Nanuqsaurus

Nanuqsaurus (meaning "polar bear lizard") is a genus of tyrannosaurine theropod dinosaur. This fascinating creature lived during the Late Cretaceous period, specifically during the latest Campanian age, in what is now the North Slope of Alaska. The only known species, Nanuqsaurus hoglundi, was discovered from a partial skull along with several other bone pieces that have not yet been fully described. Nanuqsaurus gives us important clues about life in the cold, far-north regions of the ancient world, showing that large meat-eating dinosaurs could survive in chilly climates.

Discovery and naming

Before scientists described Nanuqsaurus, many teeth from the Prince Creek Formation in Alaska were thought to belong to other dinosaurs called Gorgosaurus or Albertosaurus. Later, when scientists learned the rocks were younger than they first thought, they changed their minds about which dinosaur the teeth belonged to.

In 2006, scientists found the remains of a medium-sized dinosaur in Alaska. They found pieces of its skull, such as parts of the nose, forehead, and jaw. These pieces helped scientists estimate that the dinosaur’s skull was about 600–700 mm long (24–28 in). After studying these pieces at the Perot Museum of Nature and Science, scientists realized they had found a new kind of dinosaur. They named it Nanuqsaurus.

The name Nanuqsaurus comes from the Iñupiaq word for "polar bear," nanuq, and the Greek word sauros, meaning "lizard." The species name, hoglundi, honors Forrest Hoglund for his support of cultural institutions.

Description

Nanuqsaurus was a type of dinosaur that lived a very long time ago. At first, scientists thought it was about 5–6 meters (16–20 feet) long, but later they found more fossils. Now, they believe Nanuqsaurus was probably closer in size to other big dinosaurs, maybe around 7 meters (23 feet) long. It likely had feathers to stay warm in cold places.

Nanuqsaurus probably looked similar to other big dinosaurs called tyrannosaurines. It had special features in its skull that help scientists tell it apart from other dinosaurs.

Classification

Nanuqsaurus is closely related to Daspletosaurus and Tyrannosaurus. Scientists use special diagrams to show how these dinosaurs are connected to each other.

Some recent studies say it is hard to know exactly where Nanuqsaurus fits in, and another study found it to be closely related to a dinosaur called Asiatyrannus from South China. These connections are shown in another diagram.

cladogram

Paleobiology

Reproduction at polar latitudes

Studies of fossils from Nanuqsaurus and other dinosaurs in the Prince Creek Formation show that many young dinosaurs lived there. These fossils come from seven major groups, including birds, Hadrosauridae, Thescelosauridae, Leptoceratopsidae, Ceratopsidae, Tyrannosauridae, Dromaeosauridae, Troodontidae, and Avialae. This means that Nanuqsaurus and the dinosaurs it may have eaten stayed in the Arctic all year, even during the dark winter months. Scientists think these dinosaurs probably laid their eggs in the spring, when there was constant daylight, so the eggs could warm up and hatch.

Paleoecology

Nanuqsaurus lived alongside many other dinosaurs during a time called the Edmontonian faunal stage. It lived in a very cold place, near the North Pole, with average temperatures just above freezing.

Other animals that lived with Nanuqsaurus include different types of dinosaurs like Edmontosaurus, Pachyrhinosaurus perotorum, Alaskacephale, Dromaeosaurus, and Saurornitholestes, as well as some early mammals such as Unnuakomys, Gypsonictops, and Cimolodon. Because of the cold weather, many cold-blooded animals did not live there, suggesting that the animals that did live there could keep warm.