- For turtles, see Anapsida.
The Anaspida ("Without Shields") are stem gnathostomes,[1] and are classically regarded as the ancestors of lampreys.[2] 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,[3] during the late Devonian, where most species, save for lampreys, went extinct due to the environmental upheaval during that time. The gills opened as a row of holes along either side of the animal that typically numbered anywhere from from 6-15 pairs.
- ^ Ahlberg, Per Erik (2001). Major events in early vertebrate evolution: palaeontology, phylogeny, genetics, and development. Washington, DC: Taylor & Francis. pp. p188. ISBN 0-415-23370-4, http://books.google.com/books?id=zeyRZNZl-74C&pg=PA188&dq=Anaspida+%22stem+gnathostomes%22&as_brr=3&ei=2KN-SNeSF6HOjgGr-NDHCA&sig=ACfU3U2_2PVl8IEP8mBW5PCch2Wr3OzTQw.
- ^ Patterson, Colin (1987). Molecules and morphology in evolution: conflict or compromise?. Cambridge, UK: Cambridge University Press. pp. p142. ISBN 0-521-32271-5, http://books.google.com/books?id=DL_KQPX3AmIC&pg=PA142&dq=Anaspida+gnathostomes&ei=W6F-SO-2E5XCigHs-L2_CA&sig=ACfU3U203AXE0jY6Q46goxR6Jeiswg7P_A.
- ^ Hall, Brian Keith; Hanken, James (1993). The Skull. Chicago: University of Chicago Press. pp. p131. ISBN 0-226-31568-1, http://books.google.com/books?id=fB-hO7i50esC&pg=PA131&dq=Anaspida+gnathostomes&ei=W6F-SO-2E5XCigHs-L2_CA&sig=ACfU3U2Ztylrkp1nwc-wUCb4UF0rLqUF5w.
