We report on the natural history and web building behavior of the South American austrochilids Thaida peculiaris and Austrochilus forsteri, relatively basal lineages within Araneomorphae. Species of these two cribellate genera construct large, two-dimensional sheet webs with a funnel retreat. When combing cribellate silk, austrochilids use both fourth legs, like entelegyne spiders, and unlike Hypochilidae and Filistatidae. Furthermore, the alternancy of combing legs IV is determined by the leg III involved in the attachment of a cribellate segment; the leg IV ipsilateral to the leg III that made the attachment will comb the next segment, except for the first segment. This similarity to Entelegynae in combing with both fourth legs contradicts current hypotheses of basal araneomorph relationships and suggests that the Austrochilidae may be the sister group of entelegyne spiders.