Ilaria Rosella Pagliaro What happens when curious paleontologists venture off the beaten path in Patagonia? They discover extraordinary creatures like Guemesia ochoai, a tiny, hornless, and virtually armless dinosaur. And, no, it's not just another relative of T. rex.
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Among the fossilized remains of the Los Blanquitos Formation in the remote Amblayo region, researchers have found the skull of a newly identified species of abelisaurid, which they have named Guemesia ochoai, dating back some 70 million years to a time when the Gondwana supercontinent was breaking up. The discovery, in the Salta Province, provides a glimpse into a region that has largely been bypassed by paleontologists, who have traditionally looked for fossils in Patagonia.
The nearly complete skull of the fossil speaks to a different story than that of its southern relatives. Unlike its fellow abelisaurids, Guemesia ochoai lacked horns and had a surprisingly small brain, about 70% smaller than its nearest relatives. It is this simplicity in structure that makes it a truly unique find.
The rise of “small-brained” abelisaurids
Abelisaurids, theropod dinosaurs known for their almost useless forelimbs, were nature’s prehistoric answer to “make the most of what you’ve got.” Despite their tiny arms and robust, often ornamented skulls, these dinosaurs were fearsome predators, capable of taking down massive prey like sauropods.
However, Guemesia ochoai stands out for a number of reasons. The complete absence of horns on its skull suggests it was a very primitive species, probably one of the earliest in its group. Besides, the skull features foramina-small openings that might have helped the dinosaur dissipate heat and regulate body temperature, an intelligent evolutionary adaptation for survival in the harsh, arid conditions of the Late Cretaceous.
This extremely unusual dinosaur reflects just how different the fauna of northwestern Argentina was from the rest of the country,” said Professor Anjali Goswami of the Natural History Museum in London. “It reinforces the idea of highly distinct ecosystems during the South American Cretaceous.”
Argentina’s overlooked dinosaur treasure trove
While Patagonia has long been the Mecca for paleontologists because of the spectacular discoveries of fossils there, northwestern Argentina has been the Cinderella of paleontology. But with the discovery of Guemesia ochoai, this region is slowly carving its place in the map for important findings.
The species is named after Martín Miguel de Güemes, a hero of Argentine independence, and Javier Ochoa, the museum technician who discovered the fossil.
This dinosaur lived during a time when Gondwana was splitting into the southern continents we know today. Its unique ecological context serves to underscore how geographical separation likely fostered the development of distinct ecosystems waiting to be uncovered. As Professor Goswami noted:
“To understand global events like mass extinctions, we need to dig into the planet’s less-explored regions. And here, in northwestern Argentina, there is so much more to discover.”
Guemesia ochoai is no small feather, so to speak, added into a most extraordinary collection which makes the first big discovery by Argentina in any country’s lot on Earth of some 35 different varieties of abelisaurids, hailing nowhere in particular other than Patagonia; and so he hopes, to bring new elements to that ever-surprising document depicting the dinosaurs and their evolvements.
