Whales are among the most fascinating marine animals today, mainly because of their remarkable evolutionary journey, impressive size, and unique adaptation.
The blue whale is not just the largest marine animal; it is also the largest animal known from the current fossil record, surpassing the size of any other known species.
The ancestors of this marine beast were land-dwelling mammals that began their sea-bound migration about 55 million years ago.
Over the course of the Cenozoic Era, whales gradually developed adaptations that made them better suited for life in their new home in the marine ecosystem.
According to recent research, the closest living relatives to these whales are the hippos.
In the journey from terrestrial to full aquatic lifestyle, there have been numerous prehistoric whales, with most of them being considerably different from modern species in terms of their overall appearance and ecological position.
In this article, we’ll list some whale species that have lived over the past 55 million years and provide an overview of some of the most fascinating facts about them.
15. Pakicetus
| Name | Pakicetus |
| Name Meaning | “Whale of Pakistan” |
| Pronunciation | Pack-ih-se-tuss |
| Era | Cenozoic — Paloegene |
| Classification | Mammalia, Artiodactyla, Pakicetidae |
| Diet | Carnivorous (Piscivorous) |
| Length | 4 to 6 feet (1.2 to 2 meters) |
| Weight | 45 kg (100 pounds) |
| Location | Pakistan (Asia) |
Before whales made the transition to a fully aquatic lifestyle, prehistoric whales like the Pakicetus lived on land.
This wolf-sized mammal was alive about 50 million years ago during the Eocene Epoch.
The Pakicetus is considered one of the earliest ancestors of modern whales.
The Pakicetus’ body resembled that of a typical terrestrial mammal, but its head was distinctively whale-like.
It was amphibious, meaning it spent part of its time on land but also spent considerable amounts of time in the water, hunting fish and other small animals.
14. Kutchicetus
| Name | Kutchicetus |
| Name Meaning | “Named after the Kutch region in India” |
| Pronunciation | Kutch-i-see-tuss |
| Era | Cenozoic — Palaeogene |
| Classification | Mammalia, Artiodactyla, Remingtonocetidae |
| Diet | Carnivorous |
| Length | 9 to 10 feet (2.7 to 3 meters) |
| Weight | 150 kilograms (330 pounds) |
| Location | India & Pakistan (Asia) |
Kutchicetus was a prehistoric whale that lived on the coastal border of India and Pakistan about 45 million years ago.
It is similar to other early-form cetaceans but was a slightly smaller size.
In fact, the Kutchicetus is considered the smallest of all the early cetaceans of the Eocene Epoch.
It had short limbs but was still quite gracile on land.
In the water, the Kutchicetus could swim actively using undulatory movements of its body and its robust tail.
This is similar to how semi-aquatic mammals like otters swim today.
This prehistoric whale had a relatively short snout and likely fed on small fish and squid.
13. Ambulocetus
| Name | Ambulocetus |
| Name Meaning | “Walking whale” |
| Pronunciation | Am-byoo-loh-see-tus |
| Era | Cenozoic — Paleogene |
| Classification | Mammalia, Artiodactyla, Ambulocetidae |
| Diet | Carnivorous |
| Length | 3 to 3.5 meters (10 to 11.5 feet) |
| Weight | 300 kilograms (660 pounds) |
| Location | Pakistan (Asia) |
The Ambulocetus is one of the best-known prehistoric whales, thanks to a fairly complete skeleton recovered from Pakistan in 1992.
It lived in parts of Pakistan about 47 million years ago.
Ambulocetus had a robust, streamlined body, but its feet were short and webbed.
The prehistoric whale had a broad snout, with eyes positioned on top of its head like that of modern crocodilians.
It was capable of walking on land, but given the size of its limbs, it probably waddled awkwardly like modern sea lions when on land.
