The End of Earthly Oceans - Ocean Worlds: The Story of Seas on Earth and Other Planets - page 199

The resulting extinction, on land, of the dinosaurs—of the non-
avian dinosaurs, that is—is now as much a part of popular as of scien-
tific culture. But much else died out as well, especially in the sea. Of
the impressively monstrous creatures, the mosasaurs and plesiosaurs
vanished. Among the small fry, the ammonites and belemnites were
lost, and most species of brachiopods (lamp shells). Among the crea-
tures that really count, those at the base of the food chain, many
species of planktonic algae disappeared too.
It was a catastrophe, a body blow to the biological fabric of the
Earth. But, as with all such mass clearings-out of species, there are
opportunities too for those that survive. The following several mil-
lions of years saw extraordinary evolutionary radiations. On land,
famously, the mammals took over the upper echelons of the food
web. In the sea the mammals also prospered. The whales, originally
those wolf-like creatures paddling along the shoreline, dipped more
than a toe in the water to take over much of the territory formerly
occupied by the marine saurians. The brachiopods never really recov-
ered (they are still clinging on, just), while the resurgent bivalve mol-
luscs and gastropods prospered. From among the microscopic forms,
giants developed, such as the nummulites; single-celled foraminiferan
protists they may have been, but nevertheless they built centimetre-
sized shells in such numbers that Egyptian kings would find the
resulting rock the material of choice to build their pyramids with.
But who could have predicted, as a thoughtful spectator amid the
rubble of the dying Cretaceous world, what would have emerged?
That there would arise such creatures as penguins and walruses, sea
horses, nummulites, and narwhals? Evolution, especially as regards
its more baroque creations, is not directly predictable.
One can have fun trying, though. Some years ago the science writer
and illustrator Dougal Dixon wrote and illustrated the topic After
Man . 115 This zoology of the far future is set some 50 million years