Millions of years before the most famous meat-eating dinosaurs, such as Tyrannosaurus rex and Spinosaurus aegyptiacus, roamed the planet, other massive creatures claimed the role of apex predators in the Triassic period — which stretched from 252 million years to 201 million years ago.
One of those was Fasolasuchus tenax, a nearly ten-meter (about 32 feet) relative of the early ancestor of modern-day crocodiles. Lesser known than many of those massive meat-eating dinosaurs that dominated later periods of the Mesozoic era, this species recently rose to fame on the big screen.
When Did Fasolasuchus Live?
Found in northwestern Argentina, Fasolasuchus is the largest representative of a loose agglomeration of species traditionally known as the rauisuchians, which included creatures that claimed the role of apex predator for much of the Triassic period.
During this period, life was recovering after a mass extinction — known as the Great Dying. This era ended with another smaller extinction event, which ultimately wiped out species like Fasolasuchus and the rauisuchians, paving the way for the rise and eventual dominance of the dinosaurs.
Read More: The Permian Extinction: Life on Earth Nearly Disappeared During the ‘Great Dying’
Rauisuchian Lineage and Diversity
Prior to that time, their lineage diversified greatly, leading to a huge array of animals, some enormous and others far smaller and quirky. As such, what exactly a rauisuchian is, still remains somewhat of an enigma, says Marcel Lacerda, a paleontologist at Brazil’s Museu Nacional. Rather, it’s a term used by paleontologists to gather up somewhat similar species that don’t quite fit elsewhere on a taxonomic tree of life.
“It would appear that they do have the same common ancestor,” Lacerda says. “But the problem is most of these species are known by very incomplete specimens.”
During the Triassic, a broad group known as the archosaurs evolved and eventually split into two major lineages. “One of them that led to the birds, which include dinosaurs, and the second represented today only by the crocodilians,” says Lacerda. This second branch is known as the pseudosuchians, of which the rauisuchians are a part.
Read More: First Ancient Crocodile Relative from 237 Million Years Ago Was Unearthed in Brazil
Evolutionary Traits of Rauisuchian and Fasolasuchus
Despite their early evolutionary history remaining a mystery, these creatures are known to have had particular traits in common. For instance, they evolved a unique hip-bone joint that meant their legs were straight like pillars, giving them a common gait. Many also had two rows of osteoderms, plate-like scales made from bone that lined their back. Many of these creatures also walked on all fours, but some could have stood on their hind legs for short periods of time to capture prey, such as Prestosuchus, or were mostly bipedal.
Fasolasuchus, meanwhile, is known from only two incomplete skeletons, including a skull equipped with long, recurve, and serrated teeth. It’s known to have sported osteoderms along its back, possibly weighed as much as three tons, and had massive jaws, not dissimilar to that of a large theropod.
“At present, it is considered as possibly the largest of the rauisuchians that we have found,” says Lacerda. “There might be even larger individuals, but they weren't well preserved or have not been found yet.”
Until relatively recently, saurischians and other Triassic species received little research attention compared to the more popularly studied dinosaurs, says Lacerda. As a result, there are massive knowledge gaps about the evolutionary history of these creatures. But this is now slowly changing: “We now have a better understanding of how these animals grew, walked, and might have behaved,” Lacerda continues.
Read More: A Complete Dinosaur Timeline to Extinction: How Long Did They Roam Earth?
Diet and Feeding Habits of Rauisuchians
What these creatures ate, for example, is still poorly known — again partly on account of a lack of fossil discoveries — but their diet likely consisted of large herbivores. One study focused on another species of rauisuchian — Saurosuchus galilei, which was also discovered in South America — suggests that its bite force was relatively weak, equivalent to that of a modern-day gharial.
This means it may have bitten down on softer tissues rather than bone, according to the study. Whether or not this applies to all species, like Fasolasuchus, is not yet known. Other studies indicate that rauisuchians may have eaten one another, either after fighting or scavenging.
Read More: 6 Ancient Mega-Predators that Once Ruled the World
Future Research of Triassic Fossils
Ultimately, however, creatures such as fasolasuchus played a massive role as apex predators, shaping Triassic ecosystems in which they ruled supreme. But much more remains to be learned about their evolution.
“Along with the results of fieldwork, there is a revaluation of a lot of Triassic fossil finds underway that were locked away or forgotten in museum drawers,” Lacerda says. “A new picture is emerging about how Triassic groups like the rauisuchians, lived and evolved, and I have no doubt many more interesting finds will occur in the future.”
Read More: Do We Still Have Any Species Today That Are Descendants of Dinosaurs?
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Geological Society, London, Special Publications. Rauisuchia
Britannica. Archosaur
Anatomical Record. Reassessment of the enigmatic “Prestosuchus” loricatus (Archosauria: Pseudosuchia) from the Middle-Late Triassic of southern Brazil
Anatomical Record. Functional morphology of the Triassic apex predator Saurosuchus galilei (Pseudosuchia: Loricata) and convergence with a post-Triassic theropod dinosaur
Die Naturwissenschaften. Direct evidence of trophic interactions among apex predators in the Late Triassic of western North America
Sean Mowbray is a freelance writer based in Scotland. He covers the environment, archaeology, and general science topics. His work has also appeared in outlets such as Mongabay, New Scientist, Hakai Magazine, Ancient History Magazine, and others.
