Produced by the Population Genetics and Evolution class, Furman University

The Devonian: Attercopus
Attercopus fimbriungus was once believed to be the oldest-known true spider (Strickland 2008). Recent analysis, however, showed that what was believed to be the spinneret, the silk-producing structure that is the distinguishing feature of modern spiders, was not a spinneret at all (Sheldon, Shear, and Sutton 2008). Instead, they had two rows of spigots on plates located along the underside of their abdomen (Sheldon, Shear, and Sutton 2008). Another of the many other differences between Attercopus and modern spiders is the presence of a long tail (ScienceDaily 2009). With this reexamination, as well as the discovery of other spider-like organisms that also have spigots and tails, Attercopus fimbriungus has since been re-identified as a protospider, representing an important link in spider evolution (Sheldon, Shear, and Sutton 2008). Attercopus could produce sheets of silk but, without the precision that spinnerets would provide, was unable to spin webs (ScienceDaily 2009). They possibly used the silk to line burrows, to guide themselves back to safety in a retreat, or to cover egg sacs (Sheldon, Shear, and Sutton 2008). Web building would seem unlikely since flying insects would not appear until much later in time (Strickland 2008).

Page by Lin Lin Zhao
Fossil of Attercopus fimbriungus, a protospider. Photo Credit: Smithsonian.com

ScienceDaily. 2009. How the spider spun its web: ‘missing link’ in spider evolution discovered. Accessed February 22, 2010.

Sheldon PA, Shear WA, and Sutton MD. 2008. Fossil evidence for the origin of spider spinnerets, and a proposed arachnid order. PNAS 105: 20781-20785.

Strickland E. 2008. Spider ancestor made silk—possibly using it for sex—but couldn’t spin a web. www.discovermagazine.com. Accessed February 22, 2010.