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. Tympanic bulla

4. Indohyus

5. Involucrum
Indohyus
Fin whale

7. Thewissen et al. (2009)

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

10. 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,

11. Thewissen et al. (2009)

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

14. Ambulocetus
Fossils found in probable estuarine sediments

15. Thewissen et al. (2009)

17. Kutchicetus Probably smallest Eocene cetacean Extremely narrow snout
By Momotarou Own work, CC BY-SA 3.0,
Probably smallest Eocene cetacean
Extremely narrow snout
Strong tail
Very short limbs

20. Pakicetus
Kutchicetus
Durodon
Thewissen et al. (2009)

22. Rodhocetus Fossils from the Eocene ~ 8 feet long
Short limbs with long hands and
feet
Hands and feet were probably
webbed
Probably swam with alternating
strokes of hind feet
Probably insulated with fur

24. Durodon Fossils from the Eocene ~ 16 feet long Forelimbs are flippers
Tiny hindlimbs
Possessed a tailfluke
Fed on small fish and mussels
Lived in warm seas around the world

25. Thewissen et al. (2009)

27. Femur
Pelvis
Fibula
Tarsals
Tibia
Metatarsals
Phalanges

28. Spotted Dolphin Embryo
Thewissen et al. (2009)

29. Thewissen et al. (2009)

30. 5 2 4 1 3 Durodon Ambulocetus Rodhocetus Pakicetus Kutchicetus
Thewissen et al. (2009)