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'{{Short description|Genus of extinct fishes}} {{Use dmy dates|date=November 2023}} {{Automatic taxobox | fossil_range = [[Late Devonian]] ([[Frasnian]] to [[Famennian]]), {{Fossil range|382|358}} | image = Dunkleosteus terrelli (fossil fish) (Cleveland Shale Member, Ohio Shale, Upper Devonian; Rocky River Valley, Cleveland, Ohio, USA) 21 (34001200911).jpg | image_caption = Partially reconstructed ''D. terrelli'' skull and trunk armor (specimen CMNH 5768), [[Cleveland Museum of Natural History]] | taxon = Dunkleosteus | authority = [[Jean-Pierre Lehman|Lehman]], 1956 | type_species = {{extinct}}'''''Dinichthys terrelli''''' | type_species_authority = Newberry, 1873 | subdivision_ranks = [[Species]] | subdivision = {{collapsible list| {{extinct}}''D. amblyodoratus'' <small>Carr & Hlavin, 2010</small><br /> {{extinct}}''D. belgicus (?)'' <small>(Newberry, 1873)</small><br /> {{extinct}}''D. denisoni'' <small>(Kulczycki, 1957)</small><br /> {{extinct}}''D. magnificus'' <small>(Hussakof & Bryant, 1919)</small><br /> {{extinct}}''D. marsaisi'' <small>Lehmann, 1956</small><br /> {{extinct}}''D. missouriensis'' <small>(Branson, 1914)</small><br /> {{extinct}}''D. newberryi'' <small>(Clarke, 1885)</small><br /> {{extinct}}''D. raveri'' <small>Carr & Hlavin, 2010</small><br /> {{extinct}}''D. terrelli'' <small>(Newberry, 1873 [originally ''[[Dinichthys]]''])</small><br /> {{extinct}}''D. tuderensis'' <small>Lebedev et. al., 2023</small><br /> }} }} '''''Dunkleosteus''''' is an [[extinct]] [[genus]] of large [[arthrodira|arthrodire]] ("jointed-neck") fish that existed during the [[Late Devonian]] period, about 382–358 [[million years ago]]. It was a [[pelagic fish]] inhabiting open waters, and one of the first [[apex predator]]s of any [[ecosystem]].<ref>{{Cite news |last=Tamisiea |first=Jack |date=4 March 2023 |title=Dunk Was Chunky, but Still Deadly |language=en |work=New York Times |url=https://www.nytimes.com/2023/03/04/science/chunky-dunk-fossil.html |access-date=29 July 2023}}</ref> ''Dunkleosteus'' consists of ten species, some of which are among the largest [[placoderm]]s ("plate-skinned") to have ever lived: '''''D. terrelli''''', '''''D. belgicus''''', '''''D. denisoni''''', '''''D. marsaisi''''', '''''D.''' '''magnificus''''', '''''D. missouriensis''''', '''''D. newberryi''''', '''''D. amblyodoratus''''', '''''D. raveri''''', and '''''D. tuderensis'''.'' The largest and best known species is ''D. terrelli''. Since body shape is not known, various methods of estimation put the living total length of the largest known specimen between {{convert|4.1|to|10|m|ft|abbr=on}} long and weigh around {{convert|1|-|4|MT|ST|abbr=on}}.<ref name=":0" /> However, lengths of {{convert|5|m|ft||abbr=|}} or more are poorly supported and the most extensive analyses support smaller size estimates.<ref name=":0" /><ref name=":2" /> ''Dunkleosteus'' could quickly open and close its jaw, creating suction like modern-day [[Aquatic feeding mechanisms#Suction feeding|suction feeders]], and had a bite force that is considered the highest of any living or fossil fish, and among the highest of any animal. [[Fossil|Fossils]] of ''Dunkleosteus'' have been found in [[North America]], [[Poland]], [[Belgium]], and [[Morocco]]. ==Discovery== ''Dunkleosteus'' fossils were first discovered in 1867 by Jay Terrell, a hotel owner and amateur [[paleontologist]] who collected fossils in the cliffs along [[Lake Erie]] near his home of [[Sheffield Lake, Ohio]] (due west of [[Cleveland]]), United States. Terrell donated his fossils to [[John Strong Newberry]] and the Ohio Geological Survey, who in 1873 described all the material as belonging to a single new [[genus]] and [[species]]: ''[[Dinichthys|Dinichthys herzeri]]''. However, with later fossil discoveries, by 1875 it became apparent multiple large fish species were present in the [[Ohio Shale]]. ''[[Dinichthys|Dinichthys herzeri]]'' came from the lowermost layer, the [[Huron Shale]], whereas most of the fossils were coming from the younger [[Cleveland Shale]] and represented a distinct species.<ref name=":1" /> Newberry named this more common species "''Dinichthys''" ''terrelli'', after Terrell.<ref>"Dunkleosteus terrelli: Fierce prehistoric predator" page at ''Cleveland Museum of Natural History''. https://www.cmnh.org/dunk {{Webarchive|url=https://web.archive.org/web/20210519150010/https://www.cmnh.org/dunk |date=19 May 2021 }}</ref> Most of Terrell's original collection does not survive, having been destroyed by a fire in [[Elyria, Ohio|Elyria]], Ohio, in 1873.<ref name=":1" /><ref>{{Cite journal |last=Claypole |first=E. W. |date=1893 |title=The three great fossil placoderms of Ohio |url=https://www.biodiversitylibrary.org/item/240810#page/107/mode/1up |journal=American Geologist |volume=12 |pages=89–99}}</ref> Dunkleosteus fossils can also be found in the ''[[Birdsong Shale]]'' formation in Tennessee. The largest collection of ''Dunkleosteus'' fossils in the world is housed at the [[Cleveland Museum of Natural History]],<ref>{{cite web |url=https://www.cmnh.org/dunk |title=Dunkleosteus terrelli: Fierce prehistoric predator |author=<!--Not stated--> |website=Cleveland Museum of Natural History |access-date=21 July 2022 |archive-date=19 May 2021 |archive-url=https://web.archive.org/web/20210519150010/https://www.cmnh.org/dunk |url-status=dead }}</ref> with smaller collections (in descending order of size) held at the [[American Museum of Natural History]],<ref>{{cite web |url=https://www.amnh.org/exhibitions/permanent/vertebrate-origins/dunkleosteus |title=Dunkleosteus |author=<!