Name: Megarachne (Large spider).
Phonetic: Meg-ah-rak-ney.
Named By: Mario A. Hünicken - 1980.
Classification: Arthropoda, Merostomata, Eurypterida, Hibbertopteroidea, Mycteroptidae.
Species: M. servinei (type).
Type: Carnivore.
Size: Reconstructed as a eurypterid, length estimated to be about 54 centimetres long.
Known locations: South America, Argentina.
Time period: Pennsylvanian of the Carboniferous.
Fossil representation: Two specimens of partial remains.

       To begin we need to be clear about one thing: Megarachne was never a spider. Forget what you may have seen in the BBC documentary 'Walking With Monsters, although in their defence they were following the original fossil study during production, and did change the name to Mesothelae for broadcast to try and prevent confusion. Also this means that previous reconstructions as seen in museums for twenty-five years between its discovery and re-examination have unfortunately been incorrect. Still, this is not the first time that an extinct creature has been incorrectly interpreted, nor is likely the last.
       When first discovered the specimen was thought to represent a spider but in 2005, the specimen was re-examined along with a second specimen by Paul Seldon, José Corronca and Mario Hünicken and actually found to be a eurypterid. Eurypterids are essentially sea scorpions and given that they are related to arachnids and have four pairs of legs, the fossilised remains can look spider like. Although not a giant spider, Megarachne has proven not to be a disappointment and as a Eurypterid it displays morphological features that distinguish it from among the other members of its family.

More information on these - Eurypterus, Jaekelopterus, Megalograptus, Megarachne, Pterygotus.

Further reading
- A giant fossil spider (Megarachne servinei) from Bajo de Véliz, Upper Carboniferous, Argentina - Boletin de la Academia Nacional de Ciencias, Córdoba, Argentina 53: 317–341. - Mario A. Hünicken - 1980.
- The true identity of the supposed giant fossil spider Megarachne. - Biology Letters 1 (1): 44–48. - Paul A. Selden, José A. Corronca & Mario A. Hünicken - 2005.


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