Pawpawsaurus is a lot older than its prehistoric cousin, the famously tank-like, club-tailed Ankylosaurus, and it lacks the tail weaponry. But this early armored dinosaur did, however, have a surprisingly acute sense of smell, and that may have helped this plant-eater avoid its would-be predators. The findings are published in PLOS One this week.
The well-preserved skull of Pawpawsaurus campbelli was discovered in the 100-million-year-old upper Albian Paw Paw Formation in Tarrant County, Texas, back in 1992. It was named a few years later. Pawpawsaurus lived along the shores of an inland sea that used to split the North American continent. This herbivorous dinosaur had armored plates across its back and on its eyelid like Ankylosaurus, which arrived some 35 million years later. Over the course of armored dino evolution, they developed club-like tails and a stable gaze that helped them maintain balance while wielding their heavy clubs.
Now, a team led by Ariana Paulina-Carabajal of CONICET-INIBIOMA has imaged the Pawpawsaurus skull using CT scanning, allowing them to digitally reconstruct 3D models of its braincase and inner ear.
Their work revealed an enlarged nasal cavity. "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," Paulina-Carabajal explained in a statement.
Based on the ratio of its olfactory bulb to its cerebral hemisphere, Pawpawsaurus didn’t have as good a sense of smell as Anklyosaurus. These later ankylosaurians also had bony ridges in their nasal cavity to guide airflow. But it was still sharper than that of carnivores and other dinosaurs at the time. "It probably relied on that to look for food, find mates and avoid or flee predators," Paulina-Carabajal added. Its sense of smell was exceeded only by carcharodontosaurids and tyrannosaurids.
Additionally, when the team examined a portion of the dinosaur’s inner ear called the lagena – which perceives sounds – they found that Pawpawsaurus likely had a similar sense of hearing as that of living crocodiles.
Image in the text: Pawpawsaurus illustration by Karen Carr
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