Many dinosaurs were built for combat, with fighters consisting of plant-loving herbivores, as well as meat-craving carnivores, suggests a new study.
The paper, published in the Journal of Zoology, strengthens earlier theories that body spikes, horns and other impressive dinosaur features could do serious damage to others. Combat, according to author Andrew Farke, likely took many forms.
"Examples include horn locking, biting, use of tail clubs or spikes and ramming," explained Farke, who is a paleontologist at the Raymond M. Alf Museum of Paleontology. "Purposes include, but are not limited to, defense against predators, contests for social dominance, mating competitions or any other number of behaviors."
Heterodontosaurus, for example, might have used its sharp teeth as a weapon. Farke pointed out that even juveniles of this species are known to have had prominent teeth. Perhaps they sank them into flesh, as well as plants.
"Thumbs up" took on new meaning with Iguanodon, which likely rammed its thumbs into other animals. As Farke noted, "The use of the iguanodont 'thumb spike' as a combat weapon seems quite likely on morphological grounds."
This basically means that if it looked dangerous, then it probably was. The thumb spikes likely also had some role in plant food processing, he added.
This is an artist's interpretation showing 190-million-year-old nests, eggs, hatchlings and adults of the prosauropod dinosaur Massospondylus in Golden Gate Highlands National Park, South Africa.
Looking at the adults' sharp teeth and claws, it is hard to believe that these large dinosaurs did not use them to safeguard their eggs, much less themselves.
Even the dinosaur dwarf Pegomastax from South Africa evolved a ferocious-looking beak and teeth. Its jaws were only an inch long, but Pegomastax, aka "Thick Jaw," probably scared away many would-be attackers.
This fleshed-out artist's rendering of the Mexican horned dinosaur Coahuilaceratops reveals what a sturdy beast it was.
Paleontologists like Farke perform clever detective work, piecing together known evidence to discover how this and other dinosaurs likely behaved. For dinosaurs with apparent combat structures, Farke presents three lines of evidence that the appendages functioned in combat. The first is that many of these features, such as horns and beaks, are part of modern animals that use them to fight. The second is that biomechanical analysis and simulation often support their usage as weapons.
The third and final line of evidence is perhaps the most convincing: paleopathology. This refers to fossils showing damage likely resulting from battles with other animals. Remains for a Triceratops, for example, were found with a broken and healed horn that suggests a fight had happened sometime beforehand.
Stegosaurus appears to have been built for battle. Farke said that the spikes of stegosaurs are "commonly accepted as combat weapons." He added that other studies show that the tail spikes, in particular, "could inflict considerable force when swung with the tail, potentially even piercing bone."
"Clubbing contests" could have occurred between two Ankylosaurus, according to Farke. Imagine one swinging into another's head, a move that would have been an effective predator deterrent.
Another theory holds that the clubs evolved to look like faux heads, literally faking out hungry attackers that probably got a rude surprise if they tried to take a bite.
A separate study conducted by Shoji Hayashi of Hokkaido University and colleagues concluded that the spikes of Gastonia and related dinosaurs were "probably used as defensive and/or offensive weapons."
Hayashi and other researchers also suspect that spikes, plates and clubs might have functioned for display and thermoregulation purposes, in addition to looking just plain scary.
Herbivores often had one big advantage over carnivores: size. Camarasaurus, for example, grew to about 75 feet long and weighed approximately 51.8 tons.
Even if it lacked sharp spikes and horns, its sheer girth could have stomped some pests and smaller attackers to smithereens. Such a stomp could have been made more ferocious by its large, sharpened claws, which were located on the inner toe of each front limb.
There is no question that it was a dinosaur-eat-dinosaur world during the Mesozoic Era, when these animals dominated the planet. Like Batman villains going against each other, the dinosaurs used their unique weapons against other specialized forms of combat and defense. "Thumb Spike" (Iguanodon) might have waged battles with "Long Claw" (Baryonyx, a likely predator).
Likewise, a fight between Acrocanthosaurus and a large sauropod, seen here, pitted teeth and claws against the size and brute force strength of the sauropod. Each had a good chance of winning but, by the looks of this particular recreation, the gaping wound inflicted by meat-loving Acrocanthosaurus must have later led to a super-sized dinner.