Patella present in the living monotremes, the platypus and the echidna. In more primitive tetrapods, including living amphibians and most reptiles (except some Lepidosaurs), the muscle tendons from the upper leg are attached directly to the tibia, and a patella is not present. In 2017 it was discovered that frogs have kneecaps, contrary to what was thought. This raises the possibility that the kneecap arose 400 million years ago when tetrapods first appeared, but that it disappeared in some animals. The word "patella" originated in the late 17th century from the diminutive form of Latin ' or ' or "paten", meaning
Development of the human body characteristics, the "filling in" of the child's body; from girl to woman, from boy to man. Biologically, an adult is a human or other organism that has reached sexual maturity. In human context, the term "adult" additionally has meanings associated with social and legal concepts. In contrast to a "minor", a legal adult is a person who has attained the age of majority and is therefore regarded as independent, self-sufficient, and responsible. The typical age of attaining adulthood is 18, although definition may vary by legal rights and country. Human adulthood encompasses psychological adult development. Definitions of adulthood are often