Definitions

saurischian dinosaur

Grallator

Grallator is an ichnogenus representative of a bipedal theropod dinosaur which roamed the supercontinent Pangea in the Late Triassic and the Early Jurassic. The trackmaker likely resembled Coelophysis. The name Grallator translates into "stilt walker", although the actual length of its legs is unknown because the exact species of dinosaur that made the tracks has not been identified. The prefix "Grallae" refers to the group of birds that includes storks and herons. These footprints were given this name by their discover, Edward Hitchcock, in 1858.

Grallator footprints are three-toed (tridactyl) and range from 5 to 15 centimeters (or 2 to 6 inches) long. They are found in the United States, Canada and Europe but are most abundant on the east coast of North America (especially the formations of the northern part of the Newark Supergroup). Footprints in Australia have also been referred to Grallator. Though the tracks show only three toes, the trackmakers likely had five toes on their feet. Footprints show digits II, III and IV, but no trace of the shorter digits I and V. The outer two digits were stubby and ineffective, not touching the ground during walking or running. Despite losing most of their effectiveness, dinosaur evolution had not yet removed the these digits to fully streamline the foot. This is known because rare specimens are found with traces of these outer digits. Digits II, III and IV have 3, 4 and 5 phalanges respectively, giving Grallator a ?-3-4-5-? digital formula.

Although Grallator tracks were made by a bipedal saurischian dinosaur, they can easily be mistaken for those of the late Triassic ichnogenus Atreipus. The trackmaker of Atreipus prints was a quadrupedal ornithischian. The reason for this similarity is a lack of divergence in the foot evolution of the two distinct groups of dinosaurs: ornithischians and saurischians.

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