Our research underscores the value of studying on non-model, "aberrant" organisms like Osedax, whose unique, temporally restricted chaetogenesis provided insights into elevated gene expression across specific larval stages and led to the identification of genes critical for chaetae formation. The genes identified as directly involved in chaetogenesis lay the groundwork for future comparative studies across Annelida and Spiralia, potentially elucidating the homology of chaetae-like chitinous structures and their evolution.