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Filtration mechanisms in the mouthparts of tetrapulmonate arachnids (Trigonotarbida, Araneae, Amblypygi, Uropygi, Scizomida)

Jason A. Dunlop
Department of Geology, University of Manchester, Manchester, M13 9PL

The comparative anatomy of filtration mechanisms in the mouthparts of living and extinct tetrapulmonate arachnids is described. All taxa studied possess plumose, preoral setae. A pharyngeal palate plate is an autapomorphic filtering mechanism for spiders. Amblypygi and Uropygi have no such pharyngeal filter, however, these orders have a dense mat of filtering setae on the pedipalpal coxae which in Uropygi lines a preoral trough formed in conjunction with the labrum, but comprises a more open preoral channel in Amblypygi. The extinct trigonotarbids had a series of cuticular projections between the labrum and labium which is interpreted as being a preoral filtration mechanism, similar to that reported for palpigrades. Comparisons are made between these tetrapulmonate filtration mechanisms, and the term preoral cavity is considered inappropriate for some arachnids. A filtering structure in the fossil record dates liquid feeding in tetrapulmonates to at least the Lower Devonian.

Bulletin of the Britsih Arachnological Society, 9, 267-273 (1994)

Author's comments:

I should have made more of the similarities between trigonotarbids and palpigrades which appear to have very similar filtering system morphologies. Palpigrades are, of course, thought to be primitive arachnids.
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