Fossils from the USA

The United States is one of the most fossil-rich countries in the world, with an enormous number of important sites across almost every geological period. This is a very short overview — many excellent localities are not mentioned here.

The Agate Fossil Beds National Monument, in Nebraska, is known for its well-preserved Miocene mammals, including relatives of pigs, horses, and rhinocerases.

Beecher’s Trilobite Bed, in New York, is famous for its pyritised trilobites from the Ordovician. The preservation is exceptional, with fine details often visible, and it remains one of the most important soft-tissue trilobite sites in the world.

Brule Formation, mostly exposed in the Great Plains, is part of the White River Group and preserves Oligocene terrestrial vertebrates — a key unit for fossil mammals.

Calvert Cliffs State Park, in Maryland, is a Miocene marine deposit. Shark teeth, cetacean bones, and molluscs are commonly found in the eroding cliff faces.

Dinosaur State Park, in Connecticut, features an impressive collection of Early Jurassic dinosaur tracks, preserved in a sandstone surface from the Newark Supergroup.

Dinosaur Valley State Park, part of the Glen Rose Formation in Texas, preserves excellent Cretaceous dinosaur tracks. These can be seen along the riverbed.

The Green River Formation, spread across Wyoming, Colorado, and Utah, is one of the most important Eocene Lagerstätten in North America. It is best known for exquisitely preserved fossil fish — including Knightia, Diplomystus, and Priscacara — but also yields birds, insects, plants, and reptiles.

The Hell Creek Formation, spanning parts of Montana, the Dakotas, and Wyoming, is one of the most iconic Late Cretaceous deposits. It contains dinosaurs like Tyrannosaurus, Triceratops, and a wide range of plants and mammals. It is also well known for preserving the K-Pg boundary.

The La Brea Tar Pits, in Los Angeles, are a classic Pleistocene site. Thousands of Ice Age mammals — including mammoths, sabre-toothed cats, and dire wolves — have been pulled from the asphalt seeps.

The Mazon Creek fossil beds, in Illinois, are known for their Carboniferous fossils preserved in ironstone concretions. Both flora and fauna are found, including the famous Tullimonstrum.

The Morrison Formation, from the Late Jurassic, is probably the best-known dinosaur-bearing unit in the US. It spans several states and contains famous taxa like Stegosaurus, Allosaurus, Apatosaurus, and Diplodocus.

The Parker Slate, in Vermont, is Cambrian in age and has yielded trilobites and other invertebrates. Fossils are not especially common but do occur in some exposures.

The Poleta Formation, in Nevada, is Cambrian and known for its exceptional preservation of trilobites and other early marine life, often compared to the Burgess Shale.

The Rochester Shale or Clinton Group, from the Silurian of New York, preserves diverse marine invertebrates, particularly crinoids, trilobites, and brachiopods. Fossils from here are typically very well preserved and sought after by collectors.

The Spencer Shale, in Tennessee, is known for well-preserved Cambrian trilobites, often found in association with brachiopods and other marine invertebrates.

The Wheeler Shale, in Utah, is another Cambrian Lagerstätte. It is especially well known for trilobites, particularly Elrathia kingii, which is widely collected.

These sites cover only a small part of the fossil heritage of the United States, and many other formations and fossil localities — from Florissant to Oligocene mammal sites in the Dakotas — have been left out for brevity.

The US also has thousands of acres of petrified wood forest, and areas where petrified wood can be found – coastal sites in North Carolina, South Carolina and Florida can yield Megalodon and other fossil sharks teeth.

Spirifer and other winged brachiopods seem to be reasonably common finds in various areas, too.

United States of America