Complex sentence: It is middle to late Miocene in age (Lindsay, 1972), and lends its' name to the Barstovian North American land mammal age (NALMA).
Split into simpler sentences: It is middle to late Miocene (Barstovian) in age (Lindsay, 1972). The formation lends its' name to the Barstovian North American land mammal age (NALMA).