page_title: Carcinosoma
section_title: History of research
hierarchical_section_title: Carcinosoma / History of research
caption_attribution_description: English: Fossil specimen of eurypterid Carcinosoma scorpioides.
context_page_description: Carcinosoma is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Carcinosoma are restricted to deposits of late Silurian age. Classified as part of the family Carcinosomatidae, which the genus lends its name to, Carcinosoma contains seven species from North America and Great Britain.
  Carcinosomatid eurypterids had unusual proportions and features compared to other eurypterids, with a broad abdomen, thin and long tail and spined and forward-facing walking appendages. They were not as streamlined as other groups but had considerably more robust and well developed walking appendages. In Carcinosoma, these spined walking appendages are thought to have been used to create a trap to capture prey in. The telson of Carcinosoma appears to have possessed distinct segmentation, Carcinosoma is the only known eurypterid to possess this feature.
  At 2.2 meters in length, the species C. punctatum is the largest carcinosomatoid eurypterid by far and is among the largest eurypterids overall, rivalling the large pterygotid eurypterids in size. Other species of the genus were considerably smaller, with most ranging from 70 centimeters to 100 centimeters in length.
context_section_description: Carcinosoma was first described under the name Eurysoma (meaning "wide body", deriving from Greek εὐρύς, "wide", and Latin soma, "body") by British American geologist and paleobotanist Edward Waller Claypole in 1890, who named the type species of the new genus E. newlini in honor of a C. E. Newlin who had collected the fossils. The Eurysoma specimens had been discovered in deposits of Early Pridoli age in the Kokomo Formation of Indiana alongside several other eurypterid specimens, all of which at the time were referred to Eurypterus lacustris (though Claypole noted in the same paper that this may have been done hastily). Later in the same year, Claypole discovered that the name Eurysoma was preoccupied and thus not available to be used for his genus of eurypterids. Eurysoma had been named in 1831 for a genus of modern beetles and is today considered synonymous with the genus Brachygnathus. Claypole replaced the name Eurysoma with the new name Carcinosoma. Carcinosoma means "crab body" deriving from Latin cancer, "crab", and soma, "body".
  In 1868, English geologist and paleontologist Henry Woodward named a new species of Eurypterus, E. scorpioides, based on fossils from Lanarkshire, Scotland. Woodward could easily distinguish the species from other genera present at the locality, such as Slimonia and Pterygotus. Another species of Eurypterus, E. scoticus was named in 1899 by Scottish zoologist and paleontologist Malcolm Laurie based on fragmentary remains recovered in deposits of Llandovery age in Scotland.
  In 1912, American paleontologists John Mason Clarke and Rudolf Ruedemann noted that Carcinosoma was sufficiently similar to the related eurypterid Eusarcus to be designated as synonymous with it. As Eusarcus had been named in 1875, fifteen years earlier than Carcinosoma, its name had priority and replaced Carcinosoma. At this time, the combined genus of Eusarcus contained several species that are today seen as Carcinosoma, including C. newlini, C. scoticus and C. scorpioides, which Clarke and Ruedemann had referred to the genus on account of their similarities with C. newlini and species previously referred to Eusarcus. In 1934, 59 years after it had been described, Eusarcus was recognized as a name preoccupied by a harvestman. The Norwegian geologist Leif Størmer proposed that the name of the taxon should be next oldest available and valid name for the genus, Carcinosoma. During the preparation for his paper on the issue, Størmer also discussed the situation with fellow Norwegian researcher Embrik Strand, who helped confirm that Carcinosoma was not preoccupied.
  Strand would subsequently propose the replacement name Eusarcana in 1942, despite the problem having been dealt with by Størmer, who he had been in contact with, eight years earlier. The reasons for proposing the name during the circumstances of the time remains unknown, but critique from contemporary researchers of Strand for his studies in systematics and an apparent desire to name as many taxa as possible may explain the situation somewhat. As it was seen as completely unnecessary at the time, Strand's Eusarcana was overlooked and not even mentioned in subsequent eurypterid studies.
  In 1961, American paleontologist Erik N. Kjellesvig-Waering classified Eurypterus punctatus (originally described as Pterygotus punctatus by English paleontologist and prominent eurypterid researcher John William Salter in 1859) as Carcinosoma punctatum and named a new species C. harleyi based on fossils from the Ludlow epoch of the Welsh Borderland. Kjellesvig-Waering could differentiate C. harleyi from C. punctatum based on C. harleyi lacking serrations on the eighth podomere of the swimming leg and the serrations of the ninth podomere being less developed.
  C. punctatum was diagnosed by Kjellesvig-Waering in 1961 based on the considerably pronounced serrations of the distal parts of its swimming leg, but the diagnosis is only valid for the lectotype specimen of the species, BGS GSM89435 (compromising the distal parts of a swimming leg discovered in deposits of Middle Ludlow ag
caption: Fossil of C. scorpioides
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