Organismal grade multicellularity has been achieved only in animals, plants, and fungi. All three kingdoms manifest phenotypically disparate body plans, but their evolution has only been considered in detail for animals. Here we seek to test the general relevance of hypotheses on the evolution of animal body plans by characterising the evolution of fungal phenotypic variety (disparity). The distribution of living fungal form is defined by four distinct morphotypes: flagellated, zygomycetous, sac-bearing, and club-bearing. The discontinuity between morphotypes is a consequence of the extinction of phylogenetic intermediates, indicating that a complete record of fungal disparity would present a much more homogeneous distribution of form. Fungal phenotypic variety gradually expands through time for the most part but sharply increases with the emergence of multicellular body plans. Simulations show these temporal trends to be decidedly non-random, and at least partially shaped by hierarchical contingency. Fungal phenotypic distance is decoupled from changes in gene number, genome size, and taxonomic diversity. Only differences in organismal complexity, the number of traits that constitute an organism, at the cellular and multicellular levels present a meaningful relationship with fungal disparity. Both animals and fungi exhibit a gradual increase in disparity through time, resulting in distributions of form made discontinuous by the extinction of phylogenetic intermediates. These congruences hint at a common mode of multicellular body plan evolution.

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