A Beginners Guide To Identifying Cincinnatian Crinoids
By Jack Kallmeyer

Inadunata - Disparida

Cincinnaticrinus varibrachialus
Cincinnaticrinus pentagonus
Ohiocrinus
 Dystactocrinus
Ectenocrinus simplex
 Drymocrinus geniculatus 
Iocrinus subcrassus
Anomalocrinus incurvus

Crinoid Anatomical Glossary

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Cincinnaticrinus varibrachialus



5 mm scale. Photos by Jack Kallmeyer		 Cincinnaticrinus as a genus is found throughout the Cincinnatian. C. varibrachialus is found in the Kope and Fairview Formations. This is a very small crinoid just considering the cup. However, if you consider the stem length approaching a meter, C. varibrachialus isn’t so small after all. This extra-long stem and very small cup explains why stem pieces are found more often than cups.

The cup of C. varibrachialus is smooth with a diameter that is wider than the stem at the base of the cup. The arms branch multiple times above the cup with each branch being equal in diameter. The arms do not bear pinnules. The anal series branches off of the top of the cup near the base of an arm and appears as an unbranched straight tube tucked inside of the arm circlet.


Lower Kope Formation. Collected by Cole Simpson.
Prepared by Ken De la Vega   Photo by Jack Kallmeyer
The column of C. varibrachialus changes morphology from the distal end (holdfast end) up to the base of the cup. Columnals at the distal end are pentameric, that is, each columnal is comprised of five individual plates. The mid portion of the stem produces columnals that are most readily identified as Cincinnaticrinus. These columnals are round in cross section with rounded edges giving them the shape of a thin donut. The articulating surface of the columnals is also typical of Cincinnaticrinus as they bear five ovoid petal impressions. The proximal portion of the column up to the cup is pentagonal in shape. Individual columnals are thick relative to their diameter. The specimen illustrated at left, collected by Cole Simpson, shows the change in stem morphology. The section nearest the cup is pentagonal while further down it transitions to fully round.


Cincinnaticrinus columnals are the most common stems found throughout the Cincinnnatian. Stems are up to a meter in length. Shape shown is consistent through most of that length. Shape changes to pentagonal near the cup and pentameric at the distal end.
Drawings by Jack Kallmeyer
 More Cincinnaticrinus stem sketches

Lichenocrinus tuberculatus
10 mm scale
Photo and artwork by Jack Kallmeyer

 The holdfast of C. varibrachialus is of the form genus “Lichenocrinus".


This is a commonly found form of crinoid holdfast throughout the Cincinnatian. These disc shaped structures can be smooth or very bumpy. The remainder of the pentameric stem can be found in well preserved Lichenocrinus.

The above Lichenocrinus tuberculatus drawing and photo is not from Cincinnaticrinus.  This is only one form of many types that exist in the Cincinnatian and these illustrations are used only as a representation of how Lichenocrinus appears in general.  

See photos of Cincinnaticrinus specimens found on Dry Dredgers field trips.


Cincinnaticrinus pentagonus


5 mm scale, Photos by Jack Kallmeyer		 While the cups of this species are larger than C. varibrachialus, they approximate the diameter of the proximal column unlike C. varibrachialus.

Stem and holdfast morphology is the same as C. varibrachialus.

10 mm scale
Photo by Jack Kallmeyer

This species is found from the Maysvillian through the Richmondian.

See photos of Cincinnaticrinus specimens found on Dry Dredgers field trips.

Cincinnaticrinus Lookalikes

There are two other genera in the Cincinnatian whose cups look like Cincinnaticrinus that deserve mention here: Ohiocrinus and Dystactocrinus. As isolated cups with no arms attached it would be difficult to differentiate between these and Cincinnaticrinus. The distinctive feature of Ohiocrinus is a spiral anal sac within the arm circlet (in contrast, Cincinnaticrinus has a straight tubular anal sac). The arms of Dystactocrinus flare widely above the cup contrary to the straighter vertical arm groupings of Cincinnaticrinus. In addition, Dystactocrinus also has small armlets that branch multiple times above the cup.

 

Ectenocrinus simplex


10 mm scale
 Photo by Jack Kallmeyer		 Like Cincinnaticrinus varibrachialus, Ectenocrinus simplex is very abundant in the Kope, occurring in pockets of hundreds of individuals. The cup of E. simplex is smooth and larger than C. varibrachialus. The anal sac is arm-like and branches off of the top of the cup. The arms branch once above the cup and bear pinnule-like ramules. The ramules are not always evident as most specimens are preserved with the arms folded, thus obscuring them.

Ectenocrinus simplex is found in the Kope Formation and into the lower Maysvillian Stage.


