Crinoid

1. Schedexocrinus gibberellus
2. Parethelocrinus ellipticus
3. Stellarocrinus petalosus

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

Size: 7 cm crown for the Schedexocrinus

1. Back in 1961 when Strimple first described the Holdenville crinoids, he claimed this species to be "by far the most spectacular of the crinoids found" in this fauna, and it's not hard to see why. This is a pirasocrinid, which are members of the cladids that are almost exclusively of Pennsylvanian age. This specimen proudly showcases some of the classic pirasocrinid characteristics, such as a very shallow dorsal cup, axillary brachials produced as prominent spines, and most notably a remarkable "umbrella-like" or "mushroom-like" anal sac, which terminates above the arms as a wide platform surrounded by outwardly radiating spinose plates.