Cincinnaticrinus varibrachialis

Classification
Phylum: Echinodermata
Class: Crinoidea
Order: Disparida
Family: Heterocrinidae
Genus: Cincinnaticrinus
Species: Cincinnaticrinus varibrachialis (Warn & Strimple, 1977)

C.varibrachialis_paleoeco

Taxonomic Details

Formerly: Heterocrinus heterodactylus

Stratigraphic Occurrences

C.varibrachialis_strat

Geographic Occurrences

		
Map point data provided by iDigBio.

Stratigraphic Description

Sequences (Formations)

  • C1 Sequence (Clays Ferry/Kope: McMicken, Southgate, Economy/Fulton)

Identification in Hand Sample

  • Cup is slightly smaller than stem
  • Very small cup
  • Several small lichenocrinus-like holdfasts
  • Pentagonal columns
  • Each columnal is made of 5 fused plates
  • Juvenile specimens tend to have more globular calyces

Cincinnaticrinus varibrachialus from the Waynesville C5 Formation of Waynesville, Ohio (OUIP 1432)

Published Description

Holland (UGA Strat Lab, 2013):

  • Cup is slightly wider than stem; very small cup.

Ausich & Webster (2008):

  • Brower (2005) illustrated an example of lichenocrinus-type holdfasts on columns of C. varibrachialis from the Mohawkian Rust Limestone (Trenton Group) in New York State. Similarly, Figure 2.4C shows a column of C. varibrachialis from the Edenian Kope Formation in Ohio with several small lichenocrinus-like holdfasts and dististeles attached that presumably belonged to this species. These observations demonstrate gregarious settlement of juveniles in the vicinity of established adults; whether the settling larvae were genuinely selecting for adults or merely utilizing the limited substrates available in their environments is unclear.
  • Simple disparids crinoids had long, robust columns in proportion to their small crowns. In addition, Ectenocrinus simplex Hall, 1847, and Cincinnaticrinus varibrachialis Warn and Strimple, 1977, possessed small crowns with low density and open filtration fans (Fig. 2.3; Brower, 2005).

Warn & Strimple (1977):

  • C. varibrachialus has a column with a relatively consistent width (proximal column diameter is about half distal cup diameter) through Edenian and into Maysvillian time.
  • C. varibrachialus, in addition to generic and higher characters, has BB (Text-fig. 9) and RR that expand distally and make the dorsal cup conical. This is more obvious in juveniles, which have globular calyces. With growth, the angle formed by the edges of the cup (in lateral view) decreases as the sides of the BB and RR approach a parallel condition (compare PI. 5, figs. 1-2 and 12-13). No new cup plates are added during ontogeny (that is, during that part of the ontogeny that is known), and shapes and relative size ratios of cup ossicles change little, other than widening of the bottoms of the BB and RR. Thus, the smallest (youngest) and largest (oldest) crinoids have dorsal cups that are nearly identical except for size.
  • The adult Cincinnaticrinus varibrachialus column is either pentagonal proximally grading distally into terete, or round throughout. The proximal pentagonal part can be made up of two sets of columnals: larger, more rounded columnals and smaller, markedly pentagonal columnals inserted between the larger columnals. Each columnal is composed of five fused plates with each plate forming a point in the pentagonal columnals. With secondary secretion of stereom (seemingly a normal feature of column aging), the column becomes round, but the former pentagonal column can be seen inside the round sheath in cross-section.