Early Silurian - Late Devonian |image = Jamoytius_kerwoodi.jpg |image_caption = Jamoytius kerwoodi | regnum = Animalia | phylum = Chordata | subphylum = Vertebrata | classis = Anaspida }} » For turtles, see Anapsida. The Anaspida are stem gnathostomes, and are classically regarded as the ancestors of lampreys. Anaspids were small marine agnathans that lacked scales and paired fins. They first appeared sometime during the early Silurian, and flourished until the Late Devonian Extinction Event, du… (More on Anaspida)