A BSTRACT We present an exon-capture system for an entire class of marine invertebrates, the Ophiuroidea, built upon a phylogenetically diverse transcriptome foundation. The system captures ~90 percent of the 1552 exon target, across all major lineages of the quarter-billion year old extant crown group. Key features of our system are: 1) basing the target on an alignment of orthologous genes determined from 52 transcriptomes spanning the phylogenetic diversity and trimmed to remove anything difficult to capture, map or align, 2) use of multiple artificial representatives based on ancestral states rather than exemplars to improve capture and mapping of the target, 3) mapping reads to a multi-reference alignment, and 4) using patterns of site polymorphism to distinguish among paralogy, polyploidy, allelic differences and sample contamination. The resulting data gives a well-resolved tree (currently standing at 417 samples, 275,352 bp, 91% data-complete) that will transform our understanding of ophiuroid evolution and biogeography.