Millions of years before dolphins were around, dolphin-like marine reptiles roamed the oceans. They were called ichthyosaurs.
A new species has now been uncovered in the Paja Formation in Colombia's eastern Andes.
The 130-million-year-old creature had a very strange nose, unlike that of any reptile alive today.
Each nostril was split into two separate openings, a feature that distinguished it from all other known ichthyosaurs. It has been named Muiscasaurus catheti.
It is hard to reconstruct exactly how it looked, says Erin Maxwell of the Natural History Museum in Stuttgart, Germany, who analysed the fossil.
Like others in its group, M. catheti had large eyes, slender jaws and small teeth. It ate small fish.
The fossil is of an infant only about 3m long. Adults may have reached 5m.
"I could tell it was a juvenile based on the size of its eyes relative to the rest of the skull," says Maxwell. "In reptiles, babies have very big eyes and heads compared to their body."
What's more, the creature's bones were porous, indicating it was still growing. Only its skull was discovered, so it is unclear how the rest of its body might have looked.
The new find is described in the journal Papers in Palaeontology.
Ichythosaurs like M. catheti roamed the ocean from the Triassic period to the Cretaceous, between 250 and 100 million years ago. That is twice as long as modern whales have been around.
Much of their existence coincided with that of the dinosaurs, but they went extinct tens of millions of years before them. M. catheti lived only 15 million years before the ichthyosaurs died out.
Why they disappeared remains a mystery.
Maxwell says it was particularly exciting to find the fossil in the tropics.
"Today the tropics hold the highest number of marine vertebrate species, but very, very few species are known from these latitudes in the early Cretaceous," she says.
"The new fossils from Colombia will greatly aid in understanding if the tropical seas always were biodiversity hotspots, or if this was a relatively recent phenomenon."