The Morphodynamics of Dinosaurs, Other Archosaurs, and their Trackways - Holistic Insights into Relationships Between Feet, Limbs, and the Whole Body

Organisms are homeostatic organic wholes. Their organization is understandable, and fractally repeated, from the level of the cell to whole individual organisms, through higher taxonomie groups up to the level of the biosphere. This is not fully appreciated by most biologists and paleontologists owing to emphasis on investigation of the parts (individual organs) that constitute static anatomy, rather than the dynamic morphological interrelationships. The morphodynamic approach, which is largely synonymous with a holistic heterochronic approach, also allows us to view organisms as complex systems: i.e., as manifestations of iterative or recursive fractal organization.

Using the Schadian paradigm, already successfully applied to an understanding of modern mammals, and the relationships between morphology (form), physiology, and behavior, it is possible to gain insight into reiterating, recursive, or fractal patterns of organization in dinosaurs, pterosaurs, and other extinct archosaurs. Once these whole-body morphodynamic relationships are understood, as inherent, intrinsic, or “formal” aspects of vertebrate development, all natural groups of organisms can be seen in a new light: i.e., recurrent patterns of morphological organization (convergence) are seen as necessary correlates of physiological organization and behavior. In turn, all these organic attributes help us understand dynamic evolutionary development of any natural taxonomic group (clade). Thus, ontogeny reiterates and creates phylogeny (and vice versa) in a series of fractal, recursive manifestations of form, physiology, and behavior.

Appreciation of the intricacy of this complex fractal organization is an exercise in pattern recognition, with surprising implications, especially for paleontology. First, it confirms the interrelatedness of all organisms, one of the central tenets of modern evolutionary theory. Second, it supports the view that higher natural taxonomic groups, already recognized by biology and paleontology, are in reality superorganisms, with inherently similar organizational structure, modified only by spatial and temporal scaling (heterochrony). Thus, all have their own inherent spatio-temporal developmental trajectories (form, life span, and relative emphasis of proximal and distal—or inner and outer/peripheral organs). Third, convergence and iterative evolution can be understood as an inherent quality of a reiterating or recursive fractal system and not merely as an adaptation to external pressures of the environment. This inference is strongly supported by evo-devo studies. Fourth, the modification of the natural organic system, in part or wholly, will lead to a compensation or ripple effect throughout the whole system. Moreover, the phylogeny of a particular group may not be controlled by external environmental pressures to the degree often supposed. Rather, such phylogenies may be natural heterochronic cycles of repeated growth at levels of organization corresponding to higher taxonomic groups (= superorganisms). Such intricate, inherent (or formal) organic organization reveals lawful patterns of morphological relationships that extend beyond isolated and/or shared character recognition. Thus, it may be possible to predict the general form and physiology of the whole animal from an analysis or understanding of the parts (a process akin to modeling). This is particularly useful in paleontology. The morphodynamic approach does more than revive Cuvier’s principle of the correlation of “some” parts. It impels us to recast our previously static understanding of morphology in the light of the inherently dynamic nature of complex systems, showing us how “all” parts are ultimately related.