A fossil discovered in Brazil could help shed light on the rise of dinosaurs. The ancient reptile resembles a cross between a crocodile and a dinosaur but was alive before the creatures grew to dominate Earth.

Physician Pedro Lucas Porcela Aurelio first uncovered the fossil in 2014. He donated it to a local university, launching three years of research. Now, paleontologists have published their findings in the journal Gondwana Research. The new creature, named Gondwanax paraisensis, dates back some 237 million years—roughly the time when the dinosaurs began to dominate the world.

Gondwanax paraisensis belongs to a group of reptiles called silesaurids, which straddle the line between dinosaur and non-dinosaurian reptiles. The researchers believe this fossil is one of the earliest examples of this clade and may be an essential link in the evolutionary chain leading to dinosaurs.

Not only is the fossil itself significant, but it also reveals how sauropterygians could navigate across a vast ocean that covered a single supercontinent. The reptiles swam with their limbs, which could be used as paddles to push them through water — a process known as “paddle swimming.” Until now, the fossil record for these animals has been sparse. However, the discovery of Gondwanax paraisensis shows that this type of aquatic movement by these animals was widespread, even at the dawn of the dinosaurs.

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Paleontologists found the fossil — including a vertebra and other skeletal elements — in southern Brazil in rock layers dating back to the Triassic period when dinosaurs first emerged. The new species is the oldest example of this clade outside of Africa. It is also the first to date to the southern region of the extinct supercontinent Pangaea, which Gondwanax paraisensis was likely native to.

The fossil was so well preserved that it took a team of scientists from across the globe to identify it. The team also compared it to a skull belonging to another sauropterygian lizard, a New Zealand nothosaur called Kopidosaurus Perplexus. The lizard had distinctive teeth with a distinct curve, which helped to place it within the clade of nothosaurs.

Unlike nothosaurs, who swam with two limbs and a long neck, Gondwanax paraisensis swam with four limbs and a tail. It was about the size of a small dog with a long tail, or about 1 meter (39 inches) long, and weighed between 3 and 6 kg (7 to 13 pounds), the scientists said in a statement on Monday. The fossils suggest that the world was warming up and breaking apart into its current continents by the time this creature existed. These changes were a key reason for the rise of dinosaurs, which diversified to take advantage of their expanding habitat and abundant resources. It is thought that Gondwanax paraisensis would have hunted seafloor in shallow waters and fed on fish and other marine plants. Despite its small size, this creature was a powerful predator.