Pentaceratops lived around 76–73 million years ago, its remains having been mostly found in the Kirtland Formation[1] in the San Juan Basin in New Mexico.

One exceptionally large specimen later became its own genus, Titanoceratops, due to its more derived morphology, similarities to Triceratops, and lack of unique characteristics shared with Pentaceratops.

In 1922 Sternberg decided to work independently and began a dig north of Tsaya Trading Post, in the Fossil Forest of San Juan County.

[5] The name had been suggested to Osborn by William Diller Matthew; the specific epithet served as a consolation to the almost bankrupt Sternberg whose 1923 fossils were initially not acquired by the museum that had to use its 1923/1924 budget to process the finds of the great Asian expeditions by Roy Chapman Andrews.

In their opinion, it may be identical to Navajoceratops or Terminocavus, but the state of preservation of the remains makes it impossible to precisely determine the systematics of its owner.

Apart from the San Juan Basin finds, a juvenile specimen of Pentaceratops, SDMNH 43470, was found in the Williams Fork Formation of Colorado in 2006.

[10][11] However, in 2011, the skeleton was renamed as a separate genus, Titanoceratops, due to its more derived morphology, similarities to Triceratops, and lack of unique characteristics shared with Pentaceratops.

[2] In 2014 Nicholas Longrich named a new species: Pentaceratops aquilonius, "the northern one", based on fragmentary fossils discovered during the 1930s near Manyberries in Alberta, Canada.

These are largest at the rear corners of the frill, and are separated by a large U-shaped notch at the midline, a feature not recognized until 1981 when specimen UKVP 16100 was described.

The rear dorsal vertebrae bear long spines from which ligaments possibly ran to the front, to balance the high frill.

Their clade was perhaps more derived than the earlier genus Chasmosaurus but more basal than Anchiceratops, the latter representing a line of which Triceratops was a member, which lived a few million years later, right at the end of the Cretaceous period, when all ceratopsians died out.

The cladogram of the phylogeny of Pentaceratops according to a study by Scott Sampson et al. in 2010 found that the genus was most closely related to Utahceratops, from a similar age and region.

CMN 8301 Anchiceratops Almond Formation chasmosaur Bravoceratops Coahuilaceratops Arrhinoceratops Titanoceratops Torosaurus T. utahensis T. horridus T. prorsus Longrich stated that the holotype and referred specimen of P. aquilonius fall within the diagnosis of Pentaceratops, and were recovered very close to the type species in the phylogeny.

It would have used its sharp ceratopsian beak to bite off the branches which were then shredded - leaves, needles, and all - by the tooth batteries, providing a self-sharpening continuous cutting edge in both upper and lower jaws.

Pentaceratops lived around 76–73 million years ago, its remains having been mostly found in the Kirtland Formation[1] in the San Juan Basin in New Mexico.