Temporal range: Late Cretaceous (Maastrichtian), 68–66 Ma
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Specimen nicknamed "Tiny", Denver Museum of Nature and Science
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Clade:
Dinosauria
Clade:
†Ornithischia
Clade:
†Ceratopsia
Family:
†Ceratopsidae
Subfamily:
†Chasmosaurinae
Tribe:
†Triceratopsini
Genus:
†Torosaurus Marsh, 1891
Type species
†Torosaurus latus
Marsh, 1891
Other species
†T. utahensis? (Gilmore, 1946) Lawson, 1976
Synonyms
Arrhinoceratops? utahensis Gilmore, 1946
Torosaurus (meaning "perforated lizard", in reference to the large openings in its frill) is a genus of herbivorous chasmosaurine ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous period, between 68 and 66 million years ago, though it is possible that the species range might extend to as far back as 69 million years ago.[1] Fossils have been discovered across the Western Interior of North America, from as far north as Saskatchewan to as far south as Texas.
Torosaurus possessed the largest skulls of any known land animal, with the frilled skull reaching 2.77 metres (9.1 ft) in length. Torosaurus is thought to have been the same size as the contemporary Triceratops,[2][3][4] but is distinguished by an elongated frill with large oval shaped openings, long squamosal bones of the frill with a trough on their upper surface, and the presence of five or more pairs of hornlets on the back of the frill.[5]Torosaurus also lacked the long nose horn seen in Triceratops prorsus. It instead resembled the earlier and more basal Triceratops horridus, thanks to having a short nose horn.[5] Three species have been named so far: Torosaurus latus, T. gladius, and T. utahensis. T. gladius is no longer considered a valid species, however.
In 2010, the validity of Torosaurus was disputed.[6] A study of fossil bone histology combined with an investigation of frill shape concluded that Torosaurus probably represented the mature form of Triceratops, with the bones of typical Triceratops specimens still immature and showing signs of a first development of distinct Torosaurus frill holes. During maturation, the skull frill would have been greatly lengthened and holes would have appeared in it.[7][8][9] In 2011, 2012, and 2013, however, studies of external features of known specimens have claimed that morphological differences between the two genera preclude their synonymy. The main problems are a lack of good transitional forms, the apparent existence of authentic Torosaurus subadults, different skull proportions independent of maturation, and hole formation at an adult stage not being part of a normal ceratopsian maturation sequence.[5][10][11] Consequently, it is still heavily debated whether Torosaurus truly is an adult Triceratops or a separate genus, though most researchers currently favor the latter interpretation.
^*Hicks, J.F., Johnson, K.R., Obradovich, J. D., Miggins, D.P., and Tauxe, L. 2003. Magnetostratigraphyof Upper Cretaceous (Maastrichtian) to lower Eocene strata of the Denver Basin, Colorado. In K.R. Johnson, R.G. Raynolds and M.L. Reynolds (eds), Paleontology and Stratigraphy of Laramide Strata in the Denver Basin, Pt. II., Rocky Mountain Geology 38: 1-27.
^Paul, G.S.; Christiansen, P. (2000). "Forelimb posture in neoceratopsian dinosaurs: implications for gait and locomotion" (PDF). Paleobiology. 26 (3): 450–465. doi:10.1666/0094-8373(2000)026<0450:FPINDI>2.0.CO;2. JSTOR 2666120. S2CID 85280946.
^Paul, G. S. (2010). The Princeton Field Guide to Dinosaurs. Princeton University Press. pp. 265–267. ISBN 978-0-691-13720-9.
^Holtz, Thomas R. Jr. (2012). Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages(PDF). Winter 2011 Appendix
^ abcLongrich, 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. Bibcode:2012PLoSO...732623L. doi:10.1371/journal.pone.0032623. PMC 3290593. PMID 22393425.
