Tetraodontiformes (), also known as the Plectognathi, is an order of ray-finned fishes which includes the pufferfishes and related taxa. This order has been classified as a suborder of the order Perciformes, although recent studies have found that it, as the Tetraodontoidei, is a sister taxon to the anglerfish order Lophiiformes, called Lophiodei, and have placed both taxa within the Acanthuriformes. The Tetraodontiformes are represented by 10 extant families and at around 430 species overall. The majority of the species within this order are marine but a few may be found in freshwater. They are found throughout the world.

Taxonomy

Tetraodontiformes is a name first used for this order in 1940 by Lev Berg, the order was originally proposed in 1817 as the "Les Plectognathes", the Plectognathi. Cuvier divided this into two families, "Les Gymnodontes" and "Les Sclerodermes". In 1940 Berg first used the term Tetraodontiformes for this order and this name is the currently accepted name as it follows the International Code of Zoological Nomenclature rule that a name for a family or higher taxa must have its root based on the type species of that grouping. In this case the type species is Tetraodon lineatus Linnaeus, 1758. The 5th edition of Fishes of the World recognises the order as a derived order within the Actinopterygii and as a monophyletic order within the Percomorpha. Other authorities have proposed that it is not an order but that it is a clade, the Tetraodontoidei, within the order Acanthuriformes and is most closely related to the Lophiodei, the anglerfishes. and Latin , meaning "form". More recent studies have also questioned the placement of the Plectrocretacicoidei in the Tetraodontiformes, due to their ancient nature contrasting with the position of the Tetraodontiformes as the most derived percomorph lineage, and the group displaying many traits that are not present in modern tetraodontiforms or are not exclusively found in them. It has thus been suggested that the Plectocretacicoidei might either represent indeterminate percomorphs or basal members of a more inclusive Acanthuriformes. If the Plectocretacicoidei are excluded, the earliest definitive fossil tetraodontiforms are a number of genera known from the earliest Eocene.

Most members of this order – except for the family Balistidae – are ostraciiform swimmers, meaning the body is rigid and incapable of lateral flexure. Because of this, they are slow-moving and rely on their pectoral, dorsal, anal, and caudal fins for propulsion rather than body undulation. However, movement is usually quite precise; dorsal and anal fins aid in manoeuvring and stabilizing. In most species, all fins are simple, small, and rounded, except for the pelvic fins which, if present, are fused and buried. Again, in most members, the gill plates are covered over with skin, the only gill opening a small slit above the pectoral fin.

The tetraodontiform strategy seems to be defense at the expense of speed, with all species fortified with scales modified into strong plates or spines – or with tough, leathery skin (the filefishes and ocean sunfish). Another striking defensive attribute found in the pufferfishes and porcupinefishes is the ability to inflate their bodies to greatly increase their normal diameter; this is accomplished by sucking water into a diverticulum of the stomach. Many species of the Tetraodontidae, Triodontidae, and Diodontidae are further protected from predation by tetrodotoxin, a powerful neurotoxin concentrated in the animals' internal organs.

thumb|[[Long-spine porcupinefish, Diodon holocanthus: On the right is a blue-spotted grouper, Cephalopholis argus.]]

Tetraodontiforms have highly modified skeletons, with no nasal, parietal, infraorbital, or (usually) lower rib bones. The bones of the jaw are modified and fused into a sort of "beak"; visible sutures divide the beaks into "teeth". Counting these teeth-like bones is a way of distinguishing similar families, for example, the Tetraodontidae ("four-toothed"), Triodontidae ("three-toothed"), and Diodontidae ("two-toothed").

Their jaws are aided by powerful muscles, and many species also have pharyngeal teeth to further process prey items, because the Tetraodontiformes prey mostly on hard-shelled invertebrates, such as crustaceans and shellfish.

The Molidae are conspicuous even within this oddball order; they lack swim bladders and spines, and are propelled by their very tall dorsal and anal fins. The caudal peduncle is absent and the caudal fin is reduced to a stiff rudder-like structure. Molids are pelagic rather than reef-associated and feed on soft-bodied invertebrates, especially jellyfish.

Families

thumb|[[Ocean sunfish]]

thumb|The [[honeycomb cowfish is part of the family Ostraciidae.]]

thumb|[[American whitespotted filefish Cantherhines macrocerus]]

The Tetraodontiformes contains the following suborders and families, based on Eschmeyer's Catalog of Fishes and Santini & Tyler (2003):

