Vertebrates Jaw Formation

420 million years
or 102 meters before today

Geolo­gi­cal era: Paleo­zoic / Silurian

At the begin­ning of the Silu­rian, verte­bra­tes deve­lop mova­ble jaws that allow them to grasp, hold and chop food. This opens up comple­tely new feeding possi­bi­li­ties for the jawed animals. Bone scales form teeth that can sit on the edges of the jaws, in the oral cavity or in the gullet. This deve­lo­p­ment is so success­ful that today there are only two jawless verte­brate groups (lampreys and hagfish).

After the end of the Ice Age at the begin­ning of the Silu­rian, a warm tempe­rate climate prevails with a global average tempe­ra­ture of about 17 °C. For the first time, the oxygen concen­tra­tion rises to 14 %, while the carbon dioxide concen­tra­tion drops below 0.4 %. The conti­nent Eurame­rica (Laurus­sia) is formed from the land masses Lauren­tia and Baltica.

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