Malacostracan phylogeny and the evolution of the caridoid facies

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Malacostraca is a highly diverse (numbering around 40,000 species) and highly disparate (17 orders) taxon within paraphyletic crustaceans. Although the anatomical complexity and/or ecological importance of many of these higher crustaceans are of pivotal interest, our understanding of the evolutionary transformations that took place within Malacostraca is impeded by the fact that the phylogenetic relationships within the taxon are still largely unresolved. This does not just mean that morphological and molecular-based analyses are not congruent. For one thing, major aspects of malacostracan phylogeny are controversial even on the basis of morphology alone and for another, molecular based analyses are relatively rare. The general objective of this proposal is a detailed investigation, using new techniques such as micro-CT and digital 3D reconstruction, of the musculature and the cuticular skeleton in various malacostracan crustaceans for use as a basis for the conceptualization of new characters and character states, which will be added to existing character matrices. The newly created character matrix will be the most extensive morphological matrix ever compiled for Malacostraca and will form the basis of various phylogenetic analyses testing the robustness of malacostracan phylogeny. The results will be contrasted with molecular phylogenetic analyses including our own phylogenomic analysis. The malacostracan phylogeny hypothesis thus obtained will be used to formulate and discuss hypotheses about evolutionary transformations (particularly those which form the focus of the present project). A revised and extended version of the caridoid facies hypothesis will be presented.