An Ultimate Guide to Andrewsarchus: Andrews’ Ruler

Leave a comment / / Updated on: 24th September 2023

Name Meaning“Andrews’ Ruler”Height1.8 meters (6 feet) 
PronunciationAn-droo-sar-kusLength4.8-5.5 meters (16-18 feet)
EraCenozoic – Paleogene PeriodWeight500–1000 kilograms (1100–2200 lbs)
ClassificationMammalia, Artiodactyla & Cetancodontamorpha LocationMongolia and China (Asia)

Andrewsarchus Pictures

3D illustration of Andrewsarchus
3D illustration of Andrewsarchus | Disneysaurus via Dinosaur Wiki

The Andrewsarchus

Gage Beasley Prehistoric's Andrewsarchus Concept
Gage Beasley Prehistoric’s Andrewsarchus Concept

Andrewsarchus was a genus of extinct mammals that lived in China during the Eocene Epoch, between 45 and 36 million years ago. 

It is often referred to as the largest carnivorous mammal to have ever lived, beating the equally massive Arctotherium (South American short-faced bear). 

Andrewsarchus was a mammal closely related to modern-day hippos and whales. 

The first fossil of this mammal was discovered in 1923 by a group of researchers on an expedition to the Irdin Manha formation located in Inner Mongolia. 

Andrewsarchus mongoliensis from the Late Eocene of Central Asia
Andrewsarchus mongoliensis from the Late Eocene of Central Asia | Image via License

The genus was named in 1924 after Roy Chapman Andrews, the American explorer that led the expedition. 

So far, only fragmentary skull remains of this mammal have been found. 

Thus, there’s limited knowledge about its anatomy and behavior.

In this article, we’ll discuss some of the facts about this prehistoric beast based on the available fossil remains and comparison to some of its relatives. 

Gage Beasley's Prehistoric Shirt Collection
Gage Beasley’s Prehistoric Shirt Collection
Gage Beasley's Prehistoric Plush Collection
Gage Beasley’s Prehistoric Plush Collection

Physical Characteristics

Gage Beasley Prehistoric's Andrewsarchus Size Comparison Chart
Gage Beasley Prehistoric’s Andrewsarchus Size Comparison Chart

Andrewsarchus is known from a partial skull and a few teeth fossils. 

The rest of the animal’s skeleton is not known, which has made it difficult to tell what it actually looked like when it was alive. 

The skull fossil measured about 83.4 centimeters (2.74 feet) in length. 

Based on this skull, scientists have estimated a length of about 3 feet for the Andrewsarchus and a height of about 1.4 meters measured from the shoulders. 

If this dimension is right, then the Andrewsarchus was one of the largest carnivorous mammals to have ever lived on land, rivaling the Arctotherium, a short-faced bear that lived in Central South America during the Pleistocene. 

The skull of the Andrewsarchus is up to two times the length of the skull of the Alaskan Brown bear and triple that of an American wolf. 

Based on estimated body proportions, Andrewsarchus was probably the size of modern horses. 

It had a narrow snout with jaws filled with a few sharp canine teeth and some flat cheek teeth. 

Andrewsarchus head model showcasing its sharp teeth
Andrewsarchus head model showcasing its sharp teeth | Ben Sutherland via Wikimedia CC BY 2.0

Its body was probably similar to that of a bear or a hyena but with a bulkier build, short legs, and a long tail. 

The Andrewsarchus’ mass was probably about 1,000 pounds or more. 

The well-preserved skull of the Andrewsarchus provides a clear picture of their possible dental structure. 

This mammal had a heterodont dentition which includes three incisors arranged in a semi-circle, one canine, four premolars, and four molars on each side. 

The second and third molars were elongated, and they had a wrinkled crown. 

The first and second molars appeared to be more worn compared to the rest of their teeth. 

The second incisor was also quite large, similar to that of many living canines. 

Habitat and Distribution

The first fossil remains of Andrewsarchus were discovered in Mongolia in the Irdin Manha formation. 

A second one was later identified in the Guangxi region of China, which suggests that this mammal inhabited what is now East Asia. 

