An Ultimate Guide to Postosuchus: The Crocodile of Post

Leave a comment / / Updated on: 23rd September 2023

NamePostosuchus DietCarnivorous
Name Meaning“The Crocodile of Post”Height1.2 meters (3.9 feet)
PronunciationP‬oest-oh-sook-us.Length5–7 meters (16–23 feet)
EraMesozoicLate TriassicWeight250–450 kg (550–990 lbs)
ClassificationPseudosuchia, Diapsida & RauisuchidaeLocationUSA (North America)

Postosuchus Pictures

Postosuchus in white background.
Postosuchus | Warpaintcobra via iStock

The Postosuchus

Gage Beasley Prehistoric's Postosuchus Concept
Gage Beasley Prehistoric’s Postosuchus Concept

Postosuchus was a genus of rauisuchid reptiles that lived in North America about 230 million years ago.

A top predator of the Triassic period, Postosuchus and its other related croc cousins ruled the North American continent long before the dinosaurs evolved into the large dominant predators that we all know and may have preyed on the primitive dinosaurs.

They grew up to 15 feet in length and were active predators. 

Postosuchus was first discovered in 1980.

The Post Quarry, located in Texas, where the first fossil of this reptilian was found, hosts several other rauisuchid fossils from the same time period.

The Postosuchus fossils discovered so far were found in very good condition, which has made it easier to get a good picture of what this reptile looked like and how they lived.

This post provides a glimpse into the life of one of Earth’s most notable predators, which scientists sometimes refer to as “the T-Rex of the Triassic.”  

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Physical Characteristics

Postosuchus, a fearsome predator from the Triassic period, showcasing its powerful jaws and reptilian prowess.
Postosuchus is a fearsome predator from the Triassic period, showcasing its powerful jaws and reptilian prowess | Kitti Kahotong via iStock

Postosuchus was a large prehistoric reptile that lived during the Triassic period, approximately 230 million years ago.

Although it shared some similarities with the dinosaurs, Postosuchus was not a dinosaur.

It belonged to a group called rauisuchidians.

Members of this group were large predatory reptiles distantly related to modern crocodiles. 

Postosuchus was a formidable predator in its days.

It was one of the largest carnivores of the Triassic, with adults reaching between five and seven feet (16–23 ft) in length from snout to tail.

Estimates of the Postosuchus’s height puts it at around 1.2 meters (3.9 feet), and it weighed between 250 and 450 kilograms (550–990 pounds).

Postosuchus was a heavily built reptile. It had a massive skull equipped with long dagger-like teeth.

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

The skull was narrow at the front but widened towards the end.

It also had an elongated neck which had at least eight cervical vertebrae.

The Postosuchus’ tail was long as well, but it had a short torso. 

Postosuchus had four limbs located underneath its body, giving it an upright stance.

The forelimbs were shorter than the hindlimbs, which has raised speculations that this reptile was bipedal.

Despite being shorter, the forelimbs were still robust and were probably used to hold prey.

Each hand had five toes, but only the first toe had a large claw that was likely used as a defensive weapon. 

Fossil dinosaur skeleton of Postosuchus kirkpatricki - a Late Triassic Period Rauisuchian dinosaur predator.
Fossil dinosaur skeleton of Postosuchus kirkpatricki – a Late Triassic Period Rauisuchian dinosaur predator | ChuckSchugPhotography via iStock

Scientists have identified thick bony scales known as osteoderms on some Postosuchus fossils.

This suggests that they had some sort of scales on their backs and necks.

The ends of the Postosuchus’ tail probably had bony plates and spikes too.

These scales would have provided added protection for the reptile. 

Postosuchus shares some similarities with other prehistoric reptiles, especially other members of the Rauisuchidae group.

It resembles the crocodylomorphs in terms of its overall body shape, with a long, low-slung body.

However, its semi-erect posture and bigger size set it apart from modern crocodiles.

In terms of size, Postosuchus was larger than most living crocodiles and comparable in size to some large predatory dinosaurs of the Mesozoic era, such as Dilophosaurus and Coelophysis. 

Habitat and Distribution

Postosuchus lived during the Late Triassic, roughly 230 million years ago.

The first fossil of this reptile ever found was discovered in a quarry in the City of Post, Texas.

Other well-preserved fossils of this dinosaur have been identified in other locations in the region of present-day Texas and New Mexico, suggesting that this area was the typical range of the Postosuchus

This area was part of the supercontinent Pangea, which was just starting to break apart during the Late Triassic.

Postosuchus most likely lived in a wide range of environments within this region.

Experts think it was a versatile predator capable of both terrestrial and semi-aquatic lifestyles.

The Postosuchus lived in an area with an abundance of floodplains, river systems, lakes, and open forest areas. 

During the Late Triassic, the North American landscape was undergoing significant changes.

Explore the unique characteristics of Postosuchus, including its elongated snout and strong limbs.
Explore the unique characteristics of Postosuchus, including its elongated snout and strong limbs | Heraldo Mussolini via GettyImages

Pangaea was experiencing increasing aridity, leading to the formation of vast deserts in some regions of the supercontinent. 

