New Study Shows Tyrannosaurus Rex Evolved Advanced Bird-Like Binocular Vision

Science News Online ^ | June 26 2006 | Eric Jbaffe

[Al Simmons]

In the 1993 movie Jurassic Park, one human character tells another that a Tyrannosaurus rex can't see them if they don't move, even though the beast is right in front of them. Now, a scientist reports that T. rex had some of the best vision in animal history. This sensory prowess strengthens arguments for T. rex's role as predator instead of scavenger.

Scientists had some evidence from measurements of T. rex skulls that the animal could see well. Recently, Kent A. Stevens of the University of Oregon in Eugene went further.

He used facial models of seven types of dinosaurs to reconstruct their binocular range, the area viewed simultaneously by both eyes. The wider an animal's binocular range, the better its depth perception and capacity to distinguish objectseven those that are motionless or camouflaged.

T. rex had a binocular range of 55, which is wider than that of modern hawks, Stevens reports in the summer Journal of Vertebrate Paleontology. Moreover, over the millennia, T. rex evolved features that improved its vision: Its snout grew lower and narrower, cheek grooves cleared its sight lines, and its eyeballs enlarged. ...

Stevens also considered visual acuity and limiting far pointthe greatest distance at which objects remain distinct. For these vision tests, he took the known optics of reptiles and birds, ranging from the poor-sighted crocodile to the exceptional eagle, and adjusted them to see how they would perform inside an eye as large as that of T. rex. "With the size of its eyeballs, it couldn't help but have excellent vision," Stevens says.

He found that T. rex might have had visual acuity as much as 13 times that of people. By comparison, an eagle's acuity is 3.6 times that of a person.

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T. rex might also have had a limiting far point of 6 kilometers, compared with the human far point of 1.6 km. These are best-case estimates, Stevens says, but even toward the cautious end of the scale, T. rex still displays better vision than what's needed for scavenging.

The vision argument takes the scavenger-versus-predator debate in a new direction. The debate had focused on whether T. rex's legs and teeth made it better suited for either lifestyle.

Stevens notes that visual ranges in hunting birds and snapping turtles typically are 20 wider than those in grain-eating birds and herbivorous turtles.

In modern animals, predators have better binocular vision than scavengers do, agrees Thomas R. Holtz Jr. of the University of Maryland at College Park. Binocular vision "almost certainly was a predatory adaptation," he says.

But a scavenging T. rex could have inherited its vision from predatory ancestors, says Jack Horner, curator of paleontology at the Museum of the Rockies in Bozeman, Mont. "It isn't a characteristic that was likely to hinder the scavenging abilities of T. rex and therefore wasn't selected out of the population," Horner says.

Stevens says the unconvincing scene in Jurassic Park inspired him to examine T. rex's vision because, with its "very sophisticated visual apparatus," the dinosaur couldn't possibly miss people so close by. Sight aside, says Stevens, "if you're sweating in fear 1 inch from the nostrils of the T. rex, it would figure out you were there anyway."

Stevens, K.A. 2006. Binocular vision in theropod dinosaurs. Journal of Vertebrate Paleontology 26(June):321-330.

[CarolinaGuitarman]

"blah, blah, blah"

That was the most intelligent thing you've posted so far. No wonder you didn't post to to anybody.

[Centurion2000]

Interesting.

[CarolinaGuitarman]

"Less often than elephants and aligators."

You have a citation for that?

[xpertskir]

Well I believe in the Christian God and believe that species on the world have and continue to evolve.

I have read your "paradox" quite a few times and am having problems wrapping my head around it. Is it from the bible, or a philosopher, or what?

[Mogollon]

The T Rex birth rate is too low to support Evolutionary arguments of random mutations occuring fast enough to bring about species change.

Shhh!! Don't be putting facts contrary to the darwininan fundies orthodoxy on theses threads...orionblamblam will have a hissy.

[CarolinaGuitarman]

"It's "the wages of sin is death" paradox. If death is the result of sin..."

Did the cells of Adam's body die before the Fall? Did viruses and bacteria exist before the Fall? Why is it not considered death when an animal eats a plant? Are not plants alive?

"Maybe God is right and he really did create all things in 6 literal days and created light even before the sun, moon and stars..... or Man is right and life on earth evolved over time and God had nothing to do with it."

Or maybe that's a false dichotomy.

[Southack]

"My point in discussing dogs is that one shouldn't confuse variation in size and bone length with large changes in the genome. Small changes in regulatory genes account for the difference between wolves and chihuahuas."

Really?! Regulatory genes control the different skulls between wolves and chihuahuas, you say?!

Chihuahuas skull.

Wolf Skull.

Oh, by the way...When do the modified T Rex skulls appear in the timeline? At the beginning of the T Rex species, middle, or at extinction?

