Crinoids From the Nada Member of the Borden Formation (Lower Mississippian) in Eastern Kentucky

Abstract

Thirty-four crinoid species, including four new species, are reported from the Nada Member of the Borden Formation in eastern Kentucky. The dominant crinoid group is monobathrids (18 species), but diplobathrids, disparids, cladids, and flexibles are also present. The four new species are the camerates Blairocrinus protuberatus, Uperocrinus acuminatus, and Aorocrinus nodulus, and the cladid Atelestocrinus kentuckyensis. The majority of the species in this fauna were previously known from what has traditionally been considered the ''upper part'' of the Burlington Limestone in the Mississippi River Valley and what is now recognized as the Burlington Pelmatozoan Assemblage III. The current study confirms the conclusion of Lane and DuBar (1983) that the Nada is middle Osagean in age, being deposited earlier than the well-documented Borden delta crinoid assemblages of north-central Kentucky and Indiana. The middle Osagean age of the fauna indicates a previously unrecognized unconformity between the Nada and the overlying Meramecianage Renfro Member of the Slade Formation. In addition, this is the first well-documented middle Osagean fauna from a siliciclastic facies in North America. The dominance by camerate crinoids is enigmatic, but may be related to either a low rate of sedimentation or greater larval dispersal abilities.

Generic concepts in the Actinocrinitidae Austin and Austin, 1842 (class Crinoidea) and evaluation of generic assignments of species

“…Abactinocrinus rossei has a small swelling at the anal opening while A. devonicus and A. burlingtonensis have an anal opening flush with the tegmen. Lee et al, 2005;and Blairocrinus smalleyi (Weller, 1909) [new combination].…”

“…Webster (2003) considered both species to be in Cactocrinus (with B. arrosus also considered in the genus Aacocrinus), and presumably, synonymous homonyms. However, B. arrosus was correctly assigned to Blairocrinus by Miller (1892), a view endorsed by Brower (1967) and Lee et al (2005) (Laudon, 1933) [new combination]; Cactocrinus lucina (Hall, 1861b); Cactocrinus magnidactylus Laudon and Severson, 1953; Cactocrinus multibrachiatus (Hall, 1858); Cactocrinus obesus (Keyes, 1894); Cactocrinus opusculus (Hall, 1859); Cactocrinus platybrachiatus (Wood, 1914); Cactocrinus sexarmatus (Hall, 1859); Cactocrinus springeri (Rowley, 1900); and Cactocrinus thalia (Hall, 1861b).…”

“…North American species include Blairocrinus arrosus Miller, 1892; Blairocrinus macurdai Rhenberg and Kammer, 2013; Blairocrinus protuberus Lee et al, 2005; and Blairocrinus smalleyi (Weller, 1909) [new combination].…”

Systematics, Phylogenetics, and Biogeography of Early Mississippian Camerate Crinoids of the Nunn Member, Lake Valley Formation, in south-central New Mexico

“…Other species.-Abactinocrinus devonicus Waters et al 2003. Blairocrinus macurdai Rhenberg and Kammer, ms; Blairocrinus protuberus Lee et al, 2005; and Blairocrinus smalleyi (Weller, 1909)…”

“…considered both species to be in Cactocrinus (with B. arrosus also considered in the genus Aacocrinus), and presumably, synonymous homonyms. However, B. arrosus was correctly assigned to Blairocrinus by Miller (1892), as regarded by and Lee et al (2005). Other species.-Cactocrinus arrosus ; Cactocrinus bacatus Wood, 1914; Cactocrinus bischoffi [new combination]; Cactocrinus clarus ; Cactocrinus extensus ; Cactocrinus fossatus ; Cactocrinus glans (Hall, 1859a); Cactocrinus hurdianus [new combination]; Cactocrinus imperator [new combination]; Cactocrinus lucina ; Cactocrinus magnidactylus Laudon and Severson, 1953; Cactocrinus multibrachiatus ; Cactocrinus obesus (Keyes, 1894c); Cactocrinus opusculus (Hall, 1859a); Cactocrinus platybrachiatus (Wood, 1914); Cactocrinus sexarmatus (Hall, 1859a);…”