It’s difficult to determine the exact habitat and geographic range of the Andrewsarchus due to limited fossil records, but they are believed to have inhabited the open habitats of the region.

Andrewsarchus was alive during the Eocene Epoch, a time characterized by a relatively warm climate, with temperatures higher than present-day. 

The specific environment in which Andrewsarchus lived was probably characterized by a mix of forests, woodlands, and open grassy plains. 

The Eocene Epoch was a time of significant diversification of mammalian life, and large creatures like the Andrewsarchus were quite common across different continents. 

Behavior and Diet

Due to limited fossil records, the limb structure of Andrewsarchus is not well known. 

However, this mammal most likely had a quadrupedal stance, with short limbs adapted for both mobility and support.

It moved on all fours, and if the predicted carnivorous diet is correct, then it must have been capable of walking and running quickly to chase prey. 

Andrewsarchus was quadrupedal which means it moved on all fours
Andrewsarchus was quadrupedal, which means it moved on all fours | Disneysaurus via Walking With Wikis

The social behavior of Andrewsarchus is uncertain. 

However, if they’re anything like modern carnivores, then they probably lived largely solitary lives, with adults living and hunting alone. 

It’s also plausible that they formed small packs that controlled specific territories or hunting grounds. 

Although the Andrewsarchus is often referred to as the largest meat-eating land mammal ever discovered, some experts think this might be inaccurate.  

Some paleontologists, including some members of the expedition party that discovered the Andrewsarchus believe the skull belonged to a member of a group of pig-like mammals that were omnivorous rather than herbivorous. 

But the Andrewsarchus’s skull looks like the beast was well-adapted to a flesh-based diet.

Whether or not this animal was an active predator or just a scavenger is still up for debate. 

Andrewsarchus may have either been a scavenger, predator, or both
Andrewsarchus may have either been a scavenger, predator, or both | The dragnor via Prehistoric Wiki

If the carnivorous diet is right, the Andrewsarchus’s diet would have consisted of smaller mammals and other herbivorous animals in its ecosystem. 

Its sharp teeth were well-adapted for holding prey and tearing flesh, while the cheek teeth were useful for crushing bones.  

Obtaining food may have involved stalking or ambushing prey, then chasing them down with bursts of speed. 

A carnivore with such a large and powerful jaw would have been capable of taking down relatively large prey, whether hunting individually or working as a pack. 

Life Cycle

The life cycle of the Andrewsarchus is not well understood, but based on what is known about other carnivorous mammals, we can speculate that they reproduced sexually. 

It’s also likely that males and females engaged in various mating behaviors, but there’s no evidence for this. 

Like modern mammals, Andrewsarchus females gave birth to live young after a long gestation period. 

Young Andrewsarchus would have had to depend on parental care for protection during the early months or years of their life. 

A computer generated image of a juvenile Andrewsarchus
A computer-generated image of a juvenile Andrewsarchus | Xenephos via Jurassic World: The Game Wiki

Predator mammals often remain with their parents until they’re capable of hunting prey on their own. 

Evolution and History

Andrewsarchus was initially classified as a member of an extinct family of mammals known as mesonychids

Mesonychids represent a primitive branch in the mammalian evolutionary tree. They’re believed to be closely related to hoofed mammals like hippos (ungulates) and cetaceans (whales and dolphins).

Andrewsarchus was previously thought to belong to an extinct mammalian family called Mesonychians
Andrewsarchus was previously thought to belong to an extinct mammalian family called Mesonychians | Apokryltaros via Wikimedia CC BY-SA 3.0

However, recent evolutionary analysis shows that the Andrewsarchus isn’t a mesonychid, but it is still related to modern whales since they’re both part of an order of mammals known as the artiodactyls. 

All members of this order evolved during the Early Eocene, about 53 million years ago, and diversified into various forms. 

This includes aquatic groups like whales and terrestrial forms like the hippos, Andrewsarchus, Entledonts, and other groups of hoofed land mammals. 

Interactions With Other Species

Given its size and jaw structure, Andrewsarchus probably occupied a prominent position as a top predator in Asia’s Middle Eocene ecosystem. 

