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Acutiramus
''Acutiramus'' is an extinct genus〔Tollerton, V. P. Jr 1997 "The Type Species of the Eurypterid Genus ''Acutiramus'' Ruedemann, 1935" ''Journal of Paleontology'' 71(5):950-951〕 of eurypterid which lived in the Late Silurian (Ludlow) to Early Devonian.
''Acutiramus'' is one of the largest eurypterids with pincers 5 cm and length about 2 m. It is related to another large eurypterid, ''Pterygotus''.
==Description==
Pterygotidae, which lived from the Ordovician to Devonian periods, were characterized by small to large exoskeletons with semilunar scales. The telson, (tail) was expanded, or flatter than it was tall. Pterygotidae also had chelicerae (claws in front of the mouth) that were large and long, with strong, well developed teeth on the claws. Their walking legs were small and slender, without spines.〔Størmer, L. 1955. Merostomata. ''Treatise on Invertebrate Paleontology, Part P Arthropoda 2, Chelicerata'', P: 30–31.〕
''Acutiramus'' is distinguishable from other Pterygotidae by the distal margin of the chelae, where the final tooth is at an acute angle to the rest of the claw (hence the name ''Acutiramus'', or “acute arm”). The large tooth in the center of the claw is distally inclined, which is to say it points forwards. The prosoma (head) is subquadrate, with compound eyes located at the edge of the front corners. The telson has a low row of knobs running down its center.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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