Ankylosaurid dinosaurs used tail for more than smashing T rex shins

[rogue06]

Seriously, is anyone really surprised that Ankylosaurs used their deadly tail clubs not just to defend themselves but also in competing for mates or over territory? I mean extant animals with specialized animal weapons like a deer's antlers and the horns of antelopes evolved to be used primarily for fighting members of the same species during such battles.

Source: The Ankylosaur’s Tail-Club Wasn’t Only Swinging at T. Rex

A dinosaur named for a demon dog in “Ghostbusters” had a sledgehammer attached to its rear. A new study found it could both shatter shins and woo potential mates.

To ward off supersized predators, many herbivorous dinosaurs were biologically armed to the teeth. Some had skulls studded with horns, while others had tails bristling with spikes. But few matched the arsenal of ankylosaurs, a group of herbivores that peaked in diversity during the Cretaceous period. Most of the ankylosaur’s body was encased in bony plates that jutted out into jagged points, and some lugged around a sledgehammer-like tail club capable of delivering a bone-cracking blow.

Because of their seemingly indestructible nature, paleoartists and researchers alike have spent decades hypothetically pitting these plant-powered tanks against tyrannosaurs and other apex carnivores. However, predators may not have been the only creatures absorbing their batterings.

In a study published Wednesday in the Biology Letters, researchers analyzed the anatomy of one of the world’s most complete ankylosaur skeletons. They discovered several broken and healed armor plates concentrated around the creature’s hips that lacked any clear signs of disease or predation. Instead, the armor appeared to have been splintered by another ankylosaur’s club.

“The injuries are right where you’d expect two battling ankylosaurs would break things,” said Victoria Arbour, a paleontologist at the Royal BC Museum in British Columbia and an author of the study.

The exquisitely preserved ankylosaur skeleton, which sports a full suit of armor plates called osteoderms, was accidentally unearthed in 2014 by commercial fossil hunters excavating a nearby tyrannosaur in Montana’s Judith River Formation. When the Royal Ontario Museum in Toronto acquired it, the bulk of the creature’s skeleton was still entombed in a 35,000-pound slab of sandstone, leaving just its skull and tail free.

Based on the ankylosaur’s skull and its club at the end of a thorny tail, it was clear the animal was a unique species. The dinosaur’s horn-encrusted head reminded Dr. Arbour, then a postdoctoral researcher at the Ontario museum, of the gnarly mug of Zuul, the terror dog from the film “Ghostbusters.” In 2017, she and her colleague christened the new species Zuul crurivastator, or “Zuul, the destroyer of shins.”

The rest of Zuul’s body remained trapped in the stone for more than a year as fossil preparators painstakingly chipped away at the rock. They eventually uncovered fossilized skin dotted with osteoderms. As they worked their way toward Zuul’s backside, they discovered that some spikes along the animal’s hips were missing their tips and that the bony sheaths encasing these osteoderms had broken and healed into blunt points.

bb052a80-a262-4ce2-9b02-923d29cf8ed0.jpg
Zuul crurivastator’s injuries, with injured spikes in red

Because the damaged plates were clustered around Zuul’s hips, Dr. Arbour and her colleagues began to question whether they were defensive scars from a failed attack. Bipedal hunters like Gorgosaurus, a lanky cousin of the Tyrannosaurus rex, would have attacked Zuul from above instead of smashing into its flank. And few spots were as unappetizing as Zuul’s spike-covered haunches, which were within striking distance of its club.

Instead, Dr. Arbour and her team concluded that the placement of the battered plates, along with an absence of bite marks, were consistent with a crack from another Zuul’s tail club. Because the damaged osteoderms were at different stages of healing, it was likely that this ankylosaur took its fair share of thumpings 76 million years ago.

The authors proposed that the injuries occurred during combat between Zuul and its brawny brethren. Like today’s head-butting bighorn sheep or neck-swinging giraffes, competing ankylosaurs may have established dominance by landing armor-shattering body blows with their tail clubs.

