniques of broad-side display through their history, and
>thus there was alteration in the location of plates along the back.

        Well, keep in mind here that not all the species of _Steogsaurus_
lived simultaneously!  We don't have to be as concerned as you suggest with
sympatricity and the resultant differentiation in feeding habits because
the Morrison is a _thick_ unit of rocks, with the majority of the fossils
occuring (a) low in the formation and (b) high in the formation, so there
is a substantial gap between the two kinds.  Bakker does describe this --
and is correct -- that very large species (if not genera) of various
Morrison beasties show up high in the section -- _Apatosaurus excelsus_
(low) is smaller than _Apatosaurus ajax_ (high), for example.  That's also
part of his reasoning in defining _Diracodon_:  this species occurs low in
the Morrison (although I think it's got bigger plates than the later ones).
The species _armatus_ (including, probably, _ungulatus_) occurs high, if I
remember correctly.  I don't know where _longispinus_ fits in.  _The
Dinosauria_ notes that  _duplex_ is probably conspecific with _armatus_,
too.  Another interesting tidbit:  Bakker wanted to name a new species of
_Stegosaurus_ based on the old Denver Museum mount (found in Canon City,
not 100 yards from where the new one was found, in the 1930's), due to
their unique plate shape.  However, only one plate is real:  one of the
tiny ones from over the head!  So I'm skeptical of how he defines things...
I wonder how he drew the head of _Haplocanthosaurus_ in that ish of
_Earth_ awhile back, since no skull is known for that genus...



Jerry D. Harris
Denver Museum of Natural History
2001 Colorado Blvd.
Denver, CO  80205
(303) 370-6403
Internet:  jdharris@teal.csn.net
CompuServe:  73132,3372

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