Examine individual changes

'{{automatic taxobox | fossil_range = [[Frasnian]]-[[Famennian]], {{Fossil range|382|358}} | image = Dunkleosteus (15677042802).jpg | image_caption = Reconstructed skull, [[Vienna Natural History Museum]] | taxon = Dunkleosteus | authority = Lehman, 1956 | type_species = ''[[Dinichthys]] terrelli'' | type_species_authority = [[John Strong Newberry|Newberry]], 1873 | subdivision_ranks = [[Species]] | subdivision = {{collapsible list| ''D. terrelli'' <small>(Newberry, 1873 [originally ''[[Dinichthys]]''])</small><br> ''D. ? belgicus'' <small>(Newberry) 1873</small><br> ''D. denisoni'' <small>(Kulczycki) 1957</small><br> ''D. marsaisi'' <small>Lehmann, 1956</small><br> ''D. magnificus'' <small>(Hussakof & Bryant) 1919</small><br> ''D. missouriensis'' <small>(Branson) 1914</small><br> ''D. newberryi'' <small>(Clarke) 1885</small><br> ''D. amblyodoratus'' <small>Carr & Hlavin, 2010</small><br> ''D. raveri'' <small>Carr & Hlavin, 2010</small> }} }} '''''Dunkleosteus''''' is an [[Extinction (biology)|extinct]] [[genus]] of [[arthrodire]] [[placoderm]] [[fish]] that existed during the [[Late Devonian]] period, about 358–382 [[million years ago]]. The name ''Dunkleosteus'' combines the [[Greek language|Greek]] ''osteus'' (οστεος), meaning "bone", and ''Dunkle'', in honor of David Dunkle of the [[Cleveland Museum of Natural History]]. It consists of ten species: ''D. terrelli'', ''D. belgicus'', ''D. denisoni'', ''D. marsaisi'', ''D. magnificus'', ''D. missouriensis'', ''D. newberryi'', ''D. amblyodoratus'', and ''D. raveri''; some of which are among the largest placoderms to have ever lived. The largest species, ''D. terrelli'' grew up to {{convert|6|m|ft|1|abbr=on}} long and {{convert|1|MT|ST|abbr=on}} in weight. Few other placoderms rivaled ''Dunkleosteus'' in size. Dunkleosteus could quickly open and close its jaw, like modern day [[Aquatic feeding mechanisms#Suction feeding|suction feeders]], and had a bite force of {{convert|6000|N|kg-f lb-f|0|abbr=on}} at the tip and {{convert|7400|N|kg-f lb-f|0|abbr=on}} at the blade edge. In recent decades, ''Dunkleosteus'' has achieved recognition in popular culture, with a large number of specimens on display, and notable appearances in entertainment media like ''[[Sea Monsters - A Walking with Dinosaurs Trilogy]]'' and ''[[River Monsters]]''. Numerous [[fossils]] of some species have been found in [[North America]], [[Poland]], [[Belgium]], and [[Morocco]]. ==Taxonomy== [[File:Dunkleosteus BW.jpg|thumb|Restoration of ''D. terreli'']] ''Dunkleosteus'' was named in 1956 to honour [[David Dunkle]], then curator of [[vertebrate paleontology]] at the [[Cleveland Museum of Natural History]]. The [[type species]] ''D. terrelli'' was originally described in 1873 as a species of ''[[Dinichthys]]''. ''Dunkleosteus'' is an [[arthrodire]] originally placed in the family [[Dinichthyidae]], which is composed mostly of large, carnivorous fish like ''[[Gorgonichthys]]''. Anderson (2009) suggests, because of its primitive [[Fish jaw|jaw structure]], ''Dunkleosteus'' should be placed outside the family Dinichthyidae, perhaps close to the base of the clade Pachyosteomorpha, near ''[[Eastmanosteus]]''. Carr and Hlavin (2010) resurrect [[Dunkleosteidae]] and place ''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| url =| doi =10.1111/j.1096-3642.2009.00578.x}}</ref> Dinichthyidae, in turn, is made into a [[Monotypic taxon|monospecific]] family.<ref name=Carr1995>{{cite journal|last=Carr|first=Robert K.|author2=William J. Hlavin|title=Dinichthyidae (Placodermi):A paleontological fiction?