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.

[Southack]

"Show us where you got the information regarding mutation rates in alligators."

See post #159, then grow your mind from your micro-level focus up to the bigger macro-level picture and you'll have your answer.

[drhogan]

"Night of the Lepus"
giant rabbits.

[js1138]

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.

Show us where you got you information showing that the mutation rate for alligators is low.

[Southack]

"Show us where you got you information showing that the mutation rate for alligators is low."

See post #151.

[js1138]

More specifically, what do you mean by a micro-mutation as opposed to a macro-mutation?

[js1138]

I've look at all your posts. Show us where you got you information showing that the mutation rate for alligators is low.

[js1138]

I've look at all your posts. Show us where you got you information showing that the mutation rate for alligators is low.

[CarolinaGuitarman]

"No, what you said all along was/is untrue. You are confused by the difference between macro and micro derivation of a conclusion."

I said you were making it all up. That's true, as you have no clue what the mutation rates are (nor did you have a clue about the breeding rate of T-rex or of alligators). Your continued evasions only further my case.

"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."

Depends what the meaning of *is* is...

As was already pointed out, they are not the same species. Alligator/crocodile are not species designations.

"Which is to say, I know the macro rate of mutation."

No you don't.

Again, it has not gone unnoticed you are still avoiding the fact you claimed that alligators bred slowly, and alleged this supported your claim that T-rex bred even slower. Since it was pointed out you made an error, you have changed the topic to alligators instead of the T-rex.

You are still flailing...

[Southack]

"More specifically, what do you mean by a micro-mutation as opposed to a macro-mutation?"

Oh, good grief.

Micro means small. Macro means large.

If you know the random mutation rate at the micro level then you would know something at a low level, such as actual numbers of mutations per generation.

In contrast, if you look at the big picture, the macro level, and see that a species is little-changed over a vast quantity of generations, then you have a more general amount of knowledge about the numbers/rate of random mutations.

[CarolinaGuitarman]

"See post #151."

Your link does not in any way show what the mutation rate is for alligators.

[RobRoy]

I agree. But like I said, even if I were not a Christian, I would not buy evolution as taught. Ann's book and Fredoneverything.net cover it better than I can. They both have the same problems with it that I do.

It is not that it denies Christianity that is the problem. The problem is that it is more like Ptolemy's mathematical model of the solar system. It held water - to a point - and then finally had to be abandoned. Evolution as espoused by some True Believers is on a similar footing. What must be added to that is that some "examples for the layperson" being used today have been disproved for decades, but because of the simplicity of the examples, are still being used to illustrate the concept. That is intellectually dishonest.

Such examples are mentioned in Ann's book.

As I've said before, the subtypes of evolution that are provable and have been observed are hard to argue with, but there are too many logical fallacies being applied to "prove" the lions share of evolution "theory".

[Southack]

"I said you were making it all up. That's true, as you have no clue what the mutation rates are..."

Incorrect. You're still lost on the difference between micro and macro picture.

I know the macro...the big picture. That means that I have a clue.

You claim otherwise, that I have no clue.

And you'll be in error as long as you maintain that view.

[ufans]

"Crocodilia is an order of large reptiles that appeared about 220 million years ago. They are the closest living relatives of birds." From wikipedia.org

"Crocodiles are an ancient group of animals. The earliest species, the Sphenosuchians, evolved during the Late Triassic. They were highly gracile, terrestrial forms built like greyhounds. Several terrestrial species during the Cretaceous evolved herbivory (Simosuchus clarki and Chimaerasuchus paradoxus). During the Jurassic and the Cretaceous marine forms in the family Metriorhynchidae such as Metriorhynchus evolved forelimbs that were paddle-like and had a tail similar to modern fish. Dakosaurus andiniensis a closely related species to Metriorhynchus had a skull that was adapted to eat large sea reptiles. When examining extinct species, crocodiles have been a very diverse and adaptive group of reptiles." Also from wikipedia.org

Modern day Crocodiles are still around since the nitch that they found in the past is still around today. The others died out because there nitches disappeared.

[Southack]

"Your link does not in any way show what the mutation rate is for alligators."

That's incorrect. It doesn't show the mutation rate at the micro level, but it does in some form or fashion or "way" show that the mutation rate over time was very little.

That's the big picture.

[Southack]

"Modern day Crocodiles are still around since the nitch that they found in the past is still around today. The others died out because there nitches disappeared."

You are talking about Selection. Selection is not in dispute.

[CarolinaGuitarman]

"Incorrect. You're still lost on the difference between micro and macro picture."

The picture anybody reading your posts is getting is that you don't have the integrityu to admit you made a mistake. You have no clue what the mutation rate is for alligators, nor did you ever have a clue what the breeding rate for a T-rex was. You made it all up, then changed your position when it was pointed out alligators do indeed bred quickly, something you said wasn't true.

Again, it has not gone unnoticed you are still avoiding the fact you claimed that alligators bred slowly, and alleged this supported your claim that T-rex bred even slower. Since it was pointed out you made an error, you have changed the topic to alligators instead of the T-rex.

You are still flailing...

[CarolinaGuitarman]

That should be *integrity*.

[CarolinaGuitarman]

"It doesn't show the mutation rate at the micro level, but it does in some form or fashion or "way" show that the mutation rate over time was very little."

Keep flailing.

[RobRoy]

>>No, they are not the same thing. Alligator is not a species designation, nor is crocodile. The species of both alive today are not the same ones alive 200 million years ago. They speciated.<<

Prove it.

[Southack]

"You have no clue what the mutation rate is for alligators, nor did you ever have a clue what the breeding rate for a T-rex was."

That will be incorrect no matter how many times you repeat yourself (no doubt until you decide to mock me, claim you don't have enough time, or otherwise flee from this thread with your tail between your legs - which will happen).

The big picture...the *clue* that I have contrary to your nonsensical, over-repeated assertations, is that the species in question is little-changed over 200 million years (i.e. a low random mutation rate).

The specific mutation rate may or may not be known, but over time the specific rate must be low due to the species changing so little over so much breeding.