From Tails To Horns and Shells. Here’s How Animal Weaponry Has Evolved.

Jan 24, 2018

Two Ankylosaurus exchange blows using their tail clubs.
Credit Jack Mayer Wood / Courtesy of N.C. State University

It takes a lot to evolve a tail worthy of combat. Researchers at N.C. State University have found that only huge, slow vegetarians with body armor developed weaponized tails.

"These are bits of the skeleton that have actually evolved to look like weapons,” Paleontologist Lindsay Zanno said. “So, this could be anything from clubs on the end of the tail, or spikes. You may recognize some of these these from some many famous dinosaurs like Stegosaurus or Ankylosaurus, which had bizarre, bony spikes at the end of their tails.”

It's really only if you're large, slow, and obvious that arming your tail makes evolutionary sense. -Lindsay Zanno

Zanno said animals had tail weapons to either defend themselves against predators or engage in combat with other members of the species over resources or territory or females.

“Animals that lived in the water or the trees need flexible skeletons. Animals that hunt may opt, instead, to rely on their speed or their advanced sensory capabilities. And smaller species can hide from predators," she said. "Thus, it's really only if you're large, slow, and obvious that arming your tail makes evolutionary sense.”

Zanno and her colleague Victoria Arbour found that there aren't any living creatures with tails like these. Evolution favored those which developed horns or shells instead. Most living animals with body armor today wear it on their heads, like goats and deer, she said.

Zanno's research was published in the Proceedings of the Royal Society B. It was funded by the Jurassic Foundation.