[5] Anaspids were small marine fish that lacked a heavy bony shield and paired fins, but were distinctively hypocercal.

The anaspid head and body are instead covered in an array of small, weakly mineralized scales, with a row of massive scutes running down the back, and, at least confirmed among the birkeniids, the body was covered in rows of tile-like scales made of aspidine, an acellular bony tissue.

[6] Anaspids all had prominent, laterally placed eyes with no sclerotic ring, with the gills opened as a row of holes along either side of the animal, typically numbering anywhere from 6-15 pairs.

Some recent studies have suggested that anaspids are stem-cyclostomes, more closely related to hagfish and lampreys than to jawed fish.

[5] A newer taxonomy based on the work of Mikko's Phylogeny Archive,[11] Nelson, Grande and Wilson 2016[12] and van der Laan 2018.