Pteraspis

Pteraspis (meaning "wing shield") is an extinct genus of pteraspidid heterostracan agnathan vertebrate that lived from the Lochkovian to Eifelian epochs of the Devonian period in what is now Brazil (Eifelian Maecuru Formation), Britain (Lochkovian Ditton Group), Ukraine (Lochkovian Ivane Suite, Pragian Babin Sandstone) and Belgium.
Description.
Like other heterostracan fishes, "Pteraspis" had a protective armored plating covering the front of its body. Though lacking fins other than its lobed tail, it is thought to have been a good swimmer thanks to stiff, wing-like protrusions derived from the armoured plates over its gills. This, along with the horn-like rostrum, made "Pteraspis" very streamlined in shape; a perfect quality for a good swimmer. "Pteraspis" also had some stiff spikes on its back, possibly an additional form of protection against predators. It is thought to have fed from shoals of plankton just under the ocean surface, and is found in association with marine fossils.
"Pteraspis" grew to an estimated length of .