They walked with legs beneath their bodies, nimble as mammals
En las áridas planicies de la Patagonia, donde los ríos efímeros alguna vez surcaban un paisaje casi desértico, científicos argentinos han desenterrado los restos de un cocodrilo de 85 millones de años que caminaba erguido sobre sus cuatro patas, como un mamífero. El hallazgo, realizado en Paso Córdoba por investigadores del Conicet, no solo desafía la imagen que tenemos de estos reptiles, sino que abre una ventana hacia una rama evolutiva que la Tierra ya no recuerda. En la quietud de la roca cretácica, este pequeño depredador terrestre aguardaba el momento en que la ciencia pudiera volver a darle movimiento.
- Un fragmento de cráneo encontrado casi por casualidad desencadenó una excavación que reveló vértebras, extremidades y elementos esqueléticos de un cocodrilo que nadie esperaba encontrar tan completo.
- La criatura, de aproximadamente un metro de longitud, caminaba con las patas directamente bajo el cuerpo, una postura radicalmente distinta al arrastre lateral de los cocodrilos modernos y que sugiere una agilidad sorprendente en tierra firme.
- El entorno donde vivió —ríos que aparecían y desaparecían, llanuras barridas por el viento— exigía exactamente ese tipo de locomoción terrestre, convirtiendo al animal en un depredador adaptado a condiciones que hoy asociamos con el desierto.
- Los investigadores creen que podría tratarse de Notosuchus terrestris, pero la preparación del fósil tomará meses, y existe la posibilidad de que sea una especie aún desconocida para la ciencia.
- La excepcional preservación de regiones esqueléticas raramente documentadas permitirá análisis biomecánicos inéditos y podría reescribir lo que sabemos sobre la paleobiología de los cocodrilos del Cretácico tardío en Sudamérica.
En el área natural protegida de Paso Córdoba, cerca de General Roca en la provincia de Río Negro, investigadores del Conicet descubrieron los restos de un cocodrilo de 85 millones de años que vivió durante el Cretácico tardío y que poco tiene que ver con los cocodrilos que conocemos hoy. Todo comenzó cuando el investigador posdoctoral Facundo Riguetti encontró un fragmento de cráneo. Lejos de conformarse con ese hallazgo aislado, él y la paleontóloga Agustina Lecuona decidieron ampliar la excavación. Lo que esperaban que fuera poco se convirtió en algo extraordinario: vértebras, huesos de extremidades y otros elementos esqueléticos emergieron de la roca con una claridad poco habitual.
Lo que distingue a esta criatura no es su tamaño —apenas un metro sin contar la cola— sino su forma de moverse. A diferencia de los cocodrilos actuales, que se desplazan con las patas abiertas hacia los lados y el vientre cerca del suelo, este animal caminaba con las extremidades directamente bajo el cuerpo, con una postura erguida y ágil más propia de un mamífero. Esa adaptación tenía sentido en el paisaje donde vivía: un mundo de ríos efímeros y planicies dominadas por el viento, donde moverse rápido sobre tierra seca era una ventaja decisiva.
Los investigadores sospechan que el fósil pertenece a Notosuchus terrestris, una de las especies de cocodrilos más conocidas de la Patagonia, aunque la confirmación deberá esperar meses de preparación y estudio. Lo que ya resulta valioso es la calidad de la preservación: regiones del esqueleto que en otros especímenes aparecen incompletas o deterioradas aquí se conservan con una nitidez que permitirá análisis biomecánicos detallados sobre la locomoción y la biología del animal. Y si resultara ser una especie distinta, el descubrimiento adquiriría una dimensión aún mayor, sumando una nueva pieza a un registro fósil que en Paso Córdoba es todavía escaso y fragmentario.
In the protected natural area of Paso Córdoba, near the town of General Roca in Río Negro province, scientists working for Argentina's national research council have unearthed the remains of a creature that challenges what we think we know about crocodiles. The fossil, dating back 85 million years to the Late Cretaceous period, belongs to a relative of modern crocodilians—but one so fundamentally different that it might as well be from another world.
