This project addresses a fundamental question in the study of life: can we predict the evolutionary success of animals based on their forms Crabs are one of the most iconic groups of invertebrates, playing an integral role in aquarium trade, fisheries, and aquaculture, and are celebrated in cultures around the world through festivals and parades. This research aims to build the tree of life for all known living and fossil crab families, to investigate how these animals have changed over 200 million years of history. The typical body form that characterizes crabs has evolved separately several times from lobster-like ancestors, and also has been lost several times in different groups of crabs. The new crab tree of life will reveal whether the independent gains and losses of the crab shape predict the immense biodiversity and ecological versatility of the group. The inspiring diversity of crab form and function will engage high school students through museum activities, and undergraduate students in primary research and classroom modules incentivizing critical thinking. Fieldwork will be conducted in Panama, where a training course in tropical crab taxonomy will immerse US and Latin American scientists in the techniques used to expand and investigate the crab tree of life.The acquisition of a crab-like body form has evolved four to five times among decapod crustaceans, and has been proposed as a contributing factor to the immense diversification and ecological success within the infraorders Brachyura (>7000 species of true crabs), and Anomura (>2500 species including porcelain crabs, hermit crabs, and king crabs). The objectives of this project are: (1) To construct a well-supported backbone phylogeny for false and true crabs using genomic (extant) and morphological (extant and fossil) data. (2) To employ fossils as age calibrations to construct an evolutionary timeline; this will serve as the foundation for inferring the pattern and geological timing of crab body plan evolution. (3) To test if the rate of diversification has increased in crab-like lineages relative to their sister groups, and likewise has decreased when the crab-like body was secondarily lost. The researchers hypothesize that at least some traits comprise a possible key innovation. These objectives will be achieved by sequencing 500 crab species using target enrichment methods, morphological coding and imaging of living and fossil taxa (including representatives of all crab families), and the deployment of cutting-edge strategies for divergence time analysis and phylogenetic comparative methods.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.