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Lamsdell, James C.; Legg, David A. (2010). "An isolated pterygotid ramus (Chelicerata: Eurypterida) from the Devonian Beartooth Butte Formation, Wyoming". Journal of Paleontology. 84 (6): 1206–1208. Bibcode:2010JPal...84.1206L. doi:10.1666/10-040.1. S2CID129807060.
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Lamsdell, James C.; Legg, David A. (2010). "An isolated pterygotid ramus (Chelicerata: Eurypterida) from the Devonian Beartooth Butte Formation, Wyoming". Journal of Paleontology. 84 (6): 1206–1208. Bibcode:2010JPal...84.1206L. doi:10.1666/10-040.1. S2CID129807060.
Gould, Gina C.; MacFadden, Bruce J. (2004). "Chapter 17: Gigantism, Dwarfism, and Cope's Rule: "Nothing in Evolution Makes Sense without a Phylogeny"". Bulletin of the American Museum of Natural History. 285: 219–237. doi:10.1206/0003-0090(2004)285<0219:c>2.0.co;2. S2CID73556985.