This study presents two new methodological approaches for estimating skeletal age from maturational changes in the femoral distal epiphysis. In the first approach, five maturity stages were coded based on morphological changes in the epiphysis that encompass the overall developmental process. Data were presented as age ranges for the different maturity stages in the reference sample. As this approach has a number of shortcomings for age assessment, a probabilistic approach was also used. Cross-validation was then used to compare the accuracy of the age estimation from the maturity stages with that from Pyle and Hoerr’s atlas. This study’s findings showed that Pyle and Hoerr’s atlas is more precise than our qualitative method in the oldest age categories. Nonetheless, results from the test of agreement between methods showed that skeletal age estimates from both methods are interchangeable. In the second approach, the overall shape of the femoral distal epiphyses was first analyzed based on elliptical Fourier descriptors (EFDs). Since the number of EFDs is excessively large, a principal component analysis (PCA) of these EFDs was carried out. PC1 scores were used to model the relationship between age and overall shape in a sample of 110 cases of the femoral distal epiphysis. Inverse and classical regression methods of calibration were used to explore the relationship. Based on our results, we recommend the use of a classical calibration model for those cases in which we suspect that the growth and development of the target individual is advanced or delayed relative to those of the Portuguese sample. Otherwise, the inverse calibration model is preferable. Both, quantitative and qualitative methods presented herein notably improve our abilities to estimate skeletal age using incomplete femora from skeletal samples.
