Ichthyosauria vs animal order

Ichthyosauria and animal order both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ichthyosauria	Yes	No	No	No
animal order	Yes	No	No	No

As nouns, animal order is a hypernym of Ichthyosauria; that is, animal order is a word with a broader meaning than Ichthyosauria:

Ichthyosauria (noun)	animal order (noun)
extinct marine reptiles: ichthyosaurs	the order of animals