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Fossil evidence for the origin of spider spinnerets

Paul A. Selden¹ & William A. Shear²

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1. University of Kansas, Department of Geology
2. Hampden-Sydney College, Department of Biology

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Date:

Received 18 July 2008 04:17 UTC; Posted 21 July 2008

Subjects:

Evolutionary Biology and Ecology, Genetics, Earth and Environment

Tags:

• developmental genetics
• spider
• fossil
• paleontology
• Arachnida
• Chelicerata
• Hox
• distalless
• Silk
• Evolution

Abstract:

Silk production from opisthosomal glands is a defining characteristic of spiders (Araneae). Silk emerges from spigots (modified setae) borne on spinnerets (modified appendages). Spigots from Attercopus fimbriunguis (Shear, Selden & Rolfe, 1987¹), from Middle Devonian (386 Ma) strata of Gilboa, New York were described in 1989² as evidence for the oldest spider and the first use of silk by animals. Slightly younger (374 Ma) material from South Mountain, New York, conspecific with A. fimbriunguis, includes spigots and other evidence which elucidate the evolution of early Araneae and the origin of spider silk. No known Attercopus spigots, including the original specimen², occur on true spinnerets but are arranged along the edges of plates. Spinnerets originated from biramous appendages of opisthosomal somites 4 and 5; while present in Limulus, no other arachnids have opisthosomal appendage homologues on these segments. The spigot arrangement in Attercopus shows a primitive state prior to the re-expression of the dormant genetic mechanism which gave rise to spinnerets in later spiders. The inability of Attercopus precisely to control silk weaving suggests its original use as a wrapping, lining or homing material.

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This document is licensed to the public under the Creative Commons Attribution 3.0 License

How to cite this document:

Selden, Paul and Shear, William. Fossil evidence for the origin of spider spinnerets. Available from Nature Precedings <http://hdl.handle.net/10101/npre.2008.2088.1> (2008)

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