Did placoderms have jaws?

Placoderms lacked teeth but possessed dermal bones associated with the jaws known as gnathal bones. In the Devonian, placoderms were the most diverse group of fish and more than 400 species are known which range in size from 10 mm to 7 meters (Qu, 2010).

Are placoderms jawless?

The earliest vertebrates were jawless fishes, and placoderms were among the earliest fishes to evolve jaws, an adaptive breakthrough that contributed to their rapid success.

What killed the placoderms?

With more accurate summaries of prehistoric organisms, it is now thought that they systematically died out as marine and freshwater ecologies suffered from the environmental catastrophes of the Devonian/Carboniferous extinction events.

Did placoderms have skulls?

Unlike all other jawed vertebrates, placoderms never had teeth, and did not descend from toothed ancestors. Additional peculiarities of the skull, such as nasal capsules that were not fused to the rest of the braincase, distinguish placoderms from all other jawed vertebrates.

How long did Placoderm fish live on Earth before they went extinct?

about 416 million to 359 million years ago
Placoderm, any member of an extinct group (Placodermi) of primitive jawed fishes known only from fossil remains. Placoderms existed throughout the Devonian Period (about 416 million to 359 million years ago), but only two species persisted into the succeeding Carboniferous Period.

Are there any living placoderms?

Placoderm, any member of an extinct group (Placodermi) of primitive jawed fishes known only from fossil remains. Placoderms existed throughout the Devonian Period (about 416 million to 359 million years ago), but only two species persisted into the succeeding Carboniferous Period.

Are ostracoderms extinct?

about 420 million years ago, most ostracoderm species underwent a decline, and the last ostracoderms became extinct at the end of the Devonian period.

How are placoderms similar to other jawed fish?

Placoderms also possess a support for the eye called the eyestalk similar to a structure in sharks (Long, 1995). Placoderm braincases possessed a number of structures shared among jawed fish such as the position of several arteries, the pathways of nerves, and perhaps the jaw articulation (Maisey, 2005).

How did the placoderm jaws change over time?

Placoderms dominated the oceans, rivers and lakes for some 80 million years, before their sudden extinction around 359 million years ago. This is possibly due to the depletion of trace elements in our oceans. But placoderm jaws bear no resemblance to those of any living animal.

What kind of body did a placoderm have?

Their head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches.

Where are the premaxilla and placoderm jaws found?

These two bones persist in evolution and are still present in most mammalian skulls, although in some cases, such as in humans, the premaxilla is incorporated into the maxilla. How early placoderm jaws and certain cheek bones evolved and are now incorporated into the advanced tetrapod skull.