A Beginners Guide To Identifying Cincinnatian Crinoids

By Jack Kallmeyer

Camerata - Monobathrida

Canistrocrinus typus
Glyptocrinus decadactylus
Glyptocrinus  fornshelli
                               Glyptocrinus nodosus  <=== New Species
Pycnocrinus dyeri
Pycnocrinus subglobosus
Xenocrinus baeri

Crinoid Anatomical Glossary

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Canistrocrinus typus


10 mm scale, back and front.
Photos by Jack Kallmeyer
Canistrocrinus has prominently raised rays and anal series on the calyx. The plates between the rays are large compared to those in Xenocrinus. The five rays of the cup branch to produce four free arms per ray. The arms are pinnulate.

Canistrocrinus is found in the Waynesville and Liberty Formations.

10 mm scale
Photo by Jack Kallmeyer

The stem of Canistrocrinus is round in cross-section with alternating large diameter nodals and smaller diameter internodals. Mid-stem nodals have radial nodes projecting from them.


Pycnocrinus dyeri


10 mm scale
Photos by Jack Kallmeyer
The somewhat globular cup of this species is ornamented with stellate ridges making it look superficially like Glyptocrinus decadactylus. Originally described as Glyptocrinus dyeri, it was moved in to the genus Pycnocrinus by Bassler & Moodey in 1943 based upon cup morphology. The most obvious difference between Pycnocrinus and Glyptocrinus is the location of ray branching – the five prominent rays branch only once on the calyx in Pycnocrinus but they branch twice on the calyx in Glyptocrinus. The arms are heavily pinnulate.

This crinoid is found in the Maysvillian Stage and lower Richmondian Stage.



Columns are round in cross-section with large diameter nodals alternating with multiple smaller diameter internodals.

10 mm scale
Pychnocrinus distal coil holdfast
Photo by Jack Kallmeyer
 

Attachment of the relatively short (up to about 20 cm) column is by coiling of the distal stem around another object.


Pycnocrinus subglobosus

 
10mm scale
(#1) Probable juvenile Pycnocrinus subglobosus
(#2) Cincinnati Museum Center CMCIP 39948 with permission of Brenda Hunda
Photos Jack Kallmeyer
The morphology of Pycnocrinus subglobosus is as with other members of this genus (see P. dyeri for more detail). The only exception is that the calyx plates are smooth and without ornamentation.


This crinoid was found in the Corryville Formation

 

Glyptocrinus decadactylus


10 mm scale
Photos and artwork by Jack Kallmeyer
The cup of this species is ornamented with stellate ridges making it look like Pycnocrinus dyeri (see the P. dyeri description for details of the differences).


Columns are round in cross-section with large diameter nodals alternating with multiple smaller diameter internodals.


Attachment of the relatively short (up to about 20 cm) column is by coiling of the distal stem around another object.

This species is found in the Fairmount Member of the Fairview Formation.

 

Glyptocrinus fornshelli
 

10mm scale
Miami University MUGM 28121
With permission of Kendall Hauer
Photo Jack Kallmeyer
The cup plates of this species are very thin with distinctive ornamentation comprised of fine ridges and small nodes. The Richmondian Glyptocrinus fornshelli is one of the largest crinoids in the Cincinnatian with cup heights around 75 mm, not including the arms. The heavily pinnulate arms themselves branch three times above the cup making for what had to be a very impressive and bushy crinoid. The large size coupled with the thin cup plates makes preservation of complete specimens rare. Most are found as masses of disarticulated arms and cups. 

This species appears in the Waynesville and Liberty Formations.

The stem of G. fornshelli is comprised of very thin columnals that are sharply pentagonal in outline.
10 mm scale
Photo by Jack Kallmeyer

The holdfast of G. fornshelli is of the distally coiled stem variety.
10 mm scale
Miami University MUGM 28121
With permission of Kendall Hauer

Photo by Jack Kallmeyer

 

Glyptocrinus nodosus  <=== New Species




Holotype CMCIP 71396  10 mm Scale bar
Photo by Jack Kallmeyer


The cup plates are adorned with small nodes (small conical points) rather than stellate ridges like other local Glyptocrinus species.  Ray branching is variable with some rays producing four free arms while others produce only three free arms.  The arms are heavily pinnulate. This condition produces a crinoid with 17 free arms.


An unusual glyptocrinid has recently been discovered in the Southgate Member of the Kope Formation.  Glyptocrinus nodosus was described as a new species by Kallmeyer & Ausich (2015) in the Journal of Paleontology, Volume 89, issue 6, http://dx.doi.org/10.1017/jpa.2015.72


Holotype CMCIP 71396  5 mm Scale bar
Photo by Jack Kallmeyer

 


CMCIP 72242  10 mm Scale bar
Photo by Jack Kallmeyer


The stem and holdfast are typical of other Glyptocrinidae with the exception of radial projections on the nodals of the mesistele; proximal and distal parts of the column are without these projections. The holdfast is of the distal coil type. 



 

Xenocrinus baeri


5 mm scale
Photos by Jack Kallmeyer
At first glance this crinoid may look like a small Gaurocrinus. However, Xenocrinus is a monobathrid camerate having only two circlets of plates in the cup rather than three like the diplobathrid Gaurocrinus. There are four basal plates at the base of the cup. It has prominent ray ridges that branch once on the calyx. The anal series is a prominent vertical ridge on the calyx. Calyx plates between the rays and anal series are small and irregular.


Xenocrinus is found in the Liberty and Whitewater Formations. The genus is also found in the U.K.

10 mm scale
Photo by Jack Kallmeyer
By far, the most distinguishing feature of Xenocrinus is its quadrangular stem. No other crinoid in the Cincinnatian has a square stem. Since echinoderms in general have five-part symmetry this is even more unusual.



See more Xenocrinus stem sketches

The holdfast of X. baeri is of the distally coiled stem variety.

  Crinoid Anatomical Glossary

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