Torosaurus

*Torosaurus latus*

* Jurassic Park Institute Artwork
* Robert F Walters Artwork

***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 Charles Marsh, coined the genus *Torosaurus* for them.

The name *Torosaurus* is frequently translated as "bull lizard" from the Latin noun taurus or Spanish toro but much more likely is derived from the Greek verb τορέω (toreo, "to pierce, perforate").[11] The allusion is to the fenestrae or ("window-like") holes in the elongated frill, which have traditionally served to distinguish it from the solid frill of *Triceratops*. Much of the confusion over etymology of the name results from the fact that Marsh never explicitly explained it in his papers.

Two *Torosaurus* species have been identified:

* *T. latus* Marsh, 1891 (type species). Latus means "the wide one" in Latin, in reference to the frill.
* *T. utahensis* (Gilmore, 1946) Lawson, 1976

Another species was subsequently regarded as identical to *T. latus*:

* *T. gladius* Marsh, 1891. Gladius is "sword" in Latin, in reference to the elongated shape of the squamosal.

*T. latus* was based on holotype YPM 1830, a partial skull. The holotype of *T. gladius* was specimen YPM 1831, a larger skull. Both fossils were found in the Lance Formation, dating from the Maastrichtian. Similar specimens found in Wyoming, Montana, South Dakota, North Dakota, Colorado, Utah and Saskatchewan have since been referred to *Torosaurus*. Those that can be identified with some certainty include: ANSP 15192, a smaller individual in South Dakota uncovered by Edwin Harris Colbert in 1944;[12] MPM VP6841, a partial skeleton with skull, now mounted at Milwaukee; SMM P97.6.1, a skull lacking the snout; and two partial skulls from the Hell Creek Formation reported in 2002: MOR 981, discovered in 1998, and MOR 1122, from 2001.[13] Fragmentary remains that could possibly be identified with the genus have been found in the Big Bend Region of Texas and in the San Juan Basin of New Mexico.[14] Paleontologists have observed that *Torosaurus* specimens are uncommon in the fossil record; specimens of *Triceratops* are much more abundant.

*Torosaurus utahensis* was originally described as *Arrhinoceratops utahensis* by Charles Whitney Gilmore in 1946, based on specimen USNM 15583, a frill fragment from Emery County, Utah.[15] In 1976 it was renamed *Torosaurus utahensis* by Douglas Lawson.[16] Review by Robert Sullivan et al. in 2005[17] left it as *Torosaurus utahensis* and somewhat older than *T. latus*. In 2008 Rebecca Hunt referred considerable additional material to this species.[18] However, subsequent studies suggested it may well be either *Arrhinoceratops* or a new genus, as dinosaurs from the northern Hell Creek formation and southern "*Alamosaurus* fauna" rarely overlap and were probably separated by a geographic barrier. Research has not yet been published on whether *T. utahensis* should be regarded as a new genus or, as has been suggested for *T. latus*, the mature growth stage of some species of *Triceratops*.

## Classification

*Torosaurus* belongs in the Ceratopsidae family.

## JPInstitute.com Description

Torosaurus had the largest skull of any animal that ever walked the Earth! With its large frill and pointed beak, it was more than 8 feet (2.5 m) long. It had a huge frill and long horns over its eyes. It was about the same size as the most famous member of its family, Triceratops. In fact, these dinosaurs were very closely related and one of the few differences was that Torosaurus had large openings in its frill. This could have been to make it lighter since it was so big.

As a member of one of the most successful dinosaur families, Torosaurus shared many characteristics with the ceratopsians. It was a large, stocky herbivore that fed on plants growing low to the ground. It used its sharp beak to strip the plants and its banks of cheek teeth to pulverize them. Torosaurus was likely a herd-dwelling animal.

Torosaurus's frill was huge. It would have made an impressive display when tilted up, perpendicular to the ground. It is possible that it was used as a method of intimidation or for attracting mates, or both. It would also have provided protection to the neck and upper back when attacked from above.

## Dinosaur Field Guide Description

Torosaurus ("pierced lizard") is one of the last of the ceratopsians, or horned dinosaurs. It is best known for one major feature: its frill, which is larger than its skull--which, at 10 feet (3 m), is one of the longest skulls of any land animal in Earth's history! Torosaurus's frill is so long that it severely restricted movement of the skull. The result is that Torosaurus would have had to move its whole body, and not just its head, when confronting an attacker. That is why its forelegs were so powerful and highly muscled. Its horns point up and out to the side directly at the height of an adult Tyrannosaurus's belly. Torosaurus lived at the same time as Triceratops, but the Torosaurus population appears to have been much smaller. In Torosaurus, the frill is much longer and thinner than in Triceratops, and the frill has two fenestrae, or windows, that make it much lighter.

### Fun Facts

The frill is composed of the same kind of bone matter found in human skulls.

### Trivia

The original specimen was collected by John Bell Hatcher, who was nick-named "the skull finder" He is famous for finding over fifty Triceratops skulls in just two summers.

## Appearance in other media

### *Jurassic Park*

* *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* 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.

## Links

http://web.archive.org/web/20040806052537fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_toros.html

## References

1. ↑ https://pubs.geoscienceworld.org/uwyo/rmg/article-abstract/38/1/1/87954/Magnetostratigraphy-of-Upper-Cretaceous?redirectedFrom=fulltext
2. ↑ https://press.princeton.edu/books/hardcover/9780691167664/the-princeton-field-guide-to-dinosaurs
3. ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3290593/
4. ↑ https://www.smithsonianmag.com/science-nature/the-torosaurus-identity-crisis-continues-111952707/
5. ↑ https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081608
6. ↑ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3290593/
7. ↑ https://news.yale.edu/2012/02/29/torosaurus-not-triceratops-yale-researchers-say
8. ↑ https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlab120/6540273?login=false#.Yh5Tx3f8XyY.twitter
9. ↑ https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlab120/6540273?login=false#.Yh5Tx3f8XyY.twitter