Tetrapulmonata
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Tetrapulmonata Shultz, 1990 is a non-ranked supra-ordinal group of arachnids. It is composed of Thelyphonida, Schizomida, Amblypygi and Araneae.
It receives its name from the presence of paired book lungs occupying the second and third opisthosomal segments, although the posterior pair is absent in Schizomida. Previous synonyms of this lineage are rejected; Caulogastra (Pocock, 1983) refers to pedicel, which is symplesiomorphic for the lineage and convergent with Solifugae, and Arachnidea (van der Hammen, 1977) is easily confused with Arachnida. Other synapomorphies of Tetrapulmonata include a large postcerebral pharynx (reduced in Uropygi), prossomal endosternite with four segmental components, subchelate chelicerae, a complex coxotrochanteral joint in the walking legs, a pretarsal depressor muscle arising in the patella (convergent with Dromopoda, lost in Amblypygi), a pedicel formed, in part, by ventral elements of the second opisthomal segment and a spermatozoan axoneme a 9+3 microtubule arrangement (Schultz, 1990).
[edit] References
Shultz, J. W. 1990. Evolutionary morphology and phylogeny of Arachnida. Cladistics 6:1-38.
