Ixamatus caldera, also known as the tessellated wishbone spider or volcanic ground spider, is a species of mygalomorph spider in the Microstigmatidae family. It is endemic to Australia. It was described in 1982 by Australian arachnologist Robert Raven.
The species occurs in north-eastern New South Wales in closed forest habitats. The type locality is Bar Mountain, near Kyogle in the Tweed Range.
The spiders are terrestrial predators.