For 20 Years, Scientists Thought These Tiny Fossils Were Miniature Dinosaurs. They Were Completely Wrong

For over two decades, a group of unusually small dinosaur fossils had experts scratching their heads. Once thought to belong to a miniature species, new research now confirms they are actually baby ankylosaurs, some possibly just hatched.

These fossils, first discovered in 2001, were initially puzzling due to their size, with just 40 centimeters long. While adult ankylosaurs can grow over three meters, these tiny specimens seemed like an anomaly. Some scientists even wondered if these fossils belonged to a rare miniature version or a species that spent part of its life in water. However, after studying the bones closely, researchers now know the truth.

The Dinosaur That Confused Scientists for Decades

The fossils belong to a species called Liaoningosaurus paradoxus, and this species has caused confusion for years. All known fossils of Liaoningosaurus are unusually small, which led some to think they were a separate miniature species.

These fossils were found in northeastern China, an area famous for its well-preserved Cretaceous-period remains. The study published inJournal of Vertebrate Paleontology now say these fossils are actually of young ankylosaurs, not miniature adults as once thought.

“Liaoningosaurus has caused a lot of debate because there is a lot we don’t know about this species and we haven’t managed to identify an adult,” said Professor Paul Barrett, the co-author of the study. “But our research confirms that these are baby dinosaurs rather than small adults. Fossils of young ankylosaurs are rare, so there is a lot that these remains can tell us about the early development of armored dinosaurs.”

The key to solving the puzzle was examining the bone structure of two different specimens; the smallest and one of the largest found. The absence of growth lines in the bones showed that these dinosaurs were less than a year old, with one fossil even showing signs of having just hatched.

“The smaller fossil showed characteristics that we can see in other newborn dinosaurs, such as the presence of a hatching line,” explained Professor Barrett in a statement from the Natural History Museum.

Did Baby Ankylosaurs Have Armor?

Understanding how this kind of dinosaur grew is a big deal for paleontologists, especially since juvenile ankylosaur fossils are so rare. Most juvenile ankylosaurs found so far don’t have the armor that adult are known for, leading to the belief that armor developed later in life.

“As we have found so few fossil babies, Liaoningosaurus is really the only good window we have into what ankylosaurs are like just after they hatch.” Professor Barrett added that: “The Liaoningosaurus fossils had already developed some armor. Now that we know they are babies and not miniature adults, we can say that these kinds of features came in quite early during the animal’s growth.”

To gain a deeper understanding, researchers are hoping to find an adult Liaoningosaurus fossil to compare the differences in how armor developed from youth to adulthood.

The Fossil Hotspot of Liaoning Province

The Liaoningosaurus fossils were discovered in Liaoning Province, China, a region known for its incredible fossil preservation. This area, shaped by frequent volcanic activity, has yielded many well-preserved specimens from the Cretaceous Period.

The ash from volcanic eruptions helped to preserve even the smallest details of ancient creatures, including soft tissue and fine features in bones. Liaoning has been a goldmine for paleontologists, offering fossils of famous dinosaurs like Microraptor and Sinornithosaurus.

With more fossils likely to be found, scientists are excited to keep learning about how ankylosaurs developed, especially when it comes to their distinctive armor.

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