Final answer:
The two recognized subfamilies of hadrosaurids are hadrosaurines and lambeosaurines, which had different crest structures and were herbivorous dinosaurs from the Late Cretaceous period.
Step-by-step explanation:
The two subfamilies of hadrosaurids that are recognized are the hadrosaurines and the lambeosaurines. Hadrosaurids, commonly known as duck-billed dinosaurs, were part of the Ornithischia group of dinosaurs. The hadrosaurines were characterized by their solid crests or lack thereof, while lambeosaurines had hollow crests which may have been used for communication or display purposes. Both groups thrived during the Late Cretaceous period and were known for being herbivorous dinosaurs.