Nanotyrannus
- Name meaning: Dwarf Tyrant
- juvenile length: 5.5-6 m (17-20 feet)
- Estimated length: 7-8 m (23-26 feet)
- Estimated weight: 1-2.7 tons
- Estimated height: 2-2.7 m (7-9 ft)
- time period: 69.45-65 mya
- Habitat: North America
- Speed: 40+ mph
- bite force: 8000 psi
Nanotyrannus ("dwarf tyrant") is a potentially dubious genus of tyrannosaurid dinosaur. It is known only from two specimens (possibly three), which may in fact be juvenile specimens of the contemporary Tyrannosaurus rex.
Nanotyrannus is based on CMNH 7541, a skull collected in 1942 by David Hosbrook Dunkle and described by Charles W. Gilmore in 1946, who classified it as a new species in the tyrannosaur genus Gorgosaurus as G. lancensis. 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. Their 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, named Nanotyrannus for its apparently small adult size. The specimen is estimated to have been around 5.2 metres (17 ft) long when it died. However, a detailed analysis of the specimen by Thomas Carr in 1999 showed that the specimen was in fact a juvenile, leading Carr and many other paleontologists to consider it a juvenile specimen of Tyrannosaurus rex. In 2001, a more complete juvenile tyrannosaur (nicknamed "Jane", catalogue number BMRP 2002.4.1), belonging to the same species as the original Nanotyrannus specimen, was uncovered. This discovery prompted a conference on tyrannosaurs focused on the issues of Nanotyrannus validity, held at the Burpee Museum of Natural History in 2005. Several paleontologists who had previously published opinions that N. lancensis was a valid species, including Currie and Williams, saw the discovery of "Jane" as a confirmation that Nanotyrannus was in fact a juvenile T. rex. On the other hand, some, such as Peter Larson, continued to support the hypothesis that Nanotyrannus lancensis was a separate but closely related species. In 2015, Professor Phil Manning and Dr Charlotte Brassie of Manchester University studied Jane using a LIDARs canner, and using data and computer modelling, their reconstruction of body mass suggested that Jane had a 600 kg - 900 kg body mass, far lower than would be expected for a Tyrannosaurus. Also in 2015, Assistant Professor Holly Woodward Ballard of Oklahoma State University used Histology to examine a thin slice of Jane's femur. Counting the rings within Jane's bone material showed that Jane was 11 years old, and bone histology suggests that Jane was still growing.
Nanotyrannus probably filled up a niche in the ecosystem similar to that of a Cheetah's as it could run at speeds much higher than that of a Tyrannosaurus's due to its longer and more slender legs. It probably competed with Dakotaraptor for prey as they were very similar in size, so they would've had to compete with each other for food.
he primary differences that some scientists have used to distinguish Nanotyrannus lancensis from Tyrannosaurus rex primarily concern the number of teeth. Nanotyrannus had more teeth in its upper and lower jaws than an adult Tyrannosaurus. N. lancensishad 14-15 teeth in each side of the upper jaw (maxilla) and 16 teeth in each side of the lower jaw (dentary). T. rex, on the other hand, had 11-12 tooth positions in the upper jaw and 11-14 in the lower. The exact implications of this difference in tooth count has been controversial. In his 1999 study of tyrannosaurid growth patterns, Carr showed that, in Gorgosaurus libratus, the number of teeth decreased as the animal grew, and he used this data to support the hypothesis that N. lancensis is simply a juvenile T. rex. The team of scientists who studied growth in the related Tarbosaurus bataar found little to no decrease in tooth count as that species grew, even though they had juvenile specimens much younger than the Nanotyrannus specimens. These researchers also noted, however, that in both Tyrannosaurus and Gorgosaurus, there were significant differences in tooth count between individuals of the same age group, and that tooth count may vary on an individual basis not related to growth. A juvenile Tarbosaurus skull discovered in 2006 exhibits the same tooth count as do adult Tarbosaurus skulls, supporting the retention of Nanotyrannus as a distinct genus. Larson has also contended that, along with skull features, Nanotyrannus can also be distinguished from Tyrannosaurus by proportionally larger hands with phalanges on the third metacarpal and in the furcula morphology.
Nanotyrannus is based on CMNH 7541, a skull collected in 1942 by David Hosbrook Dunkle and described by Charles W. Gilmore in 1946, who classified it as a new species in the tyrannosaur genus Gorgosaurus as G. lancensis. 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. Their 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, named Nanotyrannus for its apparently small adult size. The specimen is estimated to have been around 5.2 metres (17 ft) long when it died. However, a detailed analysis of the specimen by Thomas Carr in 1999 showed that the specimen was in fact a juvenile, leading Carr and many other paleontologists to consider it a juvenile specimen of Tyrannosaurus rex. In 2001, a more complete juvenile tyrannosaur (nicknamed "Jane", catalogue number BMRP 2002.4.1), belonging to the same species as the original Nanotyrannus specimen, was uncovered. This discovery prompted a conference on tyrannosaurs focused on the issues of Nanotyrannus validity, held at the Burpee Museum of Natural History in 2005. Several paleontologists who had previously published opinions that N. lancensis was a valid species, including Currie and Williams, saw the discovery of "Jane" as a confirmation that Nanotyrannus was in fact a juvenile T. rex. On the other hand, some, such as Peter Larson, continued to support the hypothesis that Nanotyrannus lancensis was a separate but closely related species. In 2015, Professor Phil Manning and Dr Charlotte Brassie of Manchester University studied Jane using a LIDARs canner, and using data and computer modelling, their reconstruction of body mass suggested that Jane had a 600 kg - 900 kg body mass, far lower than would be expected for a Tyrannosaurus. Also in 2015, Assistant Professor Holly Woodward Ballard of Oklahoma State University used Histology to examine a thin slice of Jane's femur. Counting the rings within Jane's bone material showed that Jane was 11 years old, and bone histology suggests that Jane was still growing.
Nanotyrannus probably filled up a niche in the ecosystem similar to that of a Cheetah's as it could run at speeds much higher than that of a Tyrannosaurus's due to its longer and more slender legs. It probably competed with Dakotaraptor for prey as they were very similar in size, so they would've had to compete with each other for food.
he primary differences that some scientists have used to distinguish Nanotyrannus lancensis from Tyrannosaurus rex primarily concern the number of teeth. Nanotyrannus had more teeth in its upper and lower jaws than an adult Tyrannosaurus. N. lancensishad 14-15 teeth in each side of the upper jaw (maxilla) and 16 teeth in each side of the lower jaw (dentary). T. rex, on the other hand, had 11-12 tooth positions in the upper jaw and 11-14 in the lower. The exact implications of this difference in tooth count has been controversial. In his 1999 study of tyrannosaurid growth patterns, Carr showed that, in Gorgosaurus libratus, the number of teeth decreased as the animal grew, and he used this data to support the hypothesis that N. lancensis is simply a juvenile T. rex. The team of scientists who studied growth in the related Tarbosaurus bataar found little to no decrease in tooth count as that species grew, even though they had juvenile specimens much younger than the Nanotyrannus specimens. These researchers also noted, however, that in both Tyrannosaurus and Gorgosaurus, there were significant differences in tooth count between individuals of the same age group, and that tooth count may vary on an individual basis not related to growth. A juvenile Tarbosaurus skull discovered in 2006 exhibits the same tooth count as do adult Tarbosaurus skulls, supporting the retention of Nanotyrannus as a distinct genus. Larson has also contended that, along with skull features, Nanotyrannus can also be distinguished from Tyrannosaurus by proportionally larger hands with phalanges on the third metacarpal and in the furcula morphology.