The major groups of living spiders (order Araneae)
Suborder Mesothelae: Segmented spider, Liphistus desultor. Photo: M Gray © Australian Museum.
Infraorder Mygalomorphae: Sydney Funnel-web Spider, Atrax robustus. Photo: M Gray © Australian Museum.
Infraorder Araneomorphae: Garden Orb Weaver, Eriophora biapicata. Photo: M Gray © Australian Museum.
Suborder Mesothelae (segmented spiders: Liphistiidae) are the most primitive spiders known. They have a segmented abdomen with eight spinnerets placed centrally on its lower surface, four abdominal book lungs (breathing organs) and dagger-like, downward striking fangs.
Suborder Opisthothelae includes all other spiders. They have the spinnerets placed at the end of the abdomen, a much more efficient position for silk spinning. The abdomen rarely shows any obvious segmentation. These spiders are placed into two groups:
Infraorder Mygalomorphae (tarantulas, trapdoor and funnel web spiders) have 4-6 spinnerets and retain the dagger-like fangs and four book lungs of ancestral ground-living spiders.
Infraorder Araneomorphae include the vast majority of spiders (such as orb weavers, redbacks and huntsman spiders). They have pincer-like fangs that are more efficient for biting and manipulating prey. Most have 6 spinnerets, with or without a cribellum (specialised spinnerets), two book lungs plus a pair of air tubes (tracheae) that typically open near the spinnerets.
