Giant 272-kg dinosaur skull 'Big Sam' unearthed in North American bonebed

A massive dinosaur skull weighing 272 kilograms has been uncovered in a dense North American bonebed. The fossil, named 'Big Sam', belongs to an adult Pachyrhinosaurus, a relative of Triceratops but without horns. Its discovery adds to the site’s reputation as one of the richest dinosaur bonebeds on the continent. The bonebed was first found around 50 years ago. It holds the remains of an entire Pachyrhinosaurus herd, with both juvenile and adult bones scattered across the area. Alongside dinosaur fossils, the site also contains the bones of turtles and lizards, with densities of 100 to 300 bones per square metre.

Sixteen years ago, another large Pachyrhinosaurus skull was unearthed in the same location. That specimen is now displayed at the Philip J. Currie Dinosaur Museum. 'Big Sam' was particularly difficult to extract because it was upside down and entangled in a cluster of around 300 bones. The skull was exceptionally well-preserved and will now be studied at the museum before going on public display.

Pachyrhinosaurus is notable for its lack of horns and the large bony bumps, or 'bosses', on its nose and above its eyes. These features set it apart from its horned cousin, Triceratops. The newly discovered skull will undergo detailed analysis before joining the museum’s exhibits. Its size and condition offer researchers fresh insights into the species. The bonebed continues to provide valuable fossils, reinforcing its importance in palaeontology.