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Re: JFC-Bloodiest Battle ??




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
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"but inventing a niche that does not currently exist is an extraordinary claim, and requires comensurate levels of evidence."Â
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What, pray tell, is the modern day niche equivalent of therezinosauroids and Mononykus and its relatives?Â
Â
DanÂ
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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
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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
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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
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ScottÂ
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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
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-----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
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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
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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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