Prehistoric Whales

Jul 21, 2024

Prehistoric Whales

Introduction

  • Many large ocean animals, including whales, have land-dwelling ancestors.
  • Whales evolved from four-legged terrestrial creatures approximately 15 million years ago.
  • Early whales often lived near lakes and rivers, hunting small animals and fish.
  • There are over 20 known species of prehistoric whales, but this lecture focuses on 13 with substantial fossil records.

Significant Prehistoric Whales

13. Maiacetus

  • Transition species between land and sea.
  • Size: ~2.6 meters (8.5 feet); Weight: 280-390 kg.
  • Sexual dimorphism: Males about 12% larger.
  • Lived on the land-sea interface.

12. Rodhocetus

  • Another four-legged whale showing land-sea transition.
  • Size: 6.6 - 9.8 feet.
  • Adaptations: Webbed feet and hands, primarily surface swimmers; tail used as a rudder.

11. Mammalodon

  • Existed 25.7 - 23.9 million years ago.
  • Baleen whale with primitive, cone-shaped teeth.
  • Size: ~11 feet.
  • Bottom filter feeder.

10. Janjuceetus

  • Medium-sized predatory whale (~11.5 meters).
  • Lived around 25 million years ago.
  • Powerful jaw muscles, fearsome teeth.

9. Ambulocetus

  • Amphibious whale from 50 million years ago.
  • Length: 11-12 feet, robust tail, crocodile-like snout.
  • Could walk on land and swim powerfully.

8. Cetotherium

  • Known as the “whale beast.”
  • Size: ~14 feet.
  • Earliest whales with sharp teeth.
  • Surface feeder and preyed upon by larger predators such as Megalodon.

7. Acrophyseter

  • Extinct sperm whale from 11.3 - 5.6 million years ago.
  • Size: 13-15 feet.
  • Known for a short, pointed snout and strong teeth (12 upper, 13 lower).
  • Likely fed on large marine vertebrates.

6. Dorudon

  • Lived about 41 million years ago.
  • Size: ~16 feet.
  • Sharp teeth, reduced hind limbs, and tail flukes.
  • Fully marine.

5. Squalodon

  • Named for shark-like teeth.
  • Size: Up to 18 feet.
  • Lived 28-15 million years ago.
  • Early ancestor to modern dolphins.

4. Aetiocetus

  • Transitional form between toothed whales and baleen filter feeders.
  • Size: 18-21.5 feet.
  • Had teeth identifiable as incisors, canines, and molars.

3. Zygophyseter

  • Sperm whale existing 11.2 - 7.6 million years ago.
  • Size: 21-23 feet.
  • Utilized echolocation and was a fast swimmer.
  • Known as a “killer sperm whale.”

2. Livyatan

  • Named after a biblical sea monster.
  • Size: 44-60 feet, Weight: 60+ tons.
  • Largest biting teeth in history (1.2 feet long).
  • Extinction possibly due to Myocene cooling event.

1. Basilosaurus

  • Giant whale from 41.3 - 33.9 million years ago.
  • Resembled a reptile with an eel-like body and sharp teeth.
  • Size: 56-66 feet, Weight: 15+ metric tons.
  • Importance: First prehistoric whale known to science.

Conclusion

  • The evolution of whales shows a remarkable transition from land to sea.
  • Prehistoric whales varied widely in size, feeding habits, and adaptations.

Thank you for watching.