Ambulocetus natans -
Early cetacean -
Ambulocetus was about 3 meters long, and looked like a cross between a crocodile and an otter. Despite this appearance it was actually a form of whale. They could survive in both fresh and salt water.
Ambulocetus was an ambush predator, lurking in the shallows and leaping out to catch unsuspecting prey.
In the heat of noon, Ambulocetus gather on the shore to rest in the shade of trees. Whether this is a social activity or a gregarious gathering is not clear.
An Ambulocetus appears through an Eocene anomaly in Episode 1.1 and attacks Connor while he was searching by the side of a river. It misses, and Abby gives it a tentative identification of a "furry crocodile" (a valid analogy).
Matt is confused that Ambulocetus is present, because it is found in a different geographical area than Gastornis. He, Connor, Becker, and a team of ARC soldiers went through the anomaly to find out, where they find a group resting on the banks.