[5] Frogfish in this family have laterally compressed, globose bodies, laterally-placed eyes and large, obliquely-slanting mouths.

The first dorsal spine is modified into an elongated, slender illicium which is tipped by an esca, a whitish, worm-like lure.

The basic colour of this well-camouflaged fish is reddish-brown, with vertical bars and patches of dark and pale brown, and whitish underparts.

[4] A benthic fish, R. filamentosus lives on the seabed and seldom swims, instead moving around with its pectoral and pelvic fins in a kind of "walk".

It is a well-camouflaged ambush predator; it rests on the seabed and when a potential prey approaches, it starts to waggle its esca.