Revision as of 16:07, 24 March 2011 edit Harry- (talk \| contribs) Extended confirmed users, Pending changes reviewers, Rollbackers 8,365 edits m Reverted edits by 66.99.218.130 (talk) to last revision by TomS TDotO (HG) ← Previous edit		Revision as of 16:10, 24 March 2011 edit undo 66.99.218.130 (talk) →Emergence of true spiders Next edit →
Line 14: ==Emergence of true spiders== At one stage the oldest fossil spider was believed to be ''[[Attercopus]]'' which lived {{Ma\|380}} during the [[Devonian]]. ''Attercopus'' was placed as the sister-taxon to all living spiders, but has now been reinterpreted as a member of a separate, extinct order [[Uraraneida]] which could produce silk, but did not have true spinnerets. [[Image:Spider silk microscopic structure.png\|thumb\|left\|Microscopic structure of [[spider silk]], possibly the most important [[adaption]] developed during the evolution of these arachnids]Pat odoneld is gay ] The oldest true spiders are thus [[Carboniferous]] in age, or ~~about~~abouodoneld is gayt 300 million years. Most of these early segmented fossil spiders from the Coal Measures of Europe and North America probably belonged to the [[Mesothelae]], or something very similar, a group of primitive spiders with the spinnerets placed underneath the middle of the abdomen, rather than at the end as in modern spiders. They were probably ground dwelling predators, living in the giant clubmoss and fern forests of the mid-late Palaeozoic, where they were presumably predators of other primitive arthropods. Silk may have been used simply as a protective covering for the eggs, a lining for a retreat hole, and later perhaps for simple ground sheet web and trapdoor construction. As plant and insect life diversified so also did the spider's use of silk. Spiders with spinnerets at the end of the abdomen ([[Mygalomorphae]] and [[Araneomorphae]]) appeared more than 250 million years ago, presumably promoting the development of more elaborate sheet and maze webs for prey capture both on ground and foliage, as well as the development of the safety dragline. The oldest mygalomorph, [[Rosamygale]], was described from the [[Triassic]] of France and belongs to the modern family [[Hexathelidae]]. [[Megarachne servinei]] from the [[Permo-Carboniferous]] was once thought to be a giant mygalomorph spider and, with its body length of 1 foot (34 cm) and leg span of above 20 inches (50 cm), the largest known spider ever to have lived on Earth, but subsequent examination by an expert revealed that it was actually a middling-sized [[sea scorpion]].

Evolution of spiders: Difference between revisions

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