Can some nine-banded armadillos have eight movable bands?

Yes, it is common for individuals of the nine-banded armadillo (Dasypus novemcinctus) to have eight movable bands in some regions.1

While these armadillos are named for the number of bands in their armor, the count can vary within the species. The nine-banded armadillo is the only species of its kind found in the United States, and despite its common name, eight-banded individuals are frequently observed in certain parts of its range.1