--Not stated--> |website=American Museum of Natural History |access-date=21 July 2022}}</ref> [[Smithsonian National Museum of Natural History]],<ref name="Smithsonian">{{cite web |title=Collections Catalog of the Department of Paleobiology of the Smithsonian National Museum of Natural History |url=https://collections.nmnh.si.edu/search/paleo/ |access-date=12 August 2022 |publisher=Smithsonian Institution}}</ref> [[Yale Peabody Museum]],<ref>{{cite web |title=Collections Database of the Yale Peabody Museum |url=https://collections.peabody.yale.edu/search/Search/Results?sort=relevance&join=AND&lookfor0%5B%5D=dunkleosteus&type0%5B%5D=AllFields&lookfor0%5B%5D=&type0%5B%5D=AllFields&lookfor0%5B%5D=&type0%5B%5D=AllFields&bool0%5B%5D=AND&lookfor1%5B%5D=VP&type1%5B%5D=CatalogNumber&lookfor1%5B%5D=VPPU&type1%5B%5D=CatalogNumber&bool1%5B%5D=OR&filter%5B%5D=%7Ecollection%3A%22Vertebrate+Paleontology%22&limit=5&daterange%5B%5D=collecting_year_first&collecting_year_firstfrom=&collecting_year_firstto= |publisher=Yale Peabody Museum |access-date=12 August 2022}}</ref> the [[Natural History Museum in London]], and the [[Cincinnati Museum Center]]. Specimens of ''Dunkleosteus'' are on display in many museums throughout the world (see table below), most of which are casts of the same specimen: CMNH 5768, the largest well-preserved individual of ''D. terrelli''.<ref name=":0" /><ref name="Ferron2017" /> The original CMNH 5768 is on display in the Cleveland Museum of Natural History. ==Taxonomy== ''Dunkleosteus'' was named by [[Jean-Pierre Lehman]] in 1956 to honour [[David Dunkle]] (1911–1984), former curator of [[vertebrate paleontology]] at the Cleveland Museum of Natural History. The genus name ''Dunkleosteus'' combines David Dunkle's surname with the Greek word {{wikt-lang|grc|ὀστέον}} ({{transliteration|grc|ostéon}} 'bone'), literally meaning "Dunkle's bone".<ref>{{citation |last=Lehman |first=Jean-Pierre |year=1956 |title=Les arthrodires du Dévonien supérieur du Tafilalet (Sud Marocain) |journal=Notes et Mémoires. Service Géologique du Maroc |volume=129 |pages=1–170 |language=fr}}</ref> Originally thought to be a member of the genus ''[[Dinichthys]]'', ''Dunkleosteus'' was later recognized as belonging to its own genus in 1956. It was thought to be closely related to ''Dinichthys'', and they were grouped together in the [[family (biology)|family]] [[Dinichthyidae]]. However, in the [[phylogenetic]] analysis of Carr and Hlavin (2010), ''Dunkleosteus'' and ''Dinichthys'' were found to belong to separate [[clade]]s of arthrodires: ''Dunkleosteus'' belonged to a group called the [[Dunkleosteoidea]] while ''[[Dinichthys]]'' belonged to the distantly related [[Aspinothoracidi]]. Carr & Hlavin resurrected the family [[Dunkleosteidae]] and placed ''Dunkleosteus'', ''[[Eastmanosteus]]'', and a few other genera from Dinichthyidae within it.<ref name="Carr+2010">{{cite journal| author =Carr R. K., Hlavin V. J.| title =Two new species of Dunkleosteus Lehman, 1956, from the Ohio Shale Formation (USA, Famennian) and the Kettle Point Formation (Canada, Upper Devonian), and a cladistic analysis of the Eubrachythoraci (Placodermi, Arthrodira)| journal =Zoological Journal of the Linnean Society| volume =159| issue =1| pages =195–222| year =2010| doi =10.1111/j.1096-3642.2009.00578.x| doi-access =free}}</ref> Dinichthyidae, in turn, is left a [[Monotypic taxon|monospecific]] family, though closely related to arthrodires like ''[[Gorgonichthys]]'' and ''[[Heintzichthys]]''.<ref name=Carr1995>{{cite journal|last=Carr|first=Robert K.|author2=William J. Hlavin|title=Dinichthyidae (Placodermi):A paleontological fiction?|journal=Geobios|date=2 September 1995|volume=28|pages=85–87|doi=10.1016/S0016-6995(95)80092-1|bibcode=1995Geobi..28...85C }}</ref> [[File:Dunkleosteus terrelli (fossil fish) (Cleveland Shale Member, Ohio Shale, Upper Devonian; Rocky River Valley, Cleveland, Ohio, USA) 25 (34091142396).jpg|thumb|right|Front view of ''D. terrelli'' skull]] The [[cladogram]] below from the study of Zhu & Zhu (2013) shows the placement of ''Dunkleosteus'' within [[Dunkleosteidae]] and ''[[Dinichthys]]'' within the separate clade [[Aspinothoracidi]]:<ref name=Zhu2013>{{Cite journal |author1=You-An Zhu |author2=Min Zhu |title=A redescription of Kiangyousteus yohii (Arthrodira: Eubrachythoraci) from the Middle Devonian of China, with remarks on the systematics of the Eubrachythoraci | journal=[[Zoological Journal of the Linnean Society]] |volume=169 |issue=4 |pages=798–819 |year=2013 |doi=10.1111/zoj12089 |doi-access=free }}</ref> {{clade| style=font-size:85%;line-height:85% |grouplabel1={{clade labels |width=10em; |label1='''Pachyosteomorphi''' |top1=65% |color1=green}} |label1='''[[Eubrachythoraci]]''' |1={{clade |1={{clade |label1='''[[Coccosteomorphi]]''' |1={{clade |1=''[[Coccosteus cuspidatus]]'' |2={{clade |1=''[[Harrytoombsia elegans]]'' |2={{clade |1=''[[Mcnamaraspis kaprios]]'' |label2=[[Incisoscutoidea]] |2={{clade |1=''[[Compagopiscis croucheri]]'' |2={{clade |1=''[[Incisoscutum ritchiei]]'' |2=''[[Incisoscutum sarahae]]'' }} |label3=[[Camuropiscidae]] |3={{clade |1=''[[Latocamurus coulthardi]]'' |2=''[[Camuropiscis laidlawi]]'' |3={{clade |1=''[[Rolfosteus canningensis]]'' |2=''[[Tubonasus lennardensis]]'' |3=''[[Fallacosteus turneri]]'' }} }} }} }} }} }} |label2='''[[Aspinothoracidi]]''' |2={{clade |1=''[[Dinichthys herzeri]]'' |barbegin1=green |2={{clade |1=''[[Hadrosteus rapax]]'' |bar1=green |2={{clade |1=''[[Gorgonichthys clarki]]'' |bar1=green |2={{clade |1=''[[Heintzichthys gouldii]]'' |bar1=green |label2=[[Selenosteidae]] |2={{clade |1=''[[Stenosteus angustopectus]]'' |bar1=green |2={{clade |1=''[[Gymnotrachelus hydei]]'' |bar1=green |2={{clade |1=''[[Rhinosteus parvulus]]'' |bar1=green |2=''[[Pachyosteus bulla]]'' |bar2=green }} }} }} }} }} }} }} }} |label2='''[[Dunkleosteoidea]]''' |2={{clade |1=''[[Westralichthys uwagedensis]]'' |bar1=green |2={{clade |1={{clade |1=''[[Protitanichthys rockportensis]]'' |bar1=green |label2=[[Panxiosteidae]] |2={{clade |1=''[[Panxiosteus ocullus]]'' |bar1=green |2=''[[Janiosteus timanicus]]'' |bar2=green |3=''[[Plourdosteus canadensis]]'' |bar3=green }} }} |label2='''[[Dunkleosteidae]]''' |2={{clade |1={{clade |1=''[[Eastmanosteus calliaspis]]'' |bar1=green |2=''[[Xiangshuiosteus wui]]'' |bar2=green }} |2={{clade |1=''[[Eastmanosteus pustulosus]]'' |bar1=green |2=''[[Kiangyousteus yohii]]'' |bar2=green |3=''[[Golshanichthys asiatica]]'' |bar3=green |4={{clade |1='''''Dunkleosteus amblyodoratus''''' |bar1=green |2='''''Dunkleosteus terrelli''''' |bar2=green |3='''''Dunkleosteus raveri''''' |barend3=green }} }} }} }} }} }} }} Alternatively, the subsequent 2016 Zhu ''et al.'' study using a larger [[morphology (biology)|morphological]] dataset