Nanotyrannus

Name: Nanotyrannus ‭(‬Dwarf tyrant‭)‬.
Phonetic: Nah-no-ty-ran-nus.
Named By: Robert T.‭ ‬Bakker,‭ ‬Phil Currie‭ & ‬Michael Williams‭ ‬-‭ ‬1988.
Synonyms: Gorgosaurus lancensis,‭ ‬Deinodon lancensis,‭ ‬Aublysodon lancensis,‭ ‬Albertosaurus lancensis.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Saurischia,‭ ‬Theropoda,‭ ‬Tyrannosauridae.
Species: N.‭ ‬lancensis‭ (‬type‭)‬.
Diet: Carnivore.
Size: Approximately‭ ‬5.2‭ ‬meters long for holotype.
Known locations: North America.
Time period: Maastrichtian of the Cretaceous.‭
Fossil representation: Single skull.

       Nanotyrannus is probably the most controversial member of the Tyrannosauridae because while some palaeontologists think that it represents a distinct genus,‭ ‬others think that it is simply a juvenile form‭ ‬of a larger tyrannosaurid genus,‭ ‬or even a dwarf species of another genus.‭ ‬Indeed when the skull was first described by Charles W.‭ ‬Gilmore in‭ ‬1946‭ ‬it was classified as a species of Gorgosaurus.
       The controversy surrounding Nanotyrannus began in‭ ‬1988‭ ‬when during a re-examination of the skull by Robert T.‭ ‬Bakker,‭ ‬Phil Currie and Michael Williams,‭ ‬the skull bones where perceived to have been fused together.‭ ‬This is typically a sign of an adult individual as the skull bones of individual animals remain separate while in the juvenile stages for easier growth.‭ ‬When the growth begins to slow down the bones become fused together for additional strength during the animal’s adult life.
       However in‭ ‬1999‭ ‬another palaeontologist named Thomas Carr conducted a detailed analysis on the skull and found that the bones were not actually fused together after all.‭ ‬This observation split palaeontologists all over the world into thinking that Nanotyrannus was either a small tyrannosaurid or a juvenile of a larger one.‭ ‬Debate continued to sway one way or the other until the discovery of a new tyrannosaur specimen that was nicknamed‭ ‘‬Jane‭’‬.‭ ‬Not only was Jane the same size and species as Nanotyrannus,‭ ‬but Jane was without doubt a juvenile tyrannosaur.‭ ‬In light of this new discovery many of the palaeontologists who had supported the idea that Nanotyrannus was a new genus now switched to the idea that Nanotyrannus really was a juvenile of another‭ ‬genus,‭ ‬including Phil Currie and Michael Williams.‭ ‬Other palaeontologists still however think that Nanotyrannus‭ ‬deserves to be placed within its own genera because it is still different enough from other known forms.
       Initially Nanotyrannus was thought to be a juvenile tyrannosaurid‭ (‬possibly of Tyrannosaurus‭) ‬because of the large number of teeth that were present a study that showed a correlation between tyrannosaurids reducing the numbers of teeth as they aged.‭ ‬The problem with this study however is that it only supplied a few examples,‭ ‬and not only do some genera like Tarbosaurus show roughly the same amount of teeth between adults and juveniles,‭ ‬but other genera show a great discrepancy between the number of teeth present in individuals of the same age and genus.‭ ‬This is why teeth count is no longer considered a reliable identifying feature for age and genus.
       There only remains one feature that is present upon the Nanotyrannus holotype and the Jane specimen that may save Nanotyrannus as being a valid genus and this is a small pit in the quadratojugal at the back of the skull.‭ ‬This remains unknown in the specimens of other juvenile tyrannosaurids and is so far not present in any known adults.‭ ‬Unless this proves to be a feature that grew out as the animal reached adulthood it may become the identifying feature of the genus.