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NANOTYRANNUS

a meat-eating albertosaurine theropod dinosaur from the Late Cretaceous of North America.
nanotyrannus.png
Pronunciation: NAN-o-ti-RAN-us
Meaning: Dwarf Tyrant
Author/s: Bakker et al. (1988)
Synonyms: See below
First Discovery: Montana, USA
Chart Position: 270

Nanotyrannus lancensis

Initially identified as a species of Gorgosaurus (Gorgosaurus lancensis) by Charles Whitney Gilmore four years after its 1942 discovery then informally tagged "Clevelanotyrannus" by Phil Currie in 1987, Nanotyrannus was given its current title by Robert T. Bakker, Michael Williams and Currie in 1988 based only on a skull from Montana's Hell Creek. "The skull bones are fused!" they said; "therefore, it represents an adult specimen." But paleontologists were split on whether it really belonged to a full grown "pygmy tyrant" or a juvenile specimen of the same area's most famous carnivore; Tyrannosaurus rex.

In 2001, a more complete "Nanotyrannus" specimen dubbed "Jane" did her bit to stir the pot, and as a result of later research, well, nothing changed. Jane had longer legs, a much more slender build, and a higher tooth count (60-62 compared to 44-52) than an adult T.rex, and a small, mysterious pit in the quadratojugal (a small bone involved with the jaw). Cross sections of a thighbone revealed annual growth rings under a microscope, just like those found in a tree, which showed that Jane was 11 years old when she died. Given that T.rex reach adulthood at around 20 years old it would take a monumental spurt for the 6.5 meter long, 700kg Nanotyrannus to double its length and pack on another six tons, even with its teenage years ahead. Nevertheless, every noted difference was smacked down as age-related by naysayers and a consensus regarding its validity was further away than ever. Even the original authors were riddled with doubt. Well, two of the three are.

It seems to us that the status of Nanotyrannus could have been settled one way or the other by a third specimen from Hell Creek. Assumed to have died as her pack attacked the as-yet unnamed, tooth-peppered ceratopsian corpse that she lay alongside, the catchily nicknamed "Bloody Mary" matches the other two Nanotyrannus individuals in size, rumour has it, and is almost complete from nose to tail tip. CT-scans and 3-d reconstructions of the skull revealed a slightly larger brain with very different blood vessel and optic nerve attachments compared to an adult T.rex, and despite a much more modest body size its arms, and, in particular, its clawed hands, were much bigger. Unfortunately, it was discovered by private collectors and has been hawked for many years as 50% of "the dueling dinosaurs" to drum up interest for auction, and because it isn't under the ownership of a Museum most paleontologists won't touch it with a bargepole. But there seemed to a breakthrough in 2015, when Joshua D. Schmerge and Bruce M. Rothschild studied the neovascular dentary groove (a groove in the lower jaw which contains pores) of 92 theropod dinosaurs and found Nanotyrannus to be a valid stand-alone critter, allied with the albertosaurines rather than tyrannosaurines. Obviously, paleontologists are queuing up to disagree.
Etymology
Nanotyrannus is derived from the Greek "nanos" (dwarf) and "tyrannos" (king) alluding to its apparently small adult size.
The species epithet (or specific name), lancensis, refers to its discovery in the upper "Lance Formation" which is now known as the Hell Creek Formation.
Discovery
The remains of Nanotyrannus were discovered in what is now the Hell Creek Formation at Sand Creek, Carter County, Montana, USA, by David Hosbrook Dunkle in 1942.
The holotype (CMNH 7541) is a skull which is currently housed at the Cleveland Museum of Natural History. Jane (BMRP 2002.4.1), whose sex is unknown—"she" was named after Burpee Museum benefactor Jane Solem—was also discovered in Montana's Hell Creek Formation.
Estimations
Timeline:
Era: Mesozoic
Epoch: Late Cretaceous
Stage: Maastrichtian
Age range: 67-66 mya
Stats:
Est. max. length: 6 meters
Est. max. hip height: 2 meters
Est. max. weight: 700 Kg
Diet: Carnivore
Synonyms
Gorgosaurus lancensis (Gilmore, 1946)
Deinodon lancensis (Gilmore, 1946)
Aublysodon lancensis (Gilmore, 1946)
Albertosaurus lancensis (Gilmore, 1946)
Tyrannosaurus lancensis? (Gilmore, 1946)
References
• C.W. Gilmore (1946) "A new carnivorous dinosaur from the Lance Formation of Montana".
• R.T. Bakker, M. Williams and P.J. Currie (1988) "Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana".
• Currie, Henderson, Horner and Williams (2005) "On tyrannosaur teeth, tooth positions and the taxonomic status of Nanotyrannus lancensis".
• Peter Larson (2005) "A case for Nanotyrannus" in "The origin, systematics, and paleobiology of Tyrannosauridae". A symposium hosted jointly by the Burpee Museum of Natural History and Northern Illinois University.
• Holtz, T.R. (2001) "The phylogony and taxonomy of the Tyrannosauridae" in Tanke and Carpenter "Mesozoic Vertebrate Life".
• Larson P (2013) "The validity of Nanotyrannus Lancensis (Theropoda, Lancian - Upper Maastrichtian of North America)". Society of Vertebrate Paleontology: 73rd annual meeting, Abstracts with Programs, p.159.
• Joshua D. Schmergea and Bruce M. Rothschild (2016) "Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988". Cretaceous Research 61: 26-33. doi:10.1016/j.cretres.2015.12.016
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To cite this page:
Atkinson, L. "NANOTYRANNUS :: from DinoChecker's dinosaur archive".
›. Web access: 27th Apr 2017.
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