Selenosteidae 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 ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of small to large-sized

arthrodire Arthrodira (Greek for "jointed neck") is an Order (biology), order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetratin ...

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 ...

s from the

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding ...

. With the exception of the Chinese '' Phymosteus'', selenosteids lived in shallow seas in what is now Eastern North America (the Cleveland Shale), Eastern Europe (

Holy Cross Mountains Sacred describes something that is dedicated or set apart for the service or worship of a deity; is considered worthy of spiritual respect or devotion; or inspires awe or reverence among believers. The property is often ascribed to objects (a ...

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

, and the Kellwasserkalk fauna of

Bad Wildungen Bad Wildungen () is a state-run spa and a small town in Waldeck-Frankenberg district in Hesse, Germany. It is located on the German Timber-Frame Road. Geography Location Bad Wildungen lies in the eastern foothills of the Kellerwald range in the ...

), and Northeastern Africa (the Anti-Atlas Mountains,

Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...

). Selenosteids have, in cross section, a rounded body, a blunt snout, and tremendous

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

. The lower jaws were slender, the inferognathals usually either being finely serrated, or adapted for crushing, though, in '' Draconichthys'', the inferognathals had long prongs for seizing prey. The rostrum is very small.

Taxonomy

Selenosteidae is a member of the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

Aspinothoracidi, which belongs to the clade Pachyosteomorphi, one of the two major clades within Eubrachythoraci. ''Gorgonichthys'' is closely related to the

Selenosteidae, and could possibly be included in the family. The

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below shows the placement of Selenosteidae within Eubrachythoraci: Below is a more detailed

of Selenosteidae, from Rücklin (2011): Denison (1978) separated Selenosteidae into two informal groups, the "American" genera (i.e., those taxa from the Upper Famennian Cleveland Shales, such as ''Selenosteus'' and ''Gymnotrachelus''), and the "European" genera (i.e., those taxa from the Upper Frasnian Kellwasserkalk facies of Germany, and later, Morocco, like ''Rhinosteus'' and ''Microsteus''). Denison notes that the differences between the two groups, such as how the American genera tend to have slightly smaller orbits, and slightly longer cheeks, may suggest the similarities between them are due to

parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and pa ...

. Rücklin (2011), on the other hand, places ''Pachyosteus'' as the most basal selenosteid, then groups the American genera (with ''Selenosteus'' grouped as the sister taxon of ''Gymnotrachelus'' and ''Stenosteus'') as being the sister group of the remaining European/Kellwasserkalk genera, plus ''Draconichthys''.

References

Placoderm families {{Placoderm-stub

Taxonomy

See also

References