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

Tympanic bulla

Indohyus

Involucrum Indohyus Fin whale

Thewissen et al. (2009)

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

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, https://commons.wikimedia.org/w/index.php?curid=36657302

Thewissen et al. (2009)

Ambulocetus Fossils from the Eocene ~ 9.8 feet long Probably ambush predators Ate larger fish and aquatic tetrapods Probably fully aquatic Slow swimmer https://www.youtube.com/watch?v=8cn0kf8mhS4

Ambulocetus Fossils found in probable estuarine sediments

Thewissen et al. (2009)

Kutchicetus Probably smallest Eocene cetacean Extremely narrow snout By Momotarou2012 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=23521423 Probably smallest Eocene cetacean Extremely narrow snout Strong tail Very short limbs

Pakicetus Kutchicetus Durodon Thewissen et al. (2009)

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

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

Thewissen et al. (2009)

Femur Pelvis Fibula Tarsals Tibia Metatarsals Phalanges

Spotted Dolphin Embryo Thewissen et al. (2009)

Thewissen et al. (2009)

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