Advanced cladid crinoids from the middle Mississippian of the east-central United States: advanced-grade calyces

Abstract

Species of the late Osagean and early Meramecian advanced cladid crinoid genera (suborder Poteriocrinina) Adinocrinus, Eratocrinus, Lekocrinus n. gen., Linocrinus, Sarocrinus, and Worthenocrinus n. gen. from Illinois, Indiana, Iowa, Kentucky, and Missouri are redescribed and redefined from study of type material and museum collections. These species are considered to have advanced-grade calyces because of the substantial size reduction of the infrabasals and basals relative to the radials. Nomenclatural and systematic changes include the following: 1) Eratocrinus coxanus (Worthen, 1882) is a senior synonym of Zeacrinus keokuk Worthen, 1882; 2) E. commaticus (Miller, 1891a) is a senior synonym of Z. blairi Miller and Gurley, 1895; 3) Lekocrinus n. gen. is described and Scaphiocrinus divaricatus Hall, 1860, and Z. planobrachiatus Meek and Worthen, 1860, are assigned to this new genus; 4) Linocrinus praemorsus (Miller and Gurley, 1890a) is a senior synonym of Poteriocrinus lautus Miller and Gurley, 1896; 5) Sarocrinus kirki n. sp. is described; 6) P. varsoviensis Worthen, 1882, is assigned to Sarocrinus and is a senior synonym of P. tentaculatus Worthen, 1883, P. granilineus Miller and Gurley, 1890a, Z. pocillum Miller, 1891b, S. nitidus Kirk, 1942, and S. plenus Kirk, 1942; 7) P. asperatus Worthen, 1882, is assigned to Sarocrinus; 8) Worthenocrinus n. gen. is described and W. paterus n. sp. is assigned to this new genus; 9) Poteriocrinus iowensis Worthen, 1882, is considered a nomen dubium and placed in incertae sedis.