recovered [[Panxiosteidae]] well outside of [[Dunkleosteoidea]], leaving the status of [[Dunkleosteidae]] as a clade grouping separate from Dunkleosteoidea in doubt, as shown in the cladogram below:<ref name=Zhu2016>{{Cite journal |last1=Zhu |first1=You-An |last2=Zhu |first2=Min |last3=Wang |first3=Jun-Qing |date=1 April 2016 |title=Redescription of Yinostius major (Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci |journal=[[Zoological Journal of the Linnean Society]] |volume=176 |issue=4 |pages=806–834 |doi=10.1111/zoj.12356|issn=0024-4082 |doi-access=free }}</ref> {{clade| style=font-size:85%;line-height:85% |label1='''[[Eubrachythoraci]]''' |1={{clade |label1='''[[Coccosteomorphi]]''' |1={{clade |label1=[[Coccosteoidea]] |1={{clade |label1=[[Coccosteidae]] |1={{clade |1={{clade |1=''[[Millerosteus minor]]'' |2=''[[Coccosteus cuspidatus]]'' }} |2={{clade |1=''[[Dickosteus threiplandi]]'' |2=''[[Watsonosteus fletti]]'' |3=''[[Protitanichthys rockportensis]]'' }} }} |label2='''[[Panxiosteidae]]''' |2={{clade |1=''[[Plourdosteus canadensis]]'' |2=''[[Panxiosteus ocullus]]'' |3=''[[Janiosteus timanicus]]'' }} }} |label2=[[Incisoscutoidea]] |2={{clade |1=''[[Harrytoombsia elegans]]'' |2={{clade |1=''[[Torosteus tuberculatus]]'' |2=''[[Torosteus pulchellus]]'' }} |3={{clade |1=''[[Mcnamaraspis kaprios]]'' |2={{clade |1=''[[Compagopiscis croucheri]]'' |2=''[[Trematosteus fontanellus]]'' |label3=[[Camuropiscidae]] |3={{clade |1={{clade |1=''[[Incisoscutum ritchiei]]'' |2=''[[Incisoscutum sarahae]]'' }} |2={{clade |1=''[[Rolfosteus canningensis]]'' |2={{clade |1=''[[Tubonasus lennardensis]]'' |2={{clade |1=''[[Fallacosteus turneri]]'' |2={{clade |1=''[[Camuropiscis laidlawi]]'' |2=''[[Latocamurus coulthardi]]'' }} }} }} }} }} }} }} }} }} |label2='''[[Pachyosteomorphi]]''' |2={{clade |1=''[[Rhachiosteus pterygiatus]]'' |2={{clade |label1='''[[Dunkleosteoidea]]''' |1={{clade |1=''[[Eastmanosteus calliaspis]]'' |2={{clade |1={{clade |1=''[[Eastmanosteus pustulosus]]'' |2=''[[Kiangyousteus yohii]]'' }} |2={{clade |1=''[[Golshanichthys asiatica]]'' |2={{clade |1=''[[Westralichthys uwagedensis]]'' |2={{clade |1={{clade |1='''''Dunkleosteus raveri''''' |2='''''Dunkleosteus terrelli''''' }} |2={{clade |1='''''Dunkleosteus amblyodoratus''''' |label2=[[Heterostiidae]] |2={{clade |1=''[[Heterosteus ingens]]'' |2=''[[Yinostius major]]'' }} }} }} }} }} }} }} |label2='''[[Aspinothoracidi]]''' |2={{clade |1=''[[Tapinosteus heintzi]]'' |2={{clade |1={{clade |1=''[[Bullerichthys fascidens]]'' |2={{clade |1=''[[Kendrickichthys cavernosus]]'' |2=''[[Bruntonichthys multidens]]'' }} }} |2={{clade |1=''[[Dinichthys herzeri]]'' |2={{clade |1=''[[Hadrosteus rapax]]'' |2={{clade |1=''[[Gorgonichthys clarki]]'' |label2=[[Selenosteidae]] |2={{clade |1=''[[Heintzichthys gouldii]]'' |2=''[[Pachyosteus bulla]]'' |3=''[[Gymnotrachelus hydei]]'' |4=''[[Stenosteus angustopectus]]'' |5=''[[Brachyosteus dietrichi]]'' |6={{clade |1=''[[Melanosteus occitanus]]'' |2=''[[Rhinosteus parvulus]]'' }} }} }} }} }} }} }} }} }} }} }} === Species === At least ten different species<ref name="Carr+2010"/><ref name=Denison>{{cite book |last=Denison |first=Robert |chapter=Placodermi |volume=2 |title=Handbook of Paleoichthyology |year=1978 |publisher=Gustav Fischer Verlag |location=Stuttgart New York |isbn=978-0-89574-027-4 |pages=128}}</ref> of ''Dunkleosteus'' have been described so far. However, many of them are poorly characterized and may be [[Synonym (taxonomy)|synonyms]] of previously named species or not pertain to ''Dunkleosteus''.<ref name=":3" /> ''Dunkleosteus'' as currently defined is a [[wastebasket taxon]] for large [[Dunkleosteoidea|dunkleosteoid]] [[Arthrodira|arthrodires]] that are more [[Apomorphy and synapomorphy|evolutionarily derived]] than ''[[Eastmanosteus]]''.<ref name=":3" /> [[File:Dunkleosteus skull steveoc.jpg|thumb|Labelled skull diagram of ''D. terrelli'']] The [[type species]], ''D. terrelli'', is the largest, best-known species of the genus. Size estimates for this species range from {{convert|4.1|-|10|m|ft|abbr=on}} in length, though estimates greater than 4.5 m are poorly supported.<ref name=":2" /><ref name=":0" /> Skulls of this species can be up to {{convert|60|-|70|cm|abbr=on|in}} in length.<ref name=":0" /> ''D. terrelli''{{'s}} fossil remains are found in Upper Frasnian to Upper Famennian Late Devonian strata of the United States ([[Huron shale|Huron]], [[Chagrin Shale|Chagrin]], and [[Cleveland Shale]]s of Ohio, the Conneaut and [[Chadakoin Formation]]s of [[Pennsylvania]], the [[Chattanooga Shale]] of Tennessee, the [[Lost Burro Formation]] of California, and possibly the Ives [[breccia]] of Texas<ref name=Denison/>) and [[Europe]]. ''D. belgicus'' (?) is known from fragments described from the [[Famennian]] of [[Belgium]]. The median dorsal plate is characteristic of the genus, but, a plate that was described as a suborbital is an anterolateral.<ref name=Denison/> Lelièvre (1982) considers this [[taxon]] a ''[[nomen dubium]]'' ("doubtful name") and suggests the material may actually pertain to ''[[Ardennosteus]]''.<ref>{{Cite journal |last=Lelièvre |first=Hervé |date=1982 |title=Ardennosteus ubaghsi n.g., n. sp. Brachythoraci primitif (vertébré, placoderme) du Famennien d'Esneux (Belgique) |url=https://popups.uliege.be/0037-9395/index.php?id=3220 |journal=Annales de la Société géologique de Belgique |volume=105 |issue=1}}</ref> ''D. denisoni'' is known from a small median dorsal plate, typical in appearance for ''Dunkleosteus'', but much smaller than normal. It is comparable in skull structure to ''D. marsaisi''.<ref name=Denison/> [[File:Dunkleosteus marsaisi 45.JPG|thumb|''D. marsaisi'' skull]] ''D. marsaisi'' refers to the ''Dunkleosteus'' fossils from the Lower Famennian Late Devonian strata of the [[Atlas Mountains]] in [[Morocco]]. It differs in size, the known skulls averaging a length of {{convert|35|cm|ft}} and in form to ''D. terrelli''. In ''D. marsaisi'', the snout is narrower, and a postpineal fenestra may be present. Many researchers and authorities consider it a synonym of ''D. terrelli''.