Open Paleo

Tatankaceratops

Ott & Larson, 2010 Disputed

From 'tatanka', the Lakota word for the American bison, for the animal's bison-like size and for the type locality near Buffalo, South Dakota, and Latin 'ceratops' ('horned face').

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Tatankaceratops is a contested genus of herbivorous chasmosaurine ceratopsid dinosaur that lived during the Late Cretaceous period (latest Maastrichtian stage, about 66 million years ago) in what is now the upper Hell Creek Formation, in South Dakota. It is known from a single fragmentary skull and partial skeleton housed at the Black Hills Institute, BHI 6226, described by Ott and Larson in 2010 as the type species Tatankaceratops sacrisonorum. Whether the specimen is a small adult of its own genus or an unusual individual of Triceratops remains unsettled.

Under dispute

Ott and Larson (2010) erected Tatankaceratops on BHI 6226, arguing that rugose surface texture, dendritic venation and extensive fusion across the skull and skeleton show an adult animal despite an estimated skull length of only about 1 m, and that its proportions differ from any contemporaneous ceratopsid. They examined and rejected paedomorphosis within Triceratops, island dwarfism, and referral to Avaceratops. Longrich (2011) instead reads the specimen as a mixture of juvenile and adult Triceratops characters, either an individual of Triceratops prorsus that stopped growing or a dwarf species derived from Triceratops, and leaves the question open; Longrich and Field (2012) place BHI 6226 in a Triceratops growth series and call it a possible aberrant individual of T. prorsus. Farke (2011) counts the genus only as possibly valid, and Lehman (2016) groups it with ceratopsians erected on immature specimens whose status is held in question. Placed at Chasmosaurinae incertae sedis, the least inclusive clade common to these readings.

Diagnosis

  1. Small adult body size
  2. No development of cornual sinuses
  3. Nasal horncore proportionally massive
  4. Nasal horn the same length as the postorbital horns
  5. Nasal horncore recurved
  6. Orbit proportionally large compared to skull size
  7. Postorbital horncores originating caudal to the orbit
  8. No overlap of the orbit by the postorbital horncore
  9. No evidence of epijugal ossifications

Species

Tatankaceratops sacrisonorum Ott & Larson, 2010 Disputed

Type species

Honors Stan and Steven Sacrison, the twin brothers who found and collected the type specimen.

Holotype
BHI 6226 , Black Hills Institute of Geological Research
Material
Fragmentary skull and partial skeleton, at least 47 identifiable elements and more than 2,000 fragments, including cranial elements, the mandible, cervical and dorsal vertebrae, ribs, an ulna fragment, a manus ungual and a phalanx.
Notes
Collected from the base of an overbank mudstone about 10 miles north-northwest of Buffalo, Harding County, the describers withholding precise locality data. The estimated skull length is about 1 m, from which the authors derive a total length of 3 to 3.5 m using the proportions of Triceratops horridus.
Horizon
Hell Creek Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Niemi Ranch, South Dakota, United States

References

  1. Ott, C. J.; Larson, P. L. (2010). A new, small ceratopsian dinosaur from the latest Cretaceous Hell Creek Formation, northwest South Dakota, United States: a preliminary description. New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium (Ryan, M. J.; Chinnery-Allgeier, B. J.; Eberth, D. A., eds.) 203-218. Indiana University Press, Bloomington. ott2010a
  2. Longrich, N. R. (2011). Titanoceratops ouranos, a giant horned dinosaur from the late Campanian of New Mexico. Cretaceous Research 32(3): 264-276. Elsevier BV. doi:10.1016/j.cretres.2010.12.007

    Reads the holotype as a mixture of juvenile and adult Triceratops characters and declines to resolve whether it is a stunted individual or a dwarf species.

    longrich2011a
  3. Farke, A. A. (2011). Anatomy and Taxonomic Status of the Chasmosaurine Ceratopsid Nedoceratops hatcheri from the Upper Cretaceous Lance Formation of Wyoming, U.S.A. PLOS ONE 6(1): e16196. doi:10.1371/journal.pone.0016196

    Counts the genus among possibly-valid late Maastrichtian chasmosaurines.

    farke2011b
  4. Longrich, N. R.; Field, D. J. (2012). Torosaurus is not Triceratops: ontogeny in chasmosaurine ceratopsids as a case study in dinosaur taxonomy. PLoS ONE 7(2): e32623. Public Library of Science (PLoS). doi:10.1371/journal.pone.0032623

    Places the holotype in a Triceratops growth series and suggests it may be an aberrant individual of Triceratops prorsus.

    longrich2012b
  5. Lehman, T. M.; Wick, S. L.; Barnes, K. R. (2016). New specimens of horned dinosaurs from the Aguja Formation of West Texas, and a revision of Agujaceratops. Journal of Systematic Palaeontology 15(8): 641-674. Informa UK Limited. doi:10.1080/14772019.2016.1210683

    Groups the name with ceratopsians erected on immature specimens whose status is held in question and which are seldom used in phylogenetic work.

    lehman2016b