Concepts of Functional, Engineering and Constructional Morphology

Why do living organisms have the designs (and especially the skeletons) that they actually possess? Is it possible, and legitimate, to infer from the fossilised remains of a long-dead creature how it functioned as a living system, with all the components operating together in harmony? Some 40 years ago there was an often stated view that studies of functional morphology in fossil animals could never be more than clever speculation. Yet as time went by, it became increasingly clear that functional interpretations, when carried out in the right way, were indeed a proper field for study in palaeontology, and that animal skeletons, of almost any kind, could yield definitive information about how their bearers had lived. We need first to consider the origins of animal skeletons. There are two important factors here. The first is contingency, in other words the `accidents of history', which established suites of body plans which could subsequently be modified in different ways. Yet as ROGER THOMAS and WOLF-ERNST REIF pointed out in their `Skeleton-Space' model (1993), there are confining physico-chemical constratints which thereafter determine evolutionary pathways. There are, in fact, only a limited number of ways in which a skeleton can be functional, as determined by the properties of the material of which it is constructed, constraints upon growth and development, and the requirement for its component parts to function in terms of the whole organism. In consequence "the discovery of `good' designs ­ those that are viable and that can be constructed with available materials ­ was inevitable, and in principle predictable. the recurring designs we observed are attractors, orderly and stable configurations of matter that must necessarily emerge in the course of evolution" (THOMAS & REIF 1993). Where then, with this in mind, do we proceed from here? Amongst compendia regarding form and function in fossils, we have the recent Functional Morphology of the Invertebrate Skeleton (1999), a fine collection of 43 papers edited by ENRICO SAVAZZI. Here one finds both specialised case histories and encompassing reviews, dealing with many kinds of invertebrate, and very useful it is regarding the various ways in which invertebrate palaeontologists study their fossils as living organisms. But the present volume is something different, for it encapsulates the refreshingly individual approach which has emerged in Germany over the last several years, most vigorously articulated by MICHAEL GUDO and his colleagues at the Senckeneberg Institute, Frankfurt am Main. Their basic concept is that the structural and functional constraints on living organisms can best be interpreted in terms of engineering analogues. Mechanical engineering, after all is about how machines are constructed and how they work, and there are simple analogues all around us. Consider, for a moment the evident correspondence between the claw of a crab and a pair of pincers, or an arthropod limb and the arm of a mechanical digger. There are surely many useful insights to be derived from an understanding of engineering principles, and the research papers collected in the present volume are a testament to the vigour of this approach. For herein we find not only concepts, but also tools and techniques in common use in engineering applied to biomechanics; computer-aided design and tomography, landmark analysis, Finite Element Analysis, and CAT-scans. Such tools give a much greater objectivity to analysis of function, for it is true enough, as Carpenter comments in this volume, that `theoretical models are often tainted with preconcieved ideas'. There are thirty papers in five sections, each of which consists of several papers, and at the beginning of each section is an explanatory introduction and summary. Section 1, Functional morphology and biomechanics. Following introductory comments by GUDO et al., there are six papers all concerned with vertebrates, and especially dinosaurs. To