Newly discovered dinosaur had elaborate head ornaments

Credit: Jack Horner.

Dinosaur fossils have always fascinated scientists with their diverse and impressive features.

From the horns of Triceratops to the crests of hadrosaurs, these ancient creatures had a wide array of bony ornaments on their skulls.

However, recent findings suggest that dinosaurs had even more intricate head decorations that were made of keratin, the same material found in human nails.

These structures were likely used as visual signals or communication tools among dinosaurs.

A new species of dome-headed dinosaur, dating back approximately 68 million years, provides further evidence of these elaborate head ornaments.

Pachycephalosaurs, which lived during the Cretaceous period, were small-to-medium-sized plant-eating dinosaurs that walked on two legs and had a stiff tail for balance.

The newly described species is based on a partial skull, including its unique bowling-ball-shaped dome, which was discovered in Montana in 2011.

Through detailed scans and analyses of the fossilized dome, paleontologists Mark Goodwin from the University of California, Berkeley, and John “Jack” Horner from Chapman University in California, concluded that the skull likely had bristles made of keratin, similar to a brush cut hairstyle.

Goodwin explains that this type of bristly, flat-topped covering “makes biological sense” as it could have served multiple functions such as display or social interactions involving visual communication.

The skull of this particular dinosaur also showed a healed gouge at the top, indicating that the creature had suffered a significant injury but survived long enough for new bone tissue to grow.

While some may jump to the conclusion that this injury resulted from head-butting, Goodwin and Horner caution against it.

They believe the injury could have been caused by various factors like a falling rock or an encounter with another dinosaur. They argue that the structure of pachycephalosaur skulls, lacking the necessary features for head-butting, suggests that any head ornaments were primarily for display purposes.

Ornamentation is common among reptiles and bird descendants of dinosaurs, serving as a means to attract mates and intimidate rivals. However, Horner and Goodwin argue that pachycephalosaurs’ skulls lack the cushioning necessary for head-butting without causing severe brain damage.

They suggest that rather than turning dinosaurs into mammals, it is important to understand them as bird-like reptiles and explore their behaviors within that framework.

The team of paleontologists, including David Evans from the University of Toronto and the Royal Ontario Museum, named the new species Platytholus clemensi in honor of the late paleontologist William Clemens from UC Berkeley, who collected numerous fossils in the same formation where the new species was found.

Pachycephalosaur skulls are relatively common in dinosaur beds, with their robust domes preserving well over time. Goodwin compares them to bowling balls in the fossil record, as they can withstand weathering and erosion.

Horner and Goodwin have a particular interest in pachycephalosaurs and have conducted extensive research on their evolution and development from juvenile to adult. Their findings indicate that the bone structure of pachycephalosaur skulls does not support head-to-head collisions or head-butting behaviors.

The recent discovery of Platytholus clemensi’s partial skull revealed intriguing characteristics that differentiate it from other pachycephalosaurs found in the same area. Blood vessels within the skull indicate the presence of a tissue covering the dome.

If this covering were made of keratin, as seen in birds or ceratopsians like Triceratops, the vessels would have spread out and left indentations or grooves.

However, the vessels ran vertically, suggesting the existence of an unknown vertical structure on top of the head.

According to Horner, pachycephalosaurs likely had an elaborate display on top of their heads that remains a mystery. As the domed heads of pachycephalosaurs changed shape and became more prominent with age, it suggests they were used for sexual display and courting.

Goodwin suggests that dinosaurs may have distinguished gender through colors, much like modern birds, using bright colors on the face and head for visual communication.

Further research will involve studying other pachycephalosaur skulls through CT scans and histology to investigate whether these dome-headed dinosaurs exhibited additional elaborate headgear.

The combination of cranial histology and CT scanning has provided valuable data and supports the hypothesis that the dome was covered with a keratinous structure that had a vertical component, unlike other dinosaurs with hard skin or closely covering keratin.

The discovery of Platytholus clemensi adds to our understanding of the remarkable diversity and intriguing features of dinosaurs.

Paleontologists continue to uncover new clues about these ancient creatures and their fascinating adaptations, shedding light on the extraordinary world that existed millions of years ago.

Source: UC Berkeley.