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.

answer:

convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.