Which Dinosaurs and Prehistoric Animals Lived in Pennsylvania?

Learn What's Been Revealed Through Footprints and Fossils

Phacops trilobyte

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Pennsylvania can be a frustrating state for dinosaur lovers: Although tyrannosaurs, raptors, and ceratopsians undoubtedly tramped across its vast hills and plains during the Mesozoic Era, they have left only scattered footprints rather than actual fossils. Even still, the Keystone State is famous for its numerous fossils of invertebrates and non-dinosaur reptiles and amphibians, as described in the following slides.

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If the name Fedexia strikes you as a bit odd, that's because this 2-foot-long, 5-pound prehistoric amphibian was discovered near a Federal Express depot at Pittsburgh International Airport. Initially, its tiny skull was mistaken for a fossilized plant. Vaguely reminiscent of an overgrown salamander, Fedexia probably subsisted on the small bugs and land animals of the late Carboniferous swamps in which it lived, about 300 million years ago.

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Rutiodon, the "wrinkle tooth," was a late Triassic phytosaur, a family of prehistoric reptiles that superficially resembled crocodiles. At about 8 feet long and 300 pounds, Rutiodon would have been one of the apex predators of its ecosystem, which ranged across the Eastern seaboard (specimens have been discovered in New Jersey and North Carolina, as well as Pennsylvania). Oddly enough, the nostrils of Rutiodon were located right next to its eyes, rather than at the tip of its snout.

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Long considered to be the first true amphibian (an honor to which it may or may not be entitled), Hynerpeton retained some features reminiscent of the lobe-finned fish (and earlier tetrapods) from which it evolved, including multiple-toed feet and a noticeable fin on its tail. This late Devonian creature's greatest claim to fame may be that its type fossil was discovered in Pennsylvania, not otherwise considered a hotbed of paleontology. 

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The plant-eating Hypsognathus ("high jaw") was one of the few anapsid reptiles to survive into the Triassic period from the preceding Permian; most of these prehistoric reptiles, which were characterized by the lack of certain holes in their skulls, went extinct about 250 million years ago. Today, the only surviving anapsid reptiles on Earth are turtles, tortoises, and terrapins, many of which can still be found in Pennsylvania.

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The official state fossil of Pennsylvania, Phacops was a common trilobite (three-lobed arthropod) of the Silurian and Devonian periods, about 400 million years ago. The persistence of Phacops in the fossil record can be partially explained by the tendency of this invertebrate (and other trilobites) to roll up into a well-protected, near-impenetrable armored ball when threatened. Sadly, Phacops and its trilobite cousins went extinct during the Permian-Triassic Extinction 250 million years ago.

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Dinosaur Footprints

The dinosaur footprints of Pennsylvania preserve a unique moment in geologic history: the late Triassic period, when the earliest dinosaurs had only recently reached (what would later become) North America from their home grounds in (what would later become) South America. A particularly rich source of footprints and track marks has been, of all places, the battlegrounds of Gettysburg in southern Pennsylvania, which were populated by various chicken-sized dinosaurs over 200 million years ago.

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Strauss, Bob. "Which Dinosaurs and Prehistoric Animals Lived in Pennsylvania?" ThoughtCo, Aug. 28, 2020, thoughtco.com/dinosaurs-and-prehistoric-animals-of-pennsylvania-1092096. Strauss, Bob. (2020, August 28). Which Dinosaurs and Prehistoric Animals Lived in Pennsylvania? Retrieved from https://www.thoughtco.com/dinosaurs-and-prehistoric-animals-of-pennsylvania-1092096 Strauss, Bob. "Which Dinosaurs and Prehistoric Animals Lived in Pennsylvania?" ThoughtCo. https://www.thoughtco.com/dinosaurs-and-prehistoric-animals-of-pennsylvania-1092096 (accessed June 5, 2023).