Drepanaspis is a genus of heterostracan (which is a jawless placoderm with two plates of armor on its head) from the Devonian Period. Drepanaspis means "sickle shield." It probably swam along the bottom in search of food, but its mouth pointed up. The main mystery about Drepanaspis is that, if its mouth pointed up, how could it be a bottom feeder? It may have eaten bits of dead animals and plants that drift down to the bottom called "marine snow." Or maybe it could have stirred the sand up so much that the food came flying up, and then Drepanaspis would be able to suck it in. But those are just my hypotheses.
This image shows Hemicyclaspis in the lower right-hand corner, which is the one with the headshield that looks like half an oval. Astraspis is in the lower left-hand corner, and is the one that only has a caudal fin and a shield that looks like half of a medicine capsule. Anglaspis is similar to Astraspis, because it has two plates of armor, and the only fin it has is a caudal fin. Anglaspis is the one in the upper right-hand corner. The other two fish in this image are Pterapis, the one in the upper left-hand corner with the long, lower lobe on the caudal find and the beak-like rostrum, and Drepanaspis, which is the one with one of its pectoral fins scraping the bottom.
Drepanaspis was usually about six inches long, but it could grow up to one foot long. Drepanaspis had a flattened, ray-like body with two wide pectoral fins.