Mystery fossil #62 is...

the crab Xantho (Lophoxanthus) scaberrimus

The dorsal view of Xantho (top) didn't give you much to work with, but in the ventral view (bottom), the large pincer makes it clear that we're looking at a fossil crab.

Crabs are crustaceans whose fossils first appear in Jurassic rocks, although there are some ambiguous fossils that may push crab origins back to the Carboniferous.

This specimen was collected from the Pliocene Bodjong Formation of western Java, Indonesia. Read more about the Bodjong Formation, or crustaceans in general, here on the UCMP site.
 

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