Crocodilian and Crocodile

Crocodilian noun - Extant archosaurian reptile.

Crocodile and crocodilian are semantically related. In some cases you can replace term "Crocodile" with "Crocodilian", this nouns are similar.

Crocodile noun - Large voracious aquatic reptile having a long snout with massive jaws and sharp teeth and a body covered with bony plates; of sluggish tropical waters.

Crocodilian and crocodile are semantically related. You can use "Crocodilian" instead a noun "Crocodile".