Re: JFC-Bloodiest Battle ??

[dinoboygraphics@aol.com]

> > > What, pray tell, is the modern day niche equivalent of 
therezinosauroids and Mononykus and its relatives? <<<

Mononykus has been compellingly linked via osteological correlates to 
myrmecophagous animals, of which there are several extant.  
Therizinosaurs appear to have been high-browsing herbivores, and while 
the giant sloths and chalicotheres that they have been compared to are 
extinct, high browsing itself is hardly a novel ecological niche.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com


-----Original Message-----
From: Dan Chure <danchure@easilink.com>
To: dinosaur@usc.edu
Cc: dinosaur@usc.edu
Sent: Sun, 24 Aug 2008 10:56 am
Subject: Re: JFC-Bloodiest Battle ??


Scott wote:Â
Â
"but inventing a niche that does not currently exist is an 
extraordinary claim, and requires comensurate levels of evidence."Â
Â
What, pray tell, is the modern day niche equivalent of 
therezinosauroids and Mononykus and its relatives?Â
Â
DanÂ
Â
dinoboygraphics@aol.com wrote:Â
> > > > My point is that the default should not be active predation -- 
other > options are viable, even if it is difficult to distinguish 
between > them morphologically. <<<Â
> Â
> Sorry, I have to disagree with Dan. In the absence of any terrestrial 
> carnivores that are not active predators, the 
burden of evidence has 
> to be on advocates to show that it's even energetically possible. Of 
> course it's entirely possible that dinosaurs (or other extinct > 
organisms) filled niches that are empty today, but inventing a niche > 
that does not currently exist is an extraordinary claim, and requires > 
comensurate levels of evidence. Furthermore, if support for such a > 
niche is possible, then we would need to evaluate osteological > 
correlates on a species by species basis.Â
> Â
> Given the excellent finite-element analysis done on allosaur skulls, 
> whose interpretted slash and rake attack style has been corroborated 
> by recent phylogenetically constrained muscle restorations, there > 
seems little reason to speculate that allosaurs filled an ecological > 
niche that does not exist in current ecosystems.Â
> Â
> ScottÂ
> Â
> Scott HartmanÂ
> Science DirectorÂ
> Wyoming Dinosaur CenterÂ
> 110 Carter Ranch Rd.Â
> Thermopolis, WY 82443Â
> (800) 455-3466 ext. 230Â
> Cell: (307) 921-8333Â
> Â
> www.skeletaldrawing.comÂ
> Â
> Â
> -----Original Message-----Â
> From: Dan Chure <danchure@easilink.com>Â
> To: habib@jhmi.eduÂ
> Cc: DML <dinosaur@usc.edu>Â
> Sent: Fri, 22 Aug 2008 2:44 pmÂ
> Subject: Re: JFC-Bloodiest Battle ??Â
> Â
> Â
> 0AMike; > > I agree. I admit it is arm waving. My point is that the 
default should > n
ot be active predation -- other options are viable, 
even if it is > difficult to distinguish between them morphologically. 
Varanoids have > low wide skulls, crudely like that of crocodilians 
(for the sake of > this argument). Allosaurus and a number of other 
large headed > theropods have extremely narrow preorbital regions, 
quite in contrast > to varanoids. Take a look at the dorsal view of the 
skull of > Monolophosaurus or Sinraptor. While vertical loads might be 
> accommodated, I am less certain about resistance to torque along the 
> long axis of the preorbital region, especially given all the 
pneumatic > penetration of the region. > > Given the lack of similarity 
between theropods and living terrestrial > vertebrates, it would not 
surprise me that they are making livings in > ways unlike anything 
around now, including a life based primarily on > scavenging. As Peter 
Dodson once wrote "let dinosaurs be dinosaurs." > > Dan > > Mike Habib 
wrote: >>> Allosaurus, like Sinraptor and Monolophosaurus, has an 
exceedingly > >> narrow preorbital region. All three are like a pair of 
scissors and > >> quite unlike Tyrannosaurus with arched and fused 
nasals. I doubt >> > Allosaurus was capable of sustaining great 
stresses, especially given > >> the extensive pneumatic system enclosed 
in the narrow skull. Given > >> the abundance of Morrison sauropoÂ
> ds, Allosaurus might have been >> primarily a scavenger, rather than 
=0
Aa > predator, although that is >> pretty much am waving. Jurassic > 
Scavenger Club anyone? >> >> An open skull construction need not mean 
that the maximum loads are > > low - depending on the particular strain 
distribution, a kinetic skull > > can often take fairly substantial 
loads without failure. A more > > heavily built skull may indeed be 
stronger still, but I would be > > hesitant to assume that a more open, 
mobile skull morphology entails > > carrion feeding. Varanids, for 
example, have a very open skull > > construction, with a high degree of 
cranial kinesis, and yet are > > active predators of a range of prey 
items. >> >> Cheers, >> >> --Mike H. >> >> >> Michael Habib, M.S. >> 
PhD. Candidate >> Center for Functional Anatomy and Evolution >> Johns 
Hopkins School of Medicine >> 1830 E. Monument Street >> Baltimore, MD 
21205 >> (443) 280-0181 >> habib@jhmi.edu >> >> >> >> No virus found in 
this incoming message. >> Checked by AVG - http://www.avg.comVersion: 
8.0.138 / Virus Database: >> 270.6.6/1627 - Release Date: 8/22/2008 
6:48 AM >> >> >> > >Â
> Â
> No virus found in this incoming message.Â
> Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus 
Database: > 270.6.7/1628 - Release Date: 8/22/2008 6:32 PMÂ
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