Lampriformes


Lampriformes is an order of ray-finned fish. Members are collectively called lamprids or lampriforms, and unite such open-ocean and partially deep-sea Teleostei as the crestfishes, oarfish, opahs, and ribbonfishes. A synonym for this order is Allotriognathi, while an often-seen, but apparently incorrect, spelling variant is Lampridiformes. They contain seven extant families which are generally small but highly distinct, and a mere 12 lampriform genera with some 20 species altogether are recognized.
The scientific name literally means "shaped bright ", as "lampr-", meaning bright, comes from lampris, the generic name for the opah. In contrast, most other living lampriforms are actually ribbon-like and not very similar to the disc-shaped opahs in habitus. They are, however, quite distinctly united by their anatomy, and the family's phylogeny, as well as the most ancient fossils of this order suggest the original lampriform was rather "opah-shaped". The scientific name is a combination of Lampris + the standard fish order suffix "-formes". It ultimately derives from Ancient Greek lamprós + Latin forma, the former in reference to brilliant coloration of opahs.

Description and ecology

These oceanic fishes are pelagic feeders that stay well above the sea floor, and normally occur in waters 100–1000 m deep. They are typically brightly coloured as adults, often with brilliant crimson fins. Lampriforms have highly variable body forms, but they are generally laterally compressed. Some are rounded in lateral view, while others are very elongated. The former are termed bathysomes—"deep-bodies", from Ancient Greek bathýs "deep" + sōma "body"—and the latter taeniosomes—"ribbon-bodies", Greek tainía "ribbon". They vary greatly in size, too, ranging from less than in the sailfin moonfishes to Regalecus glesne, the longest of all living bony fishes, which may reach in length.
The lampriforms have 84 to 96 total vertebrae; an orbitosphenoid bone is present in some members of this order. Their premaxilla completely excludes the maxilla from the gape, but the jaws are highly protrusible, nonetheless. The upper jaw's protrusion is achieved in a unique way: the maxilla, instead of being ligamentously attached to the ethmoid and palatine, slides in and out with the highly protractile premaxilla. The pelvic fins have up to 17 rays and are placed rather far toward the front of the animal, but they can be missing entirely. The dorsal fin is long, and tends to extend along most of the length of the body. Fin spines are absent in all. Some have a physoclistous gas bladder, while others have none. They either have tiny scales or naked skin.

Systematics and evolution

The Lampriformes are anatomically similar to some Acanthopterygii at a first glance, but more detailed studies reveal they are not as advanced, and many authors assign them to a basal position inside the advanced spiny-rayed Teleostei clade called Acanthomorpha, as monotypic superorder Lampridiomorpha. Unlike their presumed relatives, they lack fin spines, however, and other authors have considered them to form a lineage just outside the Acanthomorpha, and the sister taxon of the Myctophiformes. Molecular data also support the view that the Lampriformes are close to the advanced Teleostei. But the data do not agree on their exact relationships, and the Myctophiformes are also inferred to be close to the Protacanthopterygii, one of the core groups of moderately advanced teleosts. As modern taxonomy tries to avoid a profusion of small taxa, and the delimitation of the Euteleostei versus Acanthopterygii remains uncertain, the systematics and taxonomy of the Lampriformes among the teleosts are in need of further study.
, which dates from the Late Oligocene
The lampriforms diverged from other teleosts in the Cretaceous, perhaps 80 million years ago or slightly more, considering that the oldest-known lampriforms, Nardovelifer, date from the late Campanian epoch and are already clearly assignable to the present order. The basal lampriforms were bathysomes, while the taeniosome body shape is apomorphic and seems to have evolved only once. The order underwent its main radiation in the Paleocene period; the opah-like Turkmenidae were a family of lampriforms thriving at that time, but going extinct around the start of the Neogene, about 23 Mya. Other fossil Lampridiformes are Bajaichthys, Palaeocentrotus, and Veronavelifer.

Classification

The order is occasionally divided into the Bathysomi and the Taeniosomi. The former are a paraphyletic assemblage, thus effectively synonymous with the entire order, while the latter can be considered a valid suborder. Including fossil taxa, the classification of the Lampriformes in phylogenetic sequence, with the number of living genera and species, can thus be given as:
Basal and incertae sedis
Suborder Taeniosomi

ImageSize = width:1000px height:auto barincrement:15px
PlotArea = left:10px bottom:50px top:10px right:10px
Period = from:-66 till:10
TimeAxis = orientation:horizontal
ScaleMajor = unit:year increment:5 start:-66
ScaleMinor = unit:year increment:1 start:-66
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: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:space
bar:period
bar:space
bar:era
PlotData=
align:center textcolor:black fontsize:M mark: width:25
shift:

bar:periodtop
from: -66 till: -55.8 color:paleocene text:Paleocene
from: -55.8 till: -33.9 color:eocene text:Eocene
from: -33.9 till: -23.03 color:oligocene text:Oligocene
from: -23.03 till: -5.332 color:miocene text:Miocene
from: -5.332 till: -2.588 color:pliocene text:Plio.
from: -2.588 till: -0.0117 color:pleistocene text:Pleist.
from: -0.0117 till: 0 color:holocene text:H.
bar:eratop
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:paleocene bar:NAM1 from: -66 till: -61.7 text: Bathysoma
color:paleocene bar:NAM2 from: -58.7 till: -55.8 text: Turkmene
color:paleocene bar:NAM3 from: -58.7 till: -55.8 text: Palaeocentrotus
color:paleocene bar:NAM4 from: -58.7 till: -55.8 text: Danatinia
color:eocene bar:NAM5 from: -55.8 till: -33.9 text: Velifer
color:eocene bar:NAM6 from: -55.8 till: -33.9 text: Bajaichthys
color:eocene bar:NAM7 from: -48.6 till: -37.2 text: Eolophotes
color:oligocene bar:NAM8 from: -33.9 till: -28.4 text: Analectis
color:oligocene bar:NAM9 from: -33.9 till: 0 text: Protolophotus
color:miocene bar:NAM11 from: -11.608 till: 0 text: Lampris
PlotData=
align:center textcolor:black fontsize:M mark: width:25
bar:period
from: -66 till: -55.8 color:paleocene text:Paleocene
from: -55.8 till: -33.9 color:eocene text:Eocene
from: -33.9 till: -23.03 color:oligocene text:Oligocene
from: -23.03 till: -5.332 color:miocene text:Miocene
from: -5.332 till: -2.588 color:pliocene text:Plio.
from: -2.588 till: -0.0117 color:pleistocene text:Pleist.
from: -0.0117 till: 0 color:holocene text:H.
bar:era
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.

Footnotes