MORPHOLOGICAL DISPARITY AND DEVELOPMENTAL PATTERNING: CONTRIBUTION OF PHACOPID TRILOBITES

Abstract: In trilobites as in many others extinct organisms, our understanding of the mechanisms of evolution is based on morphological and ontogenetic features. Data from ontoge-netic development are essential to provide an insight into the origins of evolutionary changes. In phacopid trilobites, detailed studies of ontogenetic series have been achieved using quanti-tative methods. A comparison of ontogenetic trajectories of closely related species has been conducted to understand how the both morphological disparity and developmental pattern-ing of different ontogenetic stages were structured and to determine how the environmental or developmental con-straints influenced morphological changes in trilobites. Study of such morphological disparity in developmental evolution requires knowledge of morphological features and timing and rate of development among closely related species. At a macro