Pygmy Tyrannosaurid

Tyrannosaurus lancensis or simply the Dwarf Tyrannosaurus, is a genus of tyrannosaurid dinosaur, and is possibly just a juvenile specimen of Tyrannosaurus rex. It is based on CMN 7541, a skull collected in 1942 and described by Charles W. Gilmore in 1946, who gave it the new species Gorgosaurus lancensis.[1] In 1988, the specimen was re-described by Robert T. Bakker, Phil Currie, and Michael Williams, then the curator of paleontology at the Cleveland Museum of Natural History, where the original specimen was housed and is currently on display. Initial research indicated that the skull bones were fused, and that it therefore represented an adult specimen. In light of this, Bakker and colleagues assigned the skull to a new genus, which they named Nanotyrannus for its apparently small size.[2] However, subsequent work has cast doubt on this, and some paleontologists no longer consider it a valid genus—since the fossil was a contemporary of Tyrannosaurus rex, many paleontologists now believe it to be a juvenile T. rex, especially since the discovery in 2001 of a new Tyrannosaurus lancensis specimen, nicknamed "Jane." The original Dwarf Tyrannosaurus specimen is estimated to have been around 17 feet (5.2 meters) long when it died.

In 2001, a more complete juvenile tyrannosaur ("Jane", catalogue number BMRP 2002.4.1), belonging to the same species as the original "Nanotyrannus" specimen, was uncovered. In 2005, a conference on tyrannosaurs focused on the issues of Tyrannosaurus lancensis validity brought about by the discovery of the Jane specimen, was held at the Burpee Museum of Natural History. Several paleontologists, such as Phil Currie and Donald M. Henderson, saw the discovery of Jane as a confirmation that Tyrannosaurus lancensis was a juvenile T. rex or closely related species.[3] [4] Peter Larson, on the other hand, continued to support a separate genus for Nanotyrannus.[5] The actual scientific study of Jane, set to be published by Bakker, Larson, and Currie, may help determine whether Nanotyrannus is a valid genus, whether it simply represents a juvenile T. rex, or whether it is a new species of a previously identified genus of tyrannosaur.[6]

Bakker has stated he believes Tyrannosaurus lancensis hunted in packs. Teeth from multiple Dwarf Tyrannosaurs have been found in the bones of herbivorous dinosaurs.[7]

In Popular Culture

 * The "Quintaglios" from Robert J. Sawyer's Quintaglio Ascension Trilogy are a race of highly evolved, sentient descendants of tyrannosaurs descended from T. lancensis.
 * In 2008, T. lancensis  was featured in the second episode of Jurassic Fight Club, a pseudo-documentary about prehistoric predators.[8] The episode addressed the ongoing scientific debate on the validity of the "Nanotyrannus" genus, presenting a speculative battle between two juvenile Tyrannosaurus rex and one Tyrannosaurus lancensis (which was possibly a juvenile Tyrannosaurus rex). The episode depicted both genera as having pronated hands (hands with downward or backward-facing palms), something tyrannosaurids could not do.[9] The episode relied heavily on speculation to determine who would be the victor in the battle between the similar (or possibly synonymous) species.
 * In the BBC documentary Walking with Dinosaurs, a Tyrannosaurus lancensis carcass was shown in a field of poisonous gas. It was then scavenged upon by a Tyrannosaurus rex.

"Nanotyrannus" Heresies
I believe Nanotyrannus should be an invalid genus and should be classified within the Tyrannosaurus genus. Yet it is so different from T. rex it should consist of its own species ''T. lancensis. ''

Evolution 

Tyrannosaurus lancensis probably evolved from Tyrannosaurus torosus or ''Tyrannosaurus rex. It has been suggested that "Nanotyrannus" is actually a Dwarf Tyrannosaurus. If true, lancensis ''probably evolved off an island in the Western Interior Sea. After some time the island reconnected to the mainland introducing it to more land expansion and distribution. Islands evolved lancensis because of limited resources. So islands evolved T. torosus or T. rex into a smaller body making it a pygmy or dwarf. Islands are surrounded by water so if a resource runs out there's no way to go but extinction (if the animal needs the resource).