My Crinoid Conundrum. Answers Appreciated.

[Indian_money]

So it seems to me that there are plenty of different variations in the outer appearance of Crinoid stems. Many have a smooth outside, while others look ribbed or like a stack of discs.

Here is my conundrum....

Attached I have photos of crinoid stems I found, that have the inside cavity exposed. I THINK THEY ARE BEAUTIFUL, and I love finding these little zombies.

How am I to know weather the stem I am finding is actually what the stem structure looked like verses it being the actual filled in cavities of the stem with the outside "casing" worn away??

In the photo where the crinoids are lined up, the last two pieces are the inside portion of a crinoid stem and the other is the outside "casing" of a crinoid stem.


Thanks for reading!! and I appreciate any input

-Alexandra

[Auspex]

This is a real neat specimen, as it shows both the outside, in-life appearance, and the internal structure in the 'cut-away':

[piranha]

If you're in the mood for a textbook description, the Treatise on Invertebrate Paleontology is always useful. Clear as mud!

AXIAL CANALS

All columnals and cirrals are pierced by an axial canal. Generally (but not invariably) it occupies the center of the columnal. Its transverse shape and relative size as shown by outline and size of the lumen on joint-faces have been described above (Fig. 54,1-5). In median longitudinal section, the axial canal of columnals may be simple (straight sided) (Fig. 54,6) or complex (provided with expansions or constrictions) (Fig. 54, 7). If present, the expansions (spatia) are located between the colurnnals, while the constriction (claustra) are placed at midheight of the columnals (Fig. 54,8). As seen in longitudinal section: the spatia may be low, or tall and laterally rounded, truncate, or pointed; the claustra, clavate, truncate, or lanceolate. Adaxial surfaces of claustra may be convex, flat, or concave, and smooth or denticulate. The part of an axial canal limited by the adaxial faces of a claustrum is called jugulum; it corresponds to a distinct local narrowing of the axial canal, narrowing that may be longitudinally very short to moderately long and transversely circular or pentagonal to strongly quinquestellate (Fig. 54,8). The adaxial part of a claustrum bordering a jugulum may be thickened and form what is designated as a jugular rampart. The jugulum and the central part of spatia were probably occupied during life by coelomic and nervous extensions from the chambered organ, whereas the remaining part of the spatia was filled with dermal fibers. Radially disposed simple or branched canals may be given off from the axial canal. If these side canals penetrate stereom and lead to cirrus scars on latera, they are termed canaliculae. If they are located between apposed joint-faces they are called fossulae (Fig. 50,3). In some stems these passageways emerge on the outer surface of columnals as small pores ( cirripores) of uncertain function (Fig. 54,9) or they terminate in diminutive nodicirral sockets or pimplelike protuberances (abortive cirri) (Fig. 54,10). In the camerate Trybliocrinus the joint-faces of columnals show radiating grooves which open into the axial canal through small vertical slits and terminate near the periphery without communicating with the exterior (Fig. 54,11). A similar canal system occurs in the grapnel-like root of the inadunate Ancyrocrinus). Apparently these passages between or through the columnals served to transmit the nutrient fluid to cells secreting the stereom and to aerate the same fluid by bringing it near the surface.

[Indian_money]

Oh...my..

[BobWill]

Interesting about the transmission of nutrient fluid in the canal. It would flow downward, opposite from a plant stem.

Thank you both for showing the odd preservation and for the quote from the Treatise.

[Indian_money]

If you're in the mood for a textbook description, the Treatise on Invertebrate Paleontology is always useful. Clear as mud!

