Lepidaspis

Lepidaspis serrata is an extinct heterostracan jawless fish from Early Devonian Canada. Its scientific name refers to the fact that the armor is composed of hundreds of tiny scales with serrated edges.
File:Lepidaspis cast.jpg|left|thumb|Lepidaspis serrata cast. Mackenzie Mountains, Northwest Territories. At the Royal [Tyrrell Museum of Palaeontology].
Although it is regarded as a heterostracan, its exact placement within Heterostraci is regarded as incertae sedis, as the fact that it is currently impossible to discern where its dorsal and ventral plates end or begin. Some experts regard it as being descended from the basal heterostracans of the Silurian.