Dinosaurs On Their World

r Pith all these trees around, there was plenty for a foraging dinosaur to eat, whether nipping at seeds and fruits from tree branches, snapping up the ground cover in the forest, or wading into ponds and streams to eat the plants that grew in the water. What effect did T. rex and other dinosaurs have on T, rex's environment?

T. rex probably didn't have a taste for plants. But other dinosaurs did, and we have a pretty good idea what plant-eating dinosaurs ate. It's not just indirect evidence, like the fact that they had flexible jaws and the best grinding teeth ever. We have hard proof—dinosaur poop.

Fossilized dinosaur scat is called coprolite. A good coprolite isn't hard to recognize. It has the same cylindrical shape as what we and Rover and many other animals turn out. And it isn't much bigger. But dinosaur poop is dry, hard, heavy, and germ-free. That's because it's been fossilized. But that doesn't mean all the organic parts are gone.

A former student of mine, Karen Chin, now doing her graduate work at the University of California, Santa Barbara, specializes in dinosaur coprolites. She has a good sense of humor about it, but don't ask her how her work is coming out.

Karen made a detailed study of what she calls a "top-of-the-line" coprolite my assistant Bob Harmon found near some plant-eating dinosaur bones around Cut Bank in western Montana. She made thin sections of the coprolite, then examined its components with X rays and analyzed them with a gas chromatograph. Karen found chewed pieces of leaves, stems, seeds, and resins from conifers, as well as algae and bacteria. She found waxes that indicated the animal was consuming the more advanced vascular plants whose leaves pro

a sierra forest with sequoia and fir trees.

duce those waxes.

Karen's finding confirms what all of us would suspect—that plant-eating dinosaurs munched on the trees and plants around them. It makes sense that dinosaurs would be keeping the vegetation down. They must have had enormous appetites. Consider the great impact elephants have upon the African landscape. Plant-eating dinosaurs must have done at least as much to crop the vegetation around them. Maybe the openness of Scott Wing's site reflects the effects of dinosaur grazing, although the absence of plants could just as easily have been the result of fire or flooding. Closed forests appear to have been more extensive at that time.

In fact, dinosaurs do not appear to have had a drastic effect on these environments. As Leo points out, dinosaurs would have been pruning the branches of large trees and lopping the tops off saplings. But the trees appear to have thrived anyway. Maybe the trees had adapted to withstand dinosaur pruning. Relatives of these conifers today reach 120 feet to 180 feet in height and hold most of their nutrition in the foliage and small branches. They self-prune all of their lower lateral branches once they grow above eighty feet high and develop an umbrella-like canopy of branches, Leo says, "almost as if they retain a genetic 'memory' of the pruning they must have taken from the dino-saurs—and so are trying to cut their losses."

Bob Bakker suggests that dinosaurs altered the entire course of plant evolution, with the advent of efficient duckbill browsers favoring the development of flowering plants some 100 million years ago. To Leo Hickey this is "hog-wash." The effects of fires, floods, and shifts in stream channels created far greater disturbances. Plants evolve very slowly compared with animals, and there's no evidence that dinosaurs directed plant evolution. If anything, I think it was the other way around. But I doubt we'll ever have any way of knowing that.

device invented in 1807 and still used) to project magnified images of the fossils themselves onto a flat surface for tracing. The display will include conifer trees of a variety of species that also grew in dinosaur habitats, particularly in the uplands. Some of these were relatives of junipers and may have looked a lot like them.

T. rex's country was, as far as we can tell, mostly a closed, high-canopy woodland. Some herbs, ferns, and perhaps pachysandra covered the areas of open land, but there were fewer of these plants than in earlier times. In moister areas, such as ponds and backwaters, the tallest trees were relatives of the bald cypress of today's southern swamps, but with leaves that didn't narrow to a littie stem. Most of the trees were big-leafed kinds, like those of the laurel family, that kept their leaves year-round. Some were extinct relatives of modern conifers like the incense cedar, with scaly foliage, though at the very end of dinosaur times climatic changes seem to have killed off many of the conifers. Sticking out above the canopy were some giant redwoods and a few Metasequoias.

The dawn redwood, the eerie Metasequoia, is one of my favorite trees, and it's among those that dwarfed even the biggest dinosaurs. Metasequoias are strange, beautiful trees. They look something like bald cypresses, only they don't live by the water, and something like redwoods, but they have softer needles (and unlike redwoods, Metasequoias shed their needles in winter). They're several feet in diameter when mature, all billowy and cone topped. They throw out shoots from old wood in their trunks, and they're incredibly knobby, with foliage everywhere. There was a full and bushy one with delicate little leaves at Princeton that I loved to sit under and imagine that I was in dinosaur time.

We know what Metasequoias looked like through a lucky accident. Metasequoias were known only as fossils until World War n, when a forester found an isolated grove still alive in China. The tree has now been cultivated and preserved. There's a nice one at the Harvard arboretum in Boston. You can walk under neath and imagine what it would be like to see the same tree from a dinosaur's eye.

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