Named By: Louis Agassiz - 1834.
Synonyms: Belonorhynchus, Brevisaurichthys, Giffonus, Ichthyorhynchus, Systolichthys.
Classification: Chordata, Actinopterygii, Saurichthyiformes, Saurichthyidae.
Species: S. apicalis (type), S. calcaratus, S. dawaziensis, S. dayi, S. elongatus, S. hamiltoni, S. ornatus, S. wimani.
Size: Approximately 1 meter long.
Known locations: Worldwide.
Time period: Triassic.
Fossil representation: Multiple specimens.
an early ray finned fish Saurichthys displays several characteristics
of a fast swimming predator, however the exact method of hunting is
still not known for certain. The caudal (tail) fin was not as
well developed as other open water fish, although the close proximity
of the dorsal (back) and anal (bottom) fins set much further
back on the body would have had a contributing effect of providing
additional thrust as Saurichthys flexed its tail from side to side.
Additionally the long torpedo-like body meant that Saurichthys would
have faced very little resistance as it swam through the water which
also suggests high swimming speed.
However it is unlikely that Saurichthys was not a pursuit predator that chased prey across open water, and this reasoning is based upon the size of the pectoral fins. Pectoral fins are essentially hydroplanes that counteract the downwards pitching effect of swimming by tail. Because the tail is on the rear of the body it pushes rather than pulls the body weight so that the main body ends up sinking without the support of fins to keep it angled in the desired direction of travel. The larger the pectoral fins, the more they can compensate and the faster the fish can swim without unavoidably pitching down. This is why the fastest swimming fish we know today have some of the proportionately largest pectoral fins.
The pectoral fins of Saurichthys however are tiny however and they would have offered very little hydroplane support in swimming. This means that while Saurichthys could combine the caudal and dorsal tail positions with the streamlined body for high speed, it could not maintain this speed over distance without pitching down for lack of support from the pectoral fins. This means that Saurichthys could only swim at speeds in short bursts, something that reveals that even though Saurichthys could not chase prey across open water, it was very well suited to the life of an ambush hunter.
Ambush hunting requires the use of cover for the predator to hide in and here the narrow body and small fins of Saurichthys would have been perfect for lurking amongst water weeds and submerged debris as it could operate in these locations without wedging its body or snagging and tearing its fins. Also while no fossil evidence exists to support this, it is reasonable to assume that in life Saurichthys would have had a mottled or striped patterning to break up the shape of its body to the eyes of prey as it lay in cover.
When prey was identified Saurichthys probably would have slowly lined itself for a strike while still in cover, constantly making fine adjustments as it watched its prey moving and approaching closer. Once Saurichthys gauged its target was within strike range it would rapidly flick its tail and use the combined push of all of its rear fins to shoot out of the undergrowth like an arrow towards its prey. Once close enough, Saurichthys could open up its elongated jaws, as much as third of the total length of the body, to seize its prey.
Saurichthys was likely a predator of fish and quite possibly other vertebrates such as amphibians. However an Italian specimen of a bolus (a collection of animal parts that are indigestible for a specific predator so they are regurgitated in pellet form) suggests that Saurichthys even included small pterosaurs in its feeding, in this case often credited as the genus Preondactylus. It is unknown if the Saurichthys in question killed the pterosaur, or was merely scavenging the carcass of a drowned individual, but it does offer a fascinating insight into the aquatic ecosystems of the Triassic.