Journeys through discrete-character morphospace: synthesising phylogeny, tempo, and disparity

Palaeontologists have long employed discrete categorical data to capture morphological variation in fossil species, using the resulting character-taxon matrices to measure evolutionary tempo, infer phylogenies, and capture morphological disparity. However, to date these have been seen as separate approaches despite a common goal of understanding morphological evolution over deep time. Here I argue that there are clear advantages to considering these three lines of enquiry in a single space: the phylomorphospace. Conceptually these high-dimensional spaces capture how a phylogenetic tree explores morphospace and allow us to consider important process questions around evolutionary rates, constraints, convergence, and directional trends. Currently the literature contains fundamentally different approaches used to generate such spaces, with no direct comparison between them despite the differing evolutionary histories they imply. Here I directly compare five different phylomorphospace approa...