interambulacral plate?

[Micah]

Hi all! I believe I just found a interambulacral plate, but have never found one before and no echinoids have been found at this site before (as far as I can discover). I'd love it if I'm right, but if not and it's some strange cirnoid  mutation that's okay as well. I found this south of Humboldt, Nebraska in what I believe is the Root formation, (but it was at the bottom of the roadcut, so it could also be from the Wood Siding or Onaga). Any help verifying/properly identifying this would be appreciated!

[BobWill]

I believe you are correct. The raised portion is where a spine attached. Often a muscle around the attachment point would allow some spines to be moved for locomotion.

[Micah]

Thanks @BobWill! I was pretty sure, but know all too well that we see what we want to see...

[doushantuo]

http://www.thefossilforum.com/index.php?/topic/73858-noi-said-miliary/&do=findComment&comment=777847

 

[doushantuo]

What Bobwill was talking about:

da Zoomogy.pdf

[Micah]

Followup question, identifying this made me want to go through some of my unidentified pieces from the same site and I think I might have some pieces of spine. Can anyone confirm or convince me otherwise?

[Ludwigia]

At least the form looks right. Too unfocussed to make out any details, though. Looks like the tip is broken off.

[Micah]

Thanks!

[doushantuo]

spines are multifarious

Stiller-2001-anisechinoiurchinspinetriassPalaeontology.pdf

[Micah]

 

6 minutes ago, doushantuo said:

spines are multifarious

Stiller-2001-anisechinoiurchinspinetriassPalaeontology.pdf

Huh interesting, a couple of those spines look more like what I associate with cirnoids. 

[Coco]

Hi,

 

I think your fossil can be a sea urchin tubercle, but the title of your subject isn't good, it can be just a part of an interambulacra plate.

 

Interambulacral plates are relatively flat plates situated between the sea urchin ambulacra. Here is a pic, interambulacra plates are indicated by the blue arrows http://www.snv.jussieu.fr/bmedia/aimar2/PAGES/244.htm

 

And here is a link toward a glossary which I made a few years ago, it is in french but contains nice explanatory pics. It is on my colleague website http://www.sciences-de-la-terre.com/Glossaire-echinodermes.php#P

 

Coco

[Micah]

Thanks @Coco that website was helpful. Like I said before this was my first encounter with echinoids so I'm still just starting to get to know them... thanks for the imput!

[TqB]

I see they're from the Carboniferous so you've probably got Archaeocidaris sp.

[BobWill]

18 hours ago, Micah said:

 

Huh interesting, a couple of those spines look more like what I associate with cirnoids. 

The pointy ends can look similar but the attachment portion of a crinoid spine is either one straight surface in the case of the radial plate spines or three straight surfaces for the anal spines that appear around the end of the tube. I haven't collected anal spines that can appear part way up the tube but it's not likely they would have the round socket seen on yours.

 

edit: The radial plate spines usually also have two surfaces on the upper portion for attachment of the arms.