Jurassic West The Dinosaurs of the Morrison Formation and Their World

Most people might not quite realise this, but our picture of dinosaurs and other prehistoric life is largely based on a small number of very-well researched fossil localities. The Morrison Formation in the American Southwest is one example, offering a window on life during the end of the Jurassic, between 157 and 150 million years ago. First published in 2007, the second edition of Jurassic West updates you on the latest findings and the many taxonomical advances and stands out for just how readable and comprehensive it is.

This book is part of one of my favourite series, Life of the Past, and is one of several books that gives an as-complete-as-possible overview of a major fossil locality. Compared to the previously reviewed Oceans of Kansas I found this one to be more suitable for a general audience, as palaeontologist John Foster makes few assumptions as to what you might already know.

This starts with a very thorough overview of the geology and the stratigraphy of the Morrison Formation. What kinds of rocks does it consist of, what do these look like in the field, and how were they laid down? What are the names of the different rock layers; where are they, both geographically and in relation to each other; how old do we think they are; and what sort of fossils have we found in them? The many photos and diagrams help to further clarify the basic setting. Then there is the history of discoveries and the people who made them, and the descriptions of fossil quarries. I had never really appreciated how unassuming some scientifically important sites are – mere patches of dirt in the middle of nowhere.

These first four introductory chapters already take you to page 165 before Foster starts describing the fauna. For groups such as fish, amphibians, turtles, snakes, lizards, pterosaurs, and the many small mammals he is necessarily brief. Beyond describing the fragmentary specimens there is simply too little information to reconstruct their lifestyle and behaviour. The bulk of the book deals with the larger dinosaurs whose bones have better withstood the rigours of the fossilization process: the theropods (especially the omnipresent Allosaurus), stegosaurs, ankylosaurs, and especially the sauropods. Because we have more complete skeletons, we can say much more about what these animals were like in life. Foster's text remains readable here, even when when he descends into technical detail, for example, the anatomical description of Diplodocus longus on page 248.

Foster makes some really interesting observations and puts forward ideas that I was not yet familiar with. For example, he points out the value of finding yet another Camarasaurus specimen: "we can't forget that the sample sizes of most dinosaur species are pathetically small" (p. 240). And trying to understand dinosaur physiology "is not a simple matter one modern analog or another. It appears more and more likely that dinosaurs were unique" (p. 244). Foster is not afraid to admit his past errors, such as the identity of a crocodyliform mandible on page 196, or to defend views that are not shared by everyone. He thinks that diplodocids did not habitually rear up on their hindquarters to browse vegetation in the treetops, an idea put forward by Hallett and Wedel in The Sauropod Dinosaurs. Or the view that most suspected gastroliths (stones that are swallowed by animals to help in mechanical digestion of food in the stomach) that have been found in the Morrison Formation are more likely pebbles that were deposited by currents.

Another aspect I understood better after reading this book is that of taxonomy and nomenclature. The way we name living biological species differs from the nomenclatural rules for fossils. Given how fragmentary the fossilised bones are that palaeontologists sometimes have to work with, it is not uncommon to apply a tentative name, a nomen dubium, only to later collapse it as more material becomes available. Foster shows the relevance of such seemingly rarefied discussions by examining the validity of Amphicoelias altus which he thinks is a large Diplodocus. If he is right, nomenclatural priority rules mean "we'd be faced with switching all of our museum Diplodocus labels to Amphicoelias" (p. 258).

The most exciting aspect of Jurassic West is that it is more than a large catalogue of specimens and localities. After 140 years of collecting we have so much information that compiling it all – a laborious job, as Foster explains – can bring fascinating insights. Chapter 7 thus digs into the palaeoecology, looking at species diversity, the distribution over different dietary guilds (herbivores, carnivores etc.), the distribution of weight and size, the geographic spread of species, and the shape of food webs. And he does so while being mindful of how these conclusions can be distorted by gaps in the rock record and the unevenness with which certain time periods have been explored in quarries. The 48-page appendix with localities of all vertebrate fossils used in the book will in itself be a goldmine for scientists.

A few final words of praise. Foster infuses his writing with the occasional touch of well-placed humour, such as when taking Tyrannosaurus rex down a notch: "in truth it has only one appeal: that it's a big walking head with huge teeth [...] I've always found the unusual ornamentation of a stegosaur skeleton far more interesting" (p. 280). He even engages in a bit of speculative fiction with the final chapter, which imagines what it would be like to trek through the area of the Morrison Formation during the Jurassic. Also noteworthy are the book's production values: Jurassic West is a chunky book with a case-printed hardcover that is chock-a-block with illustrations, photos, and diagrams. I liked the drawings by Thomas Adams, although I did think his reconstructions suffered a bit from what palaeoartists call shrink-wrapping: drawing the skin to fit tightly around the bones. I also was particularly taken by the illustrations by Brian Engh in the last chapter.

If you bought the first edition of Jurassic West I would strongly advise you to check out this new edition and consider the upgrade. If you did not, then you have no excuse. Jurassic West is a fantastic addition to this long-running series and really brings to life both the animals of this time and the science behind it. Will he update his previous book Cambrian Ocean World for a second edition next? We can but hope, but I would be first in line to read it.