  • Family Triacanthodidae <small>Gill, 1862</small> (spikefishes)
  • Subfamily Hollardiinae <small>Tyler, 1968</small>
  • Subfamily Triacanthodinae <small>Gill, 1862</small>
  • Family Triacanthidae <small>Bleeker, 1859</small> (triplespines)
  • Suborder Tetraodontoidei <small>Berg, 1940</small>
  • Superfamily Triodontoidea
  • Family Triodontidae <small>Bleeker, 1859</small> (threetooth puffers)
  • Superfamily Moloidea
  • Family Molidae <small>Bonaparte, 1835</small> (molas or ocean sunfishes)
  • Superfamily Tetraodontoidea
  • Family Diodontidae <small>Bonaparte, 1835</small> (porcupinefishes and burrfishes)
  • Family Tetraodontidae <small>Bonaparte, 1831</small> (pufferfishes)
  • Suborder Balistoidei <small>Rafinesque, 1810</small>
  • Superfamily Balistoidea
  • Family Monacanthidae <small>Nardo, 1843</small> (filefishes)
  • Family Balistidae <small>Rafinesque, 1810</small> (triggerfishes)
  • Superfamily Ostracioidea
  • Family Aracanidae <small>Hollard, 1860</small> (deepwater boxfishes)
  • Family Ostraciidae <small>Rafinesque, 1810</small> (boxfishes)

Fossil taxa

thumb|[[Eospinus, an unusual fossil balistoid from the Early Eocene of Turkmenistan]]

thumb|[[Spinacanthus from the Early Eocene of Italy]]

thumb|[[Iraniplectus from the Early Oligocene of Iran]]Based on Santini & Tyler (2003):

  • Suborder ?Plectocretacicoidei <small>Tyler & Sorbini, 1996</small>
  • Family ?Cretatriacanthidae <small>Tyler & Sorbini, 1996</small>
  • Family ?Plectocretacicidae <small>Tyler & Sorbini, 1996</small>
  • Family ?Protriacanthidae <small>Tyler & Sorbini, 1996</small>
  • Suborder Balistoidei
  • Superfamily Moclaybalistoidea
  • Family Moclaybalistidae <small>Santini & Tyler, 2003</small>
  • Genus †Iraniplectus <small>Tyler, Mirzaie & Nazemi, 2006</small> (Early Oligocene of Iran)
  • Family †Avitoplectidae <small>Bemis, Tyler, Bemis, Kumar, Rana & Smith, 2017</small>
  • Family †Balkariidae <small>Bannikov, Tyler, Arcila & Carnevale, 2016</small>
  • Family †Zignoichthyidae <small>Tyler & Sorbini, 1996</small>

This cladogram of extant Tetraodontiformes is based on Santini et al., 2013.

This cladogram of extant Tetraodontiformes is based on Santini et al., 2013.

Timeline of genera

<timeline>

ImageSize = width:1000px height:auto barincrement:15px

PlotArea = left:10px bottom:50px top:10px right:10px

Period = from:-145.5 till:15

TimeAxis = orientation:horizontal

ScaleMajor = unit:year increment:10 start:-145.5

ScaleMinor = unit:year increment:1 start:-145.5

TimeAxis = orientation:hor

AlignBars = justify

Colors =

  1. 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:cretaceous value:rgb(0.5,0.78,0.31)

id:earlycretaceous value:rgb(0.63,0.78,0.65)

id:latecretaceous value:rgb(0.74,0.82,0.37)

id:cenozoic value:rgb(0.54,0.54,0.258)

id:paleogene value:rgb(0.99,0.6,0.32)

id:paleocene value:rgb(0.99,0.65,0.37)

id:eocene value:rgb(0.99,0.71,0.42)

id:oligocene value:rgb(0.99,0.75,0.48)

id:neogene value:rgb(0.999999,0.9,0.1)

id:miocene value:rgb(0.999999,0.999999,0)

id:pliocene value:rgb(0.97,0.98,0.68)

id:quaternary value:rgb(0.98,0.98,0.5)

id:pleistocene value:rgb(0.999999,0.95,0.68)

id:holocene value:rgb(0.999,0.95,0.88)

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:NAM14

bar:NAM15

bar:NAM16

bar:NAM17

bar:NAM18

bar:NAM19

bar:NAM20

bar:NAM21

bar:NAM22

bar:NAM23

bar:NAM24

bar:NAM25

bar:NAM26

bar:NAM27

bar:NAM28

bar:NAM29

bar:NAM30

bar:NAM31

bar:NAM32

bar:NAM33

bar:NAM34

bar:NAM35

bar:NAM36

bar:NAM37

bar:NAM38

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: -145.5 till: -99.6 color:earlycretaceous text:Early

from: -99.6 till: -66 color:latecretaceous text:Late

from: -66 till: -55.8 color:paleocene text:Paleo.

from: -55.8 till: -33.9 color:eocene text:Eo.

from: -33.9 till: -23.03 color:oligocene text:Oligo.

from: -23.03 till: -5.332 color:miocene text:Mio.

from: -5.332 till: -2.588 color:pliocene text:Pl.

from: -2.588 till: -0.0117 color:pleistocene text:Pl.

from: -0.0117 till: 0 color:holocene text:H.

bar:eratop

from: -145.5 till: -66 color:cretaceous text:Cretaceous

from: -66 till: -23.03 color:paleogene text:Paleogene

from: -23.03 till: -2.588 color:neogene text:Neogene

from: -2.588 till: 0 color:quaternary text:Q.

