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Scientific Classification
Kingdom: Animalia
Phylum: Chordata
SuperOrder: Dinosauria
Order: Theropoda
Family: Tyrannosauridae
Genus: Nanotyrannus
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The Nanotyrannus was tyrannosaur that existed on the earth in the latter half of the Cretaceous period of the Mesozoic era. It is characterized by its distinctly small size as compared to the other tyrannosaurids of that time. Its length was about 16 to 18 feet and it weighed about 500 to 1000 kilos. Most other tyrannosaurids grew to about 35 feet in length.
The validity of the Nanotyrannus as a separate genus is questioned by many scientists. Some believe it to be the juvenile of a tyrannosaur, possibly the Tyrannosaurus rex itself. Others posit that it could possibly be a dwarf individual of one tyrannosaurid or the other. There is a lot of evidence supporting both the above mentioned claims and this ambivalence has divide d the scientific community.

The fossils of the Nanotyrannus were discovered in the Lance and Hell Creek Formations of North America. These were locations where the fossils of the T. rex were found aplenty, strengthening its connection to that dinosaur. Furthermore, the age of the fossils of the Nanotyrannus was 69 to 66 million Yeats ago, the exact time when the Tyrannosaurus walked the earth.

This dinosaur was carnivorous like other tyrannosaurids. It could balance itself on its hind legs, but did not walk completely erect. Although it was smaller as compared to its contemporaries, it was still large enough to be a good hunter.


The name Nanotyrannus is a combination of two separate words. The prefix 'nano' is derived from the Greek word 'nanos' which means 'dwarf' and the suffix 'tyrannus' is Latin for 'tyrant'. Thus the name of this reptile translates to 'a dwarf tyrant'. The aggressively carnivorous nature of the tyrannosaurs give them their name.

The specific name of the dinosaur, the N. lancensis, is derived from the Lance Formation where the holotype specimen was unearthed. The suffix 'ensis' denotes 'hailing from'.

The christening of the fossils was performed by paleontologist Charles Gilmore, who coined the specific name. The genus was named by Bakker, Currie and colleagues.

Discovery of fossils

The holotype of the Nanotyrannus was found in the Lance Creek Formation of Wyoming in 1942. It comprised of a single skull. This specimen was quite well preserved. It was discovered by David Hosbrook Duncle and was examined by Gilmore. He defined it in 1946.

A second more complete specimen was supposedly found in 2006 from the Hell Creek Formation in Montana. It was officially reported in 2011 and is not yet described.


When Charles W Gilmore first examines the skull of the Nanotyrannus, he presumed it to be a juvenile Gorgosaurus. He initially considered it a Deinodon; but then he believed that the Deinodon did not possess adequate fossil representation to be defined as a separate genus, hence discarded the idea. It was housed in the Cleveland Museum of Natural History.

The skull remained classified as a Gorgosaurus till 1988, when the curator of the museum, Michael Williams, along with scientists Phil Currie and Robert Bakker reexamined the skull. They found that the skull sutures were fused, which meant that belonged to an adult dinosaur.

They assigned it to a separate genus, the Nanotyrannus.

Thus, the remains are currently classified under suborder Theropoda, family Tyrannosauridae and subfamily Tyrannosaurinae. The Gorgosaurus is classified under family Albertosaurinae. Moreover, the Gorgosaurus fossil are about 10 million years older than those of the Nanotyrannus.

Evidence for the Nanotyrannus being a separate genus

One of the biggest facts pointing out to the Nanotyrannus being an adult, and thus a disparate genus, is the fusion of the sutures between the cranial bones. Juvenile animal have these sutures open.

Many scientists consider this dinosaur a juvenile T. rex. But the T. rex contained 11- 12 in its maxilla and 11- 14 in its mandible, while the Nanotyrannus contained 14- 15 teeth in its maxilla and 16 in its mandible. A study of adult and juvenile dentition of the Tarbosaurus, a tyrannosaur, showed that it did display such variations among young and adult specimens.

The Nanotyrannus also had proportionately larger hands as compared to the Tyrannosaurus and its furcula differed from the Tyrannosaurus as well.

The fusion of the skull sutures is a relative phenomenon. It occurs at different ages in different individuals. Thus, in spite of the fused sutures, the Nanotyrannus could still have been a juvenile.

A study by scientist Carr showed that in the tyrannosaur Gorgosaurus, teeth did indeed reduce in number as the dinosaurs matured. Thus he stated that the Nanotyrannus could yet be young specimen, if not necessarily of the T. rex.

Furthermore, Carr also determined that tooth number was relative to adult individuals of the same tyrannosaur species too.

In 2001, an almost complete specimen was found in Montana and it was dubbed 'Jane'. This specimen was identified as a juvenile Tyrannosaurus and was practically identical with the Nanotyrannus.

Some scientists say that Jane and the Nanotyrannus were not juveniles and were not Tyrannosaurus dinosaurs. Both of them contained a groove on the quadratojugal bone. This groove is absent in adult the adult Tyrannosaurus and may have been a characteristic unique to the Nanotyrannus. But most researchers deem that it may have been lost in adults.

Physical features

The Nanotyrannus was highly similar to the Tyrannosaurus, except smaller. Its length was about 5.2 meters which is less than half the size of the Tyrannosaurus. It had a large and elongated skull, sharp teeth and shortened forelimbs. Its hind legs were adapted for running and contained three toes each. Its tail was long, with it being very stout at the base.

Habits and habitat

The Nanotyrannus was bipedal dinosaur, with the typical hunched posture of the tyrannosaurs. It was carnivorous and terrestrial. Its habitat consisted of forests and swampy terrains.

Related species

If the Nanotyrannus did indeed belong to subfamily Tyrannosaurinae, it was related to the Tarbosaurus and Daspletosaurus. It may also have been closely related to the Tyrannosaurus.

The final notes

Paleontologists are spilt in their opinions about the Nanotyrannus. Some believe it was a valid genus while more consider it a juvenile. This disagreement can only be resolved if fresh and diagnostically relevant fossils become available soon. Moreover, the complete study of 'Jane' isn't published yet. Once it is, it may throw a new light on the discussion.