One of the most common stems found in the Kope and into the Maysvillian. Stems up to a meter long.  The stem changes below the cup rapidly tapering with very thin columnals.
Photo by Jack Kallmeyer


More Ectenocrinus stem sketches
Artwork by Jack Kallmeyer

The stems are round in cross-section and there is some variation in morphology from holdfast to the cup. The stem immediately beneath the cup is tapered and comprised of very thin columnals. The mid-section of the stem has columnals that appear trapezoidal when viewed from the side – the smaller diameter is the top of the columnal. In this section of the stem, the columnals can also have downward projecting nodes around the perimeter of the wide base of the trapezoid. Stem length in this species is thought to be close to a meter – a single column of over 70 cm has been found in-place by the author and that column had no cup or holdfast at either end.


The holdfast of E. simplex is believed to be a “Lichenocrinus” form genus similar to Cincinnaticrinus although no holdfast has been discovered attached to a confirmed Ectenocrinus column.

See photos of Ectenocrinus specimens found on field trips

 

Drymocrinus geniculatus


10 mm scale.
Cincinnati Museum Center
CMCIP 54561 With permission of Brenda Hunda
Photo Jack Kallmeyer 		While similar in cup plating to Ectenocrinus simplex, and previously classified as Ectenocrinus geniculatus, Drymocrinus has a larger anal X plate in the cup (this plate is the base of the anal sac above the cup). The anal sac is tubular in shape and can be seen clearly in the photo. Perhaps the most striking difference from Ectenocrinus is the configuration of the arms. The arm plates are somewhat wedge shaped and elongated giving the arms a zig-zag appearance.

This species is found in the Fulton Submember of the Kope Formation.
  

 

Iocrinus subcrassus


10 mm scale
Courtesy of Carolyn Greene (#1) and
Jack Kallmeyer (#2) 		This species has a short conical cup ornamented with heavy ridges. The radial plates are large and support thick arms that branch multiple times above the cup. The anal sac of Iocrinus is large and ornamented although not quite to the extent of Plicodendrocrinus casei.

Iocrinus can be found from the upper Kope Formation through the Maysvillian Stage and into the Richmondian Stage. The other recognized species in this genus is the Richmondian Iocrinus crassus, which appears to differ primarily by virtue of larger size and the height/width ratios of cup plates; it is only found in the Richmondian of  the Maquoketa Shale in Illinois but not locally. 

A number of Iocrinus species are also found in the U.K.


Stems of Iocrinus subcrassus are pentalobate
with ovoid petal impressions as well as articulating
grooves.
Photo by Jack Kallmeyer
Columnals of Iocrinus subcrassus vary from pentalobate to star shaped.
 Artwork by Jack Kallmeyer

The distally coiled stem of Iocrinus subcrassus
10 mm scale
Photo by Jack Kallmeyer
The holdfasts are of the distally coiled stem type.

 

Anomalocrinus incurvus


10 mm scale
Courtesy of Steve Brown
Photo by Jack Kallmeyer 		Anomalocrinus incurvus is by far the most robust crinoid in the Cincinnatian with column diameters up to 15 mm that rival later Misssippian crinoids. The globular cup is robust in construction with massive arms. The specimen pictured here is relatively small for this species but it is exhibits a very complete crown. Our thanks to Steve Brown for letting us photograph and illustrate this exceptional specimen.  

A complete large specimen (not pictured here) is housed in the Geier Collections and Research Center of the Cincinnati Museum Center. This specimen is approximately 60 cm from the holdfast to the base of the cup. The cup itself is completely disarticulated but all cup ossicles are present.   

Anomalocrinus is one of a few Cincinnatian crinoids that has a spiral anal sac.  While not visible in any of the photos here, it resembles a fat coiled spring between the arms.

The robust construction of A. incurvus may imply suitability for shallow, turbulent environments. As would be expected, many have been discovered in the shallow subtidal limestones of the Maysvillian Bellevue Formation. This species has also been found in the deeper, less turbulent environment of the Kope Formation.

The Stem of Anomalocrinus incurvus
10 mm scale
 Photo by Jack Kallmeyer
End of Anomalocrinus stem
10 mm Scale
Photo by Jack Kallmeyer
Column fragments, when attached to the holdfasts, show a polymeric construction, meaning that each columnal is comprised of numerous individual plates.

10 mm scale
Photo by Jack Kallmeyer		 The holdfast is of the encrusting type that sometimes shows root-like extensions. The most common holdfast type is in the form genus “Podolithus.” Holdfasts that have no column remnants attached look like small, smooth sided volcanoes.

Artwork by Jack Kallmeyer

10 mm scale
Specimen courtesy of Tom Bantel,
Photo by Jack Kallmeyer

Form genus Podolithus cemented holdfasts attributed to Anomalocrinus incurvus.  These un-weathered specimens are attached to a bryozoan and still retain a portion of the distal column.

10 mm scale
Photo by Jack Kallmeyer
Form genus Podolithus holdfasts attributed to Anomalocrinus incurvus. These specimens are attached to a hardground and show wear
and weathering from exposure after the crinoid had died.


See photos of Anamolocrinus specimens found on Dry Dredgers field trips.

  Crinoid Anatomical Glossary

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