Megarachne
genus of eurypterids
Megarachne is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Megarachne have been discovered in deposits of Late Carboniferous age, from the Gzhelian stage, in the Bajo de Véliz Formation of San Luis, Argentina. The fossils of the single and type species M. servinei have been recovered from deposits that had once been a freshwater environment. The genus name comes from Ancient Greek μέγας (mégas), meaning "great", and ἀράχνη (aráchnē), meaning "spider", and thus, "great spider"; because the fossil was misidentified as a large, prehistoric spider.
With a body length of 54 cm (21 in), Megarachne was a medium-sized eurypterid. If the original identification as a spider had been correct, Megarachne would have been the largest known spider to have ever lived. Eurypterids such as Megarachne are often called "sea scorpions", but the strata in which Megarachne has been found indicates that it dwelled in freshwater and not in marine environments.
Megarachne was similar to other eurypterids within the Mycteropoidea, a rare group known primarily from South Africa and Scotland. The mycteropoids had evolved a specialized method of feeding referred to as sweep-feeding. This involved raking through the substrate of riverbeds in order to capture and eat smaller invertebrates.
The public source identifies “Megarachne” as genus of eurypterids. This brief keeps that definition visible, then builds a research path around Megarachne, genus and eurypterids.
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The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated May 17, 2026. The linked authority identifier is Q141230. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Megarachne” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.