Armored Dino's Best Defense Was a Nose for Trouble

An early armored dinosaur lacked the weaponized tail of a famous cousin, but it made up for it with a good-enough sense of smell.

An early armored dinosaur that lived in what is now Texas lacked the weaponized tail of a famous cousin, but it made up for it with a sense of smell that found food and sniffed out trouble.

The dino, Pawpawsaurus campbelli, lived around 100 million years ago, and researchers have reported their findings on the first-ever CT scans on the animal's skull.

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The famous cousin was Ankylosaurus, the one with the sheet of thick bone running along its back, culminating in a club at the end of its tail - the better to swat away its foes:

Pawpawsaurus lived some 35 million years before that sturdy-backed creature. It was armored similarly – bony plates along its back and even on its eyelids - but, alas, it had no club on the end of its tail.

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All hope was not lost, however. It turns out the animal may have gotten by with a little help from its nose.

The CT scans allowed the researchers to use software to reconstruct the Pawpawsaurus' skull and then study its sense of hearing and smell.

They found that Pawpawsaurus didn't have a sense of smell as sharp as Ankylosaurus, but it was good enough to get by – better, say the researchers, than some other predators of its day.

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"Pawpawsaurus in particular and the group it belonged to – Nodosauridae – had no flocculus, a structure of the brain involved with motor skills, no club tail, and a reduced nasal cavity and portion of the inner ear when compared with the other family of ankylosaurs," said study co-author Paulina-Carabajal in a statement.

"But its sense of smell was very important, as it probably relied on that to look for food, find mates and avoid or flee predators," the scientist from the Biodiversity and Environment Research Institute in Argentina added.

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The researchers noted the key contribution of CT scanning technology in their study.

"CT imaging has allowed us to delve into the intricacies of the brains of extinct animals, especially dinosaurs, to unlock secrets of their ways of life," said study co-author and Southern Methodist University vertebrate paleontologist Louis Jacobs.

"We can observe the complete nasal cavity morphology with the CT scans," added Paulina-Carabajal.

Pawpawsaurus' brain case had never before been studied in such detail and the scans drew a picture of the animal's sensory pluses and minuses.

"The CT scans revealed an enlarged nasal cavity compared to dinosaurs other than ankylosaurians. That may have helped Pawpawsaurus bellow out a lower range of vocalizations, improved its sense of smell, and cooled the inflow of air to regulate the temperature of blood flowing into the brain."

The researchers findings are published in the journal PLOS ONE.

Pawpawsaurus lived 100 million years ago during the Cretaceous Period. It was first identified from a skull found in north Texas.

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.

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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.

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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.

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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."

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"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.

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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.

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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.

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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.