Description Size in green compared with selected giant theropods Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, located at the Field Museum of Natural History under the name FMNH PR and nicknamed Sue , measured Historically average adult mass estimates have varied widely over the years, from as low as 4.
The forelimbs had only two clawed fingers,  along with an additional small metacarpal representing the remnant of a third digit. The tail was heavy and long, sometimes containing over forty vertebrae , in order to balance the massive head and torso.
To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow, reducing its weight without significant loss of strength. But in other respects Tyrannosaurus's skull was significantly different from those of large non- tyrannosauroid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision.
These and other skull-strengthening features are part of the tyrannosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-tyrannosaurids. The D-shaped cross-section, reinforcing ridges and backwards curve reduced the risk that the teeth would snap when Tyrannosaurus bit and pulled. The remaining teeth were robust, like "lethal bananas" rather than daggers, more widely spaced and also had reinforcing ridges.
The largest found so far is estimated to have been Mark Norell of the American Museum of Natural History summarized the balance of evidence by stating that: As with many other coelurosaurian theropods discovered in the Yixian, the fossil skeleton was preserved with a coat of filamentous structures which are commonly recognized as the precursors of feathers.
This was based on the presence of enamel , which according to the study needs to remain hydrated, an issue not faced by aquatic animals like crocodilians or toothless animals like birds. At the center of these scales were small keratinised patches.
In crocodilians, such patches cover bundles of sensory neurons that can detect mechanical, thermal and chemical stimuli. Comparisons with crocodilian facial tissue and Thomas D. Carr's personal interpretation of the findings were cited as support for the conclusion that tyrannosaurs did not have lips. Timeline of tyrannosaur research Skeletal restoration by William D. Matthew from , the first reconstruction of this dinosaur ever published  Henry Fairfield Osborn , president of the American Museum of Natural History , named Tyrannosaurus rex in Osborn used the Latin word rex, meaning "king", for the specific name.
The full binomial therefore translates to "tyrant lizard the king" or "King Tyrant Lizard",  emphasizing the animal's size and perceived dominance over other species of the time. In the early s, John Bell Hatcher collected postcranial elements in eastern Wyoming. The fossils were believed to be from a large species of Ornithomimus O.
Vertebral fragments found by Edward Drinker Cope in western South Dakota in and assigned to Manospondylus gigas have also been recognized as belonging to Tyrannosaurus rex. Osborn originally named this skeleton Dynamosaurus imperiosus in a paper in Brown found another partial skeleton in the Hell Creek Formation in Montana in Osborn used this holotype to describe Tyrannosaurus rex in the same paper in which D.
Cope believed that they belonged to an "agathaumid" ceratopsid dinosaur, and named them Manospondylus gigas, meaning "giant porous vertebra" in reference to the numerous openings for blood vessels he found in the bone. Osborn recognized the similarity between M. Owing to the fragmentary nature of the Manospondylus vertebrae, Osborn did not synonymize the two genera.
These were judged to represent further remains of the same individual, and to be identical to those of Tyrannosaurus rex. The Fourth Edition of the ICZN, which took effect on January 1, , states that "the prevailing usage must be maintained" when "the senior synonym or homonym has not been used as a valid name after " and "the junior synonym or homonym has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years Manospondylus gigas could then be deemed a nomen oblitum "forgotten name".
This Tyrannosaurus, nicknamed Sue in her honor, was the object of a legal battle over its ownership. In this was settled in favor of Maurice Williams, the original land owner. From to Field Museum of Natural History preparators spent over 25, man-hours taking the rock off each of the bones. The finished mount was then taken apart, and along with the bones, shipped back to Chicago for the final assembly.
A study of this specimen's fossilized bones showed that Sue reached full size at age 19 and died at age 28, the longest any tyrannosaur is known to have lived. Though subsequent study showed many pathologies in the skeleton, no bite marks were found. Recent speculation indicates that Sue may have died of starvation after contracting a parasitic infection from eating diseased meat; the resulting infection would have caused inflammation in the throat, ultimately leading Sue to starve because she could no longer swallow food.
This hypothesis is substantiated by smooth-edged holes in her skull which are similar to those caused in modern-day birds that contract the same parasite. It was not collected until , as it was mistakenly thought to be a Triceratops skeleton. One of the specimens was reported to be perhaps the largest Tyrannosaurus ever found. Dubbed Jane, the find was initially considered the first known skeleton of the pygmy tyrannosaurid Nanotyrannus but subsequent research has revealed that it is more likely a juvenile Tyrannosaurus.
Jane has been examined by Jack Horner, Pete Larson, Robert Bakker , Greg Erickson , and several other renowned paleontologists , because of the uniqueness of her age. Other members of the tyrannosaurine subfamily include the North American Daspletosaurus and the Asian Tarbosaurus ,   both of which have occasionally been synonymized with Tyrannosaurus. The study further indicates the possibility that Tyrannosaurus may have driven other tyrannosaurids that were native to North America extinct through competition.
Whether or not this specimen belongs to Tyrannosaurus rex, a new species of Tyrannosaurus, or a new genus entirely is still unknown. This skull was originally classified as a species of Gorgosaurus G. Gilmore in ,  but was later referred to a new genus, Nanotyrannus.
Many paleontologists consider the skull to belong to a juvenile Tyrannosaurus rex.