Another ghost of Gondwana—Progradungula barringtonensis Michalik & Smith, sp. nov., a new species of the relict spider genus Progradungula (Araneae: Gradungulidae) from a temperate rainforest in eastern Australia

Abstract

Odd-clawed spiders (Gradungulinae), which are considered to be ‘living fossils’, are a faunal element of the mesic forests of eastern Australia and the South Island of New Zealand. To date, 16 species in seven genera are known, with most being highly endemic and hard to find, explaining their scarcity in collections worldwide. Particularly noteworthy is the Australian genus Progradungula that includes only two relict species from eastern Australia (Progradungula carraiensis from the Carrai limestone caves in northern New South Wales and Progradungula otwayensis from Nothofagus rainforests in the Otway Range, southern Victoria) and are known from only a handful of adult specimens. Both species are large nocturnal predators with a rather cryptic lifestyle, which construct unique ladder-like catching webs composed of non-combed and combed cribellate silk with exceptional properties. Here, we describe a new relict species, Progradungula barringtonensis Michalik & Smith, sp. nov., from isolated Nothofagus forest patches in Barrington Tops National Park (NSW, Australia). The male of this species is significantly larger than those of P. carraiensis and P. otwayensis and exhibits characteristics of the male genitalia of both species. The webs are similar to those of the other Progradungula species. Field observations revealed that the catching ladder had few looping segments, similar to P. otwayensis, but an immature in captivity constructed webs with more looping segments, similar to P. carraiensis, supporting the previously proposed hypothesis that food availability may explain the plasticity of the catching ladder structure.