The Science of Discworld Revised Edition

would have been something to see, with volcanoes in one hand and an asteroid in the other, trailing a cloak of ice …
    They
were
wonderfully cinematic reptiles, weren’t they? Trust the wizards to get it wrong.
    There is another lesson to be learned from our emphasis on the demise of the dinosaurs. Many other large and/or dramatic reptiles died out at the end of the Cretaceous, notably the plesiosaurs (famous as a possible ‘explanation’ of the mythical Loch Ness monster), the ichthyosaurs (enormous fish-shaped predators, reptilian whales and dolphins), the pterosaurs (strange flying forms, of which the pterodactyls appear in all the dinosaur films and are labelled, wrongly, dinosaurs), and especially the mosasaurs …
    Mosasaurs?
    What were they? They were as dramatic as the dinosaurs, but they
weren’t
dinosaurs. They didn’t have as good a PR firm, though, because few non-specialists have heard of them. They are popularly known as fish-lizards – not as good a name as ‘terrible lizard’ – and it describes them well. Some were nearly as fish-like as ichthyosaurs or dolphins, some were rather crocodile-like, some were fifty-foot predators like the great white shark, some were just a couple of feet long and fed on baby ammonites and other common molluscs. They lasted a good twenty million years, and for much of that time they seem to have been the dominant marine predators. Yet most people meet the word in stories about dinosaurs, assume that the mosasaur was a not-very-interesting kind of dinosaur, and promptly forget them.
    The other really strange thing about the K/T extinction – probably not a ‘thing’ in any meaningful sense, because in this context a thing would be an equation of unknowns, whereas what we have is a diversity of related puzzles – is which creatures
survived
it. In the sea, the ammonites all died out, as did the other shelled forms like belemnites – unrolled ammonites – but the nautilus came through, as did the cuttlefish, squids, and octopuses. Amazingly the crocodiles, which to our eyes are about as dinosaur-like as you can get without actually being one, survived the K/T event with little loss of diversity. And those little dinosaurs called ‘birds’ came through pretty well unscathed. (There’s a story here that we need to tell, quickly. Not so long ago, the idea that birds are the living remnants of the dinosaurs was new, controversial, and therefore a hot topic. Then it rapidly turned into the prevailing wisdom. New fossil discoveries, however, have shown conclusively that the major families of modern birds diverged, in an evolutionary sense, long before the K/T event. So they aren’t remnants of the dinosaurs that otherwise died – they got out early by ceasing to be dinosaurs at all.)
    Myths, not least
Jurassic Park
itself, have suggested that dinosaurs are not ‘really’ extinct at all. They survive, or so semi-fact semi-fiction accounts lead us to believe, in
Lost World
South American valleys, on uninhabited islands, in the depths of Loch Ness, on other planets, or more mystically as DNA preserved inside bloodsucking insects trapped and encased in amber. Alas, almost certainly not. In particular, ‘ancient DNA’ reportedly extracted from insects fossilized in amber comes from modern contaminants, not prehistoric organisms – at least if the amber is more than a hundred thousand years old.
    Significantly, no one has made a film bringing back dodos, moas, pygmy elephants, or mosasaurs – only dinosaurs and Hitler are popular for the reawakening myth. Both at the same time would be a good trick.
    Dinosaurs are the ultimate icon for an evolutionary fact which we generally ignore, and definitely find uncomfortable to think about:
nearly all species that have ever existed are extinct
. As soon as we realize that, we are forced to look at conservation of animal species in new ways. Does it really matter that the lesser spotted pogo-bird is down to its last hundred specimens, or that a hundred species of tree-snail on a Pacific island have been eaten out of existence by predators introduced by human activity? Some issues, like the importation of Nile Perch into Lake Victoria in order to improve the game fishing – which has resulted in the loss of many hundreds of fascinating ‘cichlid’ fish species – are regretted even by the people responsible, if only because the new lake ecosystem seems to be much less productive. Everyone (except purveyors of