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From Wikipedia, the free encyclopedia

Cyclostome is a biological term (from the Greek for "round mouth") used in a few different senses:

  • for the taxon Cyclostomi, which comprises the extant jawless fishes: the hagfish (Myxini) and the lampreys (Petromyzontidae). This was thought for a time to be a paraphyletic group and this usage of the term was deprecated by some. However, there is strong molecular evidence for cyclostome monophyly,[1] and thus the term remains in use.
  • for the Order Cyclostomatida of bryozoans, tiny animals that live in colonies and form large calcitic skeletons.
  • for one of two subgroups of braconid wasps.


  1. ^ Stock, David; Whitt GS (7 August 1992). "Evidence from 18S ribosomal RNA sequences that lampreys and hagfishes form a natural group". Science. 257 (5071): 787–9. doi:10.1126/science.1496398. PMID 1496398.