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Re: Mesozoic terrain - who needs grass anyway ?



Roy Nash wrote:
>
>I'm surprised no paleobotanists have picked up on this one. Although there
>was no grass we cannot not assume there was no ground covering vegetation
>to help bind the soil together.  Apart from the obvious ferns, mosses,
>horsetails, flowering plants began to diversify at the same time as
>dinosaurs. Many of these would have been ground covering plants.

I'm not a paleobotanist, but I've been writing some about things like the
origins of angiosperms. Small, low plants aren't good at leaving fossils,
but it's probably safe to assume some existed to bind soils together. Some
very primitive plants had rhizomes which spread underground; rhizomes and
roots together would have bound soil together even before angiosperms.

The current thinking, as I understand, is that angiosperms spread rather
extensively starting in the mid-Cretaceous; some were probably low-lying
plants. The initial origin of angiosperms is controversial (the recent
Science paper that claims to put flowering plants in the late Jurassic has
a serious problem with dates that was not caught by the referees.) The
evolutionary advantage of grasses is that their leaves continue growing
after being grazed upon (or mowed, in the case of your lawn). Other plants
regenerate in other ways after browsing, typically from branches.

The presence of low-slung grazers among dinosaurs, such as the ankylosaurs,
stegosaurs, and ceratopsians, argues strongly that there was appreciable
low plant cover during the mesozoic, even before angiosperms were widely
recognized.

Jeff Hecht