Paths from the heart: Morphology and evolution of afferent branchial arteries in Chondrichthyes

Abstract Chondrichthyes, a monophyletic group comprising sharks, batoids, and chimaeras, includes approximately 1200 valid species and displays remarkable morphological diversity, both internal and external. Among soft tissues, the heart and its associated structures in cartilaginous fishes remain understudied, with most research focusing on circulatory physiology rather than comparative anatomy. This study provides a detailed description of the morphological variation of the afferent hyoid and branchial arteries across 13 of the 14 recognized orders of Chondrichthyes. A total of 16 anatomical characters associated with this complex were analyzed, seven were previously described, with two being redefined, and nine others are proposed as new. All characters were tested cladistically in order to explore evolutionary patterns. Our findings were able to expand the current knowledge of the morphological diversity of afferent branchial arteries in Chondrichthyes and provide new insights into the evolution of cardiovascular structures within this lineage.