<ref>{{cite journal |last=Murray |first=A.M. |title=The Palaeozoic, Mesozoic and Early Cenozoic fishes of Africa |journal=Fish and Fisheries |year=2000 |volume=1 |issue=2 |pages=111–145 |doi=10.1046/j.1467-2979.2000.00015.x|bibcode=2000AqFF....1..111M }}</ref> H. Schultze regards ''D. marsaisi'' as a member of ''[[Eastmanosteus]]''.<ref name=Denison/><ref name=Schultz>{{cite journal |last=Schultz |first=H |title=Large Upper Devonian arthrodires from Iran |journal=Fieldiana Geology |year=1973 |volume=23 |pages=53–78 |doi=10.5962/bhl.title.5270 |doi-access=free}}</ref> ''D. magnificus'' is a large placoderm from the Frasnian [[Rhinestreet Shale]] of New York. It was originally described as ''[[Dinichthys]] magnificus'' by Hussakof and Bryant in 1919, then as "''Dinichthys mirabilis''" by Heintz in 1932. Dunkle and Lane (1971) moved it to ''Dunkleosteus'',<ref name=Denison/> whereas Dennis-Bryan (1987) considered it to belong to the genus ''[[Eastmanosteus]]''.<ref>{{cite journal |last1=Dennis-Bryan |first1=Kim |title=A new species of eastmanosteid arthrodire (Pisces: Placodermi) from Gogo, Western Australia |journal=Zoological Journal of the Linnean Society |date=1987 |volume=90 |issue=1 |pages=1–64 |doi=10.1111/j.1096-3642.1987.tb01347.x}}</ref> This species has a skull length of {{convert|55|cm|in||abbr=on|}} and a total estimated length of approximately {{convert|3|m|ft||abbr=on|}}.<ref name=":3" /> ''D. missouriensis'' is known from fragments from Frasnian [[Missouri]]. Dunkle and Lane regard them as being very similar to ''D. terrelli''.<ref name=Denison/> ''D. newberryi'' is known primarily from a {{convert|28|cm|in}} long infragnathal with a prominent anterior cusp, found in the Frasnian portion of the [[Genesee Group]] of New York, and originally described as ''Dinichthys newberryi''.<ref name=Denison/> Lebedev et al. (2023) noted ''D. newberryi'' has an unusually long marginal tooth row compared to other species of ''Dunkleosteus'' and lacks the accessory odontoids typical of this genus, suggesting it might not belong to ''Dunkleosteus'' or even Dunkleosteoidea.<ref name=":3" /> ''D. amblyodoratus'' is known from some fragmentary remains from Late Devonian strata of [[Kettle Point Formation]], Ontario. The species name means 'blunt spear' and refers to the way the [[nuchal]] and paranuchal plates in the back of the head form the shape of a blunted spearhead.<ref name="Carr+2010"/> ''D. raveri'' is a small species, possibly 1 meter long, known from an uncrushed skull roof found in a carbonate concretion from near the bottom of the Huron Shale, of the Famennian [[Ohio Shale]] strata. Besides its small size, it had comparatively large eyes. Because ''D. raveri'' was found in the strata directly below the strata where the remains of ''D. terrelli'' are found, ''D. raveri'' may have given rise to ''D. terrelli''. The species name commemorates Clarence Raver of [[Wakeman, Ohio]], who discovered the concretion containing the [[holotype]].<ref name="Carr+2010"/> ''D. tuderensis'' is known from an infragnathal found in the lower-middle [[Famennian]]-aged [[Bilovo Formation]] of the [[Tver Region]] in northwest Russia. The specific name refers to the [[Maliy Tuder River]] as the holotype was found on its bank.<ref name=":3">{{Cite journal |last1=Lebedev |first1=Oleg A. |last2=Engelman |first2=Russell K. |last3=Skutschas |first3=Pavel P. |last4=Johanson |first4=Zerina |last5=Smith |first5=Moya M. |last6=Kolchanov |first6=Veniamin V. |last7=Trinajstic |first7=Kate |last8=Linkevich |first8=Valeriy V. |date=May 2023 |title=Structure, Growth and Histology of Gnathal Elements in ''Dunkleosteus'' (Arthrodira, Placodermi), with a Description of a New Species from the Famennian (Upper Devonian) of the Tver Region (North-Western Russia) |journal=Diversity |language=en |volume=15 |issue=5 |pages=648 |doi=10.3390/d15050648 |issn=1424-2818 |doi-access=free }}</ref> In total, of the ten or so species listed above only four are agreed upon as valid species of ''Dunkleosteus'' by all researchers: ''D. terrelli'' (which may or may not include ''Dunkleosteus'' material from Morocco), ''D. raveri'', ''D. tuderensis'', and possibly ''D. amblyodoratus'' (which is known from limited material that appears distinct but is difficult to compare with other dunkleosteids). The taxonomy of early late [[Devonian]] ([[Frasnian]]) species is poorly established, whereas latest [[Devonian]] ([[Famennian]]) species are easily referable to this genus. This is not counting additional material assigned to ''Dunkleosteus'' [[Species affinis|sp.]] from the [[Famennian]] of California, Texas, Tennessee, and Poland.<ref name=":3" /><ref>{{Cite journal |last1=Dunkle |last2=Lane |first2=N.G. |date=1971 |title=Devonian fishes from California. Kirtlandia |journal=Kirtlandia |volume=15 |pages=1–5}}</ref> ==Description== ===Size and anatomy=== [[File:Dunkleosteus terrelli size.png|left|thumb|Comparison of multiple size estimates for ''D. terrelli'']] ''Dunkleosteus'' was covered in [[dermal bone]] forming armor plates across its skull and front half of its [[torso|trunk]]. This armor is often described as being over {{convert|2|–|3|in|cm}} thick,<ref>{{cite web |last1=Mangels |first1=John |title=My, What A Big Mouth You Have |url=https://www.cmnh.org/dunkjaws |website=Cleveland Museum of Natural History |access-date=5 February 2024}}</ref><ref name="Carr+2010" /> but this is only across the thickened nuchal plate at the back of the skull.<ref name="Carr+2010" /> Thickening of the nuchal plate is a [[Apomorphy and synapomorphy|common feature]] of [[Eubrachythoraci|eubrachythoracid]] [[Arthrodira|arthrodires]].<ref>{{cite journal |last1=Miles |first1=Roger S. |title=Features of Placoderm Diversification and the Evolution of the Arthrodire Feeding Mechanism. |journal=Transactions of the Royal Society of Edinburgh |date=1969 |volume=68 |issue=6 |pages=123–170 |doi=10.1017/S0080456800014629}}</ref><ref>{{cite journal |last1=Stensiö |first1=Erik A. |title=Anatomical studies on the arthrodiran head. Pt. 1. Preface, geological and geographical distribution, the organisation of the arthrodires, the anatomy of the head in the Dolichothoraci, Coccosteomorphi and Pachyosteomorphi |journal=Kungligar Svenska Vetenskapakadamiens Handlingar |volume=9 |page=1–419}}</ref> Across the rest of the body the armor is generally much thinner, only about {{convert|0.33|–|1|in|cm}} in thickness.