1. Fossils from the Eocene
Pig-like
Indohyus  “India’s pig”
Size of raccoon or domestic cat
Omnivorous
Shares auditory bulla structure with extinct and living cetaceans

3. Thewissen et al. (2009)

4. Femur of Indohyus
Marrow cavity only 42%
of thickness of bone
Other mammals usually 60%
Termed osteosclerotic
Thewissen et al. (2009)

5. Human femur

7. Pakicetus Fossils from the Eocene 3.3 to 6.6 feet in length
Probably carnivorous
Ate fish and small mammals
Shares auditory bulla with extinct
and living cetaceans
Probably semiaquatic
By Kevin Guertin from Ottawa, Ontario, Canada - DSCF1201, CC BY-SA 2.0,

8. Thewissen et al. (2009)

10. Ambulocetus Fossils from the Eocene ~ 9.8 feet long
Probably ambush predators
Ate larger fish and aquatic
tetrapods
Probably fully aquatic
Slow swimmer

11. Ambulocetus
Fossils found in probable estuarine sediments

12. Thewissen et al. (2009)