|journal=Geobios|date=September 2, 1995|volume=28|pages=85–87|url=http://www.sciencedirect.com/science/article/pii/S0016699595800921|doi=10.1016/S0016-6995(95)80092-1}}</ref> === Species === [[File:Dunkleosteus marsaisi 45.JPG|thumb|''D. marsaisi'' skull]] At least 10 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. The [[type species]], ''D. terrelli'', is the largest, best-known species of the genus. It has a rounded snout. ''D. terrelli''<nowiki>'</nowiki>s fossil remains are found in Upper Frasnian to Upper Famennian Late Devonian strata of the United States (Huron and [[Cleveland Shale]] of Ohio, the Conneaut of [[Pennsylvania]], Chattanooga Shale of Tennessee, Lost Burro Formation, California, and possibly 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 apparently an anteriolateral plate.<ref name=Denison/> ''D. denisoni'' is known from a small median dorsal plate, typical in appearance for ''Dunkleosteus'', but much smaller than normal.<ref name=Denison/> ''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}}</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}}</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 moved it to ''Dunkleosteus'' in 1971.<ref name=Denison/> ''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/> ''D. amblyodoratus'' is known from some fragmentary remains from Late Devonian strata of [[Kettle Point 44, Ontario|Kettle Point]], [[Canada]]. 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. Although it is known only from fragments, it is estimated to have been about {{convert|6|m|ft|1}} long in life.<ref name="Carr+2010"/> ''D. raveri'' is a small, possibly 1-m-long species 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 where the [[holotype]] was found.<ref name="Carr+2010"/> ==Description== [[File:Dunkleosteus intermedius.jpg|thumb|left|Life restoration of ''D. marsaisi'']] The largest species, ''D. terrelli'', estimated to be grew up to {{convert|6|m|ft|1|abbr=on}} in length and {{convert|1|MT|ST|abbr=on}} in weight, making it one of the largest placoderms to have existed.<ref name=Anderson&Westneat2007/><ref name=Anderson&Westneat2009/><ref name="Carr2010">{{cite journal|last1=Carr|first1=Robert K.|title=Paleoecology of Dunkleosteus terrelli (Placodermi: Arthrodira).|journal=Kirtlandia|date=2010|volume=57|url=https://www.researchgate.net/publication/235924093_The_Cleveland_Museum_of_Natural_History_PALEOECOLOGY_OF_DUNKLEOSTEUS_TERRELLI_PLACODERMI_ARTHRODIRA}}</ref> Like other placoderms, ''Dunkleosteus'' had a two-part bony, [[Armour (anatomy)|armoured]] exterior, which may have made it a relatively slow but powerful swimmer. Instead of [[teeth]], ''Dunkleosteus'' possessed two pairs of sharp bony plates which formed a beak-like structure.<ref name=Anderson&Westneat2009/> ''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|last=Ahlberg|first=Per|first2=Kate|last2=Trinajstic|first3=Zerina|last3=Johanson|first4=John|last4=Long|year=2009|title=Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires|journal=Nature |volume=460|pages=888–889|doi=10.1038/nature08176}}</ref> [[File:Dunkleosteus skull steveoc.jpg|thumb|A skull diagram of ''Dunkleosteus'']] Mainly the armoured frontal sections of specimens have been [[fossilized]], and consequently the appearance of the other portions of the fish is mostly unknown.<ref>{{cite film|last=Dash|first=Sean|title=Prehistoric Monsters Revealed|location=United States|publisher=Workaholic Productions / History Channel|date=2008|url=https://www.youtube.com/watch?v=lEEhm4rzxEg|accessdate=December 18, 2015}}</ref> Because of this, many reconstructions of the hindquarters are often based on smaller [[arthrodire]]s, such as ''[[Coccosteus]]'', which had preserved hind sections. However, an exceptionally preserved specimen of ''D. terrelli'' preserves ceratotrichia in a pectoral fin, implying that the fin morphology of placoderms was much more morphologically variable than previously thought, and was heavily influenced by locomotion 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 body shape of ''D. terrelli''. This new reconstruction gives D. terrelli a much more shark-like profile, including a strong anterior lobe on its tail, in contrast to reconstructions based on other placoderms.