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The Dunkleosteus fish

Placoderms (Class Placodermi, which means “plate-skinned”) were prehistoric fish, which roamed the ocean from the Silurian to the end of the Devonian (Age of Fish) periods, approximately 443 to 359 million years ago. They went disappeared as the ecological communities suffered the changes due to the environmental changes between the Devonian / Carboniferous extinction event (EvolutionWiki).

Their main characteristic was that the head and thorax were covered by articulated armoured plates. Usually, the head shield articulated with the thoracic armour to allow jaw movement (Systematic Biology). The rest of the body was either naked or covered with scales. Placoderms were among the first jawed fish, thus being the precursor of all jawed vertebrates. Usually, the head shield articulated with the thoracic armor to allow for movement of the jaws. They are currently known by their fossils.

One of the most famous placoderms was the Dunkleosteus (after David Dunkle and ‘osteus’, meaning bone in Greek). Dunkleosteus lived about 380–360 million years ago, during the late Devonian. The largest species was D. terrelli (or D. terelli, depending on the page), which could measure up to 10 m and weight over 2 tonnes. The D. terrelli was a carnivorous apex predator (aka, it did not have predators itself). The average Dunkleosteus would have been 6 m long, with a 1.3-m wide skull. The armoured plates were as much as five centimetres thick.

Dunkleosteus did not have teeth, but the bony plates around the jaw were shaped in a razor-like structure which sharpened against the other half. According to the University of Berkeley a fossil was found in 1997 in Antarctica which had preserved some pigment cells: the fish had a red dorsal (back) side, and an iridiscent silver ventral side, making them the oldest vertebrate whose colours we know about.

As an apex predator, the D. Terrelli would have been feeding on everything it could find, even members of its own species. It would be classified as a pelagic marine predator, as it hunted in the open ocean. It is thought that it was not a fast swimmer, due to the heavy plates, but a very powerful one.

[Base information: Wikipedia: Dunkleosteus, Placoderms.]


Dunkleosteus head fossil, National Museum of Nature and Science, Tokyo. Picture by yours truly

What do you think could happen if it were possible to bring these fishy back to life?


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