Description and Classification

Platytholus was a bipedal, herbivorous dinosaur, meaning it walked on two legs and ate plants. Like other pachycephalosaurs, its most distinctive feature was its thickened skull roof, forming a dome. In Platytholus, this dome was relatively broad and somewhat flatter compared to some of its highly domed relatives like Prenocephale or Pachycephalosaurus. The skull also featured various bumps and knobs, known as ornamentation, around the edges of the dome. While only the skull is well-known, scientists infer that Platytholus likely had a body plan typical of other pachycephalosaurs: a sturdy build, strong hind legs for running, shorter arms, and a stiff tail for balance.

Platytholus belongs to the family Pachycephalosauridae, a group of ornithischian dinosaurs known for their thickened skulls. It is classified within the larger group Marginocephalia, which also includes the horned dinosaurs (ceratopsians). Its discovery adds to the growing list of pachycephalosaur species known from Asia, suggesting this region was a hotspot for their evolution and diversity during the Late Cretaceous. It shared its environment with other pachycephalosaurs like Homalocephale and Prenocephale, indicating that different species may have specialized in slightly different food sources or habitats to coexist.

Distinguishing Features

Platytholus can be distinguished from other pachycephalosaur dinosaurs by several features of its skull:

• A frontoparietal dome (the main thickened part of the skull) that is notably broad and relatively flat on top.
• A specific pattern of ornamentation, including small bumps and nodes, particularly on the squamosal bones at the back corners of the skull.
• The way the dome is constructed, with a particular shape and arrangement of the bones that form it, differentiating it from close relatives like Prenocephale.

Paleoenvironment and Diet

Platytholus lived in the environment preserved in the Nemegt Formation of Mongolia. During the Late Cretaceous, this area was a well-watered landscape with large river systems, floodplains, and patches of forest. This lush environment supported a diverse range of dinosaurs. Besides Platytholus and other pachycephalosaurs like Prenocephale and Homalocephale, the Nemegt Formation was home to giant predators like Tarbosaurus, large duck-billed dinosaurs like Saurolophus, long-necked sauropods such as Nemegtosaurus, the unusual sickle-clawed Therizinosaurus, and the giant ornithomimosaur Deinocheirus.

As a herbivore, Platytholus likely fed on low-growing vegetation, such as ferns, cycads, and flowering plants. Its small, leaf-shaped teeth at the front of its mouth would have been suitable for nipping off plant material, while teeth further back in the jaw helped to shred it. The exact function of pachycephalosaur domes is still debated by scientists, but they may have been used for display to attract mates or to recognize members of their own species, rather than for aggressive head-butting, especially in forms with flatter domes like Platytholus.

Significance and Ongoing Research

The discovery of Platytholus is significant because it adds to our understanding of the diversity and evolution of pachycephalosaur dinosaurs, especially in Asia, which appears to have been a major center for their radiation. Its relatively flatter dome contributes to the known range of skull shapes within this group, providing more clues about how these structures evolved and what they might have been used for. Comparing Platytholus with other pachycephalosaurs from the same region and time period, such as Prenocephale and Homalocephale, helps scientists study how different species might have coexisted, possibly by specializing in different food sources or behaviors.

Ongoing research on Platytholus and other pachycephalosaurs involves looking for more complete fossil specimens. Finding more parts of the skeleton would help confirm its body size and proportions and provide a clearer picture of its overall anatomy. Further studies of its skull structure using modern imaging techniques can help refine its relationships to other pachycephalosaurs and provide more evidence about the function of its distinctive dome. Scientists continue to explore the complex evolutionary story of these unique “bone-headed” dinosaurs.