Fossils of at least three baby duck-billed dinosaurs found in the area in Mongolia well-known among experts as the "Dragon's Tomb" were recently examined by a group of paleontologists. These tiny bones will help experts fully understand the physical growth and development that a baby Saurolophus had undergone to become an adult.

Saurolophus, meaning "lizard crest", are part of the genus saurolophinae, and they are under the group of hadrosaurids which used to reside in Asia and North America. These herbivorous duck-billed dinosaurs grow up to 40-foot-long and are recognizable by the crest that protrudes backward off the top part of their skull like a rammed spike.

In a study published in the journal PLOS ONE, scientists from the Royal Belgian Institute of Natural Sciences and Ghent University inspected a piece of rock, almost 1-foot-long, which contained the fossils of three baby duck-billed dinosaurs. At first, they had no clue what the fossils were, but after careful study, they discovered that these fossils were the youngest Saurolophus angustirostris ever described.

Leonard Dewaele, lead researcher of the study, explained that the fossils had very small snouts compared to adult hadrosaurids, and that they probably haven't developed the crests on their head yet. The baby duck-billed dinosaurs also had wider eyes than the adult Saurolophus did.

"This had been anticipated by other scientists," Dewaele said. Paleontologists are still certain of the fossils' identity despite the differences in the overall skull shape, he said.

The scientists compared the remains of these baby duck-billed dinosaurs to the other known remains of Saurolophus. However, the remains were not scientifically-collected, and had originally been poached from the Dragon's Tomb and were sold to a private collector. The condition posed a challenge for scientists.

Dewaele said that most poachers don't record information about the fossils such as in what layer of rock it was found or which side of a hill, so the exact location where these fossils were found is unknown. Dewaele said that because of this, they couldn't say a lot about how these hadrosaurids had died.

Researchers said that the remains of the baby duck-billed dinosaurs most likely originated from a nest in a riverbank that was washed away and covered in sand.

"The sandy sediments in which the babies were buried lead us to assume that the nest was located on a river bank, or point bar, and got buried by sediment when water levels rose," Dewaele added.

Meanwhile, the fossils of the baby duck-billed dinosaurs are being displayed at the Institute of Paleontology and Geology at the Mongolian Academy of Sciences in Ulaanbaatar.