Tetraodontiformes


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.

Etymology

The name comes from Ancient Greek τετρα-, meaning "four", ὀδούς, meaning "tooth", and Latin formes, meaning "form".

Evolution

Traditionally, the oldest recognized tetraodontiforms are the extinct suborder Plectocretacicoidei from the Late Cretaceous of Italy and Slovenia, both in the former Tethyan region. These comprise the families Cretatriacanthidae and Protriacanthidae. Plectocretacicus from the Cenomanian of Lebanon has also been proposed as a tetraodontiform, but this has been more recently questioned. 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.

Description

Tetraodontiformes include a variety of body shapes, all radical departures from the streamlined body plan typical of most fishes. These forms range from nearly square or triangular, globose to laterally compressed. They range in size from Rudarius excelsus, measuring just in length, to the ocean sunfish, the largest of all bony fishes at up to in length and weighing over 2 tonnes.
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. 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.
Image:porcupine.pufferfish.arp.jpg|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 lower rib bones. The bones of the jaw are modified and fused into a sort of "beak"; visible sutures divide the beaks into "teeth". This is alluded to in their name, derived from the Greek words τετρα- tetra meaning "four" and ὀδούς odous meaning "tooth" and the Latin forma meaning "shape". Counting these teeth-like bones is a way of distinguishing similar families, for example, the Tetraodontidae , Triodontidae, and Diodontidae.
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

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


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 =
#legends
id:CAR value:claret
id:ANK value:rgb
id:HER value:teal
id:HAD value:green
id:OMN value:blue
id:black value:black
id:white value:white
id:cretaceous value:rgb
id:earlycretaceous value:rgb
id:latecretaceous value:rgb
id:cenozoic value:rgb
id:paleogene value:rgb
id:paleocene value:rgb
id:eocene value:rgb
id:oligocene value:rgb
id:neogene value:rgb
id:miocene value:rgb
id:pliocene value:rgb
id:quaternary value:rgb
id:pleistocene value:rgb
id:holocene value:rgb
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: width:25
shift:

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: 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: 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.