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:
"but inventing a niche that does not currently exist is an
extraordinary claim, and requires comensurate levels of evidence."
What, pray tell, is the modern day niche equivalent of
therezinosauroids and Mononykus and its relatives?
Dan
dinoboygraphics@aol.com wrote:
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. <<<
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.
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.
Scott
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: habib@jhmi.edu
Cc: DML <dinosaur@usc.edu>
Sent: Fri, 22 Aug 2008 2:44 pm
Subject: Re: JFC-Bloodiest Battle ??
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 sauropo
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 >>
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