Saurichthys

Saurichthys Temporal range: Triassic ~251.9–201.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Saurichthys fossil
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	†Saurichthyiformes
Family:	†Saurichthyidae
Genus:	†Saurichthys Agassiz, 1834
Type species
†Saurichthys apicalis Agassiz, 1834
Species
Over 50 species (see list below)
Synonyms
Belonorhynchus Bronn 1858[1] Brevisaurichthys Beltan 1972[2] Giffonus Costa 1862[1] Gymnosaurichthys Berg 1940 Ichthyorhynchus Bellotti 1857[1] Stylorhynchus Martin 1873 non-Lesson1847 non-Stein 1848 Systolichthys Beltan 1972[2]

Saurichthys (from Greek: σαῦρος saûros, 'lizard' and Greek: ἰχθῦς ikhthûs 'fish') is an extinct genus of predatory ray-finned fish from the Triassic Period. It is the type genus of the family Saurichthyidae (Changhsingian-Middle Jurassic), and the most speciose and longest lasting genus in the family. This family also includes the Permian Eosaurichthys (China) and the Jurassic Saurorhynchus (= Acidorhynchus)^[4] from Europe and North America, though it may be more appropriate to treat these as subgenera of Saurichthys, due to the genus Saurichthys otherwise being paraphyletic.^[5]

Fossils of Saurichthys have been found on all continents except South America and Antarctica.^[6][7][8] It inhabited both marine and freshwater environments.^[8][9] The oldest fossils of Saurichthys were recovered from the Wordie Creek Formation in East Greenland and are Griesbachian (Induan, Early Triassic) in age.^[10]

Over 50 species of Saurichthys have been described (see list below). The species differ in size and show variability in their skeletal features. The latter can potentially be ascribed to changes in major developmental genes.^[11] The use of subgenera (Eosaurichthys, Costasaurichthys, Lepidosaurichthys, Saurorhynchus, Sinosaurichthys) in the literature reflects differences in morphology between species groups.^[12] Several species that were described predominantly in the 19th century are based on fragmentary fossils (often isolated teeth). 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 skeletal features that he thought were intermediate to reptiles and fishes.

Their exact phylogenetic position is uncertain, though it is agreed that they are not members of Neopterygii. Historically, they have been seen as close relatives of the Acipenseriformes (which includes living sturgeon and paddlefish) as part of the Chondrostei, though this has been strongly questioned by modern studies, which suggests that it may lie outside the Actinopterygii crown group.^[5]