PlotData=

align:left fontsize:M mark:(line,white) width:5 anchor:till align:left

color:latecretaceous bar:NAM1 from:-99.6 till:-97.6 text:Plectocretacicus

color:latecretaceous bar:NAM2 from:-74.9 till:-68.9 text:Cretatriacanthus

color:latecretaceous bar:NAM3 from:-70.6 till:-48.6 text:Kankatodus

color:paleocene bar:NAM4 from:-66 till:-55.8 text:Indotrigonodon

color:paleocene bar:NAM5 from:-66 till:-55.8 text:Pisdurodon

color:paleocene bar:NAM6 from:-66 till:-33.9 text:Eotrigonodon

color:eocene bar:NAM7 from:-55.8 till:-48.6 text:Eospinus

color:eocene bar:NAM8 from:-55.8 till:-33.9 text:Eodiodon

color:eocene bar:NAM9 from:-55.8 till:-33.9 text:Eolactoria

color:eocene bar:NAM10 from:-55.8 till:-33.9 text:Eoplectus

color:eocene bar:NAM11 from:-55.8 till:-33.9 text:Eotetraodon

color:eocene bar:NAM12 from:-55.8 till:-33.9 text:Proaracana

color:eocene bar:NAM13 from:-55.8 till:-33.9 text:Prodiodon

color:eocene bar:NAM14 from:-55.8 till:-33.9 text:Protacanthodes

color:eocene bar:NAM15 from:-55.8 till:-33.9 text:Protobalistium

color:eocene bar:NAM16 from:-55.8 till:-33.9 text:Spinacanthus

color:eocene bar:NAM17 from:-55.8 till:-33.9 text:Zignoichthys

color:eocene bar:NAM18 from:-55.8 till:-33.9 text:Progymnodon

color:eocene bar:NAM19 from:-55.8 till:0 text:Amanses

color:eocene bar:NAM20 from:-55.8 till:0 text:Diodon

color:eocene bar:NAM21 from:-55.8 till:0 text:Triodon

color:eocene bar:NAM22 from:-55.8 till:0 text:Ostracion

color:eocene bar:NAM23 from:-48.6 till:0 text:Triacanthus

color:oligocene bar:NAM24 from:-33.9 till:-28.4 text:Acanthopleurus

color:oligocene bar:NAM25 from:-33.9 till:-28.4 text:Balistomorphus

color:oligocene bar:NAM26 from:-33.9 till:-28.4 text:Cryptobalistes

color:oligocene bar:NAM27 from:-33.9 till:-28.4 text:Oligobalistes

color:oligocene bar:NAM28 from:-33.9 till:-28.4 text:Oligolactoria

color:oligocene bar:NAM29 from:-33.9 till:-5.332 text:Oligodiodon

color:oligocene bar:NAM30 from:-28.4 till:0 text:Aracana

color:miocene bar:NAM31 from:-23.03 till:0 text:Marosichthys

color:miocene bar:NAM32 from:-15.97 till:-2.588 text:Trigonodon

color:miocene bar:NAM33 from:-15.97 till:0 text:Balistes

color:miocene bar:NAM34 from:-15.97 till:0 text:Tetraodon

color:miocene bar:NAM35 from:-11.608 till:0 text:Chilomycterus

color:miocene bar:NAM36 from:-11.608 till:0 text:Mola

color:pliocene bar:NAM37 from:-5.332 till:-2.588 text:Kyrtogymnodon

color:pliocene bar:NAM38 from:-5.332 till:0 text:Alutera

PlotData=

align:center textcolor:black fontsize:M mark:(line,black) width:25

bar:period

from: -145.5 till: -99.6 color:earlycretaceous text:Early

from: -99.6 till: -66 color:latecretaceous text:Late

from: -66 till: -55.8 color:paleocene text:Paleo.

from: -55.8 till: -33.9 color:eocene text:Eo.

from: -33.9 till: -23.03 color:oligocene text:Oligo.

from: -23.03 till: -5.332 color:miocene text:Mio.

from: -5.332 till: -2.588 color:pliocene text:Pl.

from: -2.588 till: -0.0117 color:pleistocene text:Pl.

from: -0.0117 till: 0 color:holocene text:H.

bar:era

from: -145.5 till: -66 color:cretaceous text:Cretaceous

from: -66 till: -23.03 color:paleogene text:Paleogene

from: -23.03 till: -2.588 color:neogene text:Neogene

from: -2.588 till: 0 color:quaternary text:Q.

</timeline>

References

  • Tree of Life: Tetraodontiformes