Polymerolepis (many part scale)
Classification: Chordata, Chondrichthyes, Elasmobranchii.
Diet: Uncertain, presumed carnivore.
Size: Uncertain due to lack of fossil material.
Known locations: Mongolia.
Time period: Late Silurian.
Fossil representation: Placoid scales.
The placoid scales of Polymerolepis date back four hundred and twenty million years, indicating that Polymerolepis was one of the earliest sharks. Unfortunately no other remains are known so it is impossible to say what Polymerolepis looked like. Two other shark ancestors from the same time period are Mongolepis and Elegestolepis.