Crinoid

Texacrinus coniformis

• Pennsylvanian
• Holdenville Formation
• Okmulgee County, Oklahoma, USA

Size: 8 cm crown

Here is a crinoid from one of my favorite crinoid localities. Texacrinus coniformis, as the species name suggests, is characterized by its particularly sharply conical cup for the genus. It also displays long, snaking, exotomously-branched arms, and the unusually-shaped radial facet-primibrachial junction occupies just a portion of the radial plates. Strimple 1961 mentioned the radial facet width to be a highly variable character within the species. However, I notice the Sam Noble Museum of Oklahoma currently names the original holotype for T. coniformis, which has primibrachials and radial facets about as wide as the radial plates, as T. californius. It is possible that there has been some species splitting or reassignment based on this trait or others since Strimple's work.