Radiographic Anatomy of the Limb Skeleton of the Neurergus kaiseri

This study investigates the radiographic anatomy of the forelimb and hindlimb skeletons in the critically endangered Kaiser’s Mountain newt (Neurergus kaiseri), an endemic Iranian salamander. Using non-invasive digital mammography (32 kVp, 80 mAs), we analyzed the osteology of 10 adult specimens (5 males, 5 females) to characterize appendicular skeletal features. The scapulocoracoid was a single bony unit with a prominent glenoid cavity and supracoracoid foramen. The humerus exhibited flattened cranial and caudal crests, while the radius and ulna remained separate, with distinct proximal/distal width patterns. The carpus comprised seven bones (ulnare, radiale, prepollicis, centrale, distal carpals 3–4, and basale commune), and the manus displayed four digits with a phalangeal formula of 2-3-2-2. The pelvic girdle fused into an ilium-ischiopubic plate, lacking an obturator foramen. The femur was longer than the humerus, featuring a medially oriented head and a hook-shaped trochanter. The tibia and fibula were equal in length but shorter than the femur. The pes had five digits (phalangeal formula: 2-2-3-3-2) and seven tarsal bones, including a fused basale commune (distal tarsals 4–5). Comparative analysis revealed key differences from related species (Hynobius setouchi, Batrachuperus londongensis), such as carpal/tarsal bone counts and fusion patterns. These findings provide foundational data for ecological, evolutionary, and conservation studies, highlighting mammography as a viable, non-invasive tool for skeletal research in delicate amphibians.