Texas Cretaceous Echinoderm Plate? Floating Crinoid? ID Help!

[JamieLynn]

Again, thank goodness for cameras and closeups!! I thougth this was a large orbitolina when I found it, but noticed that there was an odd pattern on the underside. I just figured it had some strange mishape. But then I was looking through @Uncle Siphuncle's Fossil collecting reports and ran across something that looked very similar - floating crinoid Peocilocrinus but they were from the Paw Paw formation in North Texas and this is from the lower Glen Rose in Central Texas. So I realized i needed to get a better picture and lo and behold....it has interesting pattern on the backside!! I remembered a picture I had seen of a starfish dermal plate or something that had these same striations on it. Can anyone help me ID? @erose or @JohnJ? Thanks for your time!! 

 

close up

[minnbuckeye]

 Nice find. Tiny, discoidal rugosan "button" coral looks very much like this but I know nothing about Texas fossils. Just a guess!!

 

 Mike

[Mark Kmiecik]

Button coral was my first impression, but I'm quite good at being wrong.

[DPS Ammonite]

It does look like a coral. Maybe someone with access to reference that describes Glen Rose Fm corals below can show us a description and photo: https://www.jstor.org/stable/1298104?seq=1#page_scan_tab_contents

 

Corals of the Trinity Group of the Comanchean of Central Texas

John W. Wells

Journal of Paleontology

Vol. 6, No. 3 (Sep., 1932), pp. 225-256

[JamieLynn]

the reason I am not leaning towards coral is one of the members of the Paleontology Society of Austin showed me a picture of exactly this thing found at the same place and said it was some kind of portion of an echinoderm...a pore or something like that. I cannot remember any more than that and was hoping someone would know. It very much does look like coral, but as far as I know, there is not button coral in the Glen Rose. But I am not 100% sure. Thanks for y'alls input! 

 

[JamieLynn]

oooohh...found it! Madreporite! It's part of the starfish vascular system.

 

[JamieLynn]

this is from a modern starfish, but the thought is this is an archaic version. Of course, I"m just going by what someone told me. For all I know, it's actually just a button coral that has not been identified in the Glen Rose....:D

 

[JamieLynn]

this was my other thought....a free floating crinoid. I know crinoids exist in the Glen Rose and I came across a picture of a free floating crinoid from the Fort Worth formation (from Uncle Sphincules' Fossil Report) but it looked very similar to this crinoid segment on bottom left (diferent age, I know) but  this looks very similar to the one side of mine: 

[JamieLynn]

The picture of free floating crinoids from the Fort Worth Formation 

[JamieLynn]

this is another thought : perhaps??  

[erose]

These had me flumoxed as well until just recently. Several of us had noticed them from the echinoid marker bed in Unit 2 of the Lower member of the Glen Rose Formation (Albian) here in Central Texas. All of the suggestions above, except one, were researched and discarded. But you have it correct as a madreporite. A very knowledgable local researcher gave me the ID just recently.  There are at least two types of asteroids in the marker bed and one ophiophurid. I took a look at my copy of the Treatise and found nothing associated with brittle stars that matched, but is a real good SWAG as they go.

 

Attached are some images of the starfish we find. I think these are associated with the more ornate and probably bigger genus.

[doushantuo]

edited by user

image below from Ryoji Hayashi: Studies on japanese Sea Stars,2