[Southack]

"You have a citation for that?"

For my own expectation?! Nope. No citation for my own opinion.

Nice try, though. No doubt you'll throw inane questions at me non-stop in some lame attempt at doing whatever it is that you are doing, though.

[CarolinaGuitarman]

Ping to post #45.

[StJacques]

"As I recall, one of Horner's arguments about T-Rex as a scavenger is that he thought T-Rex wasn't built as much for speed, but for long distance walking.

I've always thought that T-Rex didn't need to be fast, just faster than the prey animals. Nobody ever seems to ask Dr. Horner THAT question. If T-Rex was following large numbers of migratory prey animals, then one would expect that it would be made to walk long distances, and attack sick prey animals with short bursts of speed."

I agree with everything you posted here ex-NFO and I too am convinced that T Rex was a predator. When I asked myself what I would expect to see in T Rex that might indicate that he was primarily a scavenger I looked for traits I might commonly associate with scavengers today, such as long thin necks (condors, vultures e.g.) uncommon to predators -- T Rex's neck was very broad which I believe gave him an advantage in bringing down large prey in close contact; a mouth (or bill or jaw if you will) that was primarily designed for ripping and tearing rather than biting and crushing -- most scavengers have hooked bills with small razor-like teeth that rip unlike T Rex; and most importantly a relatively slender thoracic cavity like condors and vultures again -- can you name one robust scavenger? -- since scavengers must be able to endure relatively long periods with little or no food. T Rex had an extremely robust body that had to be sustained with an enormous amount of protein and I find it difficult to believe than any scavenger species could evolve in any environment capable of providing a protein supply sufficient to sustain that kind of bulk.

I am much more likely to associate T Rex with present-day predators such as alligators and crocodiles, who it seems to me have teeth very similar to T Rex. Both alligators and crocodiles depend upon predation as their basic means of survival, but they both will also scavenge when the occasion presents itself.

[CarolinaGuitarman]

"For my own expectation?! Nope. No citation for my own opinion."

So you don't know if they reproduced slow or fast, you just made it up and said slow. I see.

"Nice try, though. No doubt you'll throw inane questions at me non-stop in some lame attempt at doing whatever it is that you are doing, though."

Why was asking you to back up your claims *lame*?

[Southack]

"So you don't know if they reproduced slow or fast, you just made it up and said slow. I see."

It's very safe to say that T Rex had slow birth rates. That's not made up, that's derived.

Large animals have slow birth rates. Alligator. Whale. Horse. Elephant. Etc.

[js1138]

Really?! Regulatory genes control the different skulls between wolves and chihuahuas, you say?!

What do you propose as an alternative? They are pretty much the same species.

[MineralMan]

"Large animals have slow birth rates. Alligator. "

Actually, you offer a poor example. Alligators, after reaching maturity will lay their eggs each year, in rather a large clutch. What makes you think they are slow to breed?

You're just guessing. Your other examples, like Elephants and horses, have no relevance, since they are mammals.

Guessing doesn't get it. The bottom line is that you have no idea how often Rex bred. You don't know if it was an egg-layer or a live-bearer.

Essentially, you don't really know anything at all about Tyrannosaurus Rex.

Thanks for playing.

[RobRoy]

OK, I'm confused. Have we unearthed "soft tissue" or even fossilized t-rex eyeballs?

If not, what evidence gives them the conviction to state such opinions as athoritative fact rather than wild speculation?

[Lekker 1]

Alright, I admit it. The famous picture of Helen Thomas came to mind when I read this. I will spare all of you though.

[RobRoy]

>>In the 1993 movie Jurassic Park, one human character tells another that a Tyrannosaurus rex can't see them if they don't move, even though the beast is right in front of them. Now, a scientist reports that T. rex had some of the best vision in animal history. This sensory prowess strengthens arguments for T. rex's role as predator instead of scavenger. <<

I thought that was due to how the brain interpretted what the eye sees as opposed to how good the eyesite is.

You know, how you can look at a bush and not see the bird in it until the bird moves. That is due to my brain, not my eye. Last I heard, it is believed that t-rex was not all that bright.

[CarolinaGuitarman]

" It's very safe to say that T Rex had slow birth rates. That's not made up, that's derived.

Large animals have slow birth rates. Alligator. Whale. Horse. Elephant. Etc."

You said the T-Rex's rate was slower than the alligator or the elephant. You still have nothing to back that up with.

[RobRoy]

I was just staring down a mother raccoon and her four babies this morning before work. She had a pretty narrow snout too with real clear sight lines. I don't know if that means she can see six kilometers away though.

She was hissing for some reason too. ;)

[RobRoy]

>>The T Rex birth rate is too low to support Evolutionary arguments of random mutations occuring fast enough to bring about species change.<<

Spoilsport! :)