Complex sentence: Lemurs are ancestral primates, the anthropoid primates (monkeys, apes, and humans) evolved from them; they share morphological and behavioral traits with basal primates.
Split into simpler sentences: Lemurs are ancestral primates; that is, the anthropoid primates (monkeys, apes, and humans) are held to have evolved from them. They share morphological and behavioral traits with basal primates.