T. Rex Autopsy Gives Us An Anatomy Lesson On the Toothy Terror
In case you couldn’t tell by the sightings of a dinosaur corpse in London last week, the National Geographic Channel is airing a show called T. Rex Autopsy this Sunday, June 7, at 9/8C. During the two-hour event, a team of paleontologists and big animal vets will dissect a lifelike model of everybody’s favorite predator, Tyrannosaurus rex.
The word model doesn’t really do this resurrected beast justice. It’s 46 feet long,13 feet tall, and took the team that created Jabba the Hutt more than 10,000 man-hours to build. The fiberglass and clay model has innards too: realistic, glistening viscera crafted from silicone and latex, and plenty of blood (34 gallons worth!) They even stuffed its intestines full of partially-digested bones and artificial poop—scented with badger stink.
Featuring a four-member forensics team—paleobiologist Tori Herridge, veterinary surgeon Luke Gamble, natural history museum curator Matthew Mossbrucker, and paleontologist Steve Brusatte—T. Rex Autopsy is an educational bloodbath. I know, because I visited the set to speak to the experts about T. Rex anatomy, and to find out how, exactly, they were able to build such a lifelike replica based on ancient bones.
“It’s difficult because we’re working with these fossils that are 66 to 67 million years old,” says Steve Brusatte, a paleontologist at the University of Edinburgh who is part of the autopsy team. “But bones can actually tell us quite a lot.”
For instance, when Brusatte and company hack into a reconstructed T. rex eyeball the size of a grapefruit, they’re not venturing into the realm of complete imagination. They based the reconstructed eye on fossils of the sclerotic ring, a circle of bones surrounding the eyeball that helps secure surrounding muscle. These bones have been found in many different kinds of dinosaur fossils, from ichthyosaurs to the theropods, the suborder to which T. rex belonged. It’s thought that the sclerotic ring would have helped T. rex zero in on prey and change focus from foreground to background.
“The best evidence we have says T. rex would have had some pretty good binocular vision,” says John Hutchinson, a professor of evolutionary biomechanics at the Royal Veterinary College in London and a consultant on the show.
If most living reptiles are any indicator, T. rex would have also likely had color vision. Combine that with the biggest olfactory bulb in the business, and you’ve got a predator that can zoom in and sniff out a target from a long way off. (So you can officially scratch "standing still" off your list of ways to outwit a T. rex.)
What about the belly of the beast? How did the scientists build a blood-and-guts model if the squishy stuff like lungs generally don’t fossilize?
For insight, they looked to dinosaurs’ living descendants: birds. “We know that a lot of dinosaurs had air sacs like birds, because we can see the places where the air sacs go into the bone,” says Brusatte, who has named four of the known species of Tyrannosaur.
Unlike our lungs, this air sac model would allow the T. rex to acquire oxygen much more efficiently and may be indicative of an elevated metabolism. This also ties in with another largely unknown facet of T. rex anatomy—the rib-like bones known as gastralia. These bones would have protected T. rex’s low-hanging gut from triceratops horns and the like. And they may have assisted with pumping those multi-chambered super lungs. We know T. rex had these bones because two animals, nicknamed Bucky and Peck’s Rex, were found with fairly intact gastralia bones.
In fact, we have a pretty good representation of T. rex fossils—about 50 T. rex skeletons that span approximately 2 million years of the animal’s evolution. The most famous specimen, nicknamed Sue, is also the most complete. Nat Geo based much of its model on a full scan of Sue’s skeleton, which is on display at the Field Museum.
The dimensions of Sue’s ribcage were used as a starting point for creating a model of the heart—though the final version took quite a bit of fine-tuning. “When they originally made the sculpt of the heart, it was too big,” says Hutchinson.
Most animals have hearts that are around 1 percent of their overall body weight, but when they mocked up a matching organ for the seven-ton T. rex, it wouldn’t fit inside the ribcage. This tells us that T. rex likely had a smaller, more efficient ticker that was rather bird-like in nature.
Similarly, scientists can use the closest living relatives of Tyrannosaurs to make reasonable assumptions about its other organs. In crocodilians and most birds, food passes through a two-step process as it digests. Because these animals don’t chew their food—be it rotten hippo or a sunflower seed—the material must first be ground up in the ventriculus, or gizzard. What’s left is then passed on to a stomach chamber more like our own where digestive juices go to work. If crocs and birds share a trait, then it’s a good bet a dinosaur like T. rex had it, too.
Hutchinson says T. rex could have run between 15 and 25 mph, based on the tiny markers he found throughout Sue's skeleton that indicate she would have had 33 different muscle groups. One impressive muscle group ran from leg to tail, propelling the monster forwards and upwards. Analogous to our glutes, each of these hulking pieces of powerful flesh would have weighed about 220 pounds. “That’s a hell of a steak,” Hutchinson says. “It’s one of the biggest muscles in any animal ever.”
From tail to snout, the T. rex body is fascinating. But is Nat Geo’s model completely accurate? Almost certainly not. Scientists debate the details with each new fossil found. But there’s still a ton to learn this Sunday when scientists put one of these animals under the (fake) knife.
As for the "cause of death" discovered through this autopsy: Let's just say T. rex may have taken a nasty spill.
All images courtesy of National Geographic Channel.