The mollusc superfamily Galeommatoidea is a megadiverse assemblage of small often cryptic marine bivalves with a fossil record that extends to the Cretaceous. Species are found worldwide and are highly variable in soft anatomy and ecology, and many taxa exhibit pronounced shell reduction. Both free-living and commensal members are known, including common and locally abundant free-living taxa as well as more bizarre commensal representatives that inhabit the esophagus of sea cucumbers or live suspended from mantis shrimp burrows. Many undescribed species exist, relationships of the 134 genera are uncertain, and the clade is rampant with autapomorphic characteristics and monotypic taxa. Of course, many of the most wonderful weirdos are from Australia.
A new foundation based on revived assessment of shell character data from genus-level type taxa alongside soft anatomical character datasets is being assembled by a large international team. Together with contemporary genomic sampling using a transcriptomic approach to identify a larger set of informative genes, these datasets will create a more robust character matrix. This will in turn form the basis for total-evidence phylogeny that will underpin an updated systematic appraisal. Additionally, a robust comprehensive phylogeny will underpin tests of character trait evolution, coevolution and morphological disparity in the most intriguing group of bivalves in the world.