 Unlike <unk> <unk> , terrestrial <unk> have skulls that are adapted for biting land @-@ living prey . The <unk> between the bones of the skull in the <unk> <unk> are able to withstand a high degree of compression . <unk> forces would have been experienced when biting down on prey . Earlier aquatic <unk> and <unk> ancestors differ from <unk> like <unk> in that their skulls were also built to withstand tension . This tension would have been experienced during <unk> feeding underwater . <unk> like <unk> were among the first <unk> that were almost exclusively terrestrial and fed by biting . 
