In 1923, a partial skull was collected from the
Oldman Formation of
Alberta by E.J. Whitaker, as the only fossil found at a locality below
Bow Island ferry along the
South Saskatchewan River and below the top of the Oldman Formation. It was acquired by the
Geological Survey of Canada where it gained the
accession number GSC No. 8818. GSC 8818 was first described by American palaeontologists
Barnum Brown and
Erich Maren Schlaikjer in 1943 as a specimen of the
pachycephalosaur Troodon validus, which had earlier been given the name
Stegoceras validus but was not believed to be a distinct
genus by Brown and Schlaijker. This identification was disputed by American palaeontologist
Charles Mortram Sternberg in
1945, who showed that
Troodon, for a time believed to be a pachycephalosaur, was instead a carnivorous
theropod, who as a result revived
Stegoceras as well as named the new family
Pachycephalosauridae to house pachycephalosaurs. Sternberg also recognized that GSC 8818 was a separate species from
S. validus, and created the new species
Stegoceras lambei with GSC 8818 as the
holotype. The
species name was in honour of the deceased Canadian palaeontologist
Lawrence M. Lambe. The separation of
S. lambei from
S. validum was not supported by the 1987 study of American palaeontologists
Hans-Dieter Sues and British palaeontologist
Peter Galton, who considered the two species as
synonyms. However, American paleontologists Thomas E. Williamson and
Thomas D. Carr chose to retain
S. lambei as separate in 2002, finding it as a close relative of
S. validum and
Stegoceras sternbergi and more distantly related to
Stegoceras breve. These species and the general taxonomy of
Stegoceras was reviewed in 2003 by American palaeontologist
Robert M. Sullivan, who found that
S. lambei was closer to
Pachycephalosaurus than
Stegoceras and chose to give it the new
genus name Colepiocephale. The name is a combination of the
Latin word
colepium, "knuckle", in reference to the curled knuckle-like appearance of the dome, and the
Ancient Greek κεφαλή (
cephale) meaning "head". The accession number for the holotype had also changed by this time to CMN 8818, as it was now held in the
Canadian Museum of Nature. Along with the holotype, 13 other specimens were referred to
Colepiocephale lambei, held variously in the CMN,
Royal Ontario Museum,
Royal Tyrrell Museum of Palaeontology, and the
University of Alberta Laboratory of Vertebrate Palaeontology, and all these specimens come from the
Foremost Formation, part of the historical Oldman Formation. Being from the Foremost,
Colepiocephale would be one of the oldest pachycephalosaurs from North America, from the early
Campanian. A redescription and revision of
Colepiocephale was published by Canadian palaeontologists Ryan K. Schott and
David C. Evans, and Williamson, Carr and Mark B. Goodwin in 2009, including identifying the first specimen of the taxon from the
Judith River Formation of
Montana. The distinctiveness of
Colepiocephale was supported, as well as its status as an older genus, with the Judith River specimen from sediments in
Kennedy Coulee that are approximately 78
million years old, while the specimens of the Foremost are between 79.79 and 80.45 million years old. 31 specimens from the Foremost are identifiable as pachycephalosaurs, and all of them, where complete enough, show the features diagnostic to
Colepiocephale suggesting it was the only pachycephalosaur within its time and space interval. This gives the possibility that other age-equivalent specimens from Judith River could be part of the genus, though their identification is uncertain. ==References==