{{Short description|Genus of ray-finned fishes}} {{Automatic taxobox | fossil_range = {{fossil range|Middle Eocene|present}}<ref name=":0"/> | image = Shimadai.jpg | image_caption = ''O. fasciatus'' | parent_authority = Bleeker, 1853<ref name = VDLEF>{{cite journal | author1 = Richard van der Laan | author2 = William N. Eschmeyer | author3 = Ronald Fricke | name-list-style = amp |year=2014 | title = Family-group names of Recent fishes | url = https://biotaxa.org/Zootaxa/article/view/zootaxa.3882.1.1/10480 | journal = Zootaxa | volume = 3882 | issue =2 | pages = 001–230| doi = 10.11646/zootaxa.3882.1.1 | pmid = 25543675 | doi-access = free }}</ref> | display_parents = 2 | taxon = Oplegnathus | authority = J. Richardson, 1840 | type_species = ''Oplegnathus conwaii'' | type_species_authority = J. Richardson, 1840<ref name = CofFG>{{Cof record|genid=1709|title=''Oplegnathus''|access-date=11 April 2020}}</ref> | synonyms = * ''Scaradon'' <small>Temminck & Schlegel, 1844</small> * ''Ichthyorhamphos'' <small>Castelnau, 1861</small> * ''Scarostoma'' <small>Kner, 1867</small> | synonyms_ref = <ref name = CofF>{{Cof family|family=Oplegnathidae|access-date=11 April 2020}}</ref> }}

'''''Oplegnathus''''' is currently the sole recognized genus in the '''knifejaw''' family ('''Oplegnathidae''') of marine centrarchiform ray-finned fishes.<ref>{{FishBase family | family = Oplegnathidae| month = February | year = 2014}}</ref> The largest, the Cape knifejaw, can reach a maximum length around 90&nbsp;cm (35&nbsp;in). Knifejaws have teeth fused into a parrot-like beak in adulthood. They feed on barnacles and mollusks, and are fished commercially. They are native to the Indian and Pacific Oceans.<ref name = Nelson5>{{cite book |title=Fishes of the World |edition=5th |author1=J. S. Nelson |author2=T. C. Grande |author3=M. V. H. Wilson |year=2016 |pages= 437 |publisher=Wiley |isbn= 978-1-118-34233-6 |url=https://sites.google.com/site/fotw5th/ }}</ref>

The earliest records of knifejaws are fossilized beaks, with attached teeth, known from middle Eocene-aged sediments of the La Meseta Formation of Antarctica. Their early occurrence in Antarctica supports it having temperate climate during the Eocene, and that knifejaws had a wider distribution in the past than today.<ref name=":0">{{Cite web |title=An oplegnathid fish from the Eocene of Antarctica {{!}} The Palaeontological Association |url=https://www.palass.org/publications/palaeontology-journal/archive/37/4/article_pp931-940 |access-date=2025-01-27 |website=www.palass.org}}</ref>

==Species== The currently recognized species in this genus are:<ref name=FishBase>{{FishBase genus | genus = Oplegnathus| month = February | year = 2014}}</ref> * ''Oplegnathus conwayi'' <small>J. Richardson, 1840, 1840</small> (Cape knifejaw) * ''Oplegnathus fasciatus'' <small>(Temminck & Schlegel, 1844)</small> (barred knifejaw or striped beakfish) * ''Oplegnathus insignis'' <small>(Kner, 1867)</small> (Pacific beakfish) * ''Oplegnathus peaolopesi'' <small>J. L. B. Smith, 1947</small> (Mozambique knifejaw) * ''Oplegnathus punctatus'' <small>(Temminck & Schlegel, 1844)</small> (spotted knifejaw) * ''Oplegnathus robinsoni'' <small>Regan, 1916</small> (Natal knifejaw) * ''Oplegnathus woodwardi'' <small>Waite, 1900</small> (knifejaw)

==References== {{Reflist}}

{{Taxonbar|from=Q577517}}

Category:Oplegnathidae

{{Centrarchiformes-stub}} Category:Extant Eocene first appearances