^"Morph-osaurs: How shape-shifting dinosaurs deceived us – life – 28 July 2010". New Scientist. doi:10.1080/02724634.2010.483632. S2CID 86767957. Retrieved August 3, 2010. {{cite journal}}: Cite journal requires |journal= (help)
^Cite error: The named reference scannella&horner2010 was invoked but never defined (see the help page).
^Switek, Brian. "New Study Says Torosaurus=Triceratops". Dinosaur Tracking. Smithsonian.com. Archived from the original on November 13, 2013. Retrieved March 2, 2011.
^Horner, Jack (November 2011). Shape-shifting Dinosaurs. TEDX Talks. Retrieved November 20, 2012.
^Cite error: The named reference fark was invoked but never defined (see the help page).
^Cite error: The named reference Maiorino2013 was invoked but never defined (see the help page).
Texas. Torosaurus possessed the largest skulls of any known land animal, with the frilled skull reaching 2.77 metres (9.1 ft) in length. Torosaurus is thought...
fossil record, as are Torosaurus individuals too young to be considered fully mature adults. The synonymy of Triceratops and Torosaurus cannot be supported...
genera in recent years has been controversial, as some genera such as Torosaurus, Tatankaceratops, and Nedoceratops are wrapped up in debate as to whether...
needed] The museum has erected the first full-scale reproduction of a Torosaurus on Whitney Avenue next to the entrance. The 3 m (9 ft) tall, 7 m (21 ft)...
identification. In 1976, Douglas A. Lawson transferred the species to Torosaurus, as a Torosaurus utahensis. Apart from the holotype skull little fossil material...
Closer study later revealed that the animal was distinct from Torosaurus; Torosaurus has a flat midline bar of the parietal, while that of Sierraceratops...
nearest relative. An ongoing debate concerns the status of Triceratops, Torosaurus, and Nedoceratops. In a series of publications, John B. Scannella and...
which have been variously included in the species Ojoceratops fowleri and Torosaurus utahensis, are known from the same time period in New Mexico and may also...
of the parietal (Triceratops, Torosaurus); a narial strut oriented vertically with a narrow base (Triceratops, Torosaurus); an enlarged epoccipital on...
in absolute size those of larger chasmosaurines like Triceratops and Torosaurus. Its horns are estimated to have been up to 1.2 m (4 feet) long. It was...
In some genera, such as Triceratops, Pentaceratops, Centrosaurus and Torosaurus, this extension is very large. Despite the neck frill predominantly being...
Tyrannosaurus shared this ecosystem with ceratopsians Leptoceratops, Torosaurus, and Triceratops, the hadrosaurid Edmontosaurus annectens, the parksosaurid...
Canada. Based on these finds, Lambe (1914) erected Protorosaurus ("before Torosaurus"), but that name was preoccupied by the Permian reptile Protorosaurus...
openings, than those seen in other chasmosaurines like Pentaceratops and Torosaurus. The frill has deep arterial grooves on both the upper and the underside...
relatively rare. Other dinosaurs, such as Sphaerotholus, Denversaurus, Torosaurus, Struthiomimus, Acheroraptor, Dakotaraptor, Pectinodon, a possible Parasaurolophus...
a possible species of Parasaurolophus, ceratopsians like Triceratops, Torosaurus, Nedoceratops, Tatankaceratops, and Leptoceratops, the ankylosaurid Ankylosaurus...
holes in the frill. The skull and frill elongation makes the skulls of Torosaurus and Pentaceratops the largest of any known terrestrial vertebrate, at...
K.; Lehman, Thomas M. (2008). "Attributes of the ceratopsian dinosaur Torosaurus, and new material from the Javelina Formation (Maastrichtian) of Texas"...
genus similar to Torosaurus is said to exist above the base of the formation Elephant Butte (lower) Indeterminate, in abundance Torosaurus sp. Elephant Butte...
Edmontosaurus and Kritosaurus and chasmosaurines like Triceratops and Torosaurus were widespread throughout western North America, while lambeosaurines...
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