Wednesday, December 15, 2010

Therizinosaur—Mystery of the Sickle-Claw Dinosaur

How did this dinosaur get buried in mud at the bottom of the Cretaceous Western Interior Seaway? One hypothesis: Lost at sea, perhaps swept away by winds or change in currents, flailing about to protect itself from plesiosaurs and sharks until it could no longer stay afloat. An alternate hypothesis: Bloat and float. Illustration by Victor Leshyk.

Mounted skeleton of Nothronychus, the sickle-claw dinosaur from the Tropic Shale of southern Utah. The small head, tiny teeth, massive claws on the hands, expansive belly, broad hips, and short tail distinguish this dinosaur from all of its carnivorous relatives. Height as mounted is about 8 1⁄2 feet, but would be 13 feet tall in a more erect posture.

Reconstruction of Nothronychus on land. Although volcanoes are a cliche in dinosaur art, volcanic ash in the Tropic Shale indicates proximity of tectonic activity on land where these dinosaurs lived. Several Pteranodon soar safely overhead. Illustration by Victor Leshyk.

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