Partial .8" Tyrannosaur (Nanotyrannus?) Tooth - North Dakota

This is a .8" long, partial Tyrannosaur tooth from the Hell Creek Formation of North Dakota. Many people would label a tooth like this as coming from Nanotyrannus lancensis, but there is a very contentious and ongoing debate as to whether this is a distinct species, or whether it represents a juvenile Tyrannosaurus rex

It comes in an acrylic display case.

One face of the tooth is nicely preserved, while the other side is completely chipped away.

Acheroraptor temertyorum was described in 2013 from upper and lower jaw bones that contained teeth. The teeth have been known for decades, but no diagnostic material had been recovered. Acheroraptor lived in the Cretaceous period 67-66 million years ago and was relatively large for a raptor and surprisingly more closely resembled asian velociraptors than other North American Dromaeosaurs.

Smaller theropods like Velociraptor typically did not use their teeth for killing and so their teeth are much smaller in size in relation to their skulls when compared to larger therapods that used their teeth as the primary killing tool.

Acheroraptor teeth are like tiny, slightly curved daggers with rounded serrations with the posterior serrations being larger than the anterior. The most distinguishing feature are apicobasal ridges, ridges running from the base of the tooth to the apex.

Many of the raptor teeth found in the Hell Creek Formation show morphological differences that are often attributed to taxon from other formations of different ages. Among those are Saurornitholestes, Richardoestesia gilmorei, Richardoestesia isosceles, and Paronychodon. Remains of all of these species are fragmentary and some known only from teeth and there is no evidence they lived in the Hell Creek Formation.

The 2013 study found that Acheroraptor was the only dromaeosaurid from the Hell Creek Formation and concluded that dromaeosaurid teeth that had been attributed to other taxa should be identified as Acheroraptor. Any other identification is not supported scientifically until associated skeletal remains are found to indicate otherwise

Because of its age and sedimentary composition, the Hell Creek Formation has become one of the most paleontologically studied areas in the world. 158 genera of animals and 64 genera of plants are known from the formation and new discoveries are made frequently. In addition to Tyrannosaurs, Ceratopsids, and Hadrosaurs, the formation has yielded remains of amphibians, reptiles, lizards, snakes and turtles, fish and sharks, avian and non-avian dinosaurs, and mammals. The Hell Creek Formation gives the most complete understanding of the environment just before the Cretaceous-Paleogene extinction.
Nanotyrannus lancensis & Tyrannosaurus rex
Bowman County, North Dakota
Hell Creek Formation
.8" long (straightline measurement)
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