| Aspidorhynchidae | |
|---|---|
 | |
| Aspidorhynchus sanzenbacheri | |
 | |
| Belonostomus kochii | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Division: | †Aspidorhynchei |
| Order: | †Aspidorhynchiformes Bleeker, 1859 |
| Family: | †Aspidorhynchidae Bleeker, 1859 |
| Type genus | |
| †Aspidorhynchus Agassiz, 1833 | |
| Genera | |
See text | |
Aspidorhynchidae (fromNeo-Latin "shield-snouts") is anextinctfamily ofray-finned fish from theMesozoic Era. It is the only member of themonotypicorderAspidorhynchiformes. Members of the group are noted for their elongated, conicalrostrums, of varying length, formed from fusedpremaxillae. The range of the group extends from theMiddle Jurassic to the end of theMaastrichtian, with a potential record from theLate Paleocene. The family and order were described byPieter Bleeker in 1859.
Aspidorhynchiformes have generally been recovered as basal members ofTeleosteomorpha, more closely related toteleosts than toHolostei. They have often considered to have asister group relationship withPachycormiformes, another group of basal teleosteomorphs.[1] However, other studies instead suggest that they successively diverged after one another, with the aspidorhynchids actually being closer to the teleosts than the pachycormids.[2]
Aspidorhynchiformes has one family, which is divided into at least two genera:[3][4][5]: 57
Fossils range have been found in theUnited States,France,Italy,Russia,Saskatchewan,Alberta,North Dakota,Montana,Wyoming, andUzbekistan. These fossils range from 167.7mya (Aspidorhynchus) to 66 mya (Belonostomus longirostris).
The earliest known remains of the group are known from the Middle Jurassic of Europe, in what was then the westernTethys 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.[6] During the Cretaceous they dispersed worldwide.[7] Some members, likeBelonostomus, attained a global distribution in both marine and freshwater habitats; others, likeVinctifer, were restricted to the seas aroundGondwana, while others like the giantRichmondichthys were restricted to small geographic regions such as theEromanga Sea.[8]
The youngest members of the group, belonging toBelonostomus, went extinct at the end of theMaastrichtian during theK-Pg extinction. A specimen from the Late Paleocene ofNorth Dakota suggests they may have persisted into the earlyCenozoic, although this may have just been reworked from earlier formations.[9][10][11]
The most distinctive feature of the Aspidorhynchiformes are the elongated, tube-likerostrums, which are formed from fusedpremaxillary bones.[6] The scales are lepidosteoid, similar to those ofgars.[12]
Most aspidorhynchids were predatory fish, which is best exemplified by fossils ofAspidorhynchus from Germany that have been found entangled with those of the pterosaurRhamphorhynchus, which they appear to have attacked and died with. However, aspidorhynchids primarily fed on small fish and other vertebrates, with these attacks on pterosaurs appearing to be fatal mistakes.[13] In contrast to other aspidorhynchids, the largest member of the family, the giantRichmondichthys from Australia, evolved clear adaptations for aplanktivorous,filter-feeding lifestyle.[14]
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