The remains of a forest pool were found in the 80s in the Cotswolds, a picturesque region of England based on a range of low hills. Some 165 million years ago the pool teamed with life, the excavations yielding up 30,000 fossils, including parts of four dinosaurs, one of which was a stegosaur. It was only small being about 15 feet wide and a few feet deep but it was surrounded by a forest of conifers, cycads and horsetails.
The most remarkable finds were tiny teeth of an unknown bird-like dinosaur about as big as a pheasant. It is considered not to have been a bird because it pre-dated archaeopteryx, though the finds in China might have changed that view. Few people today deny that the evidence increasingly points to birds being a type of dinosaur or descended from them. They had the same hollow bones, a similar stance, laid eggs and looked after their young. Remains were also found of mammals—in those days tiny rodent-like animals that had their time cut out trying to avoid being eaten by the smaller predatory dinosaurs. There were also lots of frogs and salamanders and some fish. Trying to get them was a variety of crocodiles. Remains were also found of pterosaurs and insects. It seems that the habitat was as diverse in species as a similar place today. Plainly, the pool served as a watering hole and either sick animals fell in and died there or they were ambushed by predators. Today, we can see that prey species can be quite relaxed in the presence of a predator when they sense that it is already well fed. It will have been true then also and we can guess that predators and prey might have had a draught together when the latter were not hungry. Though the raptors are depicted as mindless killers in fiction and movies, it is unlikely to be true.
Perhaps 50,000 dinosaur genera and up to half a million individual species populated the Mesozoic from the Middle Triassic until the end of the Cretaceous, about 160 million years. As many as 90 percent of these taxa lived where their remains were not preserved as fossils and we shall therefore never know anything about them. Many of these taxa were small, crow-sized, birdlike forms seldom found fossilized even in regions favorable to fossilization because they were so small and fragile. Several thousand dinosaur genera might have been alive at any one time in the Mesozoic but only about a hundred or two of the big dinosaurs, entirely in line with ratios for extant mammals, birds, and reptiles.
People are inclined not only to believe that dinosaurs lived at the same time as cave men but that all dinosaurs also lived at the same time. The dinosaurs writ large in the film, Jurassic Park, were actually Cretaceous dinosaurs, a later age. Stegosaurs were not shown, quite rightly, because they had already died out. The long existence on earth of the dinosaurs was itself subject to several mass extinctions and apatosaurs and stegosaurs had died out millions of years before the final demise of the dinosaurs. The truth is that warm-blooded species rarely live as long as ten million years. Since humans split from their nearest relatives, Chimpanzees, about 7 million years ago, plainly we do not have long to go—in geological terms. At the rate of environmental destruction we see about us, we’ll be lucky to live another millennium. We are already losing species faster than during the mass extinction that ended the span of the dinosaurs, 65 million years ago.
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