Rosa Rubicondior: How Science Works - 'Miniature Dinosaur' Fossils Identified As Baby Ankylosaurs

Numerous fossils of Liaoningosaurus paradoxus have so far been discovered.

First armoured dinosaur hatchling discovered in China | Natural History Museum.

Unlike fundamentalist belief systems such as creationism, in which facts are either forced to fit sacred dogma or dismissed with ad hoc excuses, science readily incorporates new information and adjusts its understanding accordingly. That process was neatly illustrated by the paper published in September 2025 in the Journal of Vertebrate Paleontology, which reported a reassessment of fossils from China first described in 2001.

These fossils were initially classified as belonging to a miniature armoured ankylosaur named Liaoningosaurus paradoxus. Since then, more specimens have been found, but none exceeds 40 cm in length, which is strikingly odd for ankylosaurs, a group whose members were typically around 3 metres or more long.

Where creationism would brush aside anomalies like this with a shrug and a retreat into theology, muttering about ‘mysterious ways’ or ‘tests’, science treats them as clues that something is not yet fully understood. The existence of these fossils pointed to something that had yet to be properly integrated into our knowledge of ankylosaurs, requiring scientists to refine either their understanding of the animals themselves or of the fossils attributed to them.

Now, a re-examination by a team of four palaeontologists, including Professor Paul Barrett of the Natural History Museum, London, has shown that these specimens were not miniature adults at all, but baby ankylosaurs. That makes them the youngest ankylosaurs yet discovered. There is still much to learn, because no adult Liaoningosaurus paradoxus has yet been found. Even so, these hatchling fossils add significantly to our understanding of how ankylosaurs developed.

Ankylosaurs - the armoured dinosaurs.

Euoplocephalus, and armour-plated ankylosaur from Alberta, Canada

© The Trustees of the Natural History Museum, London.

Ankylosaurs were a group of heavily armoured, plant-eating dinosaurs that lived from the Middle Jurassic until the end of the Cretaceous, disappearing along with the rest of the non-avian dinosaurs 66 million years ago. They were four-legged, low-slung animals with broad bodies, short powerful limbs and skulls adapted for cropping low vegetation. Their most distinctive feature was their armour: a covering of bony plates and nodules, called osteoderms, embedded in the skin and often forming spikes or protective bands along the body.

The group is usually divided into two main branches. The ankylosaurids included the classic club-tailed forms such as Ankylosaurus, whose massive tail club may have been used as a defensive weapon against predators or in contests with rivals. The nodosaurids lacked a tail club but were still heavily armoured, often with prominent shoulder spikes. Together, these animals were among the best-defended herbivores of the Mesozoic.

Ankylosaurs are often described as the dinosaur equivalent of tanks, but they were not simply slow-moving fortresses. Their armour was part of a sophisticated defensive strategy that probably also included a low centre of gravity, strong limb support and, in some species, active use of the tail. Their fossils have been found in Asia, Europe and North America, showing that they were a successful and widespread group for tens of millions of years.

What makes the new Chinese fossils especially important is that ankylosaur hatchlings and juveniles are extremely rare. Most of what we know about ankylosaurs comes from larger, more mature individuals, so baby specimens can reveal how the armour, skull and body proportions changed as they grew. That is why fossils such as those assigned to Liaoningosaurus paradoxus are so valuable: they help fill in the life history of one of the most distinctive dinosaur groups ever to evolve.

The reasoning behind the team’s conclusion that these were baby ankylosaurs, not miniature adults, is set out in a Natural History Museum science news article by Emma Caton.

First armoured dinosaur hatchling discovered in China
The mystery surrounding dozens of small dinosaur fossils has finally been solved.
Remains previously thought to belong to miniature armoured dinosaurs are actually baby ankylosaurs, offering scientists new insight into how these remarkable dinosaurs developed.

Paradox in name and in nature, fossils belonging to a dinosaur called Liaoningosaurus paradoxus have puzzled scientists for more than two decades.

First described in 2001, the dinosaur was first identified as a type of armoured dinosaur known as an ankylosaur.

Since then, multiple Liaoningosaurus fossils have been discovered, but strangely none are more than 40 centimetres long. This is remarkably small compared to other fully grown ankylosaurs, which normally reach lengths of three metres or more.

As no remains belonging to a larger individuals have been discovered, some scientists considered the possibility that the dinosaur could be the first example of a miniature ankylosaur. Others have even hypothesised that they were semi-aquatic.

But new research published in the Journal of Vertebrate Paleontology has overturned these theories. Instead, the tiny reptiles are probably baby ankylosaurs. One of the fossils even showed signs that it had recently hatched, which would make this the youngest ankylosaur ever discovered.
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. 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 armoured dinosaurs.

