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Repost of reply to Tim Williams



Sorry for the repost; due to quirk of yahoo beta mail, even I couldn't figure 
out who said what. Hoping this turns out better.

'Questions/comments below.

Don

----- Original Message ----
From: Tim Williams <twilliams_alpha@hotmail.com>
To: dinosaur@usc.edu
Sent: Monday, July 3, 2006 4:40:15 PM
Subject: RE: T. rex's vision as SUPPORT for scavenging activitiy...

Don Ohmes wrote:

>>Any candidates for the role of volant scavenger(s) co-existing with T. rex?

>A scavenging lifestyle was suggested for _Quetzalcoatlus_ back in the 
>1970's, when this flying beastie was first described.  But as I learned from 
>Darren Naish's blog...

http://darrennaish.blogspot.com/2006/04/why-azhdarchids-were-giant-storks_03.html

>... the evidence to support a scavenger lifestyle for _Qutzalcoatlus_ and 
>other azhdarchids is very weak.

>I'd bet dollars to donuts that one day a Mesozoic bird (probably an 
>enantiornithean) turns up with characters consistent with specialist 
>scavenging.

When you go dollars to used donut holes, as opposed to just donuts, I'll know 
you are confident. Although I agree in the sense we aint seen much of what was 
there.

>Considering the sheer bulk of many dinosaur carcasses around in the Jurassic 
>and Cretaceous, scavenging seems like too good a niche to pass up.  Of 
>course, it helps to have a strong digestive system.

Agreed. Pack hunters may have been very efficient, though. And big prey equals 
big packs, I'm guessing. (Not to open old wounds, LOL-- How many 100 kg 
climbing "terrestrial shark analogues" could a 60 ton carcass feed?)

>>IF there is the presence of a population of volant scavengers, then timely 
>>visual cues (eg, circling vultures) to any local large animal death exist, 
>>and are detectable from distances up to 40 miles in an open environment.

>AFAIK, nobody has suggested that tyrannosaurs could fly.  Apart from George 
>Olshevsky, that is. :-)

Huh? Not me, that's for sure. Didn't follow this one, exactly. Bulky carcasses 
equals more time to walk to lunch (before it is all gone, or decomposed 
entirely).

Don

>Cheers

>Tim







>
>Don
>
>
>
>



>From: don ohmes <d_ohmes@yahoo.com>
>Reply-To: don ohmes <d_ohmes@yahoo.com>
>To: dinosaur@usc.edu
>Subject: T. rex's vision as SUPPORT for scavenging activitiy...
>Date: Mon, 03 Jul 2006 13:13:37 -0700 (PDT)
>
>In my opinion-- obligate scavenger is not the most probable lifestyle for 
>T. rex, and there are strong arguments for a top predator lifestyle, as 
>well some against the obligate scavenger hypothesis. That said, there is no 
>doubt that the ability to scavenge/co-opt fortuitous mortalities in the 
>local large animal population is potentially advantageous for top 
>predators.
>
>The ability to detect fortuitous mortality in a timely fashion is obviously 
>critically important to efficient utilization of such resources, and any 
>sense used for detection is therefore subject to strong directional 
>selection. IF there is the presence of a population of volant scavengers, 
>then timely visual cues (eg, circling vultures) to any local large animal 
>death exist, and are detectable from distances up to 40 miles in an open 
>environment.
>
>Given the large size of resource animals extant in the Cretaceous, a 
>relatively large time window for utilization would exist. An open 
>environment, very large animals, and volant scavengers seems like an ideal 
>recipe for evolving keen (ie, long-range) daytime vision in a large 
>terrestrial predator.
>
>I don't know if this has been addressed before, in print. If it has, sorry 
>about the lack of reference.