The caudal skeleton is one of the most important tools to evaluate teleostean interrelationships, but just the anatomy of few species have been investigated. Black-striped pipefish (Syngnathus abaster) has never been examined for its caudal morphology. Here, red alizaryn is applied as specific staining for calcified structures, providing a better understanding of caudal skeleton organization. Our results and interpretation just partially fit with previous knowledge on other Syngnathus species. This emphasizes both the importance of facing same problems with new technics and methodologies, and the existence of a heterogeneous situation between close-related taxa