Newfound South American Predator Snacked on Little Dinosaurs

by Charles Q. Choi  

The predatory dinosaur Tachiraptor admirabilis, unearthed in Venezuela, attacking the herbivorous dinosaur Laquintasaura. Credit: Maurílio Oliveira

A puma-sized predatory dinosaur that may have snacked on its smaller cousins while stomping about an ancient rift valley dotted with erupting volcanoes has been discovered in Venezuela. The finding could shed light on the evolution of all carnivorous dinosaurs, researchers say.
The newfound fossil, from a dinosaur named Tachiraptor admirabilis, was unearthed from the northernmost branch of the Andes Mountains at the western border of Venezuela. The only bones from the dinosaur found so far are its shinbone and part of its hip bone, but these are enough to reveal that the beast was relatively small compared with its later, giant relatives, measuring about 4.9 to 6.5 feet (1.5 to 2 meters) long.
This two-legged species is the first predatory dinosaur unearthed in Venezuela. Its name derives from three sources: Táchira, the Venezuelan state where the fossil was discovered; raptor, Latin for thief, referring to the dinosaur's probable predatory habits; and "admirabilis," for Simón Bolívar's Admirable Campaign, which freed Venezuela from Spanish control, and in which La Grita, the town close to where the bones were found, played a strategic role. The fossils were discovered in early 2013, "near where a road was cut out of La Grita," said lead study author Max Langer, a vertebrate paleontologist at the University of São Paulo in Brazil. [See Images of an Omnivorous Dinosaur from Venezuela]
The fossils are about 200 million years old. This means the animal lived during the earliest part of the Jurassic period, when dinosaurs were beginning their rise to global dominance.
Dinosaurs originated about 230 million years ago, in the late Triassic period, but their reign began after the end-Triassic mass extinction event. One of the big five mass extinctions to affect life on Earth, this event killed off a number of other reptile groups that might have been competitors, along with at least half of all species the living on Earth. The most recent extinction event, the end-Cretaceous, occurred about 67 million years ago and ended the age of dinosaurs.
Back when Tachiraptor was alive, Venezuela was part of the supercontinent Pangaea, where most of the landmasses that make up today's continents were once concentrated.
"Pangaea was in the process of breaking up back then," Langer told Live Science. This area was a rift valley, a valley created by the rifting of the land, "like what we have in East Africa now, a rift that ultimately created the northern Atlantic Ocean," Langer said. "There was a lot of volcanic activity around, and in the valley, [there was] a meandering river, along which were patches of forest where this dinosaur lived."
Dinosaur skeletons are nearly unknown from northern South America. The only other dinosaur found in Venezuela is the two-legged, fox-sized plant-eater Laquintasaura venezuelae.
"Laquintasaura may have been part of Tachiraptor's diet," Langer said. "Tachiraptor was probably a generalist predator that ate anything it could get, such as small dinosaurs and other vertebrates, such as lizards."
Nearly all predatory dinosaurs, or theropods, belonged to a group of dinosaurs known as Averostra. This included tyrannosaurs and the ancestors of birds. However, features of T. admirabilis' shinbone revealed that it belonged to a sister group of Averostra.
"By having other theropods to compare Averostra to, it helps us understand more about Averostra and how that large group evolved," Langer said.
The find also suggests the equatorial belt of Pangaea may have played a pivotal role in theropod evolution. Past research suggested that the region was too inhospitable for dinosaurs during the early Jurassic.
"Pangaea was a sort of boomerang shape, and this dinosaur came from its equatorial warm belt, which more or less included northern South America, southern North America and Africa," Langer said. "To the north and south of this belt, you had big deserts. These findings suggest this area may not have been as barren as before thought, but may have hosted more diversity than the fossil record currently indicates."
The scientists plan to go back to Venezuela to search for more dinosaur bones; they also plan to dig in rocks of similar age in Tanzania and Brazil to learn more about the spread of dinosaurs across the world.

Live Science