12. Rodhocetus
| Name | Rodhocetus |
| Name Meaning | “Rhodo whale” |
| Pronunciation | ROD-hoe-SEE-tuss |
| Era | Cenozoic — Paleogene |
| Classification | Mammalia, Artiodactyla, Protocetidae |
| Diet | Carnivorous |
| Length | 2 to 3 meters (6.6 to 9.8 feet) |
| Weight | 450 kilograms (1,000 pounds) |
| Location | Asia |
Rodhocetus was a prehistoric whale that lived about 48 million years ago.
Unlike earlier whale ancestors that had well-developed limbs, the leg bones of the Rodhocetus didn’t look like they could support much weight.
This is one of several pieces of evidence that show that the Rodhocetus spent more time in water than its land-faring predecessors.
However, experts think it was still capable of walking or dragging its large streamlined body on land when needed.
In the water, the webbed feet of the Rodhocetus were its main swimming apparatus, while the robust tail was used for steering.
11. Basilosaurus
| Name | Basilosaurus |
| Name Meaning | “The king lizard” |
| Pronunciation | Bah-sil-oh-saw-rus |
| Era | Cenozoic — Paleogene |
| Classification | Mammalia, Artiodactyla, Basilosauridae |
| Diet | Carnivorous (Piscivorous) |
| Length | 15 to 20 meters (49 to 66 feet) |
| Weight | 5.8 tons (11,600 pounds) |
| Location | North America, Africa and Asia |
The Basilosaurus is one of the first prehistoric whales ever discovered.
Fossils of this massive whale were discovered in the late 19th century, but it was erroneously labeled as an ancient lizard due to its long, serpentine body and pointed snout.
The name “Basilosaurus” translates as “king lizard,” a consequence of the initial misidentification.
Basilosaurus turned out to be one of the largest prehistoric whales ever.
It was the apex predator of the Eocene Epoch, with a varied diet that included different types of large fish, sharks, and other marine mammals.
10. Aetiocetus
| Name | Aetiocetus |
| Name Meaning | “Whale of the dawn” |
| Pronunciation | Ay-tee-oh-see-tuss |
| Era | Cenozoic — Paleogene |
| Classification | Mammalia, Artodactyla, Aetiocetidae |
| Diet | Carnivorous |
| Length | 3 to 3.5 meters long (10 to 11 feet) |
| Weight | 1 to 3 tons (2,000 to 6,000 pounds) |
| Location | Found in various locations worldwide, including North America |
Modern baleen whales lack teeth, while the older members of this whale group don’t have baleen.
Aetiocetus straddles both worlds by its possession of primitive baleen while also retaining regular teeth.
Consequently, this 23-million-year-old shark is considered a transitional form between modern baleen whales and their ancient, toothed ancestors.
Aetiocetus lived on both sides of the Pacific Ocean, but it is most commonly known in the region of present-day Japan and Mexico, where it lived during the Oligocene Epoch.
9. Odobenocetops
| Name | Odobenocetops |
| Name Meaning | “Toothed whale face” |
| Pronunciation | Oh-doh-beh-no-see-tops |
| Era | Cenozoic — Neogene |
| Classification | Mammalia, Artiodactyla, Odobenocetopsidae |
| Diet | Filter feeder |
| Length | 3 to 4 meters (9.8 to 13.1 feet) |
| Weight | 800 to 1,000 kilograms (1,800 to 2,200 pounds) |
| Location | South America |
Odobenocetops was a small, odd-looking whale that lived during the Miocene Epoch.
The most notable feature of this whale was the pair of downward-pointing tusks protruding out of its mouth like that of a walrus.
Only one other whale species is known to have a tusk like this, and that’s the Narwhal, also commonly referred to as the unicorn of the sea.
Odobenocetops had no teeth, which means it was a filter or suction-feeder.
Experts are still unsure what purpose the tusks served, but their fragile nature meant they were probably not useful for fighting, digging, or any other rigorous activity.
8. Masracetus
| Name | Masracetus |
| Name Meaning | “Egyptian Whale” |
| Pronunciation | Mass-rah-see-tuss |
| Era | Cenozoic — Tertiary |
| Classification | Mammalia, Artiodactyla, Basilosauridae |
| Diet | Carnivorous |
| Length | 8 to 10 feet (2.5 to 3 meters) |
| Weight | 500 to 800 kilograms (1,100 to 1,760 pounds) |
| Location | Egypt and Pakistan (Africa and Asia) |
The Masracetus was discovered as far back as 1905.
