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Superfamily Hibbertopteroidea Kjellesvig-Waering, 1959
Family Mycteropidae Cope, 1886

Megarachne Hünicken, 1980

Diagnosis: Woodwardopterid with sparser mucrones on carapace and first two opisthosomal tergites than the nominate genus; prominent anteromedian carapace protrusion (emended from Selden et al. 2005).

Included species:
Megarachne servinei

Age: Carboniferous-Permian; 460 mya.

Geographic Distribution: Argentina.

Maximum Size: 54 cm

Reconstruction of Drepanopterus abonensis

Reconstruction of Megarachne servinei,
from Selden et al. 2005.

Extra information: Megarachne was originally considered to be the world's largest spider, however after the discovery of a second specimen and reanalysis of the holotype it was reassigned as a mycteropid. Mycteropids are considered to be taxonomically oversplit, possibly due to poor knowledge of their ontogeny (patterns of growth), and so it is possible that Megarachne will be further revised in the future. It is one of the few eurypterids known from South America, and may bear close relation to Hastimima which is also known from the Carboniferous of the continent.

Further reading:

Hünicken, M. A. 1980. A giant fossil spider (Megarachne servinei) from Bajo de V´eliz, Upper Carboniferous,
Argentina. Boletin de la Academia Nacional de Ciencias, C´ordoba, Argentina, 53, 317–341.

Selden, P. A., Corronca, J. A. & Hünicken, M. A. 2005. The true identity of the supposed giant fossil spider Megarachne. Biology Letters, 1, 44–48.

Megarachne servinei, cast photographed at the private collection of Markus Poschmann.
(click picture to enlarge)

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