 The mandibular foramen in ambulocetids had increased in size , which indicates that a fat pad was likely to be housed in the lower jaw . In modern toothed whales , this fat pad in the mandibular foramen extends posteriorly to the middle ear . This allows sounds to be received in the lower jaw , and then transmitted through the fat pad to the middle ear . Similar to pakicetids , the orbits of ambulocetids are on the top of the skull , but they face more laterally than in pakicetids . 
