Placodermi (from the Greek πλάξ = plate and δέρμα = skin, literally "plate-skinned") is an extinct group of paraphyletic armored prehistoric "fish" (Which are also paraphyletic, hence being in quotes.) , known from fossils, which lived from the Silurian to the end of the Devonian period, being done in by mass extinctions. Their head and thorax were covered by articulated armored plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches. Placoderms are paraphyletic, and comprise several distinct outgroups or sister taxa to all living jawed vertebrates, which originated among their ranks. This is illustrated by a 419 MYA fossil, Entelognathus, from China, which is th