<ref>{{Cite journal|last=Ferrón|first=Humberto G.|last2=Martínez-Pérez|first2=Carlos|last3=Botella|first3=Héctor|date=2017-12-06|title=Ecomorphological inferences in early vertebrates: reconstructing Dunkleosteus terrelli (Arthrodira, Placodermi) caudal fin from palaeoecological data|url=https://peerj.com/articles/4081|journal=PeerJ|language=en|volume=5|doi=10.7717/peerj.4081|issn=2167-8359}}</ref> The most famous specimens of ''Dunkleosteus'' are displayed at the [[Cleveland Museum of Natural History]], and others are displayed at the [[American Museum of Natural History]], [[National Museum of Natural History]], [[State Museum of Pennsylvania]], Harrisburg and in the [[Queensland Museum]] in [[Brisbane]], Queensland.{{citation needed|date=October 2017}} ===Diet=== [[File:Dunkleosteus terrelli - MUSE.jpg|thumb|Life restoration of ''D. terrelli'']] ''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 together 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|url=http://projects.fieldmuseum.org/sites/default/files/DunkPaleoBio.pdf}}</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| url=http://rsbl.royalsocietypublishing.org/content/3/1/77.full|doi=10.1098/rsbl.2006.0569|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 produce high bite forces when closing the jaw, estimated at {{convert|6000|N|kg-f lb-f|0|abbr=on}} at the tip and {{convert|7400|N|kg-f lb-f|0|abbr=on}} at the blade edge in the largest individuals.<ref name=Anderson&Westneat2009/> 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/> 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 |accessdate=2009-04-26}}</ref> As a result, the [[fossil]] record indicates it may have routinely regurgitated prey bones rather than digest them. It probably inhabited [[inshore]] waters.{{citation needed|date=October 2017}} ===Juveniles=== Morphological studies on the lower jaws of juveniles of ''D. terrelli'' reveal they were proportionally as robust as those of adults, indicating they already had the ability to 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 tetrapods 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. |title=Functional and ontogenetic implications of bite stress in arthrodire placoderms|journal=Kirtlandia|date=2009|volume=57}}</ref> ==See also== {{Portal|Paleontology|Fish}} * [[List of placoderms]] * ==References== {{Reflist|2}} ==Further reading== * {{cite journal|first=Philip S. L.|last=Anderson|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}} ==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] * [http://www.msnbc.msn.com/id/15940709/ MSNBC: Prehistoric fish packed a mean bite] * [http://news.bbc.co.uk/1/hi/sci/tech/6195188.stm BBC: Ancient 'Jaws' had monster bite] {{Placodermi|Ar.|state=collapsed}} {{Taxonbar|from=Q131039}} [[Category:Dunkleosteidae]] [[Category:Placoderms of Africa]] [[Category:Placoderms of Europe]] [[Category:Placoderms of North America]] [[Category:Late Devonian first appearances]] [[Category:Late Devonian animals]] [[Category:Famennian extinctions]] [[Category:Fossil taxa described in 1956]] [[Category:Taxa named by John Strong Newberry]] [[Category:Paleontology in Pennsylvania]] [[Category:Paleontology in Tennessee]] [[Category:Paleontology in Belgium]] [[Category:Paleontology in Morocco]] [[Category:Paleontology in Missouri]] [[Category:Paleontology in Canada]]'