Everyone knows Ankylosaurus. It’s the epitome of the titular group of highly-armored herbivores to which it belonged, and there’s even a case to be made that it’s the best dinosaur. The living tank’s tail club certainly plays into that. It’s difficult to look at that knob of bone and not imagine it smacking into the leg of an attacking tyrannosaur or battering the side of another ankylosaur in a territorial dispute. But how did this famous piece of the dinosaur armament evolve?
North Carolina Museum of Natural Sciences paleontologist Victoria Arbour has quickly become one of the world’s foremost experts on ankylosaurs. In the past she’s helped sort out the number of ankylosaur species and looked at the biomechanical capabilities of those intriguing tail clubs. Now, along with Philip Currie, Arbour has retraced how ankylosaurs went from having flexible tails to stiffened handles supporting great protrusions of bone.
Not all ankylosaurs had tail clubs. The earliest of their kind, as well as the spiky forms called nodosaurids, lacked the famous feature. It was only among a subgroup called ankylosaurids that tail clubs evolved, and, as Arbour and Currie point out, this special appendage had two parts. There was the handle – a series of interlocking vertebrae at the end of the tail – and the knob, which is the actual bony business end.
Up until now, paleontologists have been unsure how the handle and knob evolved. Did the handle come first? The knob? Did they evolve together? A pair of ankylosaurs from Asia solve the puzzle. These two dinosaurs, named Liaoningosaurus paradoxus and Zhongyuansaurus luoyangensis, both had interlocking tail vertebrae that formed early versions of the handle but lacked tail knobs. What’s more, Arbour and Currie note, Liaoningosaurus lived about 122 million years ago and Zhongyuansaurus was shuffling around about 92 million years ago, while the first ankylosaurs with fully-formed tail clubs evolved around 75 million years ago. The handle came first.
The handle-first model makes biomechanical sense. If ankylosaurs evolved a heavy club on a flexible tail, Arbour and Currie write, then it would have been more like a flail than a club, and more likely to injure the ankylosaur wielding it. It was only after the tail became a stiff, bat-like appendage did the terminal club knobs start to grow. Yet, as the paleontologists remind us, ankylosaurs had large osteoderms running along the sides of their tails all the way back to the earliest of their ilk, like Scelidosaurus. Ankylosaurs may have been waving their tails around for defense or display since their earliest days, and we’re just starting to understand the impressive variety of ways they did so.
For more, read Arbour’s post on her new paper at Pseudoplocephalusat Pseudoplocephalus.
Reference:
Arbour, V., Currie, P. 2015. Ankylosaurid dinosaur tail clubs evolved through stepwise acquisition of key features. Journal of Anatomy. doi: 10.1111/joa.12363
Related Topics
Go Further
Animals
- These 'trash fish' are among Earth's most primitive animalsThese 'trash fish' are among Earth's most primitive animals
- These photos are works of art—and the artists are bugsThese photos are works of art—and the artists are bugs
- The epic migration of a 6-foot long, 200-pound catfishThe epic migration of a 6-foot long, 200-pound catfish
- Frans de Waal, biologist who studied animal emotion, dies at 75Frans de Waal, biologist who studied animal emotion, dies at 75
Environment
- Are synthetic diamonds really better for the planet? The answer isn't clear-cut.Are synthetic diamonds really better for the planet? The answer isn't clear-cut.
- This year's cherry blossom peak bloom was a warning signThis year's cherry blossom peak bloom was a warning sign
- The U.S. just announced an asbestos ban. What took so long?The U.S. just announced an asbestos ban. What took so long?
- The most dangerous job? Inside the world of underwater weldersThe most dangerous job? Inside the world of underwater welders
- The harrowing flight that wild whooping cranes make to surviveThe harrowing flight that wild whooping cranes make to survive
History & Culture
- Meet the powerful yokai that inspired the demon king in ‘Demon Slayer’Meet the powerful yokai that inspired the demon king in ‘Demon Slayer’
- A surprising must-wear for European monarchs? Weasels.A surprising must-wear for European monarchs? Weasels.
- Meet the woman who made Polaroid into a cultural iconMeet the woman who made Polaroid into a cultural icon
- Inside the observatory that birthed modern astrophysicsInside the observatory that birthed modern astrophysics
- See how Muslims celebrate Eid al-Fitr around the worldSee how Muslims celebrate Eid al-Fitr around the world
Science
- NASA smashed an asteroid with a rocket. The debris could hit Mars.NASA smashed an asteroid with a rocket. The debris could hit Mars.
- Humans really can have superpowers—scientists are studying themHumans really can have superpowers—scientists are studying them
- Why engineers are concerned about aging infrastructureWhy engineers are concerned about aging infrastructure
- The benefits of eating the peels on your fruits and veggiesThe benefits of eating the peels on your fruits and veggies
- The island of Santorini is hiding an explosive secretThe island of Santorini is hiding an explosive secret
Travel
- Play and stay in the mountains of eastern Nevada
- Paid Content
Play and stay in the mountains of eastern Nevada - This couple quit the city to grow wasabi in Japan's mountainsThis couple quit the city to grow wasabi in Japan's mountains
- This Swedish overnight train takes you straight to the northern lightsThis Swedish overnight train takes you straight to the northern lights