Polydesmaster tentugalensis (Soares & Devriès, 1967)

@ricardo 

 Interesting specimen.  I have seen it on your website.  Do you have any additional images of the lateral views?  Have you confirmed the apical plate orientation?  Do the ambulacral petals seem longer in your specimen compared to the one figured on The Echinoid Directory?  

On 1/16/2022 at 5:47 PM, JohnJ said:

Do you have any additional images of the lateral views?  Have you confirmed the apical plate orientation?  Do the ambulacral petals seem longer in your specimen compared to the one figured on The Echinoid Directory?  

 

Hello John. Thank you very much for the pertinent questions. I'll give you my opinion on the specimen 
In my opinion the petal extension is an optical illusion as the test end is missing.
The identification was based on the original work (since I don't have the Russian work). I compared the morphology of the apical disc with the original drawings (concerning the arrangement of the gonopores and the shape and arrangement of the madreporite) and I also compared it with the apical discs of the other Spatangoida that occur in the Formation.
The lateral profile and size is also completely different from all the others, the example being very good in the anterior side profile (the posterior side of the profile is more difficult to observe due to the matrix and part missing).

I had the opportunity a few years ago to see the holotype and the paratype, maybe one day I will be able to compare the specimens in loco.
If the identification is correct, it will be an important specimen, so I won't keep it for long. 

I have attached a photo with the side view, but it is not particularly enlightening.

Greetings,

Ricardo

Thank you for sharing the additional information, Ricardo.  The apical morphology is cited as a distinguishing characteristic.  If you have performed comparisons, using magnification, it gives great confidence to to your identification.  Congratulations on this discovery.

If you have better magnified photos of the apical disc, they would be an excellent addition to this entry.  Thanks.  

Thanks for the discussion, John.
I hope that the new images will allow a better understanding of the identification options arising from the observation of the apical disc.

Great research and images, Ricardo!

John, thank you!