The cricetids are small mammals , ranging from just 5 to 8 cm and 7 grams in weight in the New World Pygmy Mouse , up to 41 to 62 cm and 1,100 grams in the Muskrat . The cricetids are small mammals , ranging from just 5 - in length and 7 g in weight in the New World Pygmy Mouse up to 41 - and 1100 g in the Muskrat .