Light on the Triassic dark

Coelophysis, the little dinosaur of Ghost Ranch, is doubtless far less familiar to most people than its giant cousin, Tyrannosaurus. Yet Tyrannosaurus is known from a mere dozen or so skeletons, Coelophysis from more than a thousand. This palaeontological treasure has been found within a small quarry on Ghost Ranch in New Mexico, United States. Evidence suggests there maybe ten times that number of skeletons still buried in the rocks. The mystery of why so many of these small carnivorous dinosaurs, no bigger that a large dog, died in one place is just one of the fascinating questions about their life and times discussed in this book.

Edwin Colbert has written a very personal account of the dinosaur that is inextricably "his", for he has discovered, collected and studied many skeletons over a lifetime as a paleontologist. A handful of bones from New Mexico, including some neck vertebrae, were described as Coelophysis by Edward Drinker Cope in 1889, then consigned to obscurity. The story of Coelophysis began in earnest in summer 1947, when Colbert and the late George Gaylord Simpson discovered, quite by accident, a huge concentration of tiny dinosaur bones in 225-million-year-old rocks at Ghost Ranch. Colbert chronicles at length the trials and tribulations and logistics of working in a remote semi-desert area, and the physical problems of excavating, removing and shipping to the American Museum of Natural History, five-tonne blocks of sandstone full of fragile skeletons.

The detailed study of the fossils of Coelophysis itself provides the focus for interpreting the environment in which it lived, the animals and plants that shared its world and its place in dinosaur evolution. Colbert paints a vivid picture of Coelophysis as a living animal. Its anatomy is described in some detail along with structural and functional interpretations of the shape and proportions of the bones of the skeleton. He then fills out the evidence from the bony framework to discuss how Coelophysis moved, whether it was warm-blooded, what it ate. As far as its diet is concerned, Coelophysis has achieved a certain notoriety as a cannibal. The evidence is all too plain, bones of small individuals of its own species are clearly preserved inside the body cavity of two adult skeletons. We should not be too surprised; cannibalism is not uncommon among living crocodiles and alligators.

Coelophysis holds an important place in the evolution of dinosaurs. Thanks to the beautifully preserved Ghost Ranch skeletons, this representative of an early stage in the evolution of meat-eating dinosaurs is very well known. Many modern paleontological studies use the anatomy of Coelophysis as an evolutionary yardstick to assess the primitive or advanced state of the bony characters of later carnivorous dinosaurs. Coelophysis lived at the beginning of "the age of dinosaurs", late in the Triassic period. Colbert presents a vivid picture of the varied animal and plant life in the late Triassic before dinosaurs had diversified and become the dominant land animals for the next 150 million years.

This book offers a fascinating and accessible introduction to the science of paleontology and shows how the fossil remains of just one kind of animal can contribute to our understanding of the nature and history of life in the past. It is well-illustrated with black and white photographs, line drawings, maps, charts and an inset of colour paintings of Triassic life. Curiously though, the star of the book is depicted "in the flesh" only on the dust jacket.

This compact little volume will appeal to anyone with more than a passing interest in vertebrate paleontology and particularly those willing to persevere with the slightly more technical chapters and get to grips with a few anatomical names. There is an good and up-to-date bibliography to the primary scientific literature on Triassic faunas and environments.

Angela C. Milner is head, fossil vertebrates and anthropology division, Natural History Museum, London.