sticking up out of it like a scimitar. Cuvier identified this animal, too, as
some sort of lizard. The jaw would, a few decades later, be recognized as
belonging to a dinosaur.
The Maastricht animal is still on display in Paris.
The study of stratigraphy was at this point in its infancy, but it was
already understood that different layers of rocks had been formed during
different periods. The plesiosaur, the ichthyosaur, and the as-yet-
unnamed dinosaur had all been found in limestone deposits that were
attributed to what was then called the Secondary and is now known as the
Mesozoic era. So too, had the ptero-dactyle and the Maastricht animal. This
pattern led Cuvier to another extraordinary insight about the history of
life: it had a direction. Lost species whose remains could be found near the
surface of earth, like mastodons and cave bears, belonged to orders of
creatures still alive. Dig back farther and one found creatures, like the
animal from Montmartre, that had no obvious modern counterparts.
Keep digging and mammals disappeared altogether from the fossil record.
Eventually one reached a world not just previous to ours, but a world
previous to that, dominated by giant reptiles.
CUVIER’S ideas about this history of life—that it was long, mutable, and
full of fantastic creatures that no longer existed—would seem to have
made him a natural advocate for evolution. But Cuvier opposed the