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RE: Megarachne a eurypterid, not a spider

Thomas R. Holtz, Jr. wrote:


No mention of where the paper (if any) will be.

Here it is in FirstCite, at the Biology Letters website (http://www.journals.royalsoc.ac.uk):

Paul A. Selden, José A. Corronca, and Mario A. Hünicken (2005) The true identity of the supposed giant fossil spider _Megarachne_.

ABSTRACT: _Megarachne servinei_ from the Permo-Carboniferous Bajo de Véliz Formation of San Luis Province, Argentina (32° 17' S, 65° 25' E), was described as a giant mygalomorph spider ('tarantula') and, with its body length of 339 mm, the largest known spider ever to have lived on Earth. Its identification as a spider was based on interpretations of the shape of the carapace, the position of the eye tubercle, the anterior protrusion of the carapace as a pair of chelicerae, and the posterior circular structure as the abdomen. X-radiography revealed possible morphology hidden in the matrix: cheliceral fangs, sternum, labium and coxae, and so a reconstruction of _Megarachne_ as a giant spider was presented. Difficulties with the interpretation (unusual cuticular ornament, suture dividing the carapace and spade-like anterior border of the chelicera), together with non-preservation of synapomorphies of Araneae, provoked debate about its interpretation as a spider. Now, the holotype and a new specimen have become available for study. _Megarachne_ is shown to be a bizarre eurypterid ('sea-scorpion'), similar to rare forms known from Carboniferous rocks of Scotland and South Africa, and is the most complete eurypterid so far recorded from Carboniferous strata of South America.

The study refers _Megarachne_ to the eurypterid family Woodwardopteridae. _Megarachne_ is reconstructed as an aquatic sediment-feeder, although sedimontology would appear to rule out a marine habitat.