Torosaurus

Torosaurus Temporal range: Late Cretaceous PreЄ Є O S D C P T J K Pg N ↓
An artist's illustration of Torosaurus latus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
clade:	Dinosauria
Order:	†Ornithischia
Family:	†Ceratopsidae
Subfamily:	†Chasmosaurinae
Tribe:	†Triceratopsini
Genus:	†Torosaurus Marsh, 1891
Synonyms
Arrhinoceratops? utahensis Gilmore, 1946 Torosaurus gladius Paul, 2003

Torosaurus ("perforated lizard", in reference to the large openings in its frill) is a genus of large herbivorous ceratopsian dinosaur that lived during the late Maastrichtian stage of the Cretaceous period, between 68 and 66 million years ago. The species was named by Othniel Charles Marsh in 1891. Fossils have been discovered across the Western Interior of North America, from Saskatchewan to southern Texas.

Description

Torosaurus possessed one of, if not the largest skull of any known land animal. The frilled skull reached up to 2.77 meters (9.1 ft.) in length. From head to tail, Torosaurus is thought to have measured about 7.6 to 9 m (24.9 to 29.5 ft.) long and weighed four to six tones. Torosaurus is distinguished from the contemporary Triceratops by an elongate frill with large openings (fenestrae), long squamosal bones of the frill with a trough on their upper surface, and the presence of five or more pairs of hornlets (epoccipitals) on the back of the frill.

The animal is also often distinguished from Triceratops via a larger flat frill that has been shown flattened against its body. Torosaurus also lacked the long nose horn seen in Triceratops prorsus, and instead resembled the earlier and more basal Triceratops horridus in having a short nose horn. Three species have been named, Torosaurus latus, T. gladius, and T. utahensis. However, T. gladius is no longer considered a valid species and is now considered a synonym of T. latus.

Recently the validity of Torosaurus has been disputed. A 2010 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 the first development of distinct Torosaurus frill holes. During maturation, the skull frill would have been greatly lengthened and holes would have appeared in it.

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 the assertion that hole formation at an adult stage is not part of a normal ceratopsian maturation sequence.

However there are more recent studies that confirm the Torosaurus as a valid genus. An even more recent study confirmed the existence of juvenile members of Torosaurus, thus further solidified the existence of Torosaurus. The Torosaurus has been reported from Upper Maastrichtian deposits in Canada, which would mark the northernmost range of the genus, recent work has questioned the generic identity of the implicated material, which primarily consists of a pair of cranial frills.

Perhaps more problematically, the validity of the genus itself has been a subject of recent debate, with some arguing that Torosaurus is simply a skeletally mature growth form of the contemporaneous Triceratops. In this study, we describe and illustrate the relevant frill material from Canada, and determine that it is most plausibly attributable to the Torosaurus morph. Moreover, we apply for the first time osteohistological sampling to some postcranial material associated with one of the frills, and find that the animal was still growing at the time of death. This finding, in addition to other considerations presented here, leads us to conclude that Torosaurus is a valid genus, and is not simply a mature growth form of Triceratops.

Discovery and species

In 1891, two years after the naming of Triceratops, a pair of ceratopsian skulls with elongated frills bearing holes were found in southeastern Wyoming, Niobrara County, by John Bell Hatcher. Hatcher's employer, paleontologist Professor Othniel Marsh, coined the genus Torosaurus for them.

Classification

Torosaurus belongs in the Ceratopsidae family, housed in the subfamily Chasmosaurinae and the tribe Triceratopsini. The genus' closest relatives are Triceratops and Nedoceratops, which is a partial reason for the debate of Torosaurus' synonymy.

In popular culture

• Torosaurus appeared in Walking with Dinosaurs where they are first shown rutting each other and one lost its horn after challenging another for the right to mate. Later, they were shown at night being attack by two Dromaeosaurus, which successfully kill one of the youngsters closer to the morning, and the herd moves on to newer pastures.
• Torosaurus is also a creatable dinosaur in the computer game, Jurassic Park: Operation Genesis.
• Torosaurus is a creatable dinosaur in the app game, Jurassic Park: Builder.
• Torosaurus is known to have appeared in Dinosaur King.
• Torosaurus is in The Dino King where it is inaccurately is shown to live in Asia 80 million years ago.
• Torosaurus appeared in Jurassic World Evolution, where it can be mined from several North American departments, or dig sites. The Lance Formation offers several sources. It also appears in its sequel game.
• Torosaurus appeared in the documentary series Dino Hunters.

Trivia

According to Jack Horner, Torosaurus is a slighty more developed Triceratops.

Other Wikis

• https://prehistoric-wiki.fandom.com/wiki/Torosaurus

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