Dinosaur Footprints in Holyoke, Massachusetts, USA is an 8-acre (3 ha) park and wilderness reservation purchased for the public in 1935. The reservation is owned by the Trustees of Reservations and is currently managed by the Massachusetts Department of Environmental Management.
As the name implies, fossilized footprints are this park's main attraction. They were formed during the Late Triassic and Early Jurassic eras when what is now the Connecticut River Valley was a subtropical region filled with lakes and swamps. Bipedal, carnivorous dinosaurs up to 15 feet (5 m) tall and more than 20 feet (6 m) long left footprints in the ancient mudflats. These tracks were fossilized and largely hidden until many were unearthed by the construction of what is now U.S. Route 5. The area was acclaimed by 19th century paleontologists for its abundance of fossil specimens, dinosaur tracks in particular, and the reservation is popular with the ichnologists that study them. There are 134 separate dinosaur footprints in the sandstone beds of the Connecticut River.
This area was studied by Edward Hitchcock, the Amherst College professor who advanced the revolutionary notion that rather than being cold-blooded reptiles, dinosaurs were more like a sort of "reptilian bird." In the 1930s, a Springfield, Massachusetts newspaper poked fun at this notion by referring to the animals that left the fossilized footprints as "the Giant Turkeys of Prof. Hitchcock."
Smith College professor William J. Miller wrote in his Geological History of the Connecticut Valley of Massachusetts:
The largest numbers by far have been found at various localities in the general direction of Turner's Falls and South Hadley. In regard to the perfect preservation of such a vast number of geologically ancient animal tracks no district in the world is at all comparable with the Connecticut Valley ... In one case the writer is able to step, with a stride of about three and a half feet, in a series of eleven footprints, each about a foot long, exactly where a giant dinosaur left his foot print impressions on the original surface.
According to more recent analysis by Yale University researchers, the fossilized footprints on the reservation come from three related species of dinosaurs. The smallest of the dinosaurs, the Theropod Grallator cuneatus, left footprints 3 inches (76 mm) to 5 inches (127 mm) long. From 6 inches (152 mm) to 8 inches (203 mm) long, the tracks of the Prosauropod Anchisauripus sillimani are larger. Eubrontes giganteus, the largest of the three, left footprints 11 inches (279 mm) to 13 inches (330 mm) long. Close analysis of these fossil trackways led to the conclusion that the dinosaurs were gregarious and traveled in a "herd, pack, or flock."
A short boardwalk leads from the reservation entrance to the footprints. Besides the clearly-formed dinosaur tracks, visitors can see imprints left by prehistoric plants and the delicate ripple marks of an ancient pool preserved in stone near the river's west bank. Fossils in situ are located not only in the reservation itself, but on other land including a riverfront parcel owned by Holyoke Gas and Electric and managed cooperatively with the Trustees of Reservations and the Commonwealth. There is also a place to see dinosaur tracks in nearby South Hadley, Massachusetts.