Tuesday, July 13, 2010

It's official: T. rex to be renamed

It's been looming in the background for some time, unbeknownst to the great unwashed masses. It's been an open secret among paleontologists and science enthusiasts, a dirty truth none would dare speak in public. That most famous of dinosaurs, a veritable symbol of nature's majesty and the wonders of the ancient world, was given the wrong name.

Tyrannosaurus rex is no more. Get used to saying Pseudodichotomasaurus inanis.

Just kidding. But it would be a fitting name for the tyrant king, with silly passages like this popping up in the media:
Tooth marks found on the humerus of a plant-eating dinosaur found in Mongolia have revealed that Tyrannosaurs were actually scavengers and not predators, as is widely believed [emphasis mine].
Ugh, DNA India. Is this the only way to lead this story? Are stark black-and-white dichotomies the only way to make nature interesting? Another meme that will not die. It makes you wonder if griping on blogs may not be the best way to affect change in the world.

Anyway, this is actually a cool story. It doesn't deal with T. rex itself, but with its fellow pseudodichotomasaur from Asia, Tarbosaurus. Paleontologists Dave Hone and Mahito Watabe recently published a study in Acta Palaeontologica Polonica which analyzed bite marks on the humerus of a remarkably well preserved skeleton of a hadrosaur called Saurolophus. Based on the spacing of the teeth and the strength of some of the bites, it was clear that Tarbosaurus, was the most likely suspect, as it was the only large tyrannosaur known from the area and time. This is one of those rare fossils that has a a story to tell beyond the structure of the animal itself.

Based on the lack of damage to the rest of the skeleton, the scientists determined that what had probably happened was that the Saurolophus was quickly buried after death, and when our fortunate Tarbosaurus happened across the carcass, all that was accessible was the left arm. The distinct patterns of tooth marks indicate that the Tarbosaurus bit into the ends of the bone, as well as delicately scraping at whatever meat was left on the middle portion. This clearly indicates scavenging behavior, as this is hardly the choicest cut on the animal, and had it been a fresh kill, the legs, ribs, and other spots containing nice hunks of meat would certainly show evidence of predation.


Feeding strategy one: scraping. By Matt Van Rooijen, used with his permission.


Feeding strategy two: biting and dragging. By Matt Van Rooijen, used with his permission.

Especially interesting here is that a large tyrannosaur like Tarbosaurus was quite capable of delivering a bite that could crush bone, and tyrannosaurs have been found with substantial amounts of crushed bone in their guts. This Tarbosaurus, however, shows that the teeth of the front of the jaw could be used with some finesse, as a kind of comb to remove muscle from flat surfaces of bone. Combined with the deeper bites and drag marks at the bone's ends - which Hone and Watabe believe may have been used to remove cartilage or dissemble the bones at the joints - the overall picture is of a giant theropod with a surgeon's touch. Then as now, predators employ various methods to get the sustenance they need in varying conditions.

"The argument over ‘was Tyrannosaurus (or big tyrannosaurs) a predator or scavenger’ has been going on for far too long and is, I think, not only dull, but largely pointless. It rather assumes that they were one or the other, when pretty much no carnivore is, what they are, is both," Hone writes, setting things straight as usual at Archosaur Musings.

More: Matt Van Rooijen's post about his Tarbosaurus reconstructions, LiveScience.

UPDATE 7-14-10: Fixed some of the wording of the opening based on a comment left by Jay below. I love me some constructive criticism!

7 comments:

  1. I hope I never lose my sense of amazement that we can reconstruct a (in this case literal) slice of life such as this from over 65 million years ago. A carnovore comes across a free snack and takes a bite, and today we are able to reconstruct and reimagine the scene based on actual physical evidence that was left behind.

    As far as the, admittedly pointless, false dichotomy goes, where evolution is concerned design is destiny. Why evolve such huge versions of the tyrannosaur template (which we now know covers a wide variety of sizes), if your primary means of survival is trying to subsist on the scraps left behind by the primary hunters?

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  2. The black and white view of anything tends to lead away from the truth.... it's a pity it also leads to people who want a highly defined world buying papers, watching a news broadcast or clicking a link.
    I did do a picture of what didn't happen on my blog, though I took the opposite inference based on what was more fun to draw!

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  3. Scott - Agreed, big tyrannosaurs were definitely top carnivores and while they probably had the occasional giant carcass to scavenge, they probably had a hand in creating some of those carcasses themselves. Personally, I have plenty of respect for scavengers. Another of my favorite birds is the Turkey Vulture. I've been known to watch them eating roadkill from time to time...

    Matt - Love that little drawing in your post - thanks for including it, even though you didn't have to.

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  4. "Or so you'd think..."

    So, then they're not really re-naming T-Rex? The headline is confusing.

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  5. No, it's a parody. Pseudodichotomasaurus = "false dichotomy lizard." Just a jab at sensationalistic media stories about this subject.

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  6. But you're right, that wording isn't the best. I took another stab at it. I think it makes it loads clearer what I was trying to do with the title.

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  7. I, too, was worried upon first reading the title that it meant Manospondylus Gigas would be rearing its huge, ugly head.

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