A window into a world 237 million years before now
Deep in the badlands of northwestern Argentina, paleontologists have given a name and a face to a creature that ruled the Earth long before the first dinosaur ever walked: Shakajlura riojanensis, a six-meter predator from 237 million years ago whose bones quietly waited in the Chañares Formation for nearly three decades of field work to find them. The discovery, published by CONICET researchers, reminds us that dominance is never permanent — that every era has its apex, its own architecture of power, and its own eventual passing. Before the thunder lizards claimed the world, distant cousins of the crocodile held the throne, and this fossil is proof that the story of life on Earth is far older, and far stranger, than our imagination tends to allow.
- A six-meter reptile predating dinosaurs by millions of years has been formally identified, forcing a recalibration of what we thought we knew about Triassic apex predators.
- The fossil record for paracrocodilomorphs is so sparse worldwide that each new specimen carries outsized scientific weight — and this Argentine find is among the most complete.
- Bones recovered across two field campaigns in 2017 and 2018 yielded a 60-centimeter skull with anatomical details — smooth nasal bones, a unique jaw structure, a distinctive postorbital configuration — that set this creature apart from every known relative.
- Even a neighbor in time and space, Luperosuchus fractus, proved to be a genuinely different animal, underscoring just how diverse and competitive the pre-dinosaur world actually was.
- The find marks the first formally described paracrocodilomorph in Argentina since 1997, reopening scientific conversation about the full complexity of Triassic ecosystems.
In the badlands of Talampaya National Park in northwestern Argentina, paleontologists have unearthed the remains of a creature that predates the dinosaurs and reshapes our understanding of ancient predation. Named Shakajlura riojanensis, this six-meter reptile prowled the landscape 237 million years ago — a distant relative of modern crocodiles that sat at the very top of the Triassic food chain. The discovery, published in Papers in Palaeontology by researchers from CONICET, is a reminder that the age of dinosaurs was not the beginning of Earth's story, but merely one chapter in a much longer one.
Shakajlura belongs to the Paracrocodylomorpha, a group of four-legged reptiles ranging from four to ten meters that dominated ecosystems long before the thunder lizards arrived. These animals are rare finds — their fossil record is thin across the entire world — making the Argentine specimen especially significant. The bones were collected during field campaigns in 2017 and 2018 from the Chañares Formation, a geological layer spanning roughly 237 to 233 million years ago, when the continents wore shapes we would barely recognize today.
What makes Shakajlura distinct is written in the fine architecture of its bones. A 60-centimeter skull and associated skeletal material revealed smooth nasal bones, a uniquely proportioned lower jaw, and a differently configured postorbital bone — all features setting it apart from Luperosuchus fractus, another paracrocodilomorph that shared the same region and era yet was unmistakably a different creature. These anatomical signatures were sufficient to justify an entirely new genus and species designation.
The last paracrocodilomorph formally described in Argentina dates to 1997, making this find a long-overdue expansion of the known diversity of the group. The Triassic world, it turns out, was no barren prelude — it was a fully realized ecosystem with its own predators, its own hierarchies, and its own evolutionary pressures. Shakajlura riojanensis was the master of its domain, until time and transformation handed the world to others.
In the badlands of northwestern Argentina, a team of paleontologists working in Talampaya National Park has uncovered the remains of a creature that rewrites the story of Earth's ancient predators. The fossil belongs to Shakajlura riojanensis, a six-meter-long reptile that prowled the landscape 237 million years ago—long before the dinosaurs that dominate our imagination ever took their first breath. The discovery, published in Papers in Palaeontology by researchers from Argentina's National Council for Scientific and Technical Research (CONICET), reveals that the world's apex predators were not always the thunder lizards we picture, but rather distant cousins of modern crocodiles.
