Lockley, M.G. 2008. The morphodynamics of dinosaurs, other archosaurs, and
their trackways: holistic insights into relationships between feet, limbs,
and the whole body; pp. 27-51 in Bromley, R.G., Buatois, L.A., Mángano, G.,
Genise, J.F., and Melchor, R.N. (eds.), Sediment-organism Interactions: A
Multifaceted Ichnology. SEPM Special Publication 88.
ABSTRACT: Organisms are homeostatic organic wholes. Their organization is
understandable, and fractally repeated, from the level of the cell to whole
individual organisms, through higher taxonomic 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.