The fossilized remains of Llukalkan aliocranianus include a superbly preserved and uncrushed braincase and were unearthed in the Bajo de la Carpa Formation in Argentina. Llukalkan means “the one who causes fear” in the language of the indigenous Mapuche, and aliocranianus is Latin for “unusual skull.”
Part of a family of dinosaurs called abelisaurids, the creature would have broadly resembled a Tyrannosaurus rex in appearance, with tiny stubby arms. But an unusually short, deep skull, which often bore crests, bumps and horns, set it apart. At least 5 meters long — around the size of an elephant — Llukalkan aliocranianus would have roamed Patagonia and other areas of the prehistoric southern subcontinent of Gondwana, which included Africa, India, Antarctica, Australia and South America.
Its most distinctive feature was a small air-filled sinus in the middle ear zone that has not been seen in any other abelisaurid found so far, according to the research published Tuesday in the Journal of Vertebrate Paleontology,
It means that Llukalkan likely heard differently, and probably better, than other abelisaurids — more similar to the hearing of a modern-day crocodile.
“A peculiarity of this dinosaur is that it has cavities in the ear area that other abelisaurids did not have, which could have given this species different auditory capacities, possibly a greater hearing range. This, together with its keen sense of smell, would have given great capabilities as a predator to this species,” lead author Federico Gianechini, a paleontologist at the National University of San Luis, Argentina, told CNN in an email.
The fossilized remains were discovered in 2015 by accident during a dig in a place known as La Invernada, near the city of Rincón de los Sauces, in Neuquén Province, Gianechini said. The main purpose of the dig was to unearth a sauropod dinosaur (large, lumbering plant-eaters) that they had found a year earlier, but they noticed bones poking out on the surface of the ground a few days before finishing their excavation.
The dinosaur’s unique hearing mechanism suggests that abelisaurids were flourishing right before the dinosaurs’ extinction 67 million years ago.
“These dinosaurs were still trying out new evolutionary pathways and rapidly diversifying right before they died out completely,” said Ariel Mendez, a study co-author and paleontologist from the Patagonian Institute of Geology and Palaeontology, Argentina, in a news statement.