Aspidorhynchiformes (from New Latin "shield-snout forms") is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

order of ray-finned fish. It contains only a single family, the Aspidorhynchidae. Members of the group are noted for their elongated, conical rostrums, of varying length, formed from fused premaxillae. They are generally interpreted as stem-group teleosts. The range of the group extends from the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

to the late Paleocene.

Taxonomic history

The order was described by Pieter Bleeker in 1859. Aspidorhynchiformes has one family, which is divided into at least two genera: * Order †Aspidorhynchiformes Bleeker 1859 spidorhynchida; Aspidorhynchoidei Bleeker 1859** Family †Aspidorhynchidae Bleeker 1859 inctiferidae Silva Santos 1990; Diphyodontidae Jordan 1923*** Genus †'' Jonoichthys'' Gouiric-Cavalli 2015 *** Genus ?†'' Ophirachis'' Costa 1854 *** Genus †'' Platycerhynchus'' Costa 1864 *** Genus †'' Pseudovinctifer'' Arratia 2015 *** Genus †'' Richmondichthys'' Bartholomai 2004 *** Genus †''

Aspidorhynchus ''Aspidorhynchus'' (from el, ᾰ̓σπίς 'shield' and el, ῥύγχος 'snout') is an extinct genus of ray-finned fish from the Jurassic and Cretaceous periods. Fossils have been found in Europe and Antarctica. ''Aspidorhynchus'' was a ...

'' Agassiz 1833 non Fitzinger 1843 *** Genus †''

Belonostomus ''Belonostomus'' (from el, βέλος , 'dart' and el, στόμα 'mouth') is a genus of prehistoric ray-finned fish that was described by Louis Agassiz in 1844. It is a member of the order Aspidorhynchiformes, a group of fish known for their ...

'' Agassiz 1834 'Dichelospondylus'' Costa 1856; ''Hemirhynchus">Dichelospondylus.html" ;"title="'Dichelospondylus">'Dichelospondylus'' Costa 1856; ''Hemirhynchus'' Kner 1867 non Agassiz 1844 non Hodgson 1843; ''Diphyodus'' Lambe 1902] *** Genus †''Vinctifer'' Jordan 1920 Fossils range have been found in the United States, France, Italy, Russia, Saskatchewan, Alberta, North Dakota, Montana, Wyoming, and Uzbekistan. These fossils range from 167.7

mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...

(''

'') to 66 mya ('' Belonostomus longirostris'').

Anatomy

The most distinctive feature of the Aspidorhynchiformes are the elongated, tube-like rostrums, which are formed from fused premaxillary bones. The scales are lepidosteoid, similar to those of gars.

Taxonomy

Aspidorhynchiformes have generally been recovered as basal members of Teleosteomorpha, more closely related to teleosts than to Holostei. They have often considered to have a

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

relationship with Pachycormiformes, another group of basal teleosteomorphs.

Evolutionary history

The earliest known remains of the group are known from the Middle Jurassic of Europe, in what was then the western Tethys Ocean, which was likely the centre of their initial diversification, during the Late Jurassic they dispersed to the waters around the Caribbean, South America and Antarctica. During the Cretaceous they dispersed worldwide. The youngest members the group, belonging to ''

'' went extinct during the late Paleocene.

References

paleodb
Prehistoric ray-finned fish orders {{paleo-rayfinned-fish-stub