Haptopoda

Haptopoda is an extinct arachnid order known exclusively from only eight specimens from the Upper Carboniferous of Coseley, Staffordshire, United Kingdom. It is monotypic, i.e. has only one species, Plesiosiro madeleyi described by Reginald Innes Pocock in his important 1911 monograph on British Carboniferous arachnids.^[1] The original locality from which these fossils originate is no longer available thus it is unclear whether any further examples will be found.

The original fossils have been redescribed in detail by Alexander Petrunkevitch in 1949^[2] and Dunlop in 1999.^[3] A supposed example from the Coal Measures of Lancashire is a misidentification.

Relationships

Relationships with other arachnids are obscure. Plesiosiro means "close to Siro", which is a genus of cyphophthalmid (Cyphophthalmi); the most primitive group of the living harvestmen (Opiliones). These harvestmen do, in some ways, resemble the reconstructed body plan of the haptopods.

Revisions have confirmed that Haptopoda should be treated as a separate and independent order. The most recent study tentatively recognised a group named Schizotarsata Shultz, 2007^[4] comprising Haptopoda, Amblypygi (whip spiders), Uropygi (whip scorpions) and Schizomida (schizomids). All share the character of a subdivided tarsus (or foot) which gives the group its name.

Names

The order has also been called Haptopodida; the ending -ida originated when Petrunkevitch (1955)^[5] tried to standardize the endings of the arachnid orders.

Haptopoda originates from Greek "haptos" (= tangible, subject to the sense of touch) + "pous, podos" (= foot) and refers to its quite long front pair of legs with their subdivided tips which look as though they might have been used to 'feel' their way around in front of the animal.

References