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Prehistoric Whales
Jul 21, 2024
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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.
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