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Wikipedia / Pettalidae

The Pettalidae are a family of harvestmen with 75 described species in 10 genera. Several undescribed species are known or assumed in some genera.

Name

Pettalus is a name from Greek mythology that appears in Ovid's Metamorphoses.

Description

All species except the cave-dwelling South African Speleosiro argasiformis spend their entire life cycle in leaf litter.

They are two to five millimeters long, usually with an oval shaped body.

Although all Pettalidae except Parapurcellia have eyes, these were long thought to be absent in the family, mainly because they cannot be seen by scanning electron microscopy. They are often incorporated at the base of the ozophores and typically lack lenses.

Distribution

The members of this family are distributed throughout former temperate Gondwana, with genera in Chile, South Africa, Madagascar, Sri Lanka, eastern and western Australia, and New Zealand, where they are most diverse by far, with 29 species and subspecies found in three genera.

Relationships

The family Pettalidae is monophyletic, although it is at the moment (2007) unclear what the nearest relatives are. It probably originated in the southern part of Gondwana. Parsimony analysis suggests it could be a sister group to the remaining Cyphophthalmi, though this could also be the case for the Stylocellidae, or it could be related to the Sironidae, or specifically to the sironid genus Suzukielus. It is unrelated to the Troglosironidae that are endemic to New Caledonia.

The main lineages of the family may have arisen rapidly, possibly during the rapid expansion of Glossopteris forests that were predominant in temperate Gondwana. Pettalidae were likely present throughout the forests of Antarctica, which formed a land bridge between Australia and South America up until circa 50 million years ago (mya).

The Australian genera Austropurcellia (Eastern Australia: Queensland) and Karripurcellia (Western Australia) are not sister groups. It is possible that the Cyphophthalmi dispersed across Australia while the central region was covered with Nothofagus rainforest (until 37 mya), or that the ancestors of the two genera independently dispersed from adjacent landmasses now separate from Australia.

Parapurcellia from eastern South Africa is sister to all other Pettalidae, while Purcellia from western South Africa is sister to the Chilean Chileogovea. Western South Africa and southern South America were last connected during the Late Jurassic, about 150 mya. Likewise, the monotypic Neopurcellia from New Zealand appears as the sister group to all Pettalidae except for Parapurcellia, instead of being monophyletic with the other two New Zealand genera, which themselves appear as sister groups in Bayesian analysis, but not in direct optimization parsimony analyses.

Species

The family Pettalidae contains the following genera and species:

See also

Footnotes

References

  • Joel Hallan's Biology Catalog: Pettalidae

  • Checklist of the Cyphophthalmi species of the World (with pictures)

  • (1971): Les opilions cyphophthalmes cavernicoles. Notes sur Speleosiro argasiformis Lawrence. Bull. Mus. Natl Hist. Nat. 42: 864–871.

  • (eds.) (2007): Harvestmen - The Biology of Opiliones. Harvard University Press

  • (2007): A new model Gondwanan taxon: systematics and biogeography of the harvestman family Pettalidae (Arachnida, Opiliones, Cyphophthalmi), with a taxonomic revision of genera from Australia and New Zealand. Cladistics 23(4): 337-361.