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Fwd: Re: tyrannosaurs and phorusracids
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From: "Thomas R. Holtz, Jr." <email@example.com>
Subject: Re: tyrannosaurs and phorusracids
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At 10:37 AM 5/22/97 +0000, Pieter Depuydt wrote:
>You're completely right of course; there is one other similarity
>between tyrannosaurs and phorusracids: there are only some skeletons
>left of them and no human has observed a living one (except perhaps
>some Paleoindians a phorusrhacid).
>I think Marshall based his
>predatory scenario of phorusracids on observation of the nearest
>relatives of them: the seriemas, which are agressive, cursorial
>("running") birds that dash at their prey and shake it to death, just
>living theropod, the secretary bird (doesn't that one kick his prey
>too?). Of course all these extant ("now-living") dinosaurs are
>medium-sized or small hunters, and it is difficult extrapolating
>observations on them to those massive predators of the past, for
>which we have really no living analogue...
Precisely (although, as you note, the survival of close relatives to
phorusracids gives us greater insight into their anatomy and behavior
is available for tyrannosaurids).
I find the tyrannosaur/phorusrhacid comparison is very similar to other
pairs of Asiamerican Late Cretaceous dinosaurs and South American (and
southern North American) late Cenozoic vertebrates:
and therizinosaur/giant ground sloth comparisons, for example. Except
some paleoindians, no humans have seen phorusrhacids, glyptodonts, or
ground sloths, all of which might had made better "contemporary"
for certain dinosaur than are found among living animals.
>Isn't there also a record of tyrannosaur bite marks on an adult
>ceratopian pelvis, from which bite forces were estimated? (I think
>this was published in Science or Nature last year).
True, but (as I recall) there is no evidence that the Triceratops lived
after being bitten. It could, therefore, have been scavenged. Our
direct evidence that large theropods were active hunters is going to
from evidence of their failed attempts, documenting that they did
living animals. (Okay, I'd also accept a giant equivalent to the
dinosaurs" pair, with, for example, a Tyrannosaurus and Triceratops
in mortal combat, but I sincerely doubt we will ever find as
specimen as that!!).
Thomas R. Holtz, Jr.
Vertebrate Paleontologist Webpage: http://www.geol.umd.edu
Dept. of Geology Email:firstname.lastname@example.org
University of Maryland Phone:301-405-4084
College Park, MD 20742 Fax: 301-314-9661