Open Paleo

Pachyrhinosaurus

Sternberg, 1950 pak-i-RIEN-o-SAWR-us

From Ancient Greek 'pachys' meaning 'thick', 'rhino' meaning 'nose', and 'sauros' meaning 'lizard'; translates as 'thick-nosed lizard', named for the distinctive bony mass on its snout.

83.6–66.0 million years ago Campanian–Maastrichtian, Late Cretaceous
Late Cretaceous stages

Pachyrhinosaurus is a genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species have been found in Alberta and Alaska.

Diagnosis

  1. Skull large, massive, rectangular, narrowing rapidly in front to beak
  2. Top of head very broad, greatly thickened, flat or concave superiorly
  3. Broad flat superior surface probably covered with chitinous sheath forming battering-ram
  4. No horncores; external surface with vascular markings
  5. Sides of nasals coarsely striated and superior surface pitted
  6. No antorbital fossa; orbits small and circular
  7. Occipital condyle spherical, pointing strongly downward at right angles to superior skull surface
  8. Jaws short, deep, and massive; teeth short, thick with partly bifurcated roots
  9. Nasals 7-10 inches thick, composed of thick massive bone, pitted and coarsely striated

Species (3)

Pachyrhinosaurus canadensis Sternberg, 1950

Type species

Named for Canada, where the holotype specimens were discovered in Alberta.

Holotype
NMC 8867 , Canadian Museum of Nature
Material
Skull without lower jaws, lacking beak and back part of crest, laterally compressed.
Horizon
St. Mary River Formation, Campanian–Maastrichtian, Late Cretaceous , 83.6–66.0 million years ago
Locality
Little Bow River, Alberta, Canada

Pachyrhinosaurus lakustai Currie et al., 2008

Honors Al Lakusta, who discovered and reported the Pipestone Creek bonebed.

Holotype
TMP 1986.055.0258 , Royal Tyrrell Museum of Paleontology
Material
Transversely crushed adult skull, lacking most of the jugals, quadratojugals, quadrates, squamosals, and most of the parietals.
Horizon
Wapiti Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
Pipestone Creek bonebed, near Grande Prairie, Alberta, Canada
Diagnosis
  1. Smaller than P. canadensis.
  2. Nasal boss and other anterior facial ornamentation (including "fist-sized knobs") relatively less hypertrophied than in P. canadensis.
  3. Single transverse shelf of bone on the medial side of the premaxilla (a pair of shelves in P. canadensis and other centrosaurines).
  4. Short, robust premaxillary process projecting straight forward into the naris (long, slender, and finger-like, curving medially, in P. canadensis).
  5. Nasal boss fluting strong and regular, angled anterodorsally at about 45 degrees on adult nasal bosses (irregular and vertical in P. canadensis).
  6. Parietal bar curving slightly upward, with one to three median horns near the base of the midparietal bar (parietal bar essentially flat in P. canadensis).

Pachyrhinosaurus perotorum Fiorillo & Tykoski, 2012

Honors the Perot family (Margot and H. Ross Perot and their children) for their support of science and science education.

Holotype
DMNH 21200 , Denver Museum of Nature and Science
Material
Posterior part of a parietal, including the partial median bar, posterior median emargination, and autapomorphic anterior-facing horns.
Horizon
Prince Creek Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Kikak-Tegoseak Quarry, Colville River, North Slope, Alaska, United States
Diagnosis
  1. Pair of short, dorsoventrally flattened horns projecting anteromedially and slightly dorsally from the anterior margin of the parietal transverse bar (unique among ceratopsids).
  2. Paired fossae dorsal to the narial fossa.
  3. Narrow median hump on the posterior part of the nasal boss.
  4. Basal sulcus of the nasal boss extending ventrally below the dorsal rim of the narial fossa, making the boss relatively deeper dorsoventrally.
  5. Rostral comb formed by the nasals and premaxillae (present in P. lakustai, absent in P. canadensis).
  6. Nasal and supraorbital bosses nearly in contact, separated only by a narrow groove (as in P. canadensis; widely separated in P. lakustai).

Notable specimens

  • “Harvey”

    TMP 1989.055.1234 Royal Tyrrell Museum of Paleontology pathology

    Skull with severe lesions on the right side, the largest 195 mm across, producing a massive hole so deep that the left-side bones are visible within it; it partly destroyed the right eye socket and probably blinded the animal on that side. It survived and died later in a mass-death assemblage.

    Carpenter (2007)

  • DMNH 21460

    Perot Museum of Nature and Science ontogeny

    Incomplete nasal of an immature P. perotorum from the Kikak-Tegoseak Quarry, Alaska, with dorsally enlarged ornamentation marking an intermediate growth stage; its posterior part shows integument complexity (a cornified pad and sheath on the nasal boss) not previously recognized in the genus.

    Fiorillo & Tykoski (2013)

References

  1. Carpenter, K. (2007). Horns and beaks: ceratopsian and ornithopod dinosaurs. Indiana University Press, Bloomington. carpenter2007a
  2. Fiorillo, A. R.; Tykoski, R. S. (2013). An immature Pachyrhinosaurus perotorum (Dinosauria: Ceratopsidae) nasal reveals unexpected complexity of craniofacial ontogeny and integument in Pachyrhinosaurus. PLOS ONE 8(6): e65802. Public Library of Science (PLoS). doi:10.1371/journal.pone.0065802 fiorillo2013a
  3. Sternberg, C. M. (1950). Pachyrhinosaurus canadensis, representing a new family of the Ceratopsia, from southern Alberta. National Museum of Canada Bulletin 118: 109-120. doi:10.4095/105057 sternberg1950a
  4. Currie, P. J.; Langston, W.; Tanke, D. H. (2008). A new species of Pachyrhinosaurus (Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada. A New Horned Dinosaur from an Upper Cretaceous Bone Bed in Alberta 1-108. NRC Research Press.

    Erects Pachyrhinosaurus lakustai on skull TMP 1986.055.0258 from the Wapiti Formation (Pipestone Creek bonebed) of Alberta.

    currie2008a
  5. Fiorillo, A. R.; Tykoski, R. S. (2012). A new Maastrichtian species of the centrosaurine ceratopsid Pachyrhinosaurus from the North Slope of Alaska. Acta Palaeontologica Polonica 57(3): 561-573. Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). doi:10.4202/app.2011.0033

    Erects Pachyrhinosaurus perotorum on parietal DMNH 21200 from the Prince Creek Formation of the North Slope of Alaska.

    fiorillo2012a