<ref>{{cite web |title=Specimen Data – UMORF University of Michigan Online Repository of Fossils |url=https://umorf.ummp.lsa.umich.edu/wp/specimen-data/?Model_ID=1336 |website=UMORF |access-date=5 February 2024}}</ref> The plates of ''Dunkleosteus'' had both a hard [[Bone#Structure|cortical]] and a marrow-filled [[Bone#Structure|cancellous]] layer, unlike most [[teleost]] fishes and more similar to [[tetrapod]] bones.<ref name=":0" /><ref>{{cite journal |last1=Giles |first1=Sam |last2=Rücklin |first2=Martin |last3=Donoghue |first3=Philip C.J. |title=Histology of "placoderm" dermal skeletons: Implications for the nature of the ancestral gnathostome |journal=Journal of Morphology |date=June 2013 |volume=274 |issue=6 |pages=627–644 |doi=10.1002/jmor.20119|pmid=23378262 |pmc=5176033 }}</ref> Mainly the armored frontal sections of specimens have been [[fossilized]], and consequently, the appearance of the other portions of the fish is mostly unknown.<ref>{{cite AV media |url=https://www.youtube.com/watch?v=lEEhm4rzxEg |title=Prehistoric Monsters Revealed |date=2008 |last=Dash |first=Sean |publisher=Workaholic Productions / History Channel |location=United States |access-date=18 December 2015}}{{cbignore}}{{Dead YouTube link|date=February 2022}}</ref> In fact, only about 5% of ''Dunkleosteus'' specimens have more than a quarter of their skeleton preserved.<ref>Carr, R, & G.L. Jackson. 2008. [https://www.researchgate.net/publication/213769842_THE_VERTEBRATE_FAUNA_OF_THE_CLEVELAND_MEMBER_FAMENNIAN_OF_THE_OHIO_SHALE The Vertebrates fauna of the Cleveland member (Famennian) of the Ohio Shale. Society of Vertebrates Paleontology]. 1–17.</ref> Because of this, many reconstructions of the hindquarters are often based on fossils of smaller [[arthrodire]]s, such as ''[[Coccosteus]]'', which have preserved hind sections,<ref name=":0" /> leading to widely varying size estimates.<ref name=":0" /> ''Dunkleosteus terrelli'' is one of the largest known placoderms, with its maximum size being variably estimated as anywhere from {{convert|4.1|–|10|m|ft}} by different researchers.<ref name="Anderson&Westneat2007" /><ref name="Anderson&Westneat2009" /><ref name="Ferron2017" /><ref>{{cite journal|last=Williams|first=Nigel|year=2007|title=Force feeding|journal=Current Biology |volume=17 |issue=1 |pages=R3 |doi=10.1016/j.cub.2006.11.057|s2cid=36585467 |doi-access=free|bibcode=2007CBio...17...R3W }}</ref><ref name=":0">{{Cite journal |last=Engelman |first=Russell K. |date=2023|title=A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira) |journal=Diversity |language=en |volume=15 |issue=3 |pages=318 |doi=10.3390/d15030318 |issn=1424-2818 |doi-access=free }}</ref> However, most cited length estimates are speculative and lack quantitative or statistical backing, and lengths of {{convert|5|m|ft|abbr=on}} or more are poorly supported.<ref name="Ferron2017" /><ref name=":0" /> Most studies that estimate the length of ''Dunkleosteus terrelli'' do not provide information as to how these estimates were calculated, the measurements used to scale them, or which specimens were examined. Most are implied to be based on either CMNH 5768 (the largest complete armor of ''D. terrelli'') or CMNH 5936 (the largest known jaw fragment). Additionally, these longer reconstructions often require ''Dunkleosteus'' to lack many features consistent across the body plans of other arthrodires like ''[[Coccosteus]]'' and ''[[Amazichthys]].''<ref name=":4">{{Cite journal |last=Engelman |first=Russell K. |date=2024 |title=Reconstructing Dunkleosteus terrelli (Placodermi: Arthrodira): A new look for an iconic Devonian predator |url=https://palaeo-electronica.org/content/2024/5307-dunkleosteus-reconstruction |journal=Palaeontologia Electronica |doi=10.26879/1343}}</ref> {{multiple image |align=right |perrow=1 |total_width=240 |image1=Dunkleosteus terrelli 2017 reconstruction.png |caption1=[[Paleoart|Life reconstruction]] of ''D. terrelli'', as presented by Ferrón ''et al.'' 2017<ref name="Ferron2017"/> |image2=Dunkleosteus terrelli 2023 reconstruction.png |caption2=Life reconstruction of ''D. terrelli'', as presented by Engelman 2023<ref name=":0"/> }}Most of the studies with well-defined methods produce lengths of {{convert|5|m|ft}} or less for ''Dunkleosteus terrelli'',<ref name=":0" /> with the exception of Ferrón ''et al.'' (2017), which produces larger estimates of {{convert|6.88|–|8.79|m|ft}} based on upper jaw perimeter of modern sharks.<ref name="Ferron2017" /> However, arthrodires have proportionally larger mouths than modern sharks, making the lengths estimated by Ferrón ''et al.'' (2017) unreliable.<ref name=":2">{{cite journal |last=Engelman |first=Russell |date=10 April 2023 |title=Giant, swimming mouths: oral dimensions of extant sharks do not accurately predict body size in ''Dunkleosteus terrelli'' (Placodermi: Arthrodira) |journal=PeerJ |language=en |volume=11 |pages=e15131 |doi=10.7717/peerj.15131 |pmid=37065696 |pmc=10100833 |doi-access=free }}</ref> Upper jaw perimeter overestimates the size of complete arthrodires like ''[[Coccosteus]]'' and the estimates of Ferrón ''et al.'' (2017) result in ''Dunkleosteus'' having an extremely small head and hyper-elongate trunk relative to the known dimensions of the fossils.<ref name=":2" /> The reconstruction presented in Ferrón ''et al.'' (2017) is also incorrectly scaled to the known dimensions of the fossil material; if scaled to the size of CMNH 5768, it produces a length of {{convert|3.77|m|ft}}, agreeing with the shorter estimates in later studies.<ref name=":2" /> Carr (2010) estimated a {{convert|4.6|m|ft}} long adult individual of ''Dunkleosteus terrelli'' to have weighed {{convert|665|kg|lb}}, assuming a shark-like body plan and a similar length-weight relationship.<ref name="Carr 20102">{{cite journal |last1=Carr |first1=Robert K. |date=2010 |title=Paleoecology of Dunkleosteus terrelli (Placodermi: Arthrodira). |url=https://www.researchgate.net/publication/235924093 |journal=Kirtlandia |volume=57}}</ref> Engelman (2023), using an [[ellipsoid]] [[volume]]tric method, estimated weights of {{convert|950|–|1200|kg|lb}} for typical ({{convert|3.41|m|ft}} long) adult ''Dunkleosteus'', and weights of {{convert|1494|–|1764|kg|lb}} for the largest ({{convert|4.1|m|ft|1}} in this study) individual.