Crinoid

n. gen. n. sp.

• Permian
• Moran Formation
• Woodson, Texas, USA

Size: 9 cm crown

This is a Permian-aged crinoid crown from Texas and one of my most unusual fossils. According to Peter Holterhoff the upflared infrabasal plates and resulting urn-like calyx suggest assignment to the genus Ulocrinus. However, according to Georgy Mirantsev the 16 biserial arms (with four arms on the A, C and D rays) suggest closer affinity to the genus Parulocrinus. Overall this is quite an odd specimen that exhibits a combination of traits from both genera. Dr. Holterhoff believes it to have evolved either from Ulocrinus (which has 10 biserial arms) by developing >10 arms, or from a 16-armed cromyocrinid with a typically flat-to-concave base by reverting to a "primitive" urn-like calyx. In any case it does not seem to fit any pre-existing definitions and appears to be a new genus of Permian crinoid. One might informally call it something like "Neoulocrinus", given the crinoid's affinities and young age in relation to them.