IMG1.jpg

AXIAL CANALS

All columnals and cirrals are pierced by an axial canal. Generally (but not invariably) it occupies the center of the columnal. Its transverse shape and relative size as shown by outline and size of the lumen on joint-faces have been described above (Fig. 54,1-5). In median longitudinal section, the axial canal of columnals may be simple (straight sided) (Fig. 54,6) or complex (provided with expansions or constrictions) (Fig. 54, 7). If present, the expansions (spatia) are located between the colurnnals, while the constriction (claustra) are placed at midheight of the columnals (Fig. 54,8). As seen in longitudinal section: the spatia may be low, or tall and laterally rounded, truncate, or pointed; the claustra, clavate, truncate, or lanceolate. Adaxial surfaces of claustra may be convex, flat, or concave, and smooth or denticulate. The part of an axial canal limited by the adaxial faces of a claustrum is called jugulum; it corresponds to a distinct local narrowing of the axial canal, narrowing that may be longitudinally very short to moderately long and transversely circular or pentagonal to strongly quinquestellate (Fig. 54,8). The adaxial part of a claustrum bordering a jugulum may be thickened and form what is designated as a jugular rampart. The jugulum and the central part of spatia were probably occupied during life by coelomic and nervous extensions from the chambered organ, whereas the remaining part of the spatia was filled with dermal fibers. Radially disposed simple or branched canals may be given off from the axial canal. If these side canals penetrate stereom and lead to cirrus scars on latera, they are termed canaliculae. If they are located between apposed joint-faces they are called fossulae (Fig. 50,3). In some stems these passageways emerge on the outer surface of columnals as small pores ( cirripores) of uncertain function (Fig. 54,9) or they terminate in diminutive nodicirral sockets or pimplelike protuberances (abortive cirri) (Fig. 54,10). In the camerate Trybliocrinus the joint-faces of columnals show radiating grooves which open into the axial canal through small vertical slits and terminate near the periphery without communicating with the exterior (Fig. 54,11). A similar canal system occurs in the grapnel-like root of the inadunate Ancyrocrinus). Apparently these passages between or through the columnals served to transmit the nutrient fluid to cells secreting the stereom and to aerate the same fluid by bringing it near the surface.

This tells me why there are chambers and what they can look like but not how to decipher weather I have a full stem or just it's innards...

Are we saying that unless the stem is smooth surfaced and circular we are looking at filled in cavities?

[BobWill]

Yes but not chambers. The chambers are in the cephalpopds we talked about on PM. In a crinoid it's more of a channel, or canal as the paper calls them. In the stems I find here it's filled in on stems but sometimes open in individual sections. I assume on a stem worn down on the side it would show more clearly than just looking down one end of a whole one.

Fossils preserved by cast and mold can show us internal or external surfaces (or both like some of yours) depending on what eroded away first. If the outside of the animal was smooth then an external cast would be smooth. An internal surface might be less smooth so the internal cast or mold would be too. Add to that all of the different shapes crinoid stems can have and the possibilities are many.

[jkfoam]

Alexandra,

The best discussion I have ever found relative to Crinoid columns or columnals is found in a University of Kansas Paleontological Institute publication, "Echinodermata, Article 8, Article 9, and Article 10, published January 26, 1968. The specifics of the publication are as follows;

Echinodermata, Article 8, Serial Number 45, "Morphological features of Crinoid Columns", by Raymond C. Moore, Russell M. Jeffords and Theo. H. Miller.

Article 9, Serial Number 46, "Classification and Nomenclature of Fossil Crinoids Based on Studies of Dissociated Parts of Their Columns", by Raymond C. Moore and Russell M. Jeffords.

Article 10, Serial Number 47, "Ontogenetic Developement in Late Pennsylvanian Crinoid Columnals and Pluricolumnals", by Russell M. Jeffords and Theo H. Miller.

Published by the University of Kansas Paleontological Institute, The University of Kansas Publications, January 26, 1968.

I believe this publication is still in print but I don't know if it is available on-line. The publication contains a tremendous amount of information on crinoid columns (more than I ever wanted to know) and has excellent plates and descriptions.

The publication describes many crinoids based on their columns from the Pennsylvanian of Texas, Oklahoma and Kansas.

I hope this helps.

Jim

[Indian_money]

thanks!

[Pilobolus]

While this post is sure to get me labeled as a stalker....

https://kuscholarworks.ku.edu/bitstream/handle/1808/3820/paleo.article.046op.pdf?sequence=3&isAllowed=y

[erose]

Oh...my..

You asked….

Over time as you collect more crinoids in different states of preservation you will get a better handle on what you are seeing. Identifying crinoids by their columnals can also be tricky since some look virtually the same from species to species and some crinoids had stems that changed shape along the length of the stem. I'm sure there are species and maybe even genera that have been named based on crowns only with a limited knowledge of the full stem.

Piranha has the right idea and you should read a bit more about the morphology of crinoids. This has been a great book for learning about the basics of most fossil groups: MOORE, R. C. AND OTHERS. 1952. Invertebrate Fossils. McGraw Hill, NY. It can be found in used book shops or online as used copies and is still a great reference. The Treatise is harder to get your hands on unless you have access to a university or museum science library.