Cryptarcus russelli: New “Hidden Arch” Ceratopsid Reclassified from Chasmosaurus in Alberta, Canada

Paleontologists have erected a new genus of horned dinosaur, Cryptarcus russelli, after a 2026 re-examination revealed that the long-standing Chasmosaurus russelli holotype belongs to a distinct lineage. This middle Campanian chasmosaurine (~75 million years ago) from Alberta’s Dinosaur Park Formation adds fresh complexity to the evolutionary story of North American ceratopsids.

The nearly complete skull (CMNFV 8800), discovered in 1936 by Loris Shano Russell near Onefour, Alberta, was originally named Chasmosaurus russelli by Charles M. Sternberg in 1940. For decades it was treated as one of two valid Chasmosaurus species. However, meticulous re-preparation—removing decades-old plaster reconstructions and artificial sculpting—exposed unique features that no longer fit comfortably within Chasmosaurus.

Published in the Canadian Journal of Earth Sciences by Robert B. Holmes and colleagues, the study highlights a deep median embayment on the parietal frill forming an extreme “M-shaped” outline, dome-shaped and keeled epiparietals rooted unusually on the front surface, and a distinctive spatulate premaxillary process. The skull measures about 94 cm long with a rectangular frill profile more reminiscent of southern taxa such as Utahceratops and Pentaceratops.

The genus name Cryptarcus (“hidden arch”) cleverly references both its long-concealed idenтιтy inside Chasmosaurus and the striking arched frill morphology. While its exact relationships remain unresolved, the specimen may represent a separate northern lineage or convergent evolution with southern chasmosaurines.

This taxonomic revision underscores how modern preparation and phylogenetic analysis continue to refine our understanding of dinosaur diversity. As other former C. russelli material is reᴀssessed, Cryptarcus stands as a striking reminder that even iconic fossils can still reveal surprising new chapters in the Late Cretaceous.