Giant 272-kg dinosaur skull unearthed in North America's fossil treasure trove

A massive dinosaur skull has been unearthed in one of North America’s densest fossil sites. Weighing 272 kilograms, the specimen belongs to an adult Pachyrhinosaurus, a relative of Triceratops. The discovery adds to the significance of a bonebed first found roughly 50 years ago. The skull, nicknamed 'Big Sam', was recovered from a site packed with the remains of an entire Pachyrhinosaurus herd. Both juveniles and adults are present, with the area also containing fossils of turtles and lizards. Estimates suggest 100 to 300 bones can be found in a single square metre.

Extracting the skull proved difficult. It was tangled among 300 other bones and lay upside down. Despite this, the fossil remained in excellent condition, offering valuable material for research. Sixteen years earlier, another large Pachyrhinosaurus skull had been discovered in the same bonebed.

Pachyrhinosaurus stands out due to its lack of horns and the large bony bosses on its nose and above its eyes. After careful removal, 'Big Sam' was taken to the Philip J. Currie Dinosaur Museum for study and future public exhibition. The skull is now in the hands of researchers at the museum. Its well-preserved state provides new opportunities for understanding this unique dinosaur. The bonebed continues to yield important fossils, reinforcing its reputation as a major palaeontological site.