Thick- skinned rhinoceroses and elephants were once classified together as pachyderms (meaning "thick skin"). They actually descended from different ancestors that in turn evolved from a thin-skinned common ancestor that was not included in the pachyderms. Pachyderms were therefore, as a taxon.

polyphyletic

Explanation:

Polyphyletic

The organisms in this groups show similar attributes, but lack a recent common ancestor and could have risen from convergence.

Take for instance, birds and mammals in a polyphyletic group of warm-blooded animals may possess a mixture of biochemical and physiological attributes. On the other hand, their most recent common ancestor was a cold-blooded species, which shows birds and mammals had their warm-blooded nature as separate groups.

Another example is the Elephants, hippopotamuses, and rhinoceroses belongs to a polyphyletic groups with each one coming from a separate small species.