Dinosaur and Saurischian

Dinosaur noun - One that has passed the peak of effectiveness or popularity.

Saurischian and dinosaur are semantically related. In some cases you can replace term "Saurischian" with "Dinosaur", this nouns are similar.

Saurischian noun - Herbivorous or carnivorous dinosaur having a three-pronged pelvis like that of a crocodile.

Dinosaur and saurischian are semantically related. You can use "Dinosaur" instead a noun "Saurischian".