Re: Geographic Distribution of Deinonychosauria

[evelyn sobielski <koreke77@yahoo.de>]

> >  I posted some time ago about working on project,
> designated *The
> >  Geographic distribution of Maniraptora*. I
> received many helpful
> >  replies from several members, for which I am
> very appreciative. Now I
> >  am back, and I have a few questions.
> >
> >  The study will look at the geographic
> distribution of
> >  deinonychosauria (for now, it will expand later
> to Maniraptora) at
> >  the stage level. I am in need of a good analogue
> for this group, and
> >  someone suggested the following paper; *The late
> Miocene radiation of
> >  modern Felidae: a genetic assessment*.
> >
> >  My question is, are the Felidae a good analogue
> to my study group,
> >  or is there a better option? I am open to any
> and all suggestions.
> >
> >  sincerely,
> >
> >  Lonnie A. Matson
> 
> Well, there is no good analogue. Perhaps try to use
> several.
> 
> But in any case, the Mesozoic terrestrial fossil record
> simply isn't 
> detailed enough for what you want to do with it. For many
> stages there's 
> only one or two sites in the world.

True, but the stages don't last so long that one cannot infer distributions of 
nonvolant taxa fairly well from knowledge of the topographical layout 
(particularly if taking into account phylogeny). It may still be insufficient 
for such a restricted taxonomic sample.

The tricky thing is shelf/epicontinental seas; sea level fluctuates more 
rapidly than can be reliably discerned from the geological record (even in warm 
ages, we have glacial/interglacial oscillations, and these take only a few 
dozen Ka). Particularly in the Triassic/early Jurassic, this is bound to be a 
source of error because it makes it essentially impossible to distinguish 
between dispersal and vicariance.

Apart from that, one can assume that open seas/oceans are a barrier to 
dispersal until proven otherwise, and simply deal with the major land areas 
(i.e. as isolated by open sea and high mountains). 

What might be informative is the (fossil and Recent) distribution of 
Crocodylomorpha. I do not know of a major monography on the topic, but it 
should be easy to simply map the occurrences of every lineage (see e.g. 
http://www.helsinki.fi/~mhaaramo/metazoa/deuterostoma/chordata/archosauria/crocodylia/crocodyliformes.html)
 in space and time using time-slice paleomaps 
(http://geology.about.com/od/paleomaps/a/paleomapping.htm). 

As the croc fossil record is reasonably dense and as they are if anything 
slightly better ocean crossers than nonvolant theropods, the endemism patterns 
should be insightful.



Regards,

Eike