Walking Rock Crab, Aethra scutata: The Walking Rock Crab has a broadly elliptical shell (carapace), with a toothed curved front, with short fat walking legs and large wide claws with the dactyl being much smaller than the fixed finger.
The crab is a mottled light brown with a few dark brown spots.
The eyes are exceedingly small and hard to locate.
Walking Rock Crabs reach a maximum size of 12.5 cm with the males being slightly larger than the females.
In Mexican waters they are found throughout the Sea of Cortez, around the tip of Baja California, and along the coast of the Mexican mainland south to Guatemala in shallow coastal waters in and around rock rubble with sand, boulders, and ledges at depths up to 100 feet.
The Walking Rock Crab is member of the Aethridae family, which has 14 genera, and the Aethra genus of which there are four known global members which are known in Mexico as Cangrejos de Roca. They are so named due to their appearance as rocks and are only noticed when they move.