The new evidence is essential for studying the behavior of these classic, yet enigmatic, dinosaurs. “Ankylosaurs left no living descendants, so we have no living analogues to learn what ancient ankylosaurs did,” said Jordan Mallon, a paleontologist at the Canadian Museum of Nature in Ottawa, who was not involved in the study. “This is the first example where we’ve been able to marshal some evidence to support that these things were actually using their tail clubs to smash into one another in a ritualistic way.”

And this practice might have driven the evolution of gnarlier tail clubs, much like how modern elk employ their elaborate antlers not only to tussle with one another but also to impress prospective mates. “The reason that they have a tail club is probably not driven by predation, but more for intraspecific combat,” Dr. Arbour said. “It’s more sexual selection than natural selection.”

While these clubs may have evolved to help ankylosaurs bash each other, they were still capable of delivering a debilitating blow below a tyrannosaur’s knee. “The destroyer of shins is still quite apt,” Dr. Arbour said.



Source

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The entire paper, Palaeopathological evidence for intraspecific combat in ankylosaurid dinosaurs can be found by clicking the hyperlink while I made the abstract available below

Abstract

Ankylosaurid dinosaurs were heavily armoured herbivores with tails modified into club-like weapons. These tail clubs have widely been considered defensive adaptations wielded against predatory theropod dinosaurs. Here we argue instead that ankylosaurid tail clubs were sexually selected structures used primarily for intraspecific combat. We found pathological osteoderms (armour plates) in the holotype specimen of Zuul crurivastator, which are localized to the flanks in the hip region rather than distributed randomly across the body, consistent with injuries inflicted by lateral tail-swinging and ritualized combat. We failed to find convincing evidence for predation as a key selective pressure in the evolution of the tail club. High variation in tail club size through time, and delayed ontogenetic growth of the tail club further support the sexual selection hypothesis. There is little doubt that the tail club could have been used in defence when needed, but our results suggest that sexual selection drove the evolution of this impressive weapon. This changes the prevailing view of ankylosaurs, suggesting they were behaviorally complex animals that likely engaged in ritualized combat for social dominance as in other ornithischian dinosaurs and mammals.

A couple of pix of injured and healed spikes

ankylosaurs-battled-ea-2.jpg

ankylosaur.jpg

Zuul is so complete I had to include a pix of it's head and tail

Zuul_head.jpg255px-Zuul_tail.jpg

[shunyadragon]

I would like to see fossil evidence of shin bone injuries in carnivorous dinosaurs.

[rogue06]

I would like to see fossil evidence of shin bone injuries in carnivorous dinosaurs.

Possibly the most famous, and largest T rex fossil is "Sue" in the Chicago Field Museum, has a healed left fibula that has been interpreted as being an injury from an ankylosaur tail club (although a subsequent infection makes a definitive identification dicey at best).

cd46e185-7983-498e-bd68-2452d5fc12b0.jpg

As an aside, it also had a damaged humerus that researchers think may be the result of a Triceratops horn injury that tore the triceps off the arm.

Some have, for awhile, had their doubts concerning ankylosaurs battling T-rex and the like Sadly, “Ankylosaur Fight Club” Is Probably Wishful Thinking, something I meant to include in the OP, but left out.

[shunyadragon]

Possibly the most famous, and largest T rex fossil is "Sue" in the Chicago Field Museum, has a healed left fibula that has been interpreted as being an injury from an ankylosaur tail club (although a subsequent infection makes a definitive identification dicey at best).

cd46e185-7983-498e-bd68-2452d5fc12b0.jpg

As an aside, it also had a damaged humerus that researchers think may be the result of a Triceratops horn injury that tore the triceps off the arm.

Some have, for awhile, had their doubts concerning ankylosaurs battling T-rex and the like Sadly, “Ankylosaur Fight Club” Is Probably Wishful Thinking, something I meant to include in the OP, but left out.

Thank you for the reference!!