RE: Megarachne a eurypterid, not a spider

[Tim Williams <twilliams_alpha@hotmail.com>]

Thomas R. Holtz, Jr. wrote:

> http://news.bbc.co.uk/2/hi/uk_news/england/manchester/4268363.stm
>
> 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.