<ref name=":0" /> The higher weights by Engelman (2023) are mostly a result of the fact that arthrodires tend to have relatively deeper and wider bodies compared to sharks.<ref name=":0" /> An exceptionally preserved specimen of ''D. terrelli'' preserves a [[Fish fin|pectoral fin]] outline with [[wikt:ceratotrichia|ceratotrichia]], implying that the fin morphology of placoderms was much more variable than previously thought, and was heavily influenced by locomotory requirements. This knowledge, coupled with the knowledge that fish morphology is more heavily influenced by feeding niche than phylogeny, allowed a 2017 study to infer the [[Fish fin|caudal fin]] shape of ''D. terrelli'', reconstructing this fin with a strong ventral lobe, a high [[aspect ratio]], narrow [[caudal peduncle]], in contrast to previous reconstructions based on the [[Fish locomotion|anguilliform]] caudal fin of coccosteomorph placoderms.<ref name="Ferron2017">{{Cite journal|last1=Ferrón|first1=Humberto G.|last2=Martínez-Pérez|first2=Carlos|last3=Botella|first3=Héctor|date=2017|title=Ecomorphological inferences in early vertebrates: reconstructing Dunkleosteus terrelli (Arthrodira, Placodermi) caudal fin from palaeoecological data|journal=PeerJ|language=en|volume=5|pages=e4081|doi=10.7717/peerj.4081|pmid=29230354|pmc=5723140|issn=2167-8359 |doi-access=free }}</ref> The only vertebral remains known for Dunkleosteus are a small series of 16 vertebrae within the trunk armor of the specimen CMNH 50322.<ref name=":5" /> Most of these vertebrae are highly fused, and have very prominent, laterally-projecting articular facets compared to other arthrodires.<ref name=":4" /><ref name=":5" />. Although many arthrodires show the incorporation of anterior vertebrae into a [[synarcual]], in these species the fused region is small whereas the fused region of ''Dunkleosteus'' extends almost to the end of the trunk armor, which would make its spine very stiff.<ref name=":5" /><ref name=":4" /> This, along with a ridge on the inside of the trunk armor suggesting an unusually well-developed attachment for the horizontal septum, suggests ''Dunkleosteus'' may have had an anteriorly stiffened spine and specialized connective tissues to transmit force generated by the anterior trunk [[muscles]] to the tail fin, similar to [[Fish locomotion|thunniform]] vertebrates like [[Lamnidae|lamnids]] and [[tunas]].<ref name=":4" /> The pelvic girdle of ''Dunkleosteus'' is relatively small relative to the overall size of the armor.<ref name=":4" /> Several specimens preserve associated pelvic girdles, but their original position was not recorded during preservation.<ref name=":4" /> However, because these specimens were excavated from cliff faces, they were probably found in close to the armor, suggesting these fins were associated with the end of the ventral shield as in other arthrodires.<ref name=":4" /> One specimen may preserve pelvic fin basals near the end of the trunk armor.<ref name=":4" /> ====Length estimations of ''D. terrelli''==== {| class="wikitable sortable" style="margin-left: auto; margin-right: auto; border: none;" |+ Length estimates of ''Dunkleosteus terrelli'' (modified from Table 7 of Engelman 2023<ref name=":0" />) ! Study (author) ! Year ! Length ! Method ! Reference |- | Newberry || 1875 || {{convert|4.5|–|5.5|m|ft}} || '''Extrapolated from ''Coccosteus cuspidatus'', measurements and specimen used unclear''' || <ref name=":1">{{cite book |last1=Newberry |first1=John S. |url=https://www.biodiversitylibrary.org/item/116994#page/15/mode/1up |title=Report of the Geological Survey of Ohio. Volume II. Geology and Paleontology |date=1875 |publisher=Nevins and Myers, State Printers |volume=2 |location=Columbus |page=24 |contribution=Descriptions of fossil fishes}}</ref> |- | Newberry || 1889 || {{convert|4.5|m|ft}} || Unstated (implied extrapolation from ''Coccosteus'') || <ref>{{cite journal |last1=Newberry |first1=John S. |date=1889 |title=Paleozoic fishes of North America |url=https://www.biodiversitylibrary.org/item/51025#page/5/mode/1up |journal=Monographs of the U.S. Geological Survey |volume=16 |page=24}}</ref> |- | Dean || 1895 || {{convert|3|m|ft}} || Methods, measurements, and specimens unstated || <ref>{{cite book |last1=Dean |first1=Bashford |title=Fishes, Living and Fossil: An Outline of Their Forms and Probable Relationships |date=1895 |publisher=Macmillan and Company |location=London |page=130}}</ref> |- | Hussakof || 1905 || {{convert|1.67|m|ft}} (AMNH FF 195) <br /> {{convert|3.79|m|ft}} (extrapolated to CMNH 5768 by Engelman 2023<ref name=":0"/> assuming similar head-trunk proportions) || '''Entering angle of body''' || <ref>{{cite journal |last1=Hussakof |first1=Louis |title=Notes on the Devonian "placoderm" ''Dinichthys intermedius'' Newb. |journal=Bulletin of the American Museum of Natural History |date=1905 |volume=21 |pages=27–36}}</ref> |- | Anonymous|| 1923 || {{convert|7.6|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite journal |last1=Anonymous |title=Cleveland shale fishes |journal=Bulletin of the Cleveland Museum of Natural History |date=1923 |volume=9 |pages=36}}</ref> |- | Hyde || 1926 || {{convert|4.5|–|6|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite journal |last1=Hyde |first1=Jesse E. |title=Collecting fossil fishes from the Cleveland Shale |journal=Natural History |date=1926 |volume=26 |pages=497–504}}</ref> |- | Romer || 1966 || {{convert|9|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite book |last1=Romer |first1=Alfred S. |title=Vertebrate Paleontology |date=1966 |publisher=University of Chicago Press |location=Chicago |page=49 |edition=3rd}}</ref> |- | Colbert || 1969 || {{convert|9|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite book |last1=Colbert |first1=Edwin H. |title=Evolution of the Vertebrates: A History of Backboned Animals Through Time |date=1969 |publisher=John Wiley and Sons |location=Hoboken |page=36 |edition=2nd}}</ref> |- | Denison || 