There are five species of stonefish within the genus Synanceia: Synanceia horrida (previously referred to as S. trachynis), S. verrucosa, S. alula, S. nana and S. platyrhyncha. Synanceia spp. can grow 35–50 cm in length and have evolved grey and mottled skin to camouflage themselves amongst encrusted rocks and coral for predation and defense. Synanceia species have up to 15 dorsal fin spines that are erected when the fish is disturbed. Stings from this medically important group of fish are known to cause painful and lethal human envenomations. Stonefish are regarded as one of the most venomous fish in the world. Research on stonefish venom has chiefly focused on the in vitro and in vivo neurological, cardiovascular, cytotoxic and nociceptive effects of the venom.