phenogram A type of dendrogram which is based on phenetic data (see PHENETIC CLASSIFICATION). Lines called phenon lines, drawn at right angles to the dichotomously branching dendrogram, represent lines of percentage similarity of phenetic features between organisms. Because the phenetic data are based on features that appear in different organisms regardless of whether they are analagous or homologous, organisms that are evolutionarily distant may be grouped closely together. For example, in evolutionary history the tree has evolved on several independent occasions. Gymnosperm trees evolved in the Carboniferous Period, some 355–290 Ma ago. The first angiosperms evolved 120 Ma ago, but the first angiosperm trees did not evolve until 90 Ma ago. The 2 evolutions of the tree structure, then, occurred separately, and to group them together on the basis of the common structure would constitute an artificial classification.

phenogram A tree-like diagram that is used in analysis to show similarity or dissimilarity among specimens or groups of specimens.

phenogram A tree-like diagram used in analysis to show similarity or dissimilarity among specimens or groups of specimens.