Geoscience Reference
In-Depth Information
Robert Bakker was the first dinosaur paleontologist to suggest that dinosaur
feeding might have “invented” flowering plants (
angiosperms
) from non-flowering
seedplants (
gymnosperms
),suchascycads, ginkgoes,andpines.Hisreasoning was
that during the Early Cretaceous (about 135
mya
), grazing and low-level brows-
ing ornithopods mowed down gymnosperms so much that angiosperms, with their
low-lying flowers and fruits, were favored over these plants. Consequently, flower-
ing plants proliferated, diversified, and took over terrestrial ecosystems, which they
have ruled ever since. This was an imaginative idea, but Bakker was not a paleo-
botanist, so his supposed connection between herbivorous dinosaurs and flowering
plants seemed tenuous to most other paleontologists.
Among the first paleobotanists to start examining whether flowering plant and
land-dwelling vertebrate evolution went hand in hand (or rather, leaf in mouth)
were Scott Wing and Bruce Tiffney. In several articles published in the late 1980s,
they proposed that herbivorous dinosaurs and the earliest flowering plants had
what they termed a “reciprocal relationship,” which resulted in their coevolution.
This relationship meant dinosaurs that ate these plants helped with dispersing their
seeds (more on that topic later). Moreover, as angiosperm seeds were placed in
new ecosystems, this affected their natural selection and ultimately their evolution
throughouttherestoftheCretaceousPeriod.Inturn,asnewspeciesofangiosperms
arose,someproducedmorespecialized flowers andfruits,ordefenses against herb-
ivory(suchastoxinsandspines),whichcontributedtothenaturalselectionofherb-
ivorous dinosaurs. In other words, the plants were partially responsible for driving
the evolution of new species of herbivorous dinosaurs that were more specialized
in their feeding. In contrast, the first herbivorous dinosaurs to eat angiosperms may
have been more generalists, eating every item from their Early Cretaceous all-you-
can-eat salad bars.
However, other paleontologists, including some paleobotanists, have critically
examined and questioned a direct cause-and-effect of herbivorous dinosaurs on
flowering plants. In a 2001 study done by dinosaur paleontologist Paul Barrett and
