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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
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.