The skunk-like mammal inhabited southern Patagonia alongside dinosaurs.
“A global catastrophe involving a mass extinction produces a different world.”
The researchers said Ninjatitan demonstrated that the titanosaurs as a group first appeared longer ago than previously known.
The bones indicated that these were bigger than any other known dinosaur babies - three feet (1 meter) long, or the size of a medium dog.
The specimen is unusual because it is so complete: around 70% of the bones are present, and they were found aligned with each other, making it easier to reconnect them during the restoration process.
"These animals were quickly covered by fine sediment while they were still alive or just after their death," said paleontologist Pascal Godefroit of the Royal Belgian Institute of Natural Sciences.
“He showed it to scientists at the time who unfortunately misidentified it as a triceratops,” James Hyslop, Christie's head of Science and Natural History, told Reuters.
One of the fossils clearly featured the marks of the feathers on the wings.
"Evolution of gigantism from tiny ancestors is not uncommon in the fossil record."
Called the Wulong bohaiensis, which translates to "dancing dragon," this newly discovered feathered dinosaur once lived in the Jehol Province of northeastern China 120 million years ago