What does membership in Phylum Chordata signify about the squirrel's development?

Answer

At some point in their development, they possessed a notochord, which develops into a backbone

Placement in the Phylum Chordata signifies that the animal possessed a notochord during some developmental stage, which in squirrels develops into a backbone.

What does membership in Phylum Chordata signify about the squirrel's development?
taxonomyanimalclassificationsquirrel