Scientific name Opisthothelae Higher classification Spider Order Spider | Rank Suborder | |
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Lifespan Southern black widow: 1 – 3 years, Goliath birdeater: 15 – 25 years Lower classifications Araneomorphae, Mygalomorphae, Tarantula, Orb‑weaver spider, Thomisidae | ||
Opisthothelae is a taxon within order Araneae, consisting of the Mygalomorphae and the Araneomorphae, but excluding the Mesothelae. The Opisthothelae are sometimes presented as an unranked clade and sometimes as a suborder of the Araneae. In the latter case, the Mygalomorphae and Araneomorphae are treated as infraorders.
The fairly recent creation of this taxon has been justified by the requirement to distinguish these spiders from the Mesothelae, which display many more primitive characteristics. Those that distinguish between the Mesothelae and Opisthothelae are:
Among the Opisthothelae, the fangs of the Mygalomorphae point straight down in front of the mouth aperture and only allow the spider to grasp its prey from above and below, whereas in the Araneomorphae, they face one another like pincers, allowing a firmer grip. Distinguishing araneomorphs and mygalomorphs on first inspection is difficult unless the specimens are large enough to permit immediate examination of the fangs.
