allometry
allometry A differential rate of growth, such that the size of one part (or more) of the body changes in proportion to another part, or to the whole body, but at a constant exponential rate. Strictly speaking, ‘allometry’ is an umbrella term describing three distinct processes. Ontogenetic allometry refers to the differential growth rates of different body parts; i.e. juveniles are not merely diminutive adults. (For example, the extinct Irish elk (Megaceros giganteus) was the largest of all cervids (Cervidae), but its antlers were 2.5 times larger than would be predicted from its body size, and reached an adult span of up to 3.5 m in the largest individuals.) Static allometry refers to shifts in proportion among a series of related taxa of different size. Evolutionary allometry refers to gradual shifts in proportions as size changes in an evolutionary line (e.g. in the evolution of the horse the face became relatively longer and longer). In other cases allometry may be negative, leading to comparatively smaller parts.
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allometry
