'' During the Precambrian New Jersey was covered in seawater. The activities of contemporary local bacteria formed stromatolites in those waters. During the Cambrian period of Paleozoic era New Jersey was still inundated by seawater.
Cambrian life left behind few fossils in New Jersey. Among the Cambrian fossils that are present were
brachiopods and
trilobites. Stromatolites continued to form in the local area. During the ensuing Ordovician period the seas deepened. Like the Cambrian,
Ordovician life also left little evidence for paleontologists to interpret in New Jersey. Ordovician fossils include
corals,
sponges, and trilobites. Northern New Jersey was home to a river system during the Silurian. As time went on local sea levels rose and fell so the area alternated between a riverside or marine environment. In contrast to the Ordovician,
Silurian fossils were preserved in abundance near
Clinton. During the Late Silurian the area remained submerged by the shallow sea through the Devonian. The local sea was inhabited by creatures like brachiopods, bryozoans, corals, and crinoids. Local sediments were being eroded away rather than deposited from the Carboniferous to the Permian, so there are no rocks of this age in which fossils could have been preserved. During the Triassic, New Jersey was experiencing geologic upheaval caused by the breakup of Pangaea. Rifts formed in the state as the supercontinent was being disassembled. Water filled these rifts and created large lakes. Local reptiles would sometimes be preserved in the sediments of these lakes. During the
Triassic, local
dinosaurs left behind
footprints that would later fossilize. Other Triassic life included the
coelacanth Diplurus, which fossilized by the hundreds, and the
crustacean Cyzicus, which also left behind abundant fossils.
Cycads were significant members of the state's fossil
flora. In the Jurassic, Pangaea was still breaking up. Lava flows formed in New Jersey during the Jurassic. Local dinosaurs left behind footprints that would later fossilize. During the ensuing Cretaceous period the southern part of New Jersey was submerged under seawater. Invertebrate remains are the state's most common
Cretaceous fossils. Invertebrates that lived in New Jersey during the Cretaceous include the
oysters Exogyra ponderosa and
Gryphaea. Others include
mollusks and the tubular
trace fossil Halymenites major. Cephalopods were also present. More than fifty different vertebrate species from this time have been found in New Jersey.
Shark teeth are relatively common, but
bony fish remains are rare. Among the local fishes were sharks and rays. These were generally more abundant in Cretaceous New Jersey than they were at the same time in the
Seaway of the western US. The
swordfish-like bony fish
Protosphyraena has been preserved in the
Navesink Formation. The turtle
Bothremys also lived in New Jersey during the Cretaceous. Other local marine vertebrates included
plesiosaurs and
mosasaurs. Occasionally fossil footprints dating back to this age are found. Few plant fossils are known in New Jersey from this time. Northern New Jersey, in contrast to the state's southern half, was dry land. A rich flora grew in the state at the time. Local plants left behind leaves that would later fossilize. Local insect life also left behind fossils.
Dinosaurs inhabited the region in forests and swamps, such as
ornithopods like
Hadrosaurus, and theropods like
Dryptosaurus,
"Coelosaurus" antiquus, and
Dromaeosaurs, as well as
birds. In addition, there were many other reptiles found, most notably crocodilians like
Deinosuchus and
Thoracosaurus. They left behind both footprints and bones. During the Tertiary period of the ensuing Cenozoic era the local New Jersey climate was warmer than it is today. Southern New Jersey remained inundated by seawater. Brachiopods, corals, echinoderms, and sharks lived there. On land, there were at least 8 kinds of
Eocene bird in New Jersey.
Miocene life in New Jersey included a brachiopod, a crustacean, more than 60
pelecypods and more than forty
gastropods. During the Quaternary northern New Jersey was covered by glaciers. Local sea levels rose and fell in time with the melting or expansion of the glaciers.
Pleistocene deer, fish, and whale fossils have been found under the
marshes of
Atlantic and
Cape May Counties.
Mastodons living in New Jersey left behind remains in places like
Mannington Township and the region between
Hackettstown and
Vienna. Even areas off the Atlantic coast bear mastodon remains. Mammoths also inhabited the state. ==History==