Thursday, March 13, 2014

[Paleontology • 2014] Nanuqsaurus hoglundi • A Diminutive New Tyrannosaur from the Top of the World

Nanuqsaurus hoglundi Fiorillo & Tykoski 2014
 nearly 2 m. tall at the hips and 7 m. from snout to tail, about half the size of T rex.
Illustration: Karen Carr

Tyrannosaurid theropods were dominant terrestrial predators in Asia and western North America during the last of the Cretaceous. The known diversity of the group has dramatically increased in recent years with new finds, but overall understanding of tyrannosaurid ecology and evolution is based almost entirely on fossils from latitudes at or below southern Canada and central Asia. Remains of a new, relatively small tyrannosaurine were recovered from the earliest Late Maastrichtian (70-69Ma) of the Prince Creek Formation on Alaska's North Slope. Cladistic analyses show the material represents a new tyrannosaurine species closely related to the highly derived Tarbosaurus+Tyrannosaurus clade. The new taxon inhabited a seasonally extreme high-latitude continental environment on the northernmost edge of Cretaceous North America. The discovery of the new form provides new insights into tyrannosaurid adaptability, and evolution in an ancient greenhouse Arctic.

Figure 3. Nanuqsaurus hoglundi, holotype, DMNH 21461.
A. Reconstruction of a generalized tyrannosaurine skull, with preserved elements of holotype shown in white. Arrow points to autapomorphic, reduced, first two dentary teeth.
B–E. Photographs and interpretive line drawings of right maxilla piece in medial (B, C); and dorsal (D, E) views. F–I. Photographs and interpretive line drawings of partial skull roof in dorsal (F, G); and rostrolateral (H, I) views. J–M, partial left dentary in lateral (J); medial (K); dorsal (L) views; and close-up of mesial alveoli in dorsal (M) views.

Etymology: Nanuqsaurus, combination of ‘nanuq’ the Iñupiaq word for polar bear and the Greek ‘sauros’ for lizard; hoglundi, named in recognition of Forrest Hoglund for his career in earth sciences and his philanthropic efforts in furthering cultural institutions.

Theropod size comparisons, showing the newly discovered Nanuqsaurus hoglundi (A), Tyrannosaurus rex (B and C), Daspletosaurus torosus (D), Albertosaurus sarcophagus (E), Troodon formosus (F), and Troodon sp. (G).
Scale bar equals 1 metre | Doi: 10.1371/journal.pone.0091287

Anthony R. Fiorillo and Ronald S. Tykoski. 2014. A Diminutive New Tyrannosaur from the Top of the World. PLoS ONE. 9 (3): e91287.

Pygmy tyrannosaur roamed the Arctic
Newly discovered cousin of T rex, Nanuqsaurus hoglundi, inhabited an Arctic island continent around 70m years ago via @guardian