The completeness of the skull has allowed paleontologists to delve into the animal’s head to reveal the creature’s innermost secrets. In 2016 a team comprising of Ariana Paulina-Carabajal, Yuong-Nam Lee and Louis L. Jacobs went deep inside the skull by means of highly advanced X-ray CT scans at the University of Texas in Austin. The results of the study were published in the journal PLOS, along with computer models of the animal’s well-preserved skull. These scans were the first ever done on the creature, according to Jacobs, co-author of the paper and a professor from the Southern Methodist University.
The paper compared Pawpawsaurus with other armored dinosaurs like Kunbarrasaurus, Euoplocephalus, Panoplosaurus and a few others. Cranial endocasts showed that Pawpawsaurus’ brain took up about 30% of the skull, similar to those of Kunbarrasaurus and Panoplosaurus, both nodosaurs.
Euoplocephalus on the other hand is an ankylosaurid, a much more evolutionarily derived animal with a broader mouth and a bony club at the end of its tail for warding off predators. The cranial endocasts, or 3D scans of the brain showed that there were numerous intricacies to be developed in order to evolve and operate such a club.
Pawpawsaurus’ cranial scans show that it seems to have lacked a flocculus, the part of the brain concerned with fine motor skills used to operate a weapon like a bony tail club. This structure is also seen in birds, and is used to control fine movements in the wings to shift flight patterns. Yet the flocculus can also be used to stabilize the animal’s gaze. The advanced ankylosaurids certainly had this sort of gaze stabilization and so did a number of other dinosaurs like the theropods, a few sauropods and some horned and duckbill dinosaurs. In ankylosaurids, the flocculus was used to control fine head movements as well as the kind of movements needed to swing the clubbed tail around at either an attacking predator or a rival of the same species.
The study shows that the other nodosaurids also lacked this part of the brain. Jacobs revealed through this study that the club-bearing ankylosaurids had much more intricately ornate nasal structures than the nodosaurids. Ankylosaurids like Euoplocephalus are indeed known for their large noses and incredible sense of smell, while the nodosaurids like Pawpawsaurus did not. Despite this, Paulina-Carabajal of San Carlos de Bariloche, Argentina adds that smell was still important to Pawpawsaurus in finding food and mates. Its sense of smell was also much sharper than that of primitive meat-eating dinosaurs despite not being as sharp as those of more derived ankylosaurids.
Original study in PLOS ONE