subzero9285 said:
What do you think about the suggestions that it really wasn't a great predator, but rather a scavenger?
Not much to be perfectly honest, and most other paleontologists would likely tell you the same.
Jack Horner has largely been responsible for popularizing the obligate scavenger hypothesis in recent years, but even he admits that much of it is simply to be contrary and get people to look at the available evidence and not assume
T. rex was an arch predator simply because it looks so scary and formidable.
If you actually look at his arguments, most of them don't really hold up. I'll only go through a few in an attempt to keep this brief:
-- Horner believes that
T. rex teeth are too long to resist the forces associated with prey capture. However, biomechanical analyses done to estimate the force needed to generate the puncture marks seen in dinosaur bones attributed to
T. rex teeth indicate that it had a maximum bite force in the region of 15,000 to almost 40,000 lbs, depending on the study.
T. rex teeth are almost circular in cross-section, and specialized to withstand torsional forces.
-- He also maintains that the hind limb anatomy of tyrannosaurs, particularly the ratio of the tibia to femur indicates that it was a slow walker. I find this point amusing because the same evidence used to suggest
T. rex was a slowpoke shows that the herbivorous dinosaurs it was going after were even slower! Furthermore, relative to femur length, the tibia and other lower limb elements in
T. rex are more elongated than in other giant theropods. No other animal as big as tyrannosaurs would have been any faster.
-- Horner claims that
T. rex had "beady little eyes", (his words, not mine), and that it must have lacked the visual acuity of smaller theropods. This is refuted by studies that show that as overall mass increases, eye size does not scale correspondingly to skull length.
T. rex eyes are no smaller than would be expected in an animal its size. Horner also conveniently forgets to note the forward-facing eye sockets and binocular vision that's been hypothesized in
T. rex. Most other theropods lack these adaptations may not have had the depth perception enjoyed by
T. rex.
Most convincingly of all, though, are hadrosaur and ceratopsian fossils preserving trauma from failed predation attempts by
T. rex that later healed-- one specimen documents a
T. rex biting off one of the brow horns of an adult
Triceratops! There's also hadrosaur fossils with unhealed bite punctures to the head and neck, indicating that those individuals weren't quite as fortunate.
I could go on and on, but this post is dangerously long already. Besides, Thomas Holtz had a paper out last year that point-by-point devastates that scavenger hypothesis with hard, quantifiable data. Nobody believes that
T. rex didn't scavenge on occasion, like any carnivore, but the weight of the evidence certainly doesn't support Horner's claims that it was restricted to that lifestyle.
Sorry if the reply ended up being more of a thesis, but this is stuff I tend to take rather seriously!