The wide gaping jaws of Andrewsarchus made it a formidable adversary
The wide gaping jaws of Andrewsarchus made it a formidable adversary | Mario Lanzas via Wikimedia CC BY-SA 4.0

This presence of the Andrewsarchus in that region at the time represents a shift from the more generalist predators that were used to dominate the area to more specialized carnivores. 

Andrewsarchus actively hunted and preyed on a variety of smaller mammals and other herbivorous animals of its time. 

A female Andrewsarchus leads her calf to a freshly deceased carcass
A female Andrewsarchus leads her calf to a freshly deceased carcass | Apokryltaros via Wikipedia CC BY-SA 3.0

The Irdin Manha formation, where the fossil of this mammal was found, had large mammals like the Gobiatherium, Forstercooperia, Paracolodon, and Rhinotitan. 

These mammals lived in Mongolia and China between the Middle to Late Eocene epochs. 

Smaller mammals like the Sarkastodon were present as well. 

The Mesonychians, which were once considered close relatives of the Andrewsarchus, were among the dominant predator species in Mongolia during the Eocene. 

Some of them, such as the Mongolonyx, Mesonychid, and Harpagolestes, may have competed with the Andrewsarchus for prey and other resources. 

There’s no record of encounters between these carnivores, so the nature of their relationship isn’t known. 

Cultural Significance

The maxilla and upper skull of an Andrewsarchus mongoliensis
The maxilla and upper skull of an Andrewsarchus mongoliensis | Emőke Dénes via Wikipedia CC BY-SA 4.0

Andrewsarchus is a key component of the fossil record and whose discovery would have provided valuable insights into the evolution of mammals in the post-dinosaur world. 

Unfortunately, the scarcity of fossils for this genus has made it difficult to truly understand its place in mammalian diversification and adaptation during the Eocene Epoch,

As one of the largest land carnivores to have ever lived, Andrewsarchus is an important genus that may one day shed more light on the evolution of mammalian carnivores and their modern descendants.

Despite the enigmatic nature of its fossils and the controversies about the true nature of this prehistoric beast, the Andrewsarchus still stands out as an intriguing prehistoric creature to paleontologists and the general public. 

Its size and predatory nature make it an object of fascination for paleontologists. 

Since very little is known about this mammal, Andrewsarchus is not commonly referenced in popular culture.

However, it is occasionally mentioned in books, documentaries, and other media that explore prehistoric life. It is also a character in the Ark Survival game. 

An Andrewsarchus wearing the saddle as seen in ARK: Survival Evolved
An Andrewsarchus wearing the saddle as seen in ARK: Survival Evolved | Image via ARK: Survival Evolved


Andrewsarchus is a genus of extinct mammals that lived during the Middle Eocene Epoch, between 56 and 33.9 million years ago. 

Named after the leader of the expedition crew that discovered it, this large mammal lived in China and the Inner Mongolia region. 

At least two species of this predatory mammal have been identified so far. 

Due to the fragmentary nature of the Andrewsarchus fossil, very little is known about this mammal, and many of the facts remain quite controversial. 

Most scientists agree that it is related to present-day hippos and whales, but the extent of this relationship is not well-understood. 

The diet and feeding habits of the Andrewsarchus also remain controversial. 

Although it is commonly considered a carnivore, some experts think the mammal was probably an omnivore. 

Since the discovery of the second species in 1977, no other Andrewsarchus fossils have turned up, leaving so many unanswered questions about what would have been one of Earth’s most impressive creatures. 


Was Andrewsarchus a dog? 

No, Andrewsarchus was not a dog.

It was a carnivorous mammal that is often compared to wolves, but there is no evidence of a possible relationship with dogs or even wolves. 

What were the two species of Andrewsarchus

The two species in the Andrewsarchus species were Andrewsarchus mongoliensis and Andrewsarchus crassum

The first species was identified in 1923, and the second was named from fragmentary teeth fossils discovered in 1977. 

Was the Andrewsarchus the biggest predator that ever lived?

No, the Andrewsarchus was not the biggest predator that ever lived. 

It is a qualified contender for the largest predator mammal ever found, but there are larger predators (mostly dinosaurs and reptiles) that were significantly bigger than the Andrewsarchus.


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