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.

[demkicker]

For cryin' out loud man, calm down! I pinged YOU after seeing that you had "pinged a list" and merely announced that I was pinging a few atheists (I've had the misfortune of corresponding with). I thought this might be a good venue for them, but apologize if you were offended and can assure you that wasn't my intention. Not to worry, I'll never ping you again...

[CarolinaGuitarman]

"Of course it's an answer."

No it isn't. You didn't say what species you were talking about.

"You're pretending to be dense."

You're not pretending. You don't seem to know what a species is.

"Pick a species. Say Crocodylia."

Crocodylia isn't a species.

"You know this. I know this. You can *pretend* that some semantical issue warrants debate, but you are merely prolonging your inevitable loss of (probably) yet another debate."

Look, you are the one who said that *the species* is the same today as it was 200 million years ago, virtually unchanged. I asked you to name this mythical species that has lasted 200 million years. You have only answered with evasions and insults. It's clear you aren't capable of answering the question.

Alligator is not the name of a species.

"Your call. Keep pretending. Keep nitpicking semantics. Won't matter. Won't help you."

It's not nitpicking when you can't even distinguish between a Species and an Order.

Keep flailing about. It's fun to watch you sink under the weight of your own hubris.

[demkicker]

What are you then?

[js1138]

To wit: on the micro level it might be accurate to say that I don't have the specific mutation rates of alligators/crocodiles on the tip of my tongue...but at the macro level (e.g. the big picture) it is inaccurate to say the same thing...because species that are little-changed over 200 million years clearly have low mutation rates.

Which is to say, I know the macro rate of mutation. In contrast, you are desperately clinging to the fact that I don't know the specific micro level mutation rates as if that myopic viewpoint disproves the bigger picture.

Are you actually asserting that this gibberish has meaning? Again, what is your source for the mutation rates of alligators and crocodiles?

[Southack]

Pick a species. Say Crocodylia. Whatever of it is alive today has remained virtually unchanged for vast amounts of time.

"That says nothing about [the **RANDOM**] mutation rate."

Incorrect. The random mutation rate over vast amounts of time must roughly correspond to the changes seen in any given species (for Evolutionary Theory to have a snowball's chance of being correct, anyway).

[js1138]

Somatic change is constrained by selection. You haven't given a reference for the mutation rate.

[CarolinaGuitarman]

He doesn't seem to have a grasp of what a species is either...

[Southack]

"Crocodylia isn't a species."

Arguments over semantics (e.g. Group or Species) won't help you in this debate.

You lost. You nitpicked, asked, re-asked, and pretended to play dumb. Too bad.

[js1138]

Lest I be misunderstood, populations can undergo changes in the genome without displaying large outward changes in body conformation.

Second, it is possible for a species to reach a point of specialization at which nearly all change is detrimental. At such a point, any mutation that would produce a change in body conformation would be at a reproductive disadvantage, and would be selected out.

You have made a broad statement that mutations in alligators and crocodiles occur at a reduce rate. I am not aware of any research confirming this. It is up to you to defend your statement.

[beancounter13]

Again, it looks like we are pretty close on the topic. Likewise, I do not buy into the entire evolution pretext anymore that I buy into Genesis' "six literal days" (at least as humans define a day) concept.

[OmahaFields]

What are you then?

I am not an anti-evolutionist.

[CarolinaGuitarman]

"Arguments over semantics (e.g. Group or Species) won't help you in this debate."

It's actually between species and order. And it has everything to do with the discussion. It shows you don't know what the hell you are talking about, and are not big enough to admit it. Your assertion that alligators have not changed much in 200 million years is belied by the speciation events that have occurred over the time they have been on Earth. They are not the same, and you lack the integrity to own up to your mistake.

"You lost. You nitpicked, asked, re-asked, and pretended to play dumb. Too bad."

It doesn't work that way. You made the claims, and you have not been able to back up even ONE of them tonight.

You said that T-rex bred really slowly, and therefore that showed they couldn't be accounted for by evolutionary theory; and you used the alligator as part of your evidence. Oops, alligators don't breed all that slow, so you switched and said they bred TOO FAST to make sense with evolutionary theory.

You have provided no evidence that T-rex's bred slowly.
You have provided no evidence that alligators have a slow mutation rate.
You have provided no evidence at all that any species of alligator alive today was alive 160-200 million years ago.

All you have is you flailing around like a stuck pig.

That's amusement enough to continue. :)

[Al Simmons]

"Arguments over semantics (e.g. Group or Species) won't help you in this debate."

''Semantics'? *ROTFLMAO* "You lost. You nitpicked, asked, re-asked, and pretended to play dumb. Too bad."

Pot. Kettle. Black.

[demkicker]

Do you believe in God?

[Junior]

So now there are people at the time of the dinosaurs? Hmmm.

I cannot believe you read the article and then posted what you posted. He was talking about the scene in Jurassic Park.

[Uncle Vlad]

[Southack]

"You said that T-rex bred really slowly, and therefore that showed they couldn't be accounted for by evolutionary theory; and you used the alligator as part of your evidence. Oops, alligators don't breed all that slow, so you switched and said they bred TOO FAST to make sense with evolutionary theory."

T Rex did breed too slowly for random mutations to account for the changes in said beast. That's my opinion.

Alligators do breed slowly, once per year, yet are prolific (20 to 50 young at a time) and virtually unchanged over millions of years.

Remaining unchanged over vast amounts of time is contradictory to vast amounts of random mutations.

Of course, you have a problem with every word above. You have to. You have to be argumentative, as your belief-structure is threatened by such easily laid out points.

Continue on.

[OmahaFields]

Do you believe in God?

As I posted, I am not allowed to be an atheist.

[Southack]

"Southack the TROLL has information??"

Your first post is name-calling?!

Typical.