Re: Latest K dinosaurian diversity trends

[Lee Hall <paleeoguy@gmail.com>]

"If Maastrichtian dinosaurs had a tendancy towards greater ontogenetic
variation, then I suppose
morphological diversity could have been just as high in any given
ecosystem - it's just that the
diversity is encompassed by fewer actual species. Instead, the
morphological variation is due to
animals being at different life stages."

But is ontogenetic variation really equivalent to morphological
diversity?  Variation in ontogeny is still contained within a single
species.  And whos to say that only Maastrichtian dinosaurs were the
only taxa to exhibit ontogentic variation in their morphology?  Call
me crazy, but I'm pretty sure it's at *least* found in everything with
a pulse.  The hard fact of the matter is that species diversity at the
end of the Maastrichtian was just low, and not because normal
"morphological diversity" was crammed into growth stages to compensate
for there being fewer species around than what would have been in the
Campanian.

"That assumes that large ontogenetic variation correlates with changes
in behaviour and/or ecology
throughout an individuals lifetime (which may or may not have been the case)."


What?  Why is a correlation necessary, and why the assumption?  The
presence or breadth of ontogenetic variation doesn't hinge on
behavioral or ecological alteration.


Lee Hall
Paleontology Undergraduate
Museum of the Rockies
Montana State University
Bozeman, MT
lhall@montana.edu
http://sites.google.com/site/leehallpaleo/Home




On Mon, Jan 3, 2011 at 2:41 PM, Dann Pigdon <dannj@alphalink.com.au> wrote:
> On Mon, Jan 3rd, 2011 at 3:15 AM, Denver Fowler <df9465@yahoo.co.uk> wrote:
>
>> Yes, I'm not sure I have the words as to how to put this properly. Maybe this
>> works: There is less morphological diversity among late Maastrichtian 
>> dinosaurs
>> compared to Late Campanian dinosaurs. Whether or not you split the taxa into
>> multiple species does not alter this. I would say that the low morphological
>> variation is probably reflective of true taxonomic diversity, and that most 
>> of
>> the described taxonomic variation is actually ontogenetic or stratigraphic,
>> (which are both testable hypotheses and not merely individual judgement 
>> calls).
>> I'd love to go into further details of species in the Hell Creek, but its 
>> other
>> people's (in progress) research.
>
> If Maastrichtian dinosaurs had a tendancy towards greater ontogenetic 
> variation, then I suppose
> morphological diversity could have been just as high in any given ecosystem - 
> it's just that the
> diversity is encompassed by fewer actual species. Instead, the morphological 
> variation is due to
> animals being at different life stages.
>
> That assumes that large ontogenetic variation correlates with changes in 
> behaviour and/or ecology
> throughout an individuals lifetime (which may or may not have been the case).
>
> --
> _____________________________________________________________
>
> Dann Pigdon
> Spatial Data Analyst               Australian Dinosaurs
> Melbourne, Australia               http://home.alphalink.com.au/~dannj
> _____________________________________________________________
>
>