part of part of in taxon results in development of diencephalon development pineal gland development The progression of the pineal gland over time from its initial formation until its mature state. The pineal gland is an endocrine gland that secretes melatonin and is involved in circadian rhythms. GO:0021982 epiphysis development endocrine system development gland development anatomical structure development Craniata <chordates> pineal body