The very first fish had no true fins and no
jaws either, and are known as agnathans.
Their history stretches back more than 500
million years into the Cambrian. Today
fewer than 100 species survive, as eel-like,
sucker-mouthed lampreys and hagfish.
Cepbalaspis was an armoured agnathan
with a prominent flattened head shield, .
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suggesting it was a bottom-dweller. Its lack
of biting jaws meant a diet of soft-bodied
animals small enough to be swallowed
whole. Cepbalaspis also lacked mobile true
fins and, instead, possessed fleshy 'fl~ps' for
clumsy swimming. Its skull shows slightly
depressed areas - sensory plates or' fields.
These suggest nerve endings in the cheek
and forehead that could detect water
currents, ripples from the movement of prey
or perhaps tiny electrical signals from the
active muscles of prey, as in sharks today.