Nanotyrannus Teeth

Nanotyrannus lancensis is a controversial "pygmy" tyrannosaurid from the Maastrichtian aged Hell Creek and Lance Formation in the United States. The current consensus of many paleontologists and non-collector enthusiasts is that Nanotyrannus is not a valid taxon, but represents juvenile individuals of the famous Tyrannosaurus rex.

Nanotyrannus, if valid, was likely a medium tyrannosaurid similar in size to Gorgosaurus based on isolated teeth. Amongst private collectors, Nanotyrannus is largely associated with teeth that have a distinct cross-section with a pinch that gives it a hourglass or peanut-like shape. These teeth can be quite large with no evidence of transitional forms between Nanotyrannus and Tyrannosaurus. This of course does not validate Nanotyrannus as a genus as the onus lies with the holotype. These teeth could very well belong to a distinct genus or species regardless of the validity of Nanotyrannus.

The image above shows an example of a typical Nanotyrannus tooth morphology with the pinched cross-section commonly attributed to the genus.

For collectors, a major factor in properly distinguishing the morphologies is the price. True diagnostic teeth of Tyrannosaurus rex can easily be 5-10 times more expensive than Nanotyrannus (and other contemporary theropods).

It has not been made clear if these teeth are also found in the Ojo Alamo Formation in New Mexico, and the Scollard Formation in Alberta, Canada. At the very least, no papers (to our knowledge) have been published on Nanotyrannus morphology from these locales, and unfortunately, material from these locales are very rare to private collectors for any comparisons to be made.