The creature belongs to a group called Paracrocodylomorpha, four-legged reptiles that ranged from four to ten meters in length and occupied the top of the food chain during the Triassic period. What makes Shakajlura riojanensis remarkable is not just its size, but its rarity. These animals are what paleontologists call "difficult finds"—specimens so scarce that each new discovery reshapes understanding of entire ecosystems. The fossil record of paracrocodilomorphs is thin worldwide, making this Argentine specimen particularly valuable for reconstructing life in the Triassic.
The bones were collected during field campaigns in 2017 and 2018 in the Chañares Formation, a geological layer that has yielded other ancient predators. The team recovered a 60-centimeter skull along with skeletal material from the body and limbs, enough to establish both the creature's size and its distinctive anatomy. Ariel Cardillo, a doctoral fellow at CONICET's research center in La Rioja, describes the Chañares Formation as a window into a world that existed between 237 and 233 million years ago, a period when the continents were arranged in ways we would barely recognize.
What separates Shakajlura riojanensis from its known relatives is written in the fine details of bone structure. Another paracrocodilomorph, Luperosuchus fractus, inhabited the same region and lived during the same period—yet the two animals were distinctly different creatures. Luperosuchus had a curved projection along its snout near the nostrils, a feature entirely absent in Shakajlura. The newer specimen possessed straight nasal bones and a different configuration in the postorbital bone, the structure behind the eye socket that forms part of the skull. Julia Brenda Desojo, a researcher at the National University of La Plata's Faculty of Natural Sciences and Museum, emphasizes these differences as evidence of genuine distinction between the two species.
The upper jaw of Shakajlura riojanensis is notably smooth, lacking the surface ridges and texturing that characterize modern crocodilians. The shape of its lower jaw bone, the prearticular, displays proportions unlike anything else in the paracrocodilomorph family. These anatomical signatures—the smooth maxilla, the unique jaw proportions, the distinctive eye-socket bone—justified naming it as an entirely new genus and species. Each feature tells part of the story of how this predator was built and how it differed from its contemporaries.
The significance of this find extends beyond the creature itself. Shakajlura riojanensis is the first paracrocodilomorph formally described in Argentina since 1997, and it expands the known diversity of a group that dominated ecosystems before dinosaurs rose to dominance. The Triassic world was not a barren prelude to the age of dinosaurs but a fully realized ecosystem with its own apex predators, its own food webs, its own evolutionary pressures. This six-meter reptile, with its smooth jaw and distinctive skull bones, was the master of its domain—until the world changed and other creatures inherited the throne.
Notable Quotes
The Chañares Formation is a window showing us how the world looked between 237 and 233 million years ago— Ariel Cardillo, CONICET doctoral fellow
Paracrocodilomorphs are considered difficult finds because so few examples have been discovered compared to other animals from the same period— Ariel Cardillo, CONICET doctoral fellow
The Hearth Conversation Another angle on the story
Why does finding another crocodile relative matter so much? We already knew these animals existed.
Because we barely know them at all. Paracrocodilomorphs are rare in the fossil record everywhere on Earth. Each new specimen is like finding a page from a book we're still trying to read. This one tells us the group was more diverse than we thought.
What makes this particular animal different from the one found decades ago in the same location?
The details in the skull. The shape of the snout, the bones around the eye, the texture of the jaw. Luperosuchus had a curved snout; this one is straight. Small differences, but they matter—they mean two different species adapted to the same world in different ways.
So they were competitors?
Possibly. They lived in the same place at the same time. Whether they hunted the same prey or occupied slightly different niches, we don't yet know. That's part of what makes the discovery important—it raises new questions.
What does a smooth jaw tell you about how it hunted?
That's harder to say. Modern crocodiles have textured jaws, but texture isn't everything. The shape, the muscle attachment points, the overall design—those all matter. Shakajlura was built differently, which suggests it may have hunted or fed differently too.
Does this change how we think about the Triassic?
It does. We're learning that before dinosaurs took over, the world had sophisticated predators with their own specializations, their own ecological roles. The Triassic wasn't a waiting room for the dinosaur age. It was a fully formed world.