Classification: Chordata, Agnatha.
Size: Around 10 centimetres long.
Known locations: Norway.
Time period: Late Silurian.
Fossil representation: Few specimens.
Pharyngolepis was a jawless fish that seems to have been intermediate in its development towards a more open water lifestyle. The Anal fin was present, and the main tail lobe bent downwards to form a rudimentary for improved locomotion through the water. However, rather than having pectoral fins, Pharyngolepis only had a pair of spines, and a series of low crested scales than ran down its back instead of a dorsal fin. This means that Pharyngolepis could not swim for extended periods or at high speeds, because without pectoral fins to act as hydroplanes to stabilise pitch, Pharyngolepis would eventually just nosedive towards the bottom. For this reason, Pharyngolepis was probably a slow swimmer that stayed close to the sea floor where it searched for small marine organisms.
A jawless fish with much better swimming adaptations that lived at the same time as Pharyngolepis is Thelodus.