Complex sentence: Pampatheriidae ("Pampas beasts") is an extinct family of large plantigrade armored xenarthrans related to Glyptodontidae, an extinct family of much larger and more heavily armored xenarthrans, as well as to smaller extant armadillos (Dasypodidae).
Split into simpler sentences: Pampatheriidae ("Pampas beasts") is an ancient family, now extinct, of large armadillo-like plantigrade armored xenarthrans. They are related to Glyptodontidae, an extinct family of much larger and more heavily armored xenarthrans, as well as to smaller extant armadillos (Dasypodidae).