Not just giants: Fossil of the smallest dinosaur, about the size of a crow, found

What is the first thing that crosses your mind when you hear ‘dinosaur’? Mighty, towering creatures that once roamed the Earth. Well, not all dinosaurs were giants. They, too, came in all shapes and sizes. There are dinosaurs like Supersaurus, which was 54 feet tall, and there are tiny ones that could fit in your palms. That’s right! Scientists have unearthed a near-complete fossil of a tiny dinosaur in Argentina. The newly identified species, Alnashetri cerropoliciensis, is one of the world's smallest dinosaurs — so small that it is about the size of a crow.

Around 95 million years ago, Argentina’s Patagonia region was dominated by giants.
Fearsome meat-eaters like Giganotosaurus, weighing about eight tonnes, and immense long-necked plant-eaters, Argentinosaurus, weighing about 70 tonnes, stalked the landscape. But it was not just a land of giant dinosaurs — at least that’s what the new fossil discovery reveals. The researchers unearthed a well-preserved and nearly complete skeleton of one of the world's smallest-known dinosaurs. They have named it Alnashetri cerropoliciensis. This tiny dinosaur was about the size of a crow. They have nicknamed the specimen ‘Alna’.

Researchers say this tiny dinosaur probably hunted small animals like lizards, snakes, mammals, and invertebrates. This discovery offers rare insight into Alvarezsauria, an unusual family of dinosaurs within the theropods, which also includes all the meat-eating dinosaurs. The fossil was found in sandstone at a site called La Buitrera in northern Patagonia’s Rio Negro Province, where earlier, many fossils of small and medium-sized animals from the Cretaceous Period were found.

According to the researchers, Alna was a small female that lived in a desert environment and died after reaching the age of four, so was almost fully grown. The body was quickly covered by a sand dune after death, leading to its fine level of preservation.
Apart from birds, which evolved from small feathered dinosaurs, Alnashetri is the smallest dinosaur known from South America and among the tiniest ever discovered worldwide. "Alnashetri is truly tiny. Weighing in at around 0.7 kg (1.5 pounds), it is smaller than a chicken. It wouldn't even reach knee height on an average adult person," University of Minnesota palaeontologist Peter Makovicky, lead author of the research published on Wednesday in the journal Nature, said.

Alvarezsaurs were predominantly small. They had stubby but powerful forelimbs, long and gracile hindlimbs, and lightly built skulls. The researchers doubt that Alna had feathers. Despite some birdlike traits, alvarezsaurs were only distantly related to birds. They lived in a place called the Kokorkom, meaning ‘desert of the bones’ in the local language. "Although many of the inhabitants of the Kokorkom Desert were burrowers, Alnashetri was a lightweight animal that moved across the dunes on its slender legs. Its body resembled that of a rooster, but with a long tail," palaeontologist and study co-author Sebastián Apesteguía of the Felix de Azara Foundation and National Scientific and Technical Research Council in Argentina said.

He added, "Its arms were well developed, though not long enough to allow it to fly, and its tail, although not fully preserved, appears to have been as long (relative to body size) as that of any other typical carnivorous dinosaur."

Alna was about 28 inches (70 cm) in length, mostly the tail. It had a thin and fragile skeleton. The researchers were able to study its microscopic bone structures, as it was well preserved. "The level of histological detail is exquisite," Apesteguía said. It had numerous strong, pointy teeth like a small Velociraptor.
"When we think of landscapes with dinosaurs, or through the lens of film fiction, we picture vast expanses with enormous beasts roaming in the distance. But these landscapes are almost always devoid of a crucial component of the ecosystem: medium and small animals. The era in which Alnashetri, one of the smallest dinosaurs, lived coincided with what we often call the 'age of the southern giants'. Alnashetri shows us that it wasn't a time of giants, but rather a time of immense biodiversity," Apesteguía added.