Paleontology In Oklahoma

Paleontology in Oklahoma refers to paleontological research occurring within or conducted by people from the U.S. state of Oklahoma.
Oklahoma has a rich fossil record spanning all three eras of the Phanerozoic Eon. Oklahoma is the best source of Pennsylvanian fossils in the United States due to having an exceptionally complete geologic record of the epoch. From the Cambrian to the Devonian, all of Oklahoma was covered by a sea that would come to be home to creatures like brachiopods, bryozoans, graptolites and trilobites. During the Carboniferous, an expanse of coastal deltaic swamps formed in areas of the state where early tetrapods would leave behind footprints that would later fossilize. The sea withdrew altogether during the Permian period. Oklahoma was home a variety of insects as well as early amphibians and reptiles. Oklahoma stayed dry for most of the Mesozoic. During the Late Triassic, carnivorous dinosaurs left behind footprints that would later fossilize. During the Cretaceous, however, the state was mostly covered by the Western Interior Seaway, which was home to huge ammonites and other marine invertebrates. During the Cenozoic, Oklahoma became home to creatures like bison, camels, creodonts, and horses. During the Ice Age, the state was home to mammoths and mastodons. Local Native Americans are known to have used fossils for medicinal purposes. The Jurassic dinosaur '' Saurophaganax maximus'' is the Oklahoma state fossil.

Prehistory

Paleozoic

No Precambrian fossils are known from Oklahoma, and the state's fossil record begins in the Paleozoic. From the Cambrian to the Devonian, Oklahoma was covered by a sea. Cambrian life of Oklahoma included brachiopods, graptolites, sponges, and trilobites. Oklahoma's Ordovician life included several species of brachiopods, bryozoans, echinoderms, conodonts, and ostracods. Abundant remains are fossilized at Rock Crossing in the Criner Hills of southern Oklahoma. One common Oklahoman graptolite was ''Climacograptus''. High quality specimens of the trilobite ''Isotelus'' were preserved southwest of Ardmore. During the Silurian, Oklahoma was home to brachiopods, bryozoans, the trilobite ''Calymene'', echinoderms, and sponges, all of which are preserved south of Lawrence Creek. Oklahoma was home to an extremely diverse Devonian fauna in the Lawrence and White Mound areas.

During the Mississippian, Oklahoma's local fauna included ''Archimedes'', brachiopods, conodonts, echinoderms, the blastoid ''Pentremites'', and trilobites. Contemporary brachiopod families included the productids and rhynchonellida. The best source of Mississippian fossils in Oklahoma is the state's northeastern region. During the Carboniferous, Oklahoma was a terrestrial environment characterized by vast river systems and accompanying deltas. These deltas were home to vast swamps responsible for leaving behind many coal deposits. During the Carboniferous, early tetrapods left behind footprints that would later fossilize. Oklahoma's diverse Pennsylvanian life included blastoids, brachiopods, bryozoans, fusulinids, and pelecypods. Vertebrates included various fishes, and the early tetrapods likely responsible for the trackways. Occasionally during this period, sea levels would rise and cover the state again.

This sea gradually retreated from the state before the end of the Paleozoic era. Oklahoma preserves one of the richest fossil records of non-marine vertebrates from the Permian of North America with respect to both abundance of material and taxonomic diversity, with particularly notable records from early Permian sites such as Richards Spur in Comanche County and South Grandfield in Tillman County. Most of these deposits are distributed across the western half of the state, including in Logan, Noble, Grant, Garfield, Kay, Pawnee, and Payne Counties. In particular, there is extensive body fossil documentation of many groups of extinct vertebrates, including lungfish, various ' lepospondyls' like aïstopods, nectrideans, and ' microsaurs,' temnospondyl amphibians, parareptiles, eureptiles, reptiliomorphs (stem amniotes), synapsids, and diapsids. The giant Permian foraminiferan '' Pseudoschwagerina'' was preserved in the Pawnee area. Many of these tetrapods likely produced a variety of trackways also known from the early Permian of Oklahoma. There is also an extensive record of invertebrates, such as beetles and millipedes, as well as brachiopods and foraminifers.

It remains controversial whether there are any middle Permian tetrapods known from Oklahoma, which would represent perhaps the only such record from this time period in all of North America and perhaps the entire globe; if tetrapod records from the Chickasha Formation and the Flowerpot Formation in Blaine, Canadian, Grady, and Kingfisher Counties and their equivalents in Texas (the San Angelo Formation) are not considered to be middle Permian in age, there would be a hiatus in the fossil record, which is termed 'Olson's Gap,', although records from other geographic regions may fill this gap regardless of whether it existed in North America.

Mesozoic

Oklahoma was a terrestrial environment for most of the ensuing Mesozoic era. The Late Triassic Dockum Group of western Oklahoma preserved remains of archosaurs and temnospondyls, although its fossil record is restricted to a narrow region of the panhandle and is far sparser than the equivalent records in Texas, New Mexico, and Arizona. During the Late Triassic, small carnivorous dinosaurs left behind tracks near Kenton now classified in the ichnogenus ''Grallator''. The sediments preserving these tracks later became the Sheep Pen Sandstone. Other local tracks have been referred to ''Chirotherium'', but Martin G. Lockley and Adrian Hunt have speculated that these might actually be '' Pseudotetrasauropus''. The Late Jurassic fossiliferous Morrison Formation is exposed in the western part of the state and has produced extensive remains of sauropod dinosaurs. Most of Oklahoma was submerged under the Western Interior Seaway during the Cretaceous. Early Cretaceous life included "immense" ammonites, echinoids, and pelecypods. These fossils were preserved in Love and Marshall counties. The Late Cretaceous rocks of Bryan, Choctaw, and McCurtain counties bear abundant oysters like ''Exogyra'' and '' Ostraea''. However, there are also records of many terrestrial vertebrates, particularly from the Antlers and Cloverly Formations, including fish, amphibians, reptiles, crocodiles, dinosaurs, and mammals.

Cenozoic

As the Rocky Mountains rose during the early Cenozoic, rivers drained off them and into Oklahoma. Sediments deposited by these rivers would preserve petrified wood and mammal fossils. Sediments were generally being eroded away from Oklahoma during the later portion of the Cenozoic. The High Plains of the western part of Oklahoma preserve evidence for the presence of camels, creodonts, and horses during the Pliocene

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