Like its relatives,Cephalaspis was heavily armored, presumably to defend against predatoryplacoderms andeurypterids, as well as to serve as a source of calcium for metabolic functions in calcium-poor freshwater environments. It had sensory patches along the rim and center of its head shield, which were used to sense for worms and other burrowing organisms in the mud.[citation needed]
Because its mouth was situated directly beneath its head,Cephalaspis was thought of as being a bottom-feeder, akin to a heavily armouredcatfish orsturgeon. It moved its plow-like head from side to side,Cephalaspis easily stirring sand and dust into the water, along with revealing the hiding places of its prey, digging up worms or crustaceans hidden in the mud and algae, as well as sifting through detritus (inferred from its lack of jaws and inability to bite).[2]
The genusCephalaspis has long been used as awastebasket taxon sinceAgassiz erected it in 1835 for four species,C. lyelli,C. rostratus,C. lewisi andC. lloydi.[3] Later, it was eventually determined that the last three species were portions of what would eventually be described as theheterostracanPteraspis rostratus.C. lyelli, named afterSir Charles Lyell,[3] would be left to be the type species of the genus. Other researchers would continue adding other similar-looking osteostracans throughout the decades until, in 2009, Sansom reevaluated Osteostraci, and determined that onlyC. lyelli could be reliably placed withinCephalaspis, and that probably all other species would eventually need to be reexamined and be placed into other genera.[4] In the same 2009 study, Sansom also determined thatCephalaspissensu stricto was the sister-taxon of cornuate osteostracans, i.e., all osteostracans that either have, or have ancestors that had defined corners on the head-shields.[4]
The following is a list of species that have been included intoCephalaspis; most likely do not belong to the genus, but have not been formally moved.[5][6]
^L. Agassiz. 1835. Recherches Sur Les Poissons Fossiles. Tome I (livr. 18).
^Haines, Tim; Chambers, Paul (2005).The complete guide to prehistoric life. Buffalo, N.Y.: Firefly Books. p. 23.ISBN978-1-55407-181-4.
^abWhite, E. I. "OnCephalaspis lyelli Agassiz." Palaeontology 1.2 (1958): 99-105.[1]Archived 2015-10-19 at theWayback Machine
^abSansom, Robert S. "Phylogeny, classification and character polarity of the Osteostraci (Vertebrata)." Journal of Systematic Palaeontology 7.1 (2009): 95-115.[2]
^Groh, S."Appendix"(PDF).Patterns of diversification in osteostracan evolution (M.S.). Uppsala University.
^On the cephalaspid fauna of thePodolian plateau. PP Balabai - aukovi zapysky Naukovo-pryodo-znavcogomuzeâ AN URSR, L'vov, 1962
^Preliminary description of Lower Devonian Osteostraci from Podolia (Ukrainian S.S.R.). P Janvier, Bulletin of the British Museum (Natural History) Geology 38(5) pages 309--334 (1985)
Janvier, P (1996)Early Vertebrates Oxford University Press;
Donoghue and Smith (2001) The anatomy of Turinia pagei (Powrie), and the phylogenetic status of the Thelodonti, Transactions of the Royal Society of Edinburgh: Earth Sciences, 92, p. 15-37
