Skeletal Anatomy of the Newborn Primate was written to broaden our knowledge of non-human primates from a comparative and developmental perspective. This chapter explains that the main focus of our book is on the inherently risky neonatal period. The “neonate,” or newborn, is considered here to be a perinatal primate of up to seven days postnatal age. However, there is no simple way to physically identify primate newborns, not in the same many have defined “infants,” based on dental maturity. This is precisely what makes the neonatal stage so interesting: primates, like most other groups of mammals, vary in how rapidly they attain physical maturity. This introductory chapter discusses terminology and methodological challenges in studying newborns.