Perhaps Ambulocetus should be classified with the archaeocetes, perhaps not. And Basilosaurus , younger by 10 My. Specimen with complete hindlegs now shows the increased adaptation to a seemingly fully aquatic lifestyle. Legs are too small to support body weight on land. Shimamura et al.
Artiodactyls are paraphyletic, the even-toed ungulates give rise to whales.
BUT the most primitive artiodactyls appear in the early Eocene. The most diverse ungulate order. See PJH Fig. 13-1 for the historical cladogram. Note they had bird-like thin walled light bones, complete with struts.