Final answer:
The first North American dinosaurs were described by Joseph Leidy. The correct option is B.
Step-by-step explanation:
Joseph Leidy was the paleontologist who described the first North American dinosaurs, paving the way for future discoveries in paleontology. Joseph Leidy was an American paleontologist who made significant contributions to the field of paleontology during the mid-19th century.
He is known for describing some of the first dinosaur fossils found in North America. His work laid the foundation for future paleontological discoveries and set a precedent for rigorous scientific methods in the field. Hence, B is the correct option.