Leptanea (Dalman 1828) is a flat, Strophomenid type shell that develops a defined lip. This prolific and long lived genera is easily recognizable and can be found in rocks from the Ordovician through the Carboniferous. The specimen shown below is possibly L. acuticuspidata based on the book "Stratigraphy and Paleontology of the Hunton Group in the Arbuckle Mountain Region" 1958 Thomas Amsden and Arthur Boucot, Oklahoma Geological Survey, Bulletin 78 pgs:83-88.
This specimen came from an old estate collection of fossils that were collected in the 1960's to 1970's from the Haragan Formation at White Mound, OK. The Haragan formation is thought to range from the upper Silurain, 418mya, to the lower Devonian, 411mya ( Pridoli to Lochkovian). This would correspond to the Birdsong shale of Tennessee and the Helderberg Fauna of New York, Pennsylvania and Maryland.