Data and code from: Cross-species applicability of a bone-ageing method in delphinids

Radiographic evaluation of flipper ossification is a reliable technique
for age estimation in bottlenose dolphins (Tursiops truncatus), although
its applicability to other odontocetes remains untested. Interspecific
differences in flipper morphology and bone development may limit
transferability or require adjustments for robust application. This study
applies the bottlenose dolphin framework to common dolphins (Delphinus
delphis) to characterise developmental patterns, describe morphological
differences, and evaluate the interspecific application of this method.
Radiographs from 137 common dolphins aged 0–31 years were examined, with
bone maturation scored at 16 anatomical sites on the pectoral flipper.
Several differences were identified, including bilateral asymmetry between
left and right flippers and the need to adjust long and delta bone scoring
systems due to interspecific variation in bone maturation. Despite these
differences, reproducibility between observers was high, and ossification
scores correlated strongly with age, underscoring the reliability of the
method. This study provides the groundwork for a species-specific bone
ageing model for common dolphins by addressing interspecific variation in
skeletal maturation. One caveat concerns the subtle expression of
degenerative changes in this species compared with bottlenose dolphins,
which may limit age estimation precision in older individuals but is
unlikely to affect accuracy across most of the lifespan. Thus, our
findings provide the first evidence that, despite morphological
differences, the method can be successfully applied to common dolphins.