Malleolus (arthropod)

A malleolus (plural: malleoli) is a fan-shaped chemoreceptor or racquet organ, an array of which are carried in pairs on the ventral or undersides of Solifugae.

[1] They are the counterpart of pectines in scorpions, and modified walking limbs in the uropygids and amblypygids as well as the pedipalps in spiders and other arachnids.

[2][3] Generally, solifuges have five pairs of malleoli on the ventral surface of the fourth pair of legs.

Malleoli are usually larger in males.

[4] A malleolus comprises a basal stalk and a triangular fan, with epicuticular protrusions on each anterior face, and granular structures on each stalk, with undulate surfaces at each distal end.