Imagine that you are a tyrannosaur rumbling around 76 million years ago in what is now Montana. As fearsome as you are, you are in mortal danger from a low-slung herbivore half your size and weight, even though you may have one for dinner now and then. The rub is that Zuul crurivastator had a tail to kill for, or rather, to kill with. Zuul’s tail was nine feet long with a club at its terminus the size of a 3-inch-thick cafeteria tray. The knob enclosed two large, heavy osteoderms, which are bony plates in the skin seen today in armadillos, crocodiles, and Gila monsters, but with much smaller dimensions. Many dinosaurs possessed osteoderm armor, but tail clubs were unusual. If Zuul flailed its tail and hit your shin bone (remember, you are a Gorgosaurus or other tyrannosaur of the time*), it could render you much less tyrannical, perhaps fatally cripple you. And the fossil record does include various tyrannosaur skeletons with such injuries. Not coincidentally, “crurivastator” means “destroyer of shins.”
Well, the described scenario has been circulating for years and might be of interest for a Jurassic Park sequel, but evidence now suggests that it is wrong. A recent report opines that Zuul wagged its tail violently not to ward off predators but rather to fight over mates, similar to the way modern-day bison and mountain goats butt heads–not to the death, but to establish preeminence. So, you may ask, what is the evidence for a Zuul mating ritual? Intriguing to say the least.
In 2014, paleontologists were using a Bobcat frontend loader to rapidly remove a 39-foot “overburden” of stone sediment to expose the geologic layer that they were interested in exploring. The machine unexpectedly scraped across the surface of a Zuul’s tail club. Because the animal’s fossilized skeleton had not been exposed to erosive forces since it was originally covered with silt 76 million years ago, it was in pristine condition—99% complete including tail and trunk osteoderms in their original positions along with some skin and non-bony keratin scales and sheaths of the creature’s many spikes. (Keratin is the protein that constitutes nails and hair and covers bird beaks and cow horns.) Since keratin and skin are not normally preserved in the fossil record, this Zuul was deemed a “dinosaur mummy.” The Royal Ontario Museum purchased the two 15-ton blocks of stone that encased Zuul and then spent years with magnifying lenses, micro jackhammers, and paint brushes tediously extricating Zuul from its stone tomb, as highlighted in this three-minute descriptive video.
Osteoderms on the beast’s flanks were of particular interest because they showed signs of fracture, whereas signs of similar injuries to osteoderms on the rest of the body were uncommon. The injuries were not inflicted by piercing teeth or slashing claws rendered by a tyrannosaur, rather they resulted from blunt, heavy blows. Furthermore, the damaged osteoderms showed differing degrees of healing, implying that the insults were sublethal and recurrent, perhaps even ritual. Paleontologists have yet to determine the sex of any dinosaur, so you are free to speculate whether these osteoderm-damaging encounters involved competing Zuul females or males.
OK, it’s time to stop envisioning yourself as a tyrannosaur. Rather imagine the myriad yet-to-be-discovered fossils, which will reveal prehistoric animals’ anatomy and also maybe their behavior. Thank you, bone.
*The best-known species of tyrannosaurus, Tyrannosaurus rex, did not live at the same time as Zuul, but rather 8-10 million years later.
Launching June 13, 2023
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An entertaining illustrated deep dive into muscle, from the discovery of human anatomy to the latest science of strength training.
Muscle tissue powers every heartbeat, blink, jog, jump, and goosebump. It is the force behind the most critical bodily functions, including digestion and childbirth, as well as extreme feats of athleticism. We can mold our muscles with exercise and observe the results.
In this lively, lucid book, orthopedic surgeon Roy A. Meals takes us on a wide-ranging journey through anatomy, biology, history, and health to unlock the mysteries of our muscles. He breaks down the three different types of muscle―smooth, skeletal, and cardiac―and explores major advancements in medicine and fitness, including cutting-edge gene-editing research and the science behind popular muscle conditioning strategies. Along the way, he offers insight into the changing aesthetic and cultural conception of muscle, from Michelangelo’s David to present-day bodybuilders, and shares fascinating examples of strange muscular maladies and their treatment. Brimming with fun facts and infectious enthusiasm, Muscle sheds light on the astonishing, essential tissue that moves us through life.