But it did not get an official name or description until over 100 years later.
This prehistoric shark is a relative of the famous Basilosaurus and lived in Egypt about 34 million years ago.
The Masracetus was similar to the Basilosaurus in terms of its general physiology but had a proportionately shorter body.
7. Dorudon
| Name | Dorudon |
| Name Meaning | “Named after the village El-Dour” |
| Pronunciation | Door-oo-don |
| Era | Cenozoic — Tertiary |
| Classification | Mammalia, Artiodactyla, Basilosauridae |
| Diet | Carnivorous |
| Length | 4 to 5 meters (13 to 16 feet) |
| Weight | 500 to 1,000 kilograms (1,100 to 2,200 pounds) |
| Location | Worldwide |
The Dorudon is a 40-million-year-old whale closely related to the Basilosaurus.
In fact, it was so similar to the Basilosaurus that scientists once thought the fossil was simply a juvenile version of the larger whale.
Dorudon was a relatively small whale with an average length of about five meters (16 feet).
It was an active predator in warm seas all over the world, preying on small fish and hard-bodied animals such as mollusks.
Fossils of the Dorudon have been recovered from various locations that were once part of the prehistoric Tethys Sea, such as Egypt, Pakistan, the United States, and New Zealand.
6. Squalodon
| Name | Squalodon |
| Name Meaning | “Shark tooth” |
| Pronunciation | Skwah-loh-don |
| Era | Cenozoic — Tertiary |
| Classification | Mammalia, Artiodactyla, Squalodontidae |
| Diet | Carnivorous |
| Length | 2.7 to 5.5 meters (9 to 18 feet) |
| Location | Found in various locations worldwide |
The Squalodon’s name translates as “shark tooth,” a feature that sets it apart from other contemporary whale species.
By the Oligocene Period, most whales were starting to lose their prominent teeth for simple conical ones or losing them entirely.
The Squalodon was one of the few exceptions around, with prominent cheek teeth similar to that of the Squalus shark.
It lived from 28 to 14 million years ago and was a prolific predator that lived on a diet of fish and cephalopods.
Squalodon is one of the oldest cetaceans with evidence of echolocation.
5. Maiacetus
| Name | Maiacetus |
| Name Meaning | “Mother whale” |
| Pronunciation | My-ah-see-tuss |
| Era | Cenozoic — Tertiary |
| Classification | Mammalia, Artiodactyla, Protocetidae |
| Diet | Carnivorous |
| Length | 2.5 to 3 meters (8 to 10 feet ) |
| Weight | 280 to 390 kilograms (620 to 860 pounds) |
| Location | Pakistan (Asia) |
Maiacetus was an amphibious prehistoric whale that lived during the Early Miocene Epoch.
Like many prehistoric whales known from the same period, Maiacetus spent most of its time in the water but could also come on land to mate, give birth, or hunt prey.
The discovery of the fossil of a pregnant female Maiacetus with the fetus positioned head-first confirms the assumption that this whale likely gave birth on land.
Maiacetus was a medium-sized prehistoric whale with an average length of about 2.6 meters (8.5 feet) and a maximum weight of about 390 kilograms (860 pounds).
4. Janjucetus
| Name | Janjucetus |
| Name Meaning | “Named after Jan Juc” |
| Pronunciation | Jan-joo-see-tuss |
| Era | Cenozoic — Tertiary |
| Classification | Mammalia, Artiodactyla, Mammalodontidae |
| Diet | Carnivorous |
| Length | 2.5 to 3.5 meters (8 to 11 feet) |
| Weight | 300 to 500 kilograms (660 to 1,100 pounds) |
| Location | Australia |
Although it is considered a baleen whale, Janjucetus did not have baleen (the filter-feeding system in the mouth of a modern baleen whale).
Instead, this massive whale had teeth more similar to killer whales.
