The application of equation models to determine the age of Pink river dolphin skulls

In this chapter, we show that several biometric skull measurements in the pink river dolphin (Inia geoffrensis) are highly related to skull age, determined by teeth analysis. Out of 50 morphometric skull measurements, the maximum width between the zygomatic processes of the squamosal bones (V15) and the maximum width of the internal nares (V21) were highly correlated with age. Regression analyses such as linear and 24 other simple models, linear multiple regression, polynomial models, and distance multiple regression (Gower, Absolute value, Mahalanobis and Minkowski) had similar results. On average, these multiple regression equations demonstrated that the age of a dead pink river dolphin is determined by only four cranial measures which explained 64-65% of age variation.