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The
Diversity of The World of Life
Vertebrates
(Vertebrata)
Ostracoderms
(various extinct groups)
Representatives
Ostracoderms
Biology
ENVIRONMENTS
Ostracoderms are extinct, marine species.
DESCRIPTION
Typically flattened somewhat "dorsoventrally"
(from top to bottom), ostracoderms had no jaws but did possess heavy,
bony and scaly armor -- an advantage in prehistoric seas filled with such
formidable predators as "sea-scorpions" (eurypterids).
FEEDING HABITS
Ostracoderms were
typically bottom-feeders.
MOTION
The fins of fish typically help provide stability and
guidance during swimming: Apparently all ostracoderms had
"median" fins (atop the centerline of the body); some had paired
"pectoral" fins (on either side towards the front of the body);
and most had a "heterocercal" (shark-like) tail. The tail
provided forward motion; the body (typically flattened below and rounded
above) and any side fins, "lift" (See birds
for a similar discussion).
DIGESTION
Ostracoderms
were apparently filter-feeders, "vacuuming" water with food
particles into the jawless mouth, found on the underside of the head and
covered with flexible plates; the food was apparently trapped in the
pharynx (throat).
RESPIRATION
Water,
with dissolved gases, passed out of the pharynx through many small gill
slits, on either side of the body, where the gases were exchanged with
those in the blood.
COORDINATION
Ostracoderms
had a single, primitive (light-sensing but not image-resolving)
"pineal eye" atop the head (as in lampreys
and other primitive vertebrates), with a "lateral eye" to either
side. There was typically a single nostril atop the head (also as in
lampreys but unlike in any other living vertebrates), used in the sense of
smell. There were typically rather broad sensory areas on the top
and lower sides of the head (perhaps part of a "lateral line",
as in modern fishes).
Vertebrates
(Vertebrata)
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