Platysiagidae is an extinct family of stem-

neopterygian Neopterygii (from Greek νέος ''neos'' 'new' and πτέρυξ ''pteryx'' 'fin') is a subclass of ray-finned fish (Actinopterygii). Neopterygii includes the Holostei and the Teleostei, of which the latter comprise the vast majority of extant f ...

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

which lived from the

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...

to the Early Jurassic. It includes the genera ''

Helmolepis ''Helmolepis'' is an extinct genus of ray-finned fish that lived during the Early Triassic epoch in what is now Greenland, Madagascar and Canada (British Columbia). Species of ''Helmolepis'' are small (between and ). This genus is closely relat ...

'', ''

Platysiagum ''Platysiagum'' is an extinct genus of prehistoric bony fish belonging to the family Platysiagidae. Fossils are known from the Middle Triassic of China and Italy and the Early Jurassic of England. See also * Prehistoric fish The evoluti ...

'' and possibly '' Caelatichthys''. The family was formerly placed within the

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

order

Perleidiformes Perleidiformes are an extinct order of prehistoric ray-finned fish from the Triassic period Although numerous Triassic taxa have been referred to Perleidiformes, which ones should be included for it to form a monophyletic group is a matter of on ...

, but it is now considered to belong to the separate,

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

order Platysiagiformes.

References

Prehistoric neopterygii Prehistoric ray-finned fish families {{Paleo-rayfinned-fish-stub