''Gymnophyllum wardi'', commonly known as button coral, is an extinct

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

from the

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the International Commission on Stratigraphy, ICS geologic timesca ...

part of the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

period. The fossils are found in relatively few places worldwide; most specimens are known from the upper part of the Wewoka formation in and around Lake Okmulgee in Okmulgee State Park or the adjoining

Dripping Springs State Park Dripping Springs Park is located in Okmulgee County, Oklahoma, near the city of Okmulgee, Oklahoma. Previously Dripping Springs State Park, the lake and park are now owned by Okmulgee, and are approximately south of the city.Okmulgee County Okmulgee County is a county in the U.S. state of Oklahoma. As of the 2010 census, the population was 40,069. The county seat is Okmulgee. Located within the Muscogee Nation Reservation, the county was created at statehood in 1907. The name O ...

Oklahoma Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...

in the United States. ''G. wardi'' was first described by B.F. Howell in 1945, and is the only species in the genus ''Gymnophyllum''. Many specimens of ''G. wardi'' are known, ranging in age from very young and immature to very old individuals. The individuals are described as "flat disclike solitary

corallite A corallite is the skeletal cup, formed by an individual stony coral polyp, in which the polyp sits and into which it can retract. The cup is composed of aragonite, a crystalline form of calcium carbonate, and is secreted by the polyp. Corallit ...

s", with exposed

septa The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five coun ...

almost everywhere on the base, though not at the peduncle in the center, which is depressed. The top of the coral disc has a "large smooth axial area" and shorter septa. The youngest individuals have long septa, which can be somewhat crooked; the axial center has a deep fossula which contains the cardinal septum, which is thick and short. Older corals have a large axial area with the cardinal fossula and projecting septa at their edges, making them appear like a "toothed wheel". In mature specimens, the fossula has almost disappeared and the top axial area is smooth and wide with septa that project slightly starting outside this area, and continuing almost to the basal peduncle, which is small. The oldest specimens are flat, have "short deformed septa" and no fossula, but do have a theca between the basal septa. Some specimens consist of two corralites joined together. All of these physical characteristics are similar to those of some other fossil coral species, like '' Hadrophyllum orbignyi''. ''G. wardi'' and other similar fossil corals may even have been able to move along the sea floor or right themselves if tipped over. Samples of ''G. wardi'' can be in diameter. They are found in outcrops of

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

from the Wewoka formation, and may be collected along the shores of Lake Okmulgee by getting in the shallow water, "washing the edge with a container of water, and watching carefully for little discs freed from the sediment". The

University of Kansas The University of Kansas (KU) is a public research university with its main campus in Lawrence, Kansas, United States, and several satellite campuses, research and educational centers, medical centers, and classes across the state of Kansas. Tw ...

Biodiversity Research Center has a large collection of fossils. Park rangers have discouraged fossil collection in the park; fossils are on display in the park's shop and are available for sale from some dealers.

References

{{Taxonbar, from=Q5624696 Stauriida Prehistoric Hexacorallia genera Pennsylvanian animals