Dinosaur Tracks

The Dinosaur Track is Connecticut's official state fossil, designated in 1991. Eubrontes giganteus is the scientific name given to the tracks themselves, not to the animal that made them. The trackmaker was almost certainly a large theropod dinosaur. Because bones and tracks are rarely found together, the exact species that crossed this Connecticut mudflat 200 million years ago remains unknown.

Over 500 Eubrontes tracks are exposed at Dinosaur State Park in Rocky Hill, one of the largest dinosaur track sites in North America. The tracks were discovered in 1966 during excavation for a state building, and the site was quickly preserved rather than paved over.

Each Eubrontes giganteus track is three-toed and forward-pointing, about 15 inches long and 11 inches wide at the widest spread of the toes. The depth and size of the impressions suggest the trackmaker was roughly 15 to 20 feet long and walked on two legs. Multiple parallel trackways at the Rocky Hill site indicate a group of animals moving in the same direction, possibly along a riverbank or lake margin.

The tracks were pressed into soft mud near a body of water during the Early Jurassic, then buried quickly by sediment. Over millions of years, the mud lithified into the brownish-red sandstone and mudstone of the Portland Formation. When the rock eroded or was cut open, the tracks reappeared as depressions in the stone surface, preserving the exact footfall of the animal.

The name Eubrontes comes from the Greek for true thunder. The tracks are assigned to this ichnospecies based on their shape, size, and the pattern of the toes, not from any associated bones. Other ichnospecies from the same formation record smaller animals that shared the same river valley.

The scientific study of Connecticut Valley dinosaur tracks goes back nearly two centuries. Edward Hitchcock, a geologist and president of Amherst College, began collecting and cataloging tracks from the region in the 1820s and devoted much of his career to publishing detailed drawings and descriptions of the impressions. He amassed the largest collection of fossil tracks in the world at Amherst and published the definitive work on them in 1858.

Hitchcock spent his career convinced the tracks had been made by enormous ancient birds, not reptiles. The word dinosaur had only been coined in 1842, late in Hitchcock's career, and the classification of the trackmakers was not resolved until after his death in 1864. His work was still foundational: many of his ichnospecies names, including Eubrontes, are still used today.

The Rocky Hill discovery in 1966 brought national attention to Connecticut's track record. Workers excavating a site for a state building exposed a slab bearing over 500 tracks in excellent condition. The state halted construction and preserved the site. Dinosaur State Park opened in 1968, and in 1991 the legislature designated Eubrontes giganteus as Connecticut's state fossil.

Dinosaur State Park in Rocky Hill is the primary site. The park's main exhibit building was constructed over the exposed track surface to protect it from weathering. Visitors walk along an elevated platform above the actual tracks, which remain in the original rock. The park also has an outdoor area where visitors can make plaster casts from replica tracks during warmer months.

Eubrontes and other Early Jurassic tracks occur throughout the Connecticut River Valley, where the Portland Formation outcrops from New Haven County north into Massachusetts. Many tracks have been collected from road cuts, quarries, and riverbanks across this corridor over the past two centuries. Amherst College's Beneski Museum of Natural History holds Hitchcock's original collection, the largest assemblage of Jurassic dinosaur tracks from the Connecticut Valley.