The climate during this time was generally warm and dry, with seasonal variations.

The interior of Pangaea, where Postosuchus lived, had a hot and arid climate, similar to present-day desert regions.

However, there were still some lush, forested areas with extensive river systems that supported diverse ecosystems.

Reptiles like the Postosuchus dominated the Late Triassic ecosystem.

Although dinosaurs were present, they were just starting to emerge.

The crocodylomorphs, including the Postosuchus, filled the top predator niches.

Behavior and Diet

Postosuchus attacking a dicynodont in a Triassic forest 228 million years ago
Postosuchus attacking a dicynodont in a Triassic forest 228 million years ago | Stocktrek Images via GettyImages

Postosuchus was an active predator that prowled the terrestrial landscapes of Late Triassic North America.

It had long, robust limbs, which gave it an upright posture with relative agility on land.

Although it had a somewhat crocodile-like body shape, Postosuchus had a more erect stance, and it may have moved faster than modern crocodiles.

There’s an ongoing debate about whether Postosuchus and other rauisuchids moved with a bipedal or quadrupedal stance.

The reason for this argument is the relative difference in length between the forelimbs and hindlimbs of this reptile.

The two forelimbs were only about half the length of the hindlimbs, which is typical of bipedal animals.

However, it’s also possible that they were quadrupedal but capable of taking a bipedal stance. 

Like other crocodylomorphs, Postosuchus was a solitary animal.

A flock of Coelophysis attacking a Postosuchus.
A flock of Coelophysis attacking a Postosuchus | Thedark85 via WalkingWithFandom

It had limited interactions with other members of the same species except during mating season.

Scientists have found no evidence to suggest any complex group behavior in the members of this genus. 

Postosuchus was a carnivorous animal and a top predator during its days.

Its upright posture, robust skull, and sharp, serrated teeth indicate adaptations for an active hunting lifestyle.

It likely preyed on a variety of animals, including small and medium-sized reptiles, early mammals, and possibly small dinosaurs.

It may have hunted in the rivers and lakes as well, catching fish and amphibians in the coastal areas. 

One specimen of the Postosuchus discovered in 1992 but described in 2008 was found with some of its gut content preserved.

The gut content includes bones from at least four different animals, including an aetosaur, a Plinthogomphodon, a dicynodont, and a temnospondyl.

This confirms that the Postosuchus was indeed an active predator with a very diverse diet. 

Life Cycle

Postosuchus walking in a forest
Postosuchus walking in a forest | Lythronax via WalkingWithFandom

Like modern reptiles, Postosuchus probably reproduced by laying eggs.

After mating, females would have laid their eggs in suitable nesting sites or in excavated nests underground.

It is possible that Postosuchus exhibited some degree of parental care, such as guarding the nests or providing protection for the hatchlings.

Still, there is no direct evidence to support this.

The growth pattern of the Postosuchus is comparable to that of modern crocodiles and others.

They would have undergone a period of growth and development.

Hatchlings probably emerged from their eggs independent and capable of fending for themselves from an early age.

Their size and body proportions were similar to that of adult forms but smaller.

But as they grew, Postosuchus individuals would have undergone a gradual increase in size until they reached maturity. 

Evolution and History

Postosuchus drinking in a river
Postosuchus drinking in a river | SpyroGuy via WalkingWithFandom

Postosuchus belongs to a group of reptiles called pseudosuchians, which are distant relatives of modern crocodiles and birds.

Within the pseudosuchians, Postosuchus is further classified in the Rauisuchidae family.

Although members of this family are not direct ancestors of modern crocodiles, they still represent an important branch in the evolutionary tree of archosaurs (a group that includes both living and extinct birds and crocodilians).

Postosuchus emerged during the Late Triassic period, approximately 230 million years ago.

At this time, the archosaur lineage was already quite established and diversified into several groups, including the rauisuchids and some of their closest relatives. 

Postosuchus shares a common ancestor with dinosaurs.

However, Postosuchus is not a dinosaur.

It represents a parallel lineage that developed alongside (slightly earlier than) dinosaurs.

A tooth belonging to Postosuchus from the Upper Triassic Chinle Formation.
A tooth belonging to Postosuchus from the Upper Triassic Chinle Formation | Fossiladder13 via Wikipedia CC BY-SA 4.0

As they evolved, Postosuchus developed a more crocodile-like body shape, with a long, low-slung body and robust limbs.

Dinosaurs, on the other hand, had a more bird-like body structure, with limbs positioned directly beneath the body and a more erect stance.

Over the course of the Triassic, the pseudosuchians would diversify even further, evolving into various forms that became more specialized within their ecological niche.

Postosuchus exhibited various predatory adaptations, including a massive jaw, large jaws, and a heterodont dentition. 

As the Triassic period progressed, the pseudosuchians as a whole went through various changes in their body size, tooth morphology, and ecological niche.

However, an extinction event at the end of the Triassic put an end to the evolutionary progress of this group, paving the way for the dinosaurs to emerge as the top predator of the rest of the Mesozoic era. 

