Type species. Planes clypeatus Bowdich, 1825 [Type locality: northeast of Madeira, on a floating log].
Remarks. Planes currently consists of two species, namely: P. minutus (Linnaeus, 1758) and P. marinus Rathun, 1914. Planes major (MacLeay, 1838) has recently been suggested to be a junior synonym of P. minutus (see Pfaller et al. 2019a). These are oceanic species which associate with floating or swimming organisms or cling to drifting flotsam, which are occasionally washed ashore.
Planes closely resembles Pachygrapsus from which it morphologically differs in the carapace smooth or only faintly striated and in the natatory fringe of setae on the P2–P5 propodi (Chace 1951; Poupin et al. 2005). Pachygrapsus laevimanus Stimpson, 1858, was found to be sister species to Planes marinus (see Pfaller et al. 2019a. See also Ip et al. 2015) and will be likely transferred to this genus with future studies.