Petalichthyida is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

of small, flattened

placoderm Placoderms (from Ancient Greek πλάξ 'plax'', ''plakos'''Plate (animal anatomy), plate' and δέρμα 'derma'''skin') are vertebrate animals of the class (biology), class Placodermi, an extinct group of prehistoric fish known from Pal ...

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

. They are typified by their splayed pectoral fins, exaggerated lateral spines, flattened bodies, and numerous tubercles that decorated all of the plates and scales of their armor. They reached a peak in diversity during the Early

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

and were found throughout the world, particularly in Europe (especially in Germany), North America, Asia, South America, and Australia. The petalichthids ''

Lunaspis ''Lunaspis'' is an extinct genus of armor-plated petalichthyid placoderm fish that lived in shallow marine environments of the Early Devonian period, from approximately 409.1 to 402.5 million year ago.Fossilworks: Gateway to the Paleobiology dat ...

'' and '' Wijdeaspis'' are among the best known. The earliest and most primitive known petalichthyid is ''

Diandongpetalichthys ''Diandongpetalichthys liaojiaoshanensis'' is an extinct petalichthyid placoderm from the Early Devonian of China. Fossils Several specimens, in the forms of one complete and several incomplete skull roofs, disarticulated portions of the trunk s ...

'', which is from earliest Devonian-aged strata of

Yunnan Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

. The presence of ''Diandongpetalichthys'', along with other primitive petalichthyids including ''

Neopetalichthys ''Neopetalichthys yenmenpaensis'' is an extinct petalichthid placoderm from the Early Devonian of China. Fossils The holotype and only known specimen is a poorly preserved partial, and elongated skull from Emsian-aged strata in Sichuan. The s ...

'' and ''

Quasipetalichthys ''Quasipetalichthys haikouensis'' is the type and only known species of the extinct petalichthid placoderm, ''Quasipetalichthys''. Fossil remains of ''Quasipetalichthys'' have been found in the Middle Devonian, Givetian faunal stage of China ...

'', and more advanced petalichthyids, suggest that the order may have arisen in China, possibly during the late Silurian. Because they had compressed body forms, it is speculated they were bottom-dwellers that chased after or ambushed smaller fish. Their diet is not clear, as none of the fossil specimens found have preserved mouthparts.

Taxonomy

According to Zhu's 1991 redescription of ''Diandongpetalichthys'',Zhu, M. "New information on ''Diandongpetalichthys'' (Placodermi: Petalichthyida)." Early vertebrates and related problems of evolutionary biology. Science Press, Beijing (1991): 179-192. that genus represents the most basal petalichthyid known, as it has a comparatively elongated head, and shares certain anatomical features with

acanthothoraci Acanthothoraci (''spine chests'') is an extinct group of chimaera-like placoderms closely related to the rhenanid placoderms. Superficially, the acanthoracids resembled scaly chimaeras and (relatively) heavily armored ptyctodonts. They were ...

ds and primitive arthrodires such as the actinolepids. ''Quasipetalichthys'', in turn, strongly resembles ''Diandongpetalichthys'' (aside from having a much more square-looking skull). In Zhu's redescription, "Quasipetalichthyidae" (comprising ''Quasipetalichthys'', '' Eurycaraspis'', and possibly ''Neopetalichthys'') and "Macropetalichthyidae" (comprising all the other "advanced" petalichthyid genera not including ''Neopetalichthys'', or ''Diandongpetalichthys'') form a dichotomy, with ''Diandongpetalichthys'' as a sister taxon. ''Neopetalichthys'' is treated as an ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'' within Petalichthyida that may or may not be placed within or near Quasipetalichthyidae.

Timeline of genera

ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-416 till:-359.2 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:5 start:-416 ScaleMinor = unit:year increment:1 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:NAM13 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:

Lochkovian The Lochkovian is one of three faunal stages in the Early Devonian Epoch. It lasted from 419.2 ± 3.2 million years ago to 410.8 ± 2.8 million years ago. It marked the beginning of the Devonian Period, and was followed by the Pragian Stage. It is ...

from: -411.2 till: -407 color:earlydevonian text:

Pragian The Pragian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.8 ± 2.8 million years ago to 407.6 ± 2.8 million years ago. It was preceded by the Lochkovian Stage and followed by the Emsian Stage. The most important ...

from: -407 till: -397.5 color:earlydevonian text:

Emsian The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.62 ±1.95 million years ago to 393.47 ±0.99 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after ...

from: -397.5 till: -391.8 color:middledevonian text:

Eifelian The Eifelian is the first of two faunal stages in the Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage. North American ...

from: -391.8 till: -385.3 color:middledevonian text:

Givetian The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian Stage. It is named after the town of Givet in ...

from: -385.3 till: -374.5 color:latedevonian text:

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during ...

from: -374.5 till: -359.2 color:latedevonian text:

Famennian The Famennian is the later of two faunal stages in the Late Devonian epoch. The most recent estimate for its duration is that it lasted from around 371.1 to 359.3 million years ago. An earlier 2012 estimate, still used by the International Commis ...

bar:eratop from: -416 till: -359.2 color:devonian text:

PlotData= align:left fontsize:M mark:(line,white) width:5 anchor:till align:left color:earlydevonian bar:NAM1 from: -416 till: -411.2 text:

color:earlydevonian bar:NAM2 from: -407 till: -397.5 text:

color:earlydevonian bar:NAM3 from: -407 till: -397.5 text: Notopetalichthys color:earlydevonian bar:NAM4 from: -407 till: -397.5 text: Shearsbyaspis color:earlydevonian bar:NAM5 from: -407 till: -391.8 text: Wijdeaspis color:earlydevonian bar:NAM6 from: -400.67 till: -397.5 text:

color:middledevonian bar:NAM8 from: -397.5 till: -391.8 text: Xinanpetalichthys color:middledevonian bar:NAM9 from: -397.5 till: -385.3 text:

Macropetalichthys ''Macropetalichthys'' is a genus of placoderm fish, named by Norwood and Owen in 1846; the name "''Macropetalichthys''" means "armor-plated fish". It was assigned to Arthrodira by Woodward (1891); and to Petalichthida by Sepkoski (2002). Several ...

color:middledevonian bar:NAM10 from: -387.47 till: -385.3 text: Ellopetalichthys color:middledevonian bar:NAM11 from: -387.47 till: -385.3 text: Eurycaraspis color:middledevonian bar:NAM12 from: -387.47 till: -385.3 text:

color:latedevonian bar:NAM13 from: -378.1 till: -374.5 text: Epipetalichthys PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 bar:period from: -416 till: -411.2 color:earlydevonian text:

from: -411.2 till: -407 color:earlydevonian text:

from: -407 till: -397.5 color:earlydevonian text:

from: -397.5 till: -391.8 color:middledevonian text:

from: -391.8 till: -385.3 color:middledevonian text:

from: -385.3 till: -374.5 color:latedevonian text:

from: -374.5 till: -359.2 color:latedevonian text:

bar:era from: -416 till: -359.2 color:devonian text:

References

Sources

* Long, John A. ''The Rise of Fishes: 500 Million Years of Evolution'' Baltimore: The Johns Hopkins University Press, 1996. * {{Taxonbar, from=Q147585 Early Devonian first appearances Placoderm orders Late Devonian animals Late Devonian extinctions