The earliest whales were believed to be amphibious and could move about on land, similar to animals like modern seals. These cetaceans were active during the Eocene (approximately 56 to 34 million years ago) and were ancestors not only to modern whales but also to other even-toed ungulates like the semi-aquatic hippopotamus.

Why Did These Prehistoric Whales Become Extinct

Evolution led to whales becoming fully aquatic, with their semi-aquatic traits getting phased out around the Oligocene (around 34 to 23 million years ago). This made sense as while early whales were capable of amphibious movements, they were often clumsy on land and not particularly fast underwater. These limitations prevented them from effectively competing with fully aquatic species for resources like food. Changing climates also restricted their movements, leading to the habitats of these ancient whales shrinking.

As a result, whales would adapt over time to eventually resemble the cetaceans of the present day.

List of Whales That Went Extinct

Name	Characteristics	Where Did It Live
Aegyptocetus tarfa	1. Semi-aquatic 2. Could hear underwater	Egypt
Ambulocetus natans	1. Semi-aquatic 2. Displayed crocodilian behavior	Kuldana Formation, Pakistan
Artiocetus clavis	1. Small in size 2. Capable of moving like a seal on land	Balochistan Province, Pakistan
Babiacetus indicus	1. Possessed teeth  2. Primarily fed on large fish or aquatic vertebrates	Kutch District, Gujarat, India
Basilosaurus cetoides	1. Apex predator that hunted fish, sharks, and other cetaceans	Egypt, Jordan, Morocco, Pakistan, Peru, Tunisia, Western Sahara, and the southeastern United States
Cetotherium rathkii	1. Potential ancestor of the Pygmy Right Whale	Taman Peninsula, Russia
Coronodon havensteini	1. Possessed teeth  2. About 16 feet long and weighed over a ton	South Carolina, USA
Dorudon atrox	1. Possessed teeth 2. Lacked organs for echolocation	Egypt, Pakistan, New Zealand, United States
Fucaia buelli	1. Primitive baleen whale 2. Capable of both raptorial and suction feeding	Canada and the United States
Gandakasia potens	1. Freshwater whale	Pakistan
Gaviacetus razai	1. Unique rostrum 2. Pursuit predator	Punjab, Pakistan
Himalayacetus subathuensis	1. One of the oldest whales ever	Pakistan
Janjucetus hunderi	1. Apex predator 2. Behavior similar to modern seals 3. Teeth like a crabeater seal 4. Feeding habits like a leopard seal	South-east Australia
Kekenodon onamata	1. Could reach up to 30 feet in length	New Zealand
Kharodacetus sahnii	1. Larger teeth than Gaviacetus	Kutch, India
Kutchicetus minimus	1. Small in size 2. Movements similar to modern-day otters	India and Pakistan
Livyatan melvillei	1. Prehistoric sperm whale 2. Apex predator 3. Teeth that were each over 1 foot long	Argentina, Australia, Chile, Peru, South Africa, and the US (California)
Llanocetus denticrenatus	1. Large in size 2. Suction feeder like modern-beaked whales	Antarctica
Maiacetus inuus	1. Amphibious nature indicated by webbed feet	Habib Rahi Formation, Pakistan
Mammalodon colliveri	1. Closely related to Janjucetus 2. Rounded snout  3. Most likely filter fed from the bottom of the ocean floor	Australia and New Zealand
Peregocetus pacificus	1. Semi-aquatic 2. Four-legged	Peru
Perucetus colossus	1. Probably the largest prehistoric whale, reaching up to 66 feet in length and up to 340 tons in weight	Peru
Protocetus atavus	1. Streamlined body 2. Capable of hearing underwater 3. Nostrils placed further back on their head like modern whales	Cairo, Egypt
Rodhocetus balochistanensis	1. Small whale 2. Possessed five digits on its forelimbs and four digits on its hindlimbs	Pakistan
Tutcetus rayanensis	1. Smallest basilosaurid at approximately 8 feet in length	Egypt
Killer Sperm Whale (Zygophyseter varolai)	1. Prehistoric sperm whale 2. Feeding habits like modern orcas	Italy

While this list is mainly about prehistoric and early whales, it is worth mentioning that in the 18th century, the gray whale became extinct in the Atlantic Ocean as a result of excessive whaling. It is still found in the Pacific.