longitudinal scale rows are developed, with small scales in between in some species. The axial skeleton consists of ossified neural and haemal arches. Haemal arches may develop spines. The neural arches often show spines as well as other projections interpreted as prezygapophyses and postzygapophyses. Ossified centra are missing. The axial skeleton shows regionalization, meaning that there are differences in bone morphology between segments of the axial skeleton. Some species show dedifferentiation of the axial skeleton. Ecology and Evolution Large species of Saurichthys were apex predators among Triassic ray-finned fish, together with the marine Birgeria (Birgeriidae). 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 (Sinosaurichthys). Specimens showing half-swallowed conspecific individuals suggest that cannibalism was relatively common in Saurichthys. Fossil evidence, in the form of a bolus (ball-shaped mass) of bones in the same strata, indicates that Saurichthys attacked marine reptiles such as the tanystropheid Langobardisaurus, or possibly scavenged their corpses. 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. Early Triassic species of Saurichthys differ from later species most prominently in their more elongate postorbital portion of the skull (part of the skull behind the eyes) and their generally denser scale cover. Middle Triassic and Late Triassic species, on the other hand, typically have a short postorbital portion of the skull and their scale cover is reduced. This reduction includes both the number of the longitudinal scale rows and the size of individual scales. These evolutionary trends are, however, not an indication for anagenesis, but rather the result of parallel evolution in different lineages of Saurichthys. The aforementioned trends are observed only in marine species. Late Triassic freshwater species of Saurichthys (e.g., S. orientalis, S. sui) retain an elongate postorbital skull portion and a denser scale cover, suggesting that freshwater environments served as refugia for species with a more primitive appearance. Reproduction Fossils of gravid females provide evidence for (ovo-)viviparity in Saurichthys and the oldest known example for viviparity in ray-finned fishes. Internal fertilisation is also evidenced by specialized pelvic fin rays (Saurichthys calcaratus) or ventral scales