But exactly where hippos sit on the artiodactyl family tree has proved devilishly difficult to discern.
But exactly where hippos sit on the artiodactyl family tree has proved devilishly difficult to discern.
河马也属于偶蹄目，这点专家并无异议，但是牠们到底位在偶蹄动物演化树的哪个分支点上，一直都很难定论。