''.
Paleozoic No
Precambrian fossils are known from Oklahoma, and the state's fossil record begins in the
Paleozoic. 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. Oklahoma's diverse
Pennsylvanian life included blastoids, brachiopods, bryozoans,
fusulinids, and
pelecypods. and the early tetrapods likely responsible for the trackways. Occasionally during this period, sea levels would rise and cover the state again. 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. 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. 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. Most of Oklahoma was submerged under the
Western Interior Seaway during the Cretaceous. s by
Charles R. Knight.
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. Their fossils were preserved in several different regions of Oklahoma. Typical Oklahoman
proboscidean fossils are teeth and tusks, often preserved in gravel pits, but complete skeletons are also known. ==History==