Idiosoma is a genus of Australian armored trapdoor spiders that was first described by Anton Ausserer in 1871. Originally placed with the Ctenizidae, it was moved to the armored trapdoor spiders in 1985. The name is derived from the Greek ἴδιος (idios), meaning "individual, unique", and σῶμα (soma), meaning "body", referring to the distinctive structure of the abdomen. The Black rugose trapdoor spider (Idiosoma nigrum) can grow up to 30 millimetres (1.2 in) long. Males can grow up to 18 millimetres (0.71 in) in body length.