After the extinction of the non-avian dinosaurs, the role of large, terrestrial predator was
largely filled by mammals. However, one of the largest terrestrial predators during the
Age of Mammals was actually a reptile. Named Barinasuchus, it was a distant relative of
crocodilians, though it was far from semi-aquatic. It instead belonged to Sebecidae, a clade
of terrestrial crocodylomorphs who split from the linage that led to true crocodilians before
they moved to the water. Most other sebecids were also large predators, though not as massive
as Barinasuchus. Barinasuchus was first named in 2007, based on the discovery are a partial
skull in Venezuela. While other specimens have since found in different regions in South
America, such as Argentina and Peru, it is still only known from incomplete skulls. Comparisons
with other sebecids indicate the full skull was about a meter long, as large as the skull
of the theropod dinosaur Daspletosaurus. Barinasuchus’s snout was long, though not to the extent of
most crocodilians. Unlike their thin, flat skulls, the skull of Barinasuchus was narrow
and deep. Its deep skull allowed for more attachment points for its jaw muscles, resulting
in an even more powerful bite. Its teeth were also very different from crocodilians. The
straight and conical teeth of modern crocodilians are well suit for holding onto prey. Barinasuchus’s
teeth were instead serrated, blade-like and curved backwards, which made them better suit
for slicing through flesh. These teeth are similar to those of many extinct terrestrial
crocodylomorphs, Komodo Dragons, as well the theropod dinosaurs Barinasuchus had replaced.
While postcranial Barinasuchus fossils still haven’t been found, other sebecids were
quadrupedal with long legs held directly underneath their bodies. While ill-suit for the water
compared to the shorter, sprawling legs of crocodiles, these legs would have been very
well adapted for running. Given the size of its meter-long skull compared to it relatives,
Barinasuchus is estimated to have been 6 meters long or more, with a weight of 1,600 to 1,740
kilograms. Not only was Barinasuchus larger than any other known sebecid, which otherwise
didn’t exceed a length of 4 meters, its size was exceptional for a Cenozoic predator.
For comparison, this was close to the average weight of an adult Allosaurus while the largest
modern land predator, the polar bear, only weighs a maximum of 800 kilograms. Very few
of the terrestrial reptiles related to crocodilians reached such a size. One of the few exceptions
was Razanandrongobe, another terrestrial crocodylomorph. It was much older, living alongside the non-avian
dinosaurs during the Middle Jurassic period. While known from even less remains than Barinasuchus,
it seems to have been as large or even larger, large enough to hunt sauropod dinosaurs. Other
examples are more distant relations outside of Crocodylomorpha during the Triassic period.
But even though these more distant crocodilian relatives filled most of the apex predator
niches during this time, only a few, such as Prestosuchus, Saurosuchus and Fasolasuchus
matched or exceeded Barinasuchus’s estimated size. No other terrestrial Cenozoic predator
even came close to Barinasuchus. Even if it turns out to have weighed only half this initial
estimate, it would still be larger than larger than any living terrestrial predator and remain
a contender for the title of largest Cenozoic land predator. Still, being the largest terrestrial
predator is not the same as being the largest predator. Larger predators live in the oceans
today and the contemporary, semi-aquatic crocodilian Purussaurus weighed at least three times as
much as Barinasuchus. While the other sebecids were not as massive as Barinasuchus, they
were still among of the largest predators in South America for most of the “Age of
Mammals”, often serving as top predators. They were also the most primitive branch of
Crocodylomorpha known to survive past the Cretaceous period. This left the sebecids
as some of the largest predators in South America. Eventually, the gap left by the large
herbivorous dinosaurs was filled by mammals, followed by sebecids evolving larger size
to keep up, with Barinasuchus being by far the most extreme example. Though while the
other sebecids were not as large, Barinasuchus was far from a geologically brief exception
to the normal state of affairs in Cenozoic South America. Barinasuchus lived for roughly
25 million years, from the middle Eocene, at least 37 million years ago, to the mid-Miocene,
about 12 million years ago. To put this into perspective, the apparent lifespan of Barinasuchus
was about two fifths of the entire Cenozoic and was longer than the time from now to the
last common ancestor of humans and orangutans. In all likelihood, since Barinasuchus is only
known from limited remains, it more likely represents a group of closely related species
or even genera through time instead of a single, extremely long-lived species. Without even
a complete skull, there is simply not enough material to differentiate between them right
now.South America was largely isolated from the rest of the world during most of the Cenozoic
era, leading to a very unique fauna. Besides the sebecids, the other large terrestrial
predators in South America were the terror birds and the mammalian sparassodonts. The
sebecid Langstonia also lived at the same time as Barinasuchus, though it is unclear
if it lived in the same parts of South America. Either way, the massive Barinasuchus was certainly
the top predator of its time. Given its low, crocodile-like metabolism, Barinasuchus would
not have had the energy to pursue its prey far. Therefore, like the modern Komodo dragons,
Barinasuchus would have likely laid in ambush near frequently travel paths, waiting for
prey to come close before charging. While it may not have had the endurance of
most endotherms, if its legs were like those of other sebecids, its short bursts of speed
would have been even faster than those crocodilians and Komodo dragons are capable of. With its
powerful jaws and flesh cutting teeth, Barinasuchus would have then torn prey apart with ease.
Survivors of the initial attack would have often been weakened by blood loss and could
then be finished off or scavenged later. Of course, this only applies to adults. Like
Komodo dragons, younger Barinasuchus likely filled different ecological roles as grew.
Still, an adult Barinasuchus was perhaps the most dangerous terrestrial predator since
Tyrannosaurus rex. But like Tyrannosaurus, there were forces far outside of its control.
While the extinction of Tyrannosaurus rex was due to a geologically brief catastrophe,
Barinasuchus seems to have died out due to more gradual events, one of the casualties
of local climate change caused by the increasing elevation of the Andes mountains. As a large
predator, Barinasuchus was particularly vulnerable to disruptions in its environment. A contributing
factor was likely a decline in global temperature, which left large ectotherms like the Barinasuchus
at a greater disadvantage to endotherms, even in the tropics. Barinasuchus and the fellow
sebecid Langstonia finally went extinct during the middle of the Miocene, 12 million years
ago, ending the sebecid linage forever. Though now extinct, Barinasuchus had an impressive
reign. It was not only a reptilian apex predator in world dominated by mammals, but it the
largest land predator during the entire Age of Mammals. Thank you for watching and a thank
you to Alexander Class, who suggested the topic of this video. I hope enjoyed it. Have
a great day, and, if you enjoyed the video, please remember to hit the like button.