Placodermi

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Placodermi

[‚pla·kə′dər·mē]
(paleontology)
A large and varied class of Paleozoic fishes characterized by a complex bony armor covering the head and the front portion of the trunk.

Placodermi

 

a class of extinct fishes that lived during the Devonian. Their length was up to 5–6 m. The head and anterior part of the trunk were covered with an armor of bony plates of cutaneous origin. The plates were nodular and ridged. The head and trunk sections of the armor were articulated, and the jaws consisted of pointed bony plates. There were two subclasses: Arthrodira and Antiarchi (which included the genus Bothriole-pis).

REFERENCE

Drushits, V. V., and O. P. Obrucheva. Paleontologiia, 2nd ed. [Moscow] 1971.
References in periodicals archive ?
They were interpreted as the result of placoderm fish dragging or pushing off the sediment.
The blades, called gnathal plates, looked so peculiar that most scientists thought that the three-part jaw originated in an early bony fish and that placoderms were just a side branch in the vertebrate family tree.
Matt Friedman, a paleobiologist at Oxford University, said: "If you look at just the top of the skull and the body, it looks like a placoderm.
The limestone middle part (up to 10 cm) is rich in cephalopods and arthrodire placoderms.
Placoderms were also the first vertebrates to have jaws, but they still had no teeth, which appeared in later fish.
Placoderms were also some of the first vertebrates to have necks separating their heads and shoulder bones, allowing the fish to move their heads independently of the rest of their bodies.
The placoderms of the Voskresenskoye locality might have entered a separate community of their own from the tetrapod one of the Andreyevka-2 locality and have been stenohaline, possibly depending on a food type missing from the latter.
The genus Guerichosteus, which had previously been known from the Emsian of Poland (Holy Cross Mountains, placoderm sandstone, Rhinopteraspis cornubica Zone), is also found in the Lower Eifelian of Estonia.
Armored placoderms such as the gigantic Dunkleosteus and lobe-finned fishes-similar to the modern lungfish-dominated the waters, while ray-finned fishes, sharks and tetrapods were in the minority, according to Maureen Kearney, program director in the National Science Foundation (NSF)'s Division of Environmental Biology, which funded the research, along with NSF's Division of Earth Sciences.
Long said that the claspers were used by the ancient fish, an extinct class of armoured fish called placoderms, to grip inside the female while they were mating.
They are represented by undetermined placoderms, acanthodians and sarcopterygians (Fig.