Leptaena, genus of extinct brachiopods
NEW YORK FOSSILS
The sedimentary rocks of New York also record of the history of life on the earth and its evolution. New York fossils range from Precambrian stromatolites older than 1.1 billion years old that are found in marbles (metamorphosed limestones) in the Adirondack Mountains to tracks of the dinosaur Coelophysis, preserved in approximately 200 million year-old Triassic sandstones. Fossils of ancient marine animals are widely found in Cambrian to Devonian rocks in New York. These include brachiopods (clam-like forms), trilobites (extinct arthropods), corals and coral reefs, the State Fossil, the eurypterid (another extinct arthropod related to horse shoe crabs) Eurypterus remipes, and numerous other forms. Many of these were first described by the illustrious New York State Paleontologist James Hall, in his classic volumes of the 19th century, "The Palaeontology of New York." New York's rocks also record the “conquest of the land,” with rocks in the Catskill Mountains preserving the earliest-known forests with some of the oldest land plants and animals.
All of these different types of fossils are found at many localities across the state, and are preserved in the Paleontology Collection of the New York State Museum, which has over a million fossil specimens (for more information see New York Paleontology).
Study of these fossils provides not only information about the animals and plants themselves when they were alive. It also sheds light onto marine and terrestrial ecosystems of the past, climate change, and the evolution of life in deep time. The early and continuing use of fossils is that they allow determination of the relative age of New York's sedimentary rocks and their correlation with rocks of the same age in other parts of North America and the world. One of the most important uses of fossils is in the determination of relative time, known as “biostratigraphy.” Biostratigraphy reflects the facts that evolution and extinction have taken place through geologic time, and particular organisms lived for only a tiny fraction of geologic time. Biostratigraphy does not tell how old sedimentary rocks are in actual years, but only allows the geologist to determine what part of a geologic period is represented by the sedimentary rock and its fossils. However, volcanic ashes that are present in New York rocks are now being dated by uranium-lead radiometric techniques, and an increasingly precise geochronology (i.e., the actual age of rocks) is being applied to the state’s rocks. With the ability to correlate rocks globally, New York geologists and paleontologists contribute to a better understanding of the impact of major events (for instance, mass extinctions, meteorite impacts, and sea level and climate change) in the history of the planet.