540 Million Years Ago to Today
Twice in the past 230 million years, widespread extinctions brought down the
curtain on many kinds of marine life. Twice, a new cast of actors evolved to
live on the seas' stage. Fantastic marine fossils tell the story of evolution
and extinction in the seas in three acts: the Paleozoic Era (540 to 250 million
years ago), when odd creatures such as trilobites abounded; the Mesozoic Era
(250 to 65 million years ago), when marine reptiles such as mosasaurs appeared;
and the Cenozoic Era (65 million years ago to today), when the numbers and kinds
of shelled animals increased, and when the primitive whale Basilosaurus took
to the seas.
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| Trilobite | Mosasaur | Basilosaurus | Gastropod |