1978 || {{convert|6|m|ft}} || Methods, measurements, and specimens used not stated || <ref name=Denison /> |- | Williams || 1992 || {{convert|5|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite journal |last1=Williams |first1=Michael E. |title=Jaws: The Early Years |journal=Explorer |date=1992 |volume=34 |pages=4–8}}</ref> |- | Janvier || 2003 || {{convert|6|–|7|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite book |last1=Janvier |first1=P. |title=Early Vertebrates |date=2003 |publisher=Clarendon Press |location=Oxford |page=12}}</ref> |- | Young || 2003 || {{convert|6|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite journal |last1=Young |first1=Gavin C. |title=Did placoderm fish have teeth? |journal=Journal of Vertebrate Paleontology |date=24 December 2003 |volume=23 |issue=4 |pages=987–990 |doi=10.1671/31|bibcode=2003JVPal..23..987Y |s2cid=85572061 }}</ref> |- | Anderson and Westneat || 2007 || {{convert|6|m|ft}} || Methods, measurements, and specimens used not stated || <ref name="Anderson&Westneat2007" /> |- | Anderson and Westneat || 2009 || {{convert|10|m|ft}} || Methods, measurements, and specimens used not stated || <ref name="Anderson&Westneat2009" /> |- | Carr || 2010 || {{convert|4.5|–|6|m|ft}} || Methods, measurements, and specimens used not stated || <ref name="Carr 20102"/> |- | Long || 2010 || {{convert|4.5|–|8|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite book |last1=Long |first1=John A. |title=The Rise of Fishes: 500 Million Years of Evolution |date=2010 |publisher=Johns Hopkins University Press |location=Baltimore |pages=88–90 |edition=2nd}}</ref> |- | Sallan and Galimberti || 2015 || {{convert|8|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite journal |last1=Sallan |first1=Lauren |last2=Galimberti |first2=Andrew K. |title=Body-size reduction in vertebrates following the end-Devonian mass extinction |journal=Science |date=13 November 2015 |volume=350 |issue=6262 |pages=812–815 |doi=10.1126/science.aac7373|pmid=26564854 |bibcode=2015Sci...350..812S |s2cid=206640186 }}</ref> |- | Ferrón ''et al.'' || 2017 || {{convert|6.88|m|ft}} (average adult, CMNH 5768) <br /> {{convert|8.79|m|ft}} (largest individual, CMNH 5936) || '''Upper jaw perimeter''' || <ref name="Ferron2017" /> |- | Long ''et al.'' || 2019 || {{convert|6|–|8|m|ft}} || Methods, measurements, and specimens used not stated || <ref>{{cite book |last1=Long |first1=John A. |last2=Choo |first2=Brian |last3=Clement |first3=Alice |contribution=The Evolution of Fishes through Geological Time |title=Evolution and Development of Fishes |editor1-last=Johanson |editor1-first=Zerina|editor2-last=Underwood |editor2-first=Charlie|editor3-last=Richter|editor3-first=Martha| date=31 December 2018 |pages=3–29 |doi=10.1017/9781316832172.002|isbn=978-1-316-83217-2 |s2cid=134217082 }}</ref> |- | Johanson ''et al.'' || 2019 || {{convert|3|m|ft}} (CMNH 50322) <br /> {{convert|7.1|m|ft}} (extrapolated to CMNH 5768 by Engelman 2023 assuming similar head-trunk proportions) || Methods and measurements not stated || <ref name=":5">{{cite journal |last1=Johanson |first1=Zerina |last2=Trinajstic |first2=Kate |last3=Cumbaa |first3=Stephen |last4=Ryan |first4=Michael |title=Fusion in the vertebral column of the pachyosteomorph arthrodire Dunkleosteus terrelli ('Placodermi') |journal=Palaeontologia Electronica |date=2019 |volume=22.2.20A |pages=1–13 |doi=10.26879/872|s2cid=162173408 |doi-access=free }}</ref> |- | Engelman || 2023 || {{convert|3.41|m|ft}} (average adult, CMNH 5768) <br /> {{convert|4.1|m|ft|1}} (largest individual, CMNH 5936) || '''Orbit-opercular length (head length minus snout)''' || <ref name=":0" /> |- | Engelman || 2023 || {{convert|3.41|m|ft}} (average adult, CMNH 5768) || '''Skull length in ''Coccosteus''''' || <ref name=":0" /> |- | Engelman || 2023 || {{convert|5.23|m|ft}} (average adult, CMNH 5768) || '''Infragnathal length in ''Coccosteus''''' (source considers this estimate unreliable due to ''Dunkleosteus'' having a relatively larger mouth than ''Coccosteus'') || <ref name=":0" /> |- | Engelman || 2023 || {{convert|3.47|m|ft}} (average adult, CMNH 5768) || '''Entering angle of body''' || <ref name=":0" /> |- | Engelman || 2023 || {{convert|3.88|m|ft}} (average adult, CMNH 5768) || '''Length of posteroventrolateral plate''' || <ref name=":0" /> |- | Engelman || 2023 || {{convert|3.40|m|ft}} (average adult, CMNH 5768) || '''Inferred location of pelvic girdle''' || <ref name=":0" /> |- |} ==Paleobiology== ===Diet=== [[File:Dunkleosteus terrelli CMNH 5936.png|thumb|left|Partial lower jaw of CMNH 5936, the largest known individual of ''Dunkleosteus terrell''i. Scale = 10 cm.]] ''Dunkleosteus terrelli'' possessed a [[four-bar linkage]] mechanism for [[Fish jaw|jaw]] opening that incorporated connections between the skull, the thoracic shield, the lower jaw and the jaw muscles joined by movable joints.<ref name=Anderson&Westneat2009>{{cite journal |last=Anderson |first=P.S.L. |author2=Westneat, M. |title=A biomechanical model of feeding kinematics for ''Dunkleosteus terrelli'' (Arthrodira, Placodermi) |journal=Paleobiology |date=2009 |volume=35 |issue=2 |pages=251–269 |doi=10.1666/08011.1 |bibcode=2009Pbio...35..251A |s2cid=86203770 |url=http://projects.fieldmuseum.org/sites/default/files/DunkPaleoBio.pdf |access-date=29 October 2017 |archive-date=7 November 2017 |archive-url=https://web.archive.org/web/20171107014026/http://projects.fieldmuseum.org/sites/default/files/DunkPaleoBio.pdf |url-status=dead }}</ref><ref name=Anderson&Westneat2007>{{Cite journal |last=Anderson |first=P.S.L. |author2=Westneat, M. |title=Feeding mechanics and bite force modelling of the skull of Dunkleosteus terrelli, an ancient apex predator |journal=Biology Letters |volume=3 |issue=1 |pages=76–79 |date=2007 |doi=10.1098/rsbl.2006.0569 |pmid=17443970 |pmc=2373817}}</ref> This mechanism allowed ''D. terrelli'' to both achieve a high speed of jaw opening, opening their jaws in 20 milliseconds and completing the whole process in 50–60 milliseconds (comparable to modern fishes that use [[Aquatic feeding mechanisms#Suction feeding|suction feeding]] to assist in prey capture<ref name=Anderson&Westneat2007/>) and producing high bite forces when closing the jaw, estimated at {{convert|4414|N|kg-f lb-f|0|abbr=on}} at the tip and {{convert|5363|N|kg-f lb-f|0|abbr=on}} at the blade edge,<ref name=Anderson&Westneat2007/> or even up to {{cvt|6170|N|kg-f lb-f|0}} and {{cvt|7495|N|kg-f lb-f|0}} respectively.