Interactions With Other Species

Captivating dinosaur in pursuit of food in the forest
Postosuchus in pursuit of food in the forest | jordankwalker via Tumblr

As a top predator in the North American Triassic ecosystem, Postosuchus interacted with other animals within the ecosystem in prey-predator relationships as well as competition with other carnivores. 

Postosuchus was one of the largest carnivores from Triassic North America, which means it likely had very few natural predators in its ecosystem.

It occupied a dominant position in the food chain and likely faced minimal threats from other animals.

However, it is possible that some larger apex predators of the time may have posed a risk to juveniles and weak or injured Postosuchus individuals too. 

Postosuchus hunted various animals, including small to medium-sized vertebrates like fishes, early mammals, reptiles, and amphibians.

Casts of Postosuchus and Desmatosuchus on display at the Houston Museum of Natural Science, Houston, Texas, USA
Casts of Postosuchus and Desmatosuchus on display at the Houston Museum of Natural Science, Houston, Texas, USA | Evolutionnumber9 via Wikipedia CC BY-SA 4.0

Scientists have found at least one fossil of this reptile with remains of other animals in its gut. 

The Cooper Canyon Formation, where this reptile was found, had an active lake or river system with cartilaginous fishes such as the Xenacanthus and lobe-finned fishes such as Chinlea.

Postosuchus may have preyed on these fishes while in the water. 

Various animals lived on the shores of these rivers as well.

They include labyrinthodonts like the Latiscopus as well as reptiles such as the Malerisaurus and Trilophosaurus.

Other animals that this reptile may have hunted include; the Leptosuchus (a type of archosaur), Nicrosaurus (a phytosaur reptile) and Placerias (a dicynodont), and Typothorax

Cultural Significance

Uncover the intriguing evolutionary adaptations of Postosuchus, exemplified by its reptilian features and formidable size.
Uncover the intriguing evolutionary adaptations of Postosuchus, exemplified by its reptilian features and formidable size | Image via RareGallery

Since its discovery in the 1980s, the anatomy, locomotion, and predatory adaptations of Postosuchus have been extensively studied, contributing to our understanding of prehistoric reptiles and their ecosystems. 

Although not directly related to the dinosaurs that lived after them, Postosuchus represents an important transitional form between archosaurs and the dinosaurian groups.

Therefore, an understanding of this reptile’s anatomy provides some clues into the evolutionary steps that led to the rise of dinosaurs and their subsequent dominance during the Mesozoic era. 

Postosuchus and its other crocodile cousins have made quite a few appearances in popular culture, but they’re not as iconic as the more recognizable dinosaurs.

They are often mentioned in books and scientific documentaries about the prehistoric creatures of the Triassic period, such as the “Walking with the Dinosaurs” TV series.

Postosuchus drinking in a river
Postosuchus drinking in a river | Image via HooZoo

The powerful predator status of this reptile often draws comparisons between the Postosuchus and the Tyrannosaurus rex, who was the dinosaur king of the Cretaceous period.

This is why it is sometimes referred to as the “T-Rex of the Triassic.”


Postosuchus was a large crocodile-like reptile that inhabited parts of North America during the Late Triassic period about 230 million years ago.

It was one of the largest predators that lived in North America and was an active predator that dominated the ecosystem.

It was a semi-aquatic predator but was quite active on land as well, hunting mammals, other reptiles, and even dinosaurs. 

Although not as popular as the dinosaurs that came after them, Postosuchus and its relatives were the most dominant group of the Triassic, and they also hold scientific significance as a transitional form between prehistoric archosaurs and the dinosaurs that emerged later.

Their study, therefore, provides some insight into the evolution of the reptiles and the ecological dynamics that shaped the Triassic period.


What does the name “Postosuchus” mean?

The name “Postosuchus” means “Lizard of Post.”

It refers to the city of Post in Texas, where the first fossil of this ancient crocodilian was found in 1980.

Did Postosuchus live in water?

Postosuchus is primarily considered a terrestrial reptile but may have had some semi-aquatic capabilities.

Its precise relationship with water is not well-documented, but it likely inhabited areas near rivers or lakes.

Is Postosuchus related to modern crocodiles?

Postosuchus and modern crocodiles are distant relatives within the broader group of archosaurs.

While they share a common ancestry, Postosuchus represents a distinct branch in the evolutionary tree and is not directly ancestral to modern crocodiles.

Why did Postosuchus go extinct?

Postosuchus went extinct due to changes in the global climate at the end of the Triassic.

Climate change caused the North American climate to become arid, leading to the disappearance of the coastal areas and lush forests that the Postosuchus lived in.

The dinosaurs were better equipped to survive in the open country landscape that emerged, while ambush hunters like the Postosuchus naturally couldn’t compete.

This led to their decline and consequent proliferation of the dinosaurs. 


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Jerry Young is a self-proclaimed prehistoric animal nerd. He has been fascinated with these ancient creatures for as long as he can remember, and his passion for them continues to this day. With his extensive knowledge and love for prehistoric animals, he is the perfect fit for Gage Beasley Prehistoric.

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