Crinoid pluricolumnal noditaxis patterns

Heteromorphic crinoid stems show repetitive patterns in the arrangem nodal and internodal columnals' Four major types of patterns are defined based on the highest order internodals present. Type I consists of nodals and priminternodals; Type II contains nodals, priminternodals and secundinternodals; Type III nodals, priminter- nodals, secundinternodals and tertinternodals; and Type IV nodals, priminternodals, secundinternodals, tertinternodals and quartinternodals. At least 23 subtypes may be de- fined based on the repeated arrangement of the internodals. Types I and II are by far the most common and include all known subtypes. Pattern formulae are based on abbrevia- tions for the nodals and internodals present in each pattern type. Types II, III and IV are the most complex and may be polyphyletic in origin. Flexible and articulate crinoids are not known to have pattern Types III and IV. Camerate and inadunate crinoids contain representatives of all four pattern types.