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Cyclocosmia
cork-lid trapdoor spider, Oreo spider (misnomer)
Cyclocosmia is a genus of mygalomorph trapdoor spiders in the family Halonoproctidae, comprising thirteen species distributed across North America (USA, Mexico) and Southeast Asia (China, Thailand, Vietnam, Laos). These spiders are distinguished by their unique abdominal morphology: an abruptly truncated, hardened posterior disc strengthened by ribs and grooves, used to seal burrow entrances when threatened. The genus was first described by Anton Ausserer in 1871 and serves as the type genus for Halonoproctidae. Species are long-lived, slow-maturing, and have demanding habitat requirements that make them rare in collections despite local abundance.