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Specimen/Evidence:
Placoderms
Common Name:
Placoderm
Scientific Name:
Dunkleosteus terrelli
Time Period:
416-359 mya
Age range:
Early Silurian to the end of the Devonian
Key Localities:
Red Hill, central Pennsylvania
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| Dunkleosteus
terrelli, one of the largest known placoderms.
These armored fish were probably the most diverse
group of early jawed fishes. Although placoderms
evolved in the Silurian, it was during the Devonian
that this group diversified dramatically. Members
of this taxon make up more than 200 genera and show
great diversity in body morphs and ecological niches.
One genus, Dunkleosteus, grew to be more
than 20 feet long. Others are believed to be some
of the first vertebrates to inhabit freshwater niches.
Placoderms are thought of as early experiments in
jawed fishes. They had bony plates that they used,
instead of teeth, for shearing and crunching prey;
in fact, they are the only jawed vertebrates to
lack teeth. Photo by Chip Clark, NMNH.
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