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Ptyctodontida

The ptyctodontids ("folded-teeth") are placoderms of the order Ptyctodontida, containing the family Ptyctodontidae. With their big heads, big eyes, reduced armor and long bodies, the ptyctodontids bore a superficial resemblance to modern day chimaeras (Holocephali). Their armor was reduced to a pattern of small plates around the head and neck. Like the extinct and related acanthothoracids, and the living and unrelated holocephalians, most of the ptyctodontids are thought to have lived near the sea bottom and preyed on shellfish.

Timeline of genera
ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-416 till:-299 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:25 start:-416 ScaleMinor = unit:year increment:5 start:-416 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR value:claret id:ANK value:rgb(0.4,0.3,0.196) id:HER value:teal id:HAD value:green id:OMN value:blue id:black value:black id:white value:white id:paleozoic value:rgb(0.6,0.75,0.55) id:cambrian value:rgb(0.49,0.63,0.33) id:ordovician value:rgb(0,0.57,0.44) id:silurian value:rgb(0.70,0.88,0.71) id:devonian value:rgb(0.8,0.55,0.22) id:earlydevonian value:rgb(0.90,0.71,0.43) id:middledevonian value:rgb(0.96,0.81,0.51) id:latedevonian value:rgb(0.96,0.89,0.71) id:carboniferous value:rgb(0.4,0.65,0.6) id:mississippian value:rgb(0.4,0.56,0.4) id:pennsylvanian value:rgb(0.8,0.77,0.53) id:permian value:rgb(0.94,0.25,0.24) id:mesozoic value:rgb(0.38,0.77,0.79) id:triassic value:rgb(0.51,0.17,0.57) id:jurassic value:rgb(0.2,0.7,0.79) id:cretaceous value:rgb(0.5,0.78,0.31) id:cenozoic value:rgb(0.95,0.98,0.11) id:paleogene value:rgb(0.99,0.6,0.32) id:neogene value:rgb(0.999999,0.9,0.1) id:quaternary value:rgb(0.98,0.98,0.50) BarData= bar:eratop bar:space bar:periodtop bar:space bar:NAM1 bar:NAM2 bar:NAM3 bar:NAM4 bar:NAM5 bar:NAM6 bar:NAM7 bar:NAM8 bar:NAM9 bar:NAM10 bar:NAM11 bar:NAM12 bar:space bar:period bar:space bar:era PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 shift:(7,-4) bar:periodtop from: -416 till: -411.2 color:earlydevonian text:Loch. from: -411.2 till: -407 color:earlydevonian text:Prag. from: -407 till: -397.5 color:earlydevonian text:Ems. from: -397.5 till: -391.8 color:middledevonian text:Eif. from: -391.8 till: -385.3 color:middledevonian text:Givetian from: -385.3 till: -374.5 color:latedevonian text:Frasnian from: -374.5 till: -359.2 color:latedevonian text:Famennian bar:eratop from: -416 till: -359.2 color:devonian text:Devonian PlotData= align:left fontsize:M mark:(line,white) width:5 anchor:till align:left color:earlydevonian bar:NAM1 from: -411.2 till: -407 text: Tollodus color:middledevonian bar:NAM2 from: -397.5 till: -391.8 text: Goniosteus color:middledevonian bar:NAM3 from: -397.5 till: -385.3 text: Desmoporella color:middledevonian bar:NAM4 from: -397.5 till: -378.1 text: Campbellodus color:middledevonian bar:NAM5 from: -397.5 till: -374.5 text: Ctenurella color:middledevonian bar:NAM6 from: -397.5 till: -359.2 text: Denisonodus color:middledevonian bar:NAM7 from: -397.5 till: -359.2 text: Ptyctodopsis color:latedevonian bar:NAM8 from: -385.3 till: -381.7 text: Chelyophorus color:latedevonian bar:NAM9 from: -385.3 till: -381.7 text: Eczematolepis color:latedevonian bar:NAM10 from: -385.3 till: -381.7 text: Palaeomylus color:latedevonian bar:NAM11 from: -385.3 till: -381.7 text: Ptyctodus color:latedevonian bar:NAM12 from: -385.3 till: -359.2 text: Rhynchodus PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 bar:period from: -416 till: -411.2 color:earlydevonian text:Loch. from: -411.2 till: -407 color:earlydevonian text:Prag. from: -407 till: -397.5 color:earlydevonian text:Ems. from: -397.5 till: -391.8 color:middledevonian text:Eif. from: -391.8 till: -385.3 color:middledevonian text:Givetian from: -385.3 till: -374.5 color:latedevonian text:Frasnian from: -374.5 till: -359.2 color:latedevonian text:Famennian bar:era from: -416 till: -359.2 color:devonian text:Devonian ==Gallery==
Gallery
Image:Gamphacanthus.jpg|Fin spine of the ptyctodont, Gamphacanthus, showing color patterns; from the Middle Devonian of Wisconsin. Image:Ptyctodus ferox.jpg|Tooth plates from the ptyctodont Ptyctodus ferox, from the Middle Devonian of Wisconsin. Note the grinding surfaces. Image:Ptyctodont tooth plate.jpg|Beak-like tooth plate of a ptyctodont from the Middle Devonian of Wisconsin. == References ==
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