What are the major divisions of Ornithopoda, and what are their diagnostic characters?
a) Major divisions include Hadrosauridae and Iguanodontidae, with diagnostic characters such as a flattened, duck-like bill and complex dentition.
b) Major divisions include Stegosauridae and Ankylosauridae, with diagnostic characters such as prominent tail spikes and thick, bony armor.
c) Major divisions include Sauropodomorpha and Theropoda, with diagnostic characters such as elongated necks and small, sharp teeth.
d) Major divisions include Ceratopsidae and Pachycephalosauridae, with diagnostic characters such as elaborate frills and domed skulls.
