UCMP MYSTERY FOSSIL #20 is . . .
Paleophragmodictya


UCMP Mystery Fossil Number 20 Paleophragmodictya is thought to be the oldest fossil sponge, from a group called hexactinellida, the "glass sponges." In the closeup you can see faint traces of a network of spicules, similar to the structure found in hexactinellids today. Find out more about hexactinellids here.
 

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