Cephalaspis
Name: Cephalaspis
(Head shield).
Phonetic: Seff-ah-lass-pis.
Named By: Louis Agassiz - 1846?
Classification: Chordata, Osteostraci,
Cephalaspidiformes, Cephalaspidae.
Species: C. lyelli.
Diet: Carnivore/bottom feeder.
Size: Approximately 20 to 30 centimetres
long.
Known locations: Western Europe. North America.
Time period: Early Devonian.
Fossil representation: Many specimens are known.
Cephalaspis
is a good example of the jawless fish that swam through the waters of
the Devonian. Although jawless, it still had a mouth that was
situated to the underside of the head, suggesting that it was a
bottom feeder. Also there seems to be sensory organs on the underside
of the head suggesting that it searched for buried prey items such as
worms and microorganisms. It’s also likely that it would have
sifted for organic matter that had sunk to the bottom.
The
armoured head of
Cephalaspis is its most distinguishing feature
taking up about a third
of the body length and being almost as wide as it is long. With the
mouth on the bottom of the head, the eyes are situated close together
at the top of the skull. Since Cephalaspis
probably did not rely on
them for feeding, this was probably a defensive adaptation suggesting
that Cephalaspis itself was prey for the predators
of the time.
There
have been a large
number of remains attributed to the genus Cephalaspis,
ranging from
Europe to North America and further beyond. However there are many
people who remain unconvinced as to the validity of all the specimens,
hence the changing lists of species depending upon source.
Here in an attempt to avoid potential confusion, only the type
species C. lyelli described by Agassiz is noted.
Further reading
- Recherches Sur Les Poissons Fossiles. Tome I (livr. 18). - Imprimerie
de Petitpierre, Neuchatel xxxii-188. - Louis Agassiz - 1843.
- Concerning the Mouth Opening and certain features of the Visceral
Endoskeleton of Cephalaspis. - Journal of Anatomy vol65. - Edward
Phelps Allis Jr - 1931.
- On Cephalaspis magnifica Traquair, 1893, from the Middle Devonian of
Scotland, and the relationships of the last osteostracans. -
Transactions of the Royal Society of Edinburgh: Earth Sciences 9. -
Philippe Janvier & Michael J. Newman - 2004.
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