Bundenbach Crinoid?

[Mochaccino]

Hello all,

 

Thank you always for your help. This time I'm asking about a Bundenbach crinoid I came across. The seller says it's a Thallocrinus sp. but an unusual one and that "Bundenbach crinoid experts" are divided on further identification. More importantly, I have very little experience looking at these sort of crinoids and honestly this almost looks spray-painted gold to me (even though I know these are pyritized) so I wanted to consult TFF experts on it regarding its authenticity.

 

The first 2 photos taken under flash photography, the rest in natural sunlight:


 

 

 

 

If it is genuine, what do you think of the species ID? The following photo is the only other Bundenbach Thallocrinus I could find, a Thallocrinus procerus, but it has much clearer pinnules than the specimen in question.
 

 

 

I cannot tell if this is due to difference in species, incomplete prep, or worst of all bad preservation, though the seller claims poor preservation is not the case here.

 

Thank you.

Edited March 10, 2022 by Mochaccino

[Fossildude19]

This looks real to me.
Not sure of any ID for it, however.

 

@oilshale

[FossilDAWG]

Looks real to me as well, and I was also going to tag @oilshale.  The difference in appearance from the specimen in the last photo may in part be because it has been fully prepped by air abrasion to uncover all the pinnules, and your specimen has not been prepped fully.

 

Don

[oilshale]

Hard to say, that would require an x-ray and I am not a specialist for Bundenbach crinoids. 
As far as I can see this could also be a Hapalocrinus (both are relatively common).
Thallocrinus and Hapalocrinus both have no (or at most a small) anal sac; the single-lined arms bifurcate over the second brachial. This seems to be the case here.
Hapalocrinus differs from Thallocrinus in the presence of tiny three-pointed articulating spines which are inserted on the oral side of the arms (I can't tell, the picture is too blurry for that).

Four species are known of Thallocrinus and five species (or varieties) of Hapalocrinus, differing in the number and length of the arms and pinnules, the shape of the stem elements, and their robustness.

 

 

Edited March 11, 2022 by oilshale

[JohnJ]

18 hours ago, Mochaccino said:

this almost looks spray-painted gold to me

This same effect can be achieved using a brass wire brush by hand or motor driven rotary wheel.  It would take a very close in hand examination to determine if this technique was used.  Tiny wire 'scars' and color missing in pitted areas would be clues.

[Mochaccino]

6 hours ago, Fossildude19 said:

This looks real to me.
Not sure of any ID for it, however.

 

@oilshale

 

4 hours ago, FossilDAWG said:

Looks real to me as well, and I was also going to tag @oilshale.  The difference in appearance from the specimen in the last photo may in part be because it has been fully prepped by air abrasion to uncover all the pinnules, and your specimen has not been prepped fully.

 

Don

 

Thank you! Yes I was wondering if the prep was simply incomplete as I could see some pinnules almost buried in the shale. That would definitely be preferable to outright poor preservation.

 

3 hours ago, oilshale said:

Hard to say, that would require an x-ray and I am not a specialist for Bundenbach crinoids. 
As far as I can see this could also be a Hapalocrinus (both are relatively common).
Thallocrinus and Hapalocrinus both have no (or at most a small) anal sac; the single-lined arms bifurcate over the second brachial. This seems to be the case here.
Hapalocrinus differs from Thallocrinus in the presence of tiny three-pointed articulating spines which are inserted on the oral side of the arms (I can't tell, the picture is too blurry for that).

Four species are known of Thallocrinus and five species (or varieties) of Hapalocrinus, differing in the number and length of the arms and pinnules, the shape of the stem elements, and their robustness.

 

 

 

Very informative and good to know. I tried looking into some descriptions of these but literature on them seems surprisingly scare or inaccessible. X-ray also isn't exactly the easiest thing to get a hold of...so potential for either Thallocrinus or Hapalocrinus on this one.

 

2 hours ago, JohnJ said:

This same effect can be achieved using a brass wire brush by hand or motor driven rotary wheel.  It would take a very close in hand examination to determine if this technique was used.  Tiny wire 'scars' and color missing in pitted areas would be clues.

 

Are you saying those clues would indicate spray-painting as opposed to true pyritization, which would be uncovered by said techniques?

 

Thank you all!

[JohnJ]

36 minutes ago, Mochaccino said:

 

Are you saying those clues would indicate spray-painting as opposed to true pyritization, which would be uncovered by said techniques?

 

Not spray paint; rather the brass brush is soft enough to leave a thin coating of brass that imitates pyritization.

[Mochaccino]

24 minutes ago, JohnJ said:

 

Not spray paint; rather the brass brush is soft enough to leave a thin coating of brass that imitates pyritization.

 

I was not aware of that, thanks for letting me know! It is something I can ask.

[oilshale]

The fossils in Bundenbach are (almost) always pyritized - only mostly not in the form of shiny pyrite crystals but as a gray-black mass. In former times brass brushes were used to prepare the fossils. Fine details have been lost by this method, but the brass residue has given the fossils a nice shiny golden surface.

[Mochaccino]

6 minutes ago, oilshale said:

The fossils in Bundenbach are (almost) always pyritized - only mostly not in the form of shiny pyrite crystals but as a gray-black mass. In former times brass brushes were used to prepare the fossils. Fine details have been lost by this method, but the brass residue has given the fossils a nice shiny golden surface.

I see, so is the golden color here indicative of that method of prep rather than by air-abrasive?

[Fossildude19]

42 minutes ago, Mochaccino said:

I see, so is the golden color here indicative of that method of prep rather than by air-abrasive?

 

I think it is a possibility.  However, it is hard to be sure without in hand analysis.   

[Mochaccino]

27 minutes ago, Fossildude19 said:

 

I think it is a possibility.  However, it is hard to be sure without in hand analysis.   

I see...it seems like the brass itself can be washed off but what I really fear is the loss of fine detail with such a method.