The discovery began with a fragment of skull. Facundo Riguetti, a postdoctoral researcher, found it and called in Agustina Lecuona, a paleontologist at the Institute for Paleobiology and Geology. Together they decided to expand the excavation outward, carefully probing to understand what else might be preserved in the rock. They expected little. Instead, as they worked deeper, vertebrae began to emerge, pieces of limbs, other skeletal elements. What had seemed like an isolated find became something more substantial.
What makes this creature remarkable is not its size—it measured roughly one meter long, not counting the tail—but how it moved. Modern crocodiles sprawl, their legs splayed out to the sides, their bodies hugging the ground. This animal walked differently entirely. Its legs were positioned directly beneath its body, giving it an upright, nimble gait more like that of a mammal than a reptile. Lecuona explained to reporters that this posture would have made the creature far more agile, far more suited to life on land. These were not the great aquatic predators we associate with crocodiles today. They were smaller, terrestrial, adapted to a world of rivers and wind-scoured plains.
The environment itself tells part of the story. The landscape where these crocodiles lived was harsh and ephemeral—small river systems that would swell and then evaporate, interspersed with wind-dominated terrain not unlike a desert. In such a place, an upright-walking crocodile made sense. It could move quickly across dry ground, hunt small prey, survive in conditions that would have challenged a modern crocodile.
The researchers believe the fossil likely belongs to Notosuchus terrestris, one of the most abundant crocodile species known from Patagonia. They cannot be certain until the material is fully prepared and studied, a process that will take several months. But the characteristics visible in what they have recovered point in that direction. What matters more, perhaps, is what this particular specimen preserves. Notosuchus is known from many fossils, yet most are incomplete or poorly preserved in crucial areas. This find offers skeletal regions that have rarely been documented with such clarity, providing a window into the anatomy of the species that previous specimens could not offer.
That anatomical detail opens doors. Researchers can now conduct biomechanical analyses of the limbs, studying how the muscles and bones would have worked together, whether the animal could run and how. They can begin to reconstruct the paleobiology of the creature—what it ate, how it hunted, how it lived. And there is another possibility that Lecuona raised: if this is not Notosuchus terrestris after all, the discovery becomes even more significant. Paso Córdoba has yielded few crocodile species, and those that have been found are often represented by single specimens. A second well-preserved individual of a different species would be a rare gift to science.
Two years ago, another team of Conicet researchers had examined the arm and leg bones of six Notosuchus individuals, finding evidence of rapid growth periods in the structure of the bone itself. Now, with this new material in hand, the picture of these ancient crocodiles grows clearer. The work of understanding how they moved, how they lived, and what role they played in the ecosystems of ancient Patagonia is only beginning.
Citações Notáveis
They walked with legs positioned directly beneath the body, giving them an upright, nimble gait more like a mammal than a modern crocodile— Agustina Lecuona, paleontologist, Conicet
If this is not Notosuchus terrestris, the discovery would be even more significant, as few crocodile species are known from this location— Agustina Lecuona, paleontologist, Conicet
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter that this crocodile walked upright? Isn't that just a detail about posture?
It's not just posture—it's a window into an entirely different way of being a crocodile. Modern crocodiles are built for water. Their sprawled legs, their low center of gravity, their whole body plan is aquatic. This animal was built for land. That tells us the crocodile family was far more diverse than we usually think.
So these weren't apex predators?
Not at all. They were small, maybe a meter long. In an environment of ephemeral rivers and wind-scoured plains, being small and quick on land would have been an advantage. They were filling a niche that modern crocodiles never occupy.
The article mentions they still don't know for certain what species this is. How confident are they?
Confident enough to make an educated guess based on the characteristics, but not certain. What's interesting is that even if they're wrong about the species, the discovery becomes more important, not less. Paso Córdoba hasn't yielded many crocodile species, and most are known from just one specimen.
What will they do with the fossil next?
Finish preparing it—cleaning, documenting. Then biomechanical analysis. They want to understand how the legs and arms actually functioned, whether it could run, how it hunted. The skeleton is well enough preserved that they can ask those questions now.
Does this change how we understand crocodile evolution?
It adds texture to the story. We knew crocodiles existed in the Cretaceous. Now we know they were experimenting with radically different body plans, different ways of living. That's the kind of detail that makes evolution real.