The whale’s dentition consisted of large teeth, effective for gripping and shredding prey.
It is classified as a baleen whale despite the lack of baleen due to similarities in its skull anatomy and that of modern baleen whales.
Janjucetus lived during the Oligocene Epoch, about 25 million years ago.
With an average length of about 3.5 meters (11 feet), the Janjucetus is smaller than any of the living baleen whale species.
3. Mammalodon
| Name | Mammalodon |
| Name Meaning | “Mammal tooth” |
| Pronunciation | Mam-mal-oh-don |
| Era | Cenozoic — Tertiary |
| Classification | Mammalia, Artiodactyla, Mammalodontidae |
| Diet | Suction feeder |
| Length | 3 meters (9.8 feet) |
| Location | New Zealand and Australia |
Mammalodon was a genus of basal baleen whales, which means it is primitive compared to present-day relatives.
It lived during the Oligocene Epoch, about 25 million years ago.
Due to the lack of filter-feeding structures and the large space between the teeth in this whale, experts think a filter-feeding habit similar to that of modern baleen whales is unlikely for this whale.
Instead, it used the rounded snout to agitate bottom sediments and suck small bottom-dwelling organisms in.
2. Zygophyseter
| Name | Zygophyseter |
| Name Meaning | “Yoke Fin Whale” |
| Pronunciation | Zye-go-fye-seh-ter |
| Era | Cenozoic — Tertiary |
| Classification | Mammalia, Artiodactyla, Physeteroidea |
| Diet | Carnivorous |
| Length | 6.5 to 7 meters (21 to 23 feet) |
| Weight | 3,500kg (7,600 pounds) |
| Location | Worldwide |
Also commonly referred to as the killer sperm whale, Zygophyseter is an extinct whale that lived during the Miocene Epoch until about seven million years ago.
It grew to an average length of about 6.5 to 7 meters (21 to 23 feet), which makes it around the same size as a female sperm whale today.
Unlike its modern cousins, Zygophyseter had large teeth with enamel in both the upper and lower jaws.
This whale had a large head with a long snout equipped with a powerful beak for echolocating prey.
Zygophyseter was capable of swimming very fast, reaching speeds of up to four kilometers in an hour.
This is higher than the average speed of the modern sperm whale.
1. Livyatan
| Name | Livyatan |
| Name Meaning | “Derived from Hebrew mythology” |
| Pronunciation | Li-vy-a-tan |
| Era | Cenozoic — Neogene |
| Classification | Mammalia, Artiodactyla, Physeteroidea |
| Diet | Carnivorous |
| Length | 13 to 17 meters (42 to 56 feet) |
| Weight | 57 tonnes (125,663 pounds) |
| Location | Peru (South America) |
Livyatan melvillei was a 57-foot-long sperm whale that lived during the Miocene Epoch about 13 million years ago.
It is considered one of the largest sperm whale species of all time.
This massive sperm whale lived mainly in the southeastern Pacific Ocean.
It was an apex predator of the Miocene seas with a massive head and a long, powerful snout.
Each of the Livyatan’s teeth measured up to 36.2 centimeters (1.19 feet), making it the largest biting teeth of any animal (whether living or extinct).
Livyatan preyed on seals, sharks, and other whales.
Baleen whales formed a major part of the Livyatan’s diet.
It shared the same habitat with other apex predators like the famous megalodon.
The massive detention of this prehistoric whale meant it could tear a huge chunk of its prey with just one powerful bite.
Sources:
- https://www.nyit.edu/medicine/Rodhocetus_spp
- https://en.wikipedia.org/wiki/Aetiocetus
- https://www.nyit.edu/medicine/odobenocetops_explained
- https://www.fossilguy.com/gallery/vert/mammal/marine/squalodon/index.htm
- https://museumsvictoria.com.au/melbournemuseum/state-fossil-emblem/janjucetus-hunderi/
- https://en.wikipedia.org/wiki/Mammalodon
- https://www.mirror.co.uk/news/weird-news/colossal-killer-sperm-whale-57-26833000
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