Dinosaurs of the Air by Gregory Paul, Johns Hopkins University Press, 拢34.50, ISBN 0801867630 Review by Jeff Hecht
DINOSAURS no longer thunder across the land, but they do flutter among the trees and paddle around the pond. Evolutionarily speaking, modern birds from hawks to hummingbirds are avian dinosaurs, descended from swift two-legged predators like the velociraptors of Jurassic Park.
Gregory Paul鈥檚 title, Dinosaurs of the Air symbolises the compelling links that he documents. A sparrow perched on a twig is far from our usual view of the elephantine Apatosaurus (better known as Brontosaurus) or the terrifying Tyrannosaurus rex. Yet under the skin they share the same anatomical kinship as bats and whales, two mammals that evolved into profoundly different forms.
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The similarities among dinosaur and bird fossils are striking. Paul includes his own careful drawings that show how anatomical features shade gradually from dinosaur into bird. One two-page spread lines up 18 skulls, from the earliest in the dinosaur line to the modern loon, and only one 鈥� an odd beaked dinosaur called an oviraptor 鈥� looks out of place. His text catalogues many other commonalities.
A centrepiece of the book is the dramatic discovery of feathers and simpler filamentary structures on dinosaur fossils from China. Feathered dinosaurs didn鈥檛 surprise Paul; he had been drawing them before the Chinese fossils first surfaced in the West. On the dustjacket he brings matters up to date, showing an unmistakably dinosaurian Sinosauropteryx coated in small downy feathers chasing its cousin, the early bird Confuciusornis, both from the same Chinese deposits.
It鈥檚 getting hard to tell the birds from the dinosaurs, and to Paul鈥檚 credit he resists the temptation to draw a simple family tree. It鈥檚 natural to ask who is related to whom, but Paul says we don鈥檛 have enough data to give a simple answer. Instead he displays nine different family trees that noted paleontologists have compiled to explain the relationships among the same group of birds and dinosaurs. 鈥淲e do not yet have enough data in the form of transitional species鈥� to compile that definitive family tree.
Indeed, the web of relationships among birds and dinosaurs remains complex and puzzling. Paul offers his own intriguing theory 鈥� that some of the two-legged fossils we consider dinosaurs were really birds that had lost their ability to fly. That could solve some evolutionary puzzles, but may raise others.
If you want to dig seriously into one of today鈥檚 most fascinating evolutionary debates, and aren鈥檛 afraid of anatomy, you鈥檒l delight in Dinosaurs of the Air. And you鈥檒l start wondering what other creatures strutted like the neighbourhood crows.