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NATURE|Vol 440|23 March 2006 BOOKS & ARTS

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Summing up physicsThe Equations: Icons of Knowledgeby Sander BaisHarvard University Press: 2005. 96 pp.$18.95, £11.95, €17.50

Malcolm LongairPerhaps the most common comment I receiveafter delivering a public lecture is: “I enjoyedthe lecture, but I couldn’t understand themaths.” This difficulty doesn’t just affect thepublic but is one that students and scientistsencounter throughout their careers: how doesone connect the behaviour of the real worldwith the mathematics used to describe it?After years of practice and hard thinking, pro-fessionals become adept at making this con-nection, which I regard as perhaps the greatestchallenge in teaching mathematical physics.

Sander Bais’s little book The Equations tack-les this problem from the point of view of 17 of

Boning up on dinosaursThe Microstructure of Dinosaur Bone:Deciphering Biology with Fine-ScaleTechniquesby Anusuya Chinsamy-TuranJohns Hopkins University Press: 2005. 216 pp. $85, £56.50

Luis M. ChiappeStudies of the microstructure of dinosaur bonebegan soon after the first scientific reports ofthese Mesozoic behemoths, but it took nearly150 years for this discipline to enter the main-stream of dinosaur palaeontology. Nowadays,these studies are used to infer numerousaspects of dinosaur biology, from growth ratesand physiological strategies to skeletal bio-mechanics and developmental patterns, andare even used as a source of new characters forphylogenetic inference. The Microstructure ofDinosaur Bone by Anusuya Chinsamy-Turanis the first book-length review of this rapidlyadvancing line of palaeontological research.

Chinsamy-Turan begins by introducing ahost of topics, including the basics of bonecomposition, histological studies, the changesthat occur on death and fossilization, and dino-saur evolution and ecology. Next, she examinesthe biological meaning of bone microstruc-ture. She looks at bone-tissue dynamics (therate at which it is deposited, and whether itoccurs without interruption or with growthrings) and vascularization (the number ofblood vessels), and explains how they can pro-vide clues to the ontogenetic, biomechanicaland ecological contexts of bone.

After that she turns her attention to dino-saurs, with a brief history of dinosaur-bonehistology and a review of the diverse tissuesfound in their bones. We then reach the heartof the book, with a discussion of how micro-structural studies of fossil bone inform ourunderstanding of the growth patterns ofextinct vertebrates. Particularly useful is theauthor’s emphasis on the caveats for inferringsome aspects of growth dynamics from fossilbones. Then she covers a number of studies,mostly her own, on the bone histology of pre-modern, Mesozoic birds — dinosaurs’ mostimmediate descendants — and the importantchanges in growth patterns thought to haveoccurred during their evolution. Finally, shedelves into dinosaur physiology to see if bonemicrostructure can tell us whether some, all ornone of these animals were warm-blooded.

The book draws on Chinsamy-Turan’sextensive studies of the bone microstructure ofliving tetrapods. It is perhaps her deep under-standing of the complexity of skeletal growththat leads her continuously to warn againstmaking a strong connection between the dif-ferent types of tissue preserved in fossilizedbones and either specific rates of bone forma-tion or dinosaur physiology. Throughout the

book, Chinsamy-Turan is resolute in defendingher views from opposing perspectives; at timesit feels like we are watching a television com-mercial for a video-game. Fortunately, how-ever, the different contenders in the modernarena of dinosaur-bone microstructure agreeon several fundamentals. Thanks to work byChinsamy-Turan and her colleagues and men-tors, we know that even if the growth strategiesof dinosaurs varied greatly, these animals grewat rates substantially faster than extant non-avian reptiles (even the largest dinosaursreached adult size in less than three decades).We have also learned that the same rate ofbone formation may lead to the creation of different types of bone tissue, and that growthseries and data from different skeletal elementsare critical for confidently inferring the growthpatterns of extinct dinosaurs.

Not surprisingly, the area of greatest dis-agreement is the largely conjectural issue ofwhether, in a physiological sense, dinosaursmore closely resembled cold-blooded reptilesor warm-blooded birds and mammals. Mostresearchers agree that rapid growth cannot beconfidently correlated with warm-blooded-ness, and most of the disagreement seems tobe akin to whether a glass is viewed as half fullor half empty. Chinsamy-Turan highlightshow the bone microstructure of dinosaursshows features that are either frequently foundin non-avian reptiles or widespread amongbirds and mammals, but she wisely advises usnot to draw definitive physiological conclu-sions from bone microstructure.

Chinsamy-Turan is at her best when she discusses the microstructure of bone and its

significance for understanding the biology offossil vertebrates. However, her conclusionsabout the linkage between the origin of warm-bloodedness and the divergence of ornithurines(the group including Hesperornis, Ichthyornisand all living birds) are weakened by theendorsement of views that have a morphologi-cal and functional basis that is not clearly substantiated. Despite these shortcomings,Chinsamy-Turan’s book is a tour de force thatgives readers an updated synopsis of a fast-growing field of vertebrate palaeontology. Thebook is a must-read for anybody interested in the biology of one of the most fascinatinganimals in the history of our planet. ■

Luis M. Chiappe is at the Dinosaur Institute,Natural History Museum of Los Angeles County,900 Exposition Boulevard, Los Angeles,California 90007, USA.

Growth area: microstructure study reveals stagesof bone formation in the dinosaur Dryosaurus.

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the basic sets of physics equations, which thesubtitle refers to as “icons of knowledge”. In abook of only 96 pages, it is a real challenge todo much more than indicate to the reader theenormous richness of these equations and theimaginative ways they can be used to extendour understanding of the workings of nature atall levels. The equations are presented in theirfinal definitive forms without any discussionof how they came about or why they have theseforms. This latter aspect is not part of Bais’sagenda, which is a pity. Still, if it were, the bookwould have grown out of all proportion.

In the first few pages there is a lightningreview of elementary mathematical opera-tions, and this helps the reader understand the simpler equations, such as Newton’s laws ofmotion and the continuity equation. It is debat-able, however, whether these insights enablethe reader to understand the importance of

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