The Placodonts

Placodonts were relatively small marine reptiles that have been found only in western Europe, Israel, and possibly England. The earliest known taxa lived at the end of the Early Triassic and all were extinct by the end of the Late Triassic. Placodonts measured from 3.5 to 6.5 feet (1 to 2 m) long and would have been dwarfed by some other marine reptiles of the time. Unlike the ichthyosaurs and ple-siosaurs, placodonts did not have large paddles or the streamlined body adaptations needed for quick swimming and maneuvering in the water. Their legs were short and stout and barely paddlelike. Their bodies were wide and sometimes armored, and they had little means for accelerating rapidly in the water. Based on their body plan, it is assumed that placodonts lived near the shore and probably moved slowly along the floor of the shallow ocean. Placodonts have been likened in appearance to a combination of a turtle and a walrus.

The first fossil evidence of placodonts consisted of curious black, rounded teeth that were sometimes discovered in limestone quarries in Germany. One collector named Georg Münster took an interest in these "beans," as the quarry diggers called them. In 1830, Münster expressed the opinion that the teeth were from ancient fishes. It wasn't until 1858 that a skull of one of these creatures revealed that they were reptiles and not fish. The first placodonts to be described in great detail were Placodus ("flat tooth") and Cyamodus ("bean tooth") in 1863, but even these specimens were incomplete. Our understanding of placodonts changed dramatically with the discovery of a complete Placodus skeleton from the Middle Triassic of Germany. This extraordinary find provided the missing pieces of the placodont puzzle. Only eight genera of placodonts are widely understood at present.

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