Bythograeidae

The Bythograeidae are a small family of blind crabs which live around hydrothermal vents. The family contains 16 species in six genera. Their relationships to other crabs are unclear. They are believed to eat bacteria and other vent organisms. Bythograeidae are a monophyletic, sister taxon of the superfamily Xanthoidea which split to inhabit hydrothermal vents around the Eocene.

== Origins == Due to the lack of fossils found in this group the exact date of origin of Bythograeidae remains unknown. It has been suggested that bythograeidae do not originate from an ancient hydrothermal bathyal groups but instead arose from brachyuran stock that was adapted to shallow hydrothermal vents and then transitioned to deep sea hydrothermal vents around the Eocene. left|thumb|296x296px|A consortium of Cyanagraea|Cyanagraea praedator crabs in an area of hydrothermal activity