Our intrepid fossil-hunters, digging in the sun-baked Red Beds of Baylor County, face myriad dangers to life and limb (and fingers and toes). There are afternoons when the thermometer in the bone quarries reaches 140 degrees, and even Harvard PhDs have been known to hallucinate.
There are two species of rattlesnake, plus the occasional angry Black Angus bull. At times, thousands of dark, hairy tarantulas — all males — start marching on their courtship walk-about, searching for coy females tucked away in their burrows. Much worse are the fearsome foot-long centipedes who run up inside your pants to sink their venomous fangs into the soft sectors of your thigh. These will send you to the friendly folks at the emergency room at the efficient Seymour Hospital.
Could there be a more malicious menace? Our paleontologists might have found one: Paleo-Zombies!
As cable TV has taught us, the key identification mark of a zombie is its hunger for brains. Well, classical zombies are also cannibals. They are especially fond of the cerebral morsels from the heads of their own species. Given such zombie lore, how would we tell if a prehistoric critter was a zombie? Easy. It would leave gnaw marks on the skeletons of its own kind, concentrated on the braincase bones that housed the brains in life.
Since 2007, we’ve dug up hundreds of chewed reptile and amphibian bones from our Red Beds sites, which were formed during the Early Permian Period about 285 million years ago. We have thigh bones chewed on both ends, shins bitten in half, shoulders and hips deeply scarred by scavenging teeth. We’ve found the “chiropractor’s nightmare” — vertebral spines snapped in two by massive bites. Even some jaw bones and muzzles bear scars made by gnawing, gnashing fangs.
We have some fossils that are truly disturbing — bones that wrapped around the brain in the living animal. We can see clear evidence of determined nibbling and biting. Something was trying to gobble down brains — or so it seems.
The back of a Dimetrodon skull. Note the serious nibbling to the left of the brain cavity. Photo by Matt Mossbrucker, Director of the Morrison Museum in Morrison, Colorado
Our brain-bitten victim is a Dimetrodon, the top predator of early Permian times. Dimetrodon was about as heavy as a tiger, but with short legs and scaly toes. So who was the biter? We have some CSI evidence in what we call “fossil ballistics.” When Dimetrodon fed, it shed tooth crowns shark-style. A hard-gnawing D’don would lose a crown or two, but no harm done — new crowns were already growing up through the tooth sockets to replace the old ones. Crowns get fossilized in the mud next to the skeleton that was chewed. The shed crowns are like the bullets found in crime scenes today — unambiguous evidence of who chewed whom.
Our HMNS field crew is super-compulsive about “fossil ballistics.” We crawl around on hands and knees, scouring the red rock, gently extracting every scrap of dental clue. We shovel up piles of mud and then dissolve the sediment over fine-mesh screens to catch the tiniest crowns. We’ve recovered more hard evidence on gnawing than any other expedition to the famous fossil fields north of Seymour.
But enough about us. Let’s get back to our brain-bit victim, Dimetrodon. Shed teeth dug near the skeletons are strong evidence pointing to the perp. The identification of the chewer is clear: It was another Dimetrodon! That is seriously spooky. Even for a veteran dino hunter, the image of brain-crazed Permian reptiles is a bit unnerving.
A scientifically accurate reconstruction of a brain-seeking zombie Dimetrodon.
Don’t worry, no Federal funds were expended in generating this image.
(Dr. Bob drew it while eating a breakfast burrito.)
But there’s a catch. Human zombies are more efficient predators of their own kind. Human brains are huge, with each braincase offering up to three pounds of easily digested food that’s naturally low in cholesterol, to boot. (If you’re not a zombie, I’d suggest going to one of our fine Greek restaurants and sampling Miala tiganita, or fried calf brains, to get a sense.)
By comparison, Dimetrodon brains were tiny. A determined Dimetro-zombie would get only a few ounces of Permian brain-meat from an adult victim. When I cleaned out the inside of a big Dimetrodon braincase, the brain inside was smaller than a cocktail frank.
Gnawing and losing crowns just to get at a D’don brain appears to be a waste of time and teeth. So what was going on? Is there an alternative explanation for the bite marks on the braincase?
What do you think is a more believable hypothesis to replace the notion of Red Bed Paleo Zombies?
Learn more about Dimetrodons and what their extinction can tell us about our own evolution this Tuesday, Oct. 30 at a lecture I’m hosting: “Life After the Dinosaurs: Darwinian Saga of the Mammalia.” Click here for tickets.