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Placodermi, Definition from AP Dictionary of Science and Technology - English
URL: http://www.academicpress.com/inscight/08131997/placode1.htm

An extinct class of primitive jawed fishes characterized by bony plates of armor covering their head and flanks; the placoderms arose in the Silurian and flourished in the Devonian, replacing the jawless ostracoderms.

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Placodermi - English
URL: http://www.mun.ca/biology/scarr/Placoderm_radiation.htm

Placoderms are the only entirely extinct class of vertebrates. The class is distinguished by a craniovertebral joint, a ball-and-socket joint on either side of the cranium that articulates with the vertebral column.

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Basal Placodermi - English
URL: http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Placoder

Cladogram.

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Class Placodermi - English
URL: http://animaldiversity.ummz.umich.edu/chordata/placodermi.html

Species included in the Animal Diversity Web: Bothriolepis canadensis, Fallacosteus turnerae.

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Placodermi--Armored gnathostomes - English
URL: http://www.geocities.com/kajejenson/placodermi.html

Cladograms.

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Introduction to the Placodermi - English
URL: http://www.ucmp.berkeley.edu/vertebrates/basalfish/placodermi.html

The extinct armored fishes known as placoderms make up what is considered to be the earliest branch of the gnathostome family tree -- the earliest branch of the jawed fishes. Placoderms bore heavy bony armor on the head and neck, often with an unusual joint in the dorsal armor between the head and neck regions; this joint apparently allowed the head to move upwards as the jaw dropped downwards, creating a larger gape.

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