<Tr> <Td> </Td> <Td> The Mesozoic Marine Revolution begins: increasingly well adapted and diverse predators pressurize sessile marine groups; the "balance of power" in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others . </Td> </Tr> <Tr> <Td> 248 Ma </Td> <Td> Sturgeon and paddlefish (Acipenseridae) first appear . </Td> </Tr> <Tr> <Td> 245 Ma </Td> <Td> Earliest ichthyosaurs </Td> </Tr> <Tr> <Td> 240 Ma </Td> <Td> Increase in diversity of gomphodont cynodonts and rhynchosaurs </Td> </Tr>

When did plant life begin to appear on earth