<ref name=Anderson&Westneat2009/> The bite force is considered the highest of any living or fossil fish, and among the highest of any animal.<ref name="Anderson&Westneat2007" /> The pressures generated in those regions were high enough to puncture or cut through [[cuticle]] or [[dermal bone|dermal]] armor,<ref name=Anderson&Westneat2007/> suggesting that ''D. terrelli'' was adapted to prey on free-swimming, armored prey such as [[ammonite]]s and other placoderms.<ref name=Anderson&Westneat2009/> In addition, teeth of a [[Chondrichthyes|chondrichthyan]] thought to belong to ''[[Orodus]]'' (''Orodus'' spp.) were found in association with ''Dunkleosteus'' remains, suggesting that these were probably stomach contents regurgitated from the animal. ''Orodus'' is thought to be tachypelagic, or a fast-swimming [[pelagic fish]]. Thus, ''Dunkleosteus'' might have been fast enough to catch these fast organisms, and not a slow swimmer like originally thought.<ref name="Ferron2017" /> Fossils of ''Dunkleosteus'' are frequently found with [[Bolus (digestion)|bolus]]es of fish bones, semidigested and partially eaten remains of other fish.<ref name="Virtual Fossil">{{cite web|url= http://www.fossilmuseum.net/Fossil_Galleries/Fish_Devonian/Dunkleosteous/Dunkleosteus.htm |title=Dunkleosteus Placodermi Devonian Armored Fish from Morocco |work=Fossil Archives |publisher=The Virtual Fossil Museum |access-date=26 April 2009}}</ref> As a result, the [[fossil]] record indicates it may have routinely regurgitated prey bones rather than digest them. Mature individuals probably inhabited deep sea locations, like other placoderms, living in shallow waters during adolescence.<ref>{{Cite web|url=http://bioweb.uwlax.edu/bio203/f2013/peters_sadi/habitat.htm|title=UWL Website}}</ref> A specimen of ''Dunkleosteus'' (CMNH 5302), and ''[[Titanichthys]]'' (CMNH 9889), show damage said to be puncture damage from the bony fangs of other ''Dunkleosteus''.<ref name="Anderson&Westneat2009" /> ===Reproduction=== ''Dunkleosteus'', together with most other placoderms, may have also been among the first [[vertebrate]]s to [[internal fertilization|internalize egg fertilization]], as seen in some modern sharks.<ref name="Ahlberg">{{cite journal |last1=Ahlberg |first1=Per |first2=Kate |last2=Trinajstic |first3=Zerina |last3=Johanson |first4=John |last4=Long |s2cid=205217467 |year=2009 |title=Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires |journal=Nature |volume=460 |issue=7257 |pages=888–889 |doi=10.1038/nature08176|pmid=19597477 |bibcode=2009Natur.460..888A }}</ref> Some other placoderms have been found with evidence that they may have been [[viviparity|viviparous]], including what appears to have been an [[umbilical cord]].<ref>{{ cite journal | last = Long | first = J. A. |author2=Trinajstic, K. |author3=Young, G. C. |author4=Senden, T. | year = 2008 | title = Live birth in the Devonian period | journal = Nature | volume = 453 | issue = 7195 | pages = 650&ndash;652 | doi = 10.1038/nature06966 | pmid = 18509443 | bibcode = 2008Natur.453..650L | s2cid = 205213348 }}</ref> ===Growth=== {{multiple image |align=right |perrow=2 |total_width=380 |image1=Dunkleosteus juvenile fossil - Cleveland Museum of Natural History (34421618320).jpg |caption1=''D. terrelli'' juvenile specimen CMNH 7424 |image2=Dunkleosteus terrelli - Cleveland Museum of Natural History - 2014-12-26 (21137540331).jpg |caption2=''D. terrelli'' adult specimen CMNH 5768 }} [[morphology (biology)|Morphological]] studies on the lower jaws of juveniles of ''D. terrelli'' reveal they were proportionally as robust as those of adults, indicating they already could produce high bite forces and likely were able to shear into resistant prey tissue similar to adults, albeit on a smaller scale. This pattern is in direct contrast to the condition common in [[tetrapod]]s in which the jaws of juveniles are more [[gracile]] than in adults.<ref name="Snively_etal_2009">{{cite journal |last=Snively |first=E. |author2=Anderson, P.S.L. |author3=Ryan, M.J. |date=2009 |title=Functional and ontogenetic implications of bite stress in arthrodire placoderms |url=https://www.biodiversitylibrary.org/page/51811342#page/60/mode/1up |journal=Kirtlandia |volume=57}}</ref> ==See also== * [[List of placoderms]] ==References== {{Notelist}} {{reflist}} ==Further reading== * {{cite journal|first=Philip S. L.|last=Anderson|s2cid=86583150|year=2008|title=Shape Variation Between Arthrodire Morphotypes Indicates Possible Feeding Niches|journal=Journal of Vertebrate Paleontology|volume=28|number=4|pages=961–969|doi=10.1671/0272-4634-28.4.961|bibcode=2008JVPal..28..961A }} ==External links== {{Commons category|Dunkleosteus}} {{Wikispecies|Dunkleosteus}} * [http://www.ucmp.berkeley.edu/vertebrates/basalfish/placodermi.html ''Introduction to the Placodermi: Extinct Armored Fishes with Jaws''. Waggoner, Ben (2000). Retrieved Aug 1, 2005] * [https://www.nbcnews.com/id/wbna15940709 MSNBC: Prehistoric fish packed a mean bite] * [http://news.bbc.co.uk/1/hi/sci/tech/6195188.stm BBC: Ancient 'Jaws' had monster bite] {{Arthrodira|E.}} {{Taxonbar|from=Q131039|from2=Q911597|from3=Q911599|from4=Q911605|from5=Q911606|from6=Q911611|from7=Q911612|from8=Q911616|from9=Q911618|from10=Q911593|from11=Q25357547}} [[Category:Dunkleosteidae]] [[Category:Apex predators]] [[Category:Placoderms of Africa]] [[Category:Fossils of Morocco]] [[Category:Placoderms of Europe]] [[Category:Fossils of Belgium]] [[Category:Placoderms of North America]] [[Category:Fossils of Canada]] [[Category:Paleontology in Missouri]] [[Category:Paleontology in Pennsylvania]] [[Category:Paleontology in Tennessee]] [[Category:Late Devonian first appearances]] [[Category:Late Devonian animals]] [[Category:Famennian extinctions]] [[Category:Fossil taxa described in 1873]] [[Category:Fossil taxa described in 1956]] [[Category:Taxa named by John Strong Newberry]] [[Category:Symbols of Ohio]]'