Santiago:

It is possible to have a tetramerous Echinoid: Kindly see this link:

Best

Syed

http://www.clarenbach.org/My%20echinoids/Regulars/Stereocidaris%20granularis%20var.%20rubra%20tetramerous.htm

thanks for your quick response, Syed! any idea about the exact Genus or family of the one in the photo?

Santiago:

This link would provide you with important insights. Exact taxonomic assignment is not possible at the moment. Could you kindly furnish more details about the age of the calcareous soil, number of tetramerous specimens found and the associated fauna to attempt identification.

Best

Syed

https://www.cambridge.org/core/journals/paleobiology/article/biomechanical-model-for-the-morphogenesis-of-regular-echinoid-tests/4A0E960E0D35B9621A55694F6AD38D87

thanks for the link, Syed!

unfortunately, I cannot provide more details, the specimen was collected by a 9-year old little naturalist, he was very keen to learn more about it and my fossil knowledge is quite limited, so I was trying to get some help to spark his curiosity further

best

santi