Saurichthys
Saurichthys is an extinct genus of predatory ray-finned fish from the Triassic period. It is the name giving genus of the family Saurichthyidae. This family also includes the Permian Eosaurichthys and the Jurassic Saurorhynchus from Europe and North America.
Fossils of Saurichthys have been found on all continents except South America and Antarctica. It inhabited both marine and freshwater environments. The oldest fossils of Saurichthys were recovered from the Wordie Creek Formation in East Greenland and are Griesbachian in age.
Over 50 species of Saurichthys have been described. The species differ in size and show variability in their skelettal features. The latter can potentially be ascribed to changes in major developmental genes. The use of subgenera in the literature reflects differences in morphology between species groups. Several species that were described predominantly in the 19th century are based on fragmentary fossils. These are mostly considered invalid species by modern taxonomic standards.
Louis Agassiz, who described the type species of Saurichthys in 1834, named it the "lizard fish" because of skelettal features that he thought were intermediate to reptiles and fishes.
Their closest modern-day relatives include the sturgeons, paddlefish, and the bowfins. However, a recent study investigated the inner skull anatomy of Saurichthys and questioned a close affiliation with Acipenseriformes and Amiiformes.
Appearance
Saurichthys was an elongate, streamlined fish, commonly about to long. Some species were only a few decimetres long, while others could grow up to about in length.Species of Saurichthys looked superficially similar to the modern pike. Its dorsal and anal fins were placed opposite each other well back on the body, and the tail was symmetrical. These features would have made it a powerful swimmer, and it is presumed to have hunted in a similar way to the pike, attacking from an ambush at high speed. Its jaws were extremely long, making up a third of the total body length, and ended in a sharp, beak-like tip. Two to six longitudinal scale rows are developed, with small scales in between in some species. The caudal fin is abbreviate-diphycercal.
Early Triassic species of Saurichthys differ from later species most prominently in their more elongate postorbital portion of the skull and their generally denser scale cover.
Ecology
Large species of Saurichthys were apex predators among Triassic ray-finned fish, together with the marine Birgeria.Saurichthys is classically interpreted as an ambush predator. It first approached its prey and then attacked it by quick, sudden darts. Some species may have lived as subsurface cruisers.
Specimens showing half-swallowed conspecific individuals suggest that cannibalism was relatively common in Saurichthys. Fossil evidence, in the form of a bolus of bones in the same strata, indicates that Saurichthys attacked, or possibly scavenged the corpses of marine reptiles such as Langobardisaurus.
A study on the gastrointestinal tract of Saurichthys found similarities with present-day sharks and rays, in particular the many windings in the spiral valve. The many windings increased the surface area for digestion, which is sure to have provided the fish with more energy. It indicates that Saurichthys had an energy-laden lifestyle.
Reproduction
Fossils of gravid females provide evidence for viviparity in Saurichthys and the oldest known example for viviparity in ray-finned fishes. Internal fertilisation is also evidenced by specialized pelvic fin rays or ventral scales that are interpreted as copulatory organs of males.Species
- †Saurichthys Tintori 2013
- * †Saurichthys costasquamosus Rieppel 1985
- * †Saurichthys paucitrichus Rieppel 1992
- †Saurichthys Liu and Wei 1988
- * †Saurichthys chaoi
- * †Saurichthys madagascariensis Piveteau 1945
- †Saurichthys Tintori 2013
- * †Saurichthys dayi
- * †Saurichthys elongatus Stensiö 1925
- * †Saurichthys ornatus Stensiö 1925
- * †Saurichthys toxolepis Mutter et al. 2008
- * †Saurichthys wimani
- †Saurichthys Wu et al. 2009
- * †Saurichthys longipectoralis Wu et al. 2009
- * †Saurichthys longimedialis Wu et al. 2009
- * †Saurichthys minuta Wu et al. 2009
- †Saurichthys apicalis Agassiz 1834
- †Saurichthys breviabdominalis Maxwell et al. 2015
- †Saurichthys calcaratus Griffith 1977
- †Saurichthys curionii
- †Saurichthys daubreei Firtion 1934
- †Saurichthys dawaziensis Wu et al. 2009
- †Saurichthys deperditus
- †Saurichthys dianneae Maxwell et al. 2016
- †Saurichthys dongusensis Minich 1992
- †Saurichthys eximius Minikh 1982
- †Saurichthys gigas, non von Quenstedt 1858
- †Saurichthys gracilis
- †Saurichthys grignae Tintori 2013
- †Saurichthys gypsophilus Reis 1892
- †Saurichthys hamiltoni Stensiö 1925
- †Saurichthys hoffmanni Werneburg et al. 2014
- †Saurichthys huanshenensis Chou & Liu 1957
- †Saurichthys irregularis Oertle 1928
- †Saurichthys latifrons Eck 1865
- †Saurichthys lepidosteoides Frech 1903
- †Saurichthys macrocephalus
- †Saurichthys majiashanensis Tintori et al. 2014
- †Saurichthys minimahleri Werneburg et al. 2014
- †Saurichthys nepalensis Beltan & Janvier 1978
- †Saurichthys obrutchevi Minich 1981
- †Saurichthys orientalis Sytchevskaya 1999
- †Saurichthys parvidens Wade 1935
- †Saurichthys piveteaui Beltan 1968
- †Saurichthys proximus Minich 1981
- †Saurichthys rieppeli Maxwell et al. 2015
- †Saurichthys seefeldensis Kner 1867
- †Saurichthys spinosa Wu et al. 2018
- †Saurichthys stensioi Lehman 1952
- †Saurichthys striolatus Bronn 1858
- †Saurichthys tenuirostris Münster 1839
- †Saurichthys tertius Minich 1982
- †Saurichthys ultimus Minikh 1992
- †Saurichthys vjuschkovi Minikh 1983
- †Saurichthys yangjuanensis Wu et al. 2015
- †Saurichthys yunnanensis'' Zhang, Zhou, Lu & Bai 2010
Species based on fragmentary fossils
- †Saurichthys aculeatus Henry 1876
- †Saurichthys annulatus Winkler 1880
- †Saurichthys catalaunicus
- †Saurichthys indicus de Koninck 1863
- †Saurichthys listroconus Plieninger 1844
- †Saurichthys longiconus Agassiz 1834
- †Saurichthys longidens Agassiz 1844
- †Saurichthys osseus
- †Saurichthys semicostatus Münster 1839
- †Saurichthys striatulus Henry 1876
- †Saurichthys subulatus Henry 1876
Synonyms
- †Saurichthys acuminatus Agassiz 1844 → †Birgeria acuminata
- †Saurichthys acutus Agassiz 1844 → †Saurorhynchus acutus
- †Saurichthys brevirostris → †Saurorhynchus brevirostris
- †Saurichthys costatus Münster 1839 → †Birgeria? costata
- †Saurichthys elegans Stensiö 1925 → †Saurichthys elongatus
- †Saurichthys intermedius → †Saurichthys curionii
- †Saurichthys krambergeri Schlosser 1918 → †Saurichthys deperditus
- †Saurichthys mougeoti Agassiz 1844 → †Birgeria mougeoti
- †Saurichthys robustus Bassani 1886 → †Saurichthys curionii, †Saurichthys macrocephalus, †Saurichthys costasquamosus
- †Saurichthys stoppanii → †Saurichthys curionii