Bothriolepis

Bothriolepis is a genus of antiarch placoderms. It was widespread and diverse in the middle to late Devonian. 
"Bothriolepis" lived in environments across every continent including near-shore marine and freshwater settings. Most species of "Bothriolepis" were small, benthic, freshwater detritivores. They got nutrients by eating decomposing plant/animal material. They were about in length. However, the largest species, "B. maxima", had a carapace about in length. 
Over 70 species are found across the world, but this is also typical of modern bottom dwelling species around today.