Professor Paul Barrett, co-author.
Fossil Reptiles, Amphibians and Birds Section
Natural History Museum
London, U.K.,

Carefully analysing the bone structure of the fossils, such as this leg bone, can tell us how old the ankylosaurs were when they died.

© Zheng et al. 2025

How do we know the fossils are young ankylosaurs?

Because the remains of Liaoningosaurus were all similar in size, it was hard to rule out the possibility that they were miniature adult ankylosaurs based on their body size alone. To get an idea of how old these dinosaurs were at the time of death, researchers had to look in detail at their bone structure.

Bone tissue contains growth lines that can be read in a similar way to growth rings in trees, with each line representing a year in the animal’s life. The number of lines and the distance of the gap between them can tell us how old an individual was and how fast it was growing.

Researchers took samples from the bones of two Liaoningosaurus fossils to test this. One of them was the largest specimen discovered so far, while the other was one of the smallest.

The team found no growth lines in either individual, suggesting that both were less than a year old. The bone microstructure of the smaller specimen was also similar to that of other dinosaurs in an early stage of development.

The smaller fossil showed characteristics that we can see in other newborn dinosaurs, such as the presence of a hatching line. This is a small, ring-like feature in the bone that is laid down at the time the animal hatches from the egg. So, we can say that this individual had very recently hatched at the time of its death, which would make it the first hatchling ankylosaur we’ve ever discovered.

Professor Paul Barrett.

The Liaoning Province in China is well-known for the number of exceptionally well-preserved fossil from the Cretaceous Period that have been found here.
© ZCOOL HelloRF/Shutterstock

What do we know about these dinosaurs?

All Liaoningosaurus specimens come from Liaoning Province in northeastern China. Many remarkable fossils from the Cretaceous Period, between 145 and 66 million years ago, have been unearthed in this area, including feathered dinosaurs such as Microraptor and Sinornithosaurus.

Like their feathery contemporaries, the Liaoningosaurus fossils were preserved after the remains of the animals sunk to the bottom of a shallow lake. With lots of active volcanoes in the region, the lake beds were exceptionally well preserved under the ashfall. This has given us an incredibly detailed snapshot of life during this time.

But while the lack of adult Liaoningosaurus specimens means we know very little about what these dinosaurs were like in later life, we can still learn a lot about how ankylosaurs in general developed.

Fossils of young ankylosaurs are rare, and those that do exist don’t have the armour that is a prominent feature in the adults. This has led some researchers to suggest that armour is not something they are born with but develops as they age. Liaoningosaurus, however, shows that they had some armour from early in their 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. The Liaoningosaurus fossils had already developed some armour. 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. But what would give us even bigger insights is if we also found an adult. Then we can find the differences between the adults and babies of the same species and see how these features are developing.

Professor Paul Barrett.

Publication:
Zheng, W., Zhao, Q., Barrett, P. M., & Xu, X. (2025).
Bone histology of Liaoningosaurus paradoxus (Ornithischia: Ankylosauria) from the Lower Cretaceous of Liaoning Province, China. Journal of Vertebrate Paleontology, 45(4). https://doi.org/10.1080/02724634.2025.2566325

ABSTRACT The ankylosaurian dinosaur Liaoningosaurus paradoxus, from the Lower Cretaceous of Liaoning Province, China, is represented by numerous specimens identified as juvenile individuals based on their body size but without bone histological evidence. Here, we present the first osteohistological study of this species based on two referred specimens, ELDM V1121 and IVPP V 20798, the latter being the largest known L. paradoxus specimen. The femoral lengths of the two specimens are 31.5 mm and 56.5 mm, respectively, and they are about 10% and 100% longer than the holotype (28.5 mm). We sampled axial (dorsal ribs), appendicular (humerus, radius, ulna, femur, and fibula) and dermal (cervical half-ring osteoderm) bones. All thin-sections of the L. paradoxus specimens in our study lack lines of arrested growth, an external fundamental system, and secondary osteons. This indicates that both specimens were less than one year old at the time of death. Specimen ELDM V1121 exhibits highly vascularized canals, primarily arranged longitudinally and surrounded by randomly distributed osteocyte lacunae. Additionally, the presence of a hatching line indicates that ELDM V1121 was a hatchling at the time of death. Liaoningosaurus is currently the only known definitive hatchling ankylosaurian dinosaur specimen globally. Histological analysis of a cervical half-ring, the co-ossified osteoderms situated dorsolaterally on the neck, of IVPP V 20798, reveals a very thin compact cortex enclosing cancellous bone. This is similar to those of ankylosaurids and Scelidosaurus but different from the osteoderm structure typical of nodosaurids.

Zheng, W., Zhao, Q., Barrett, P. M., & Xu, X. (2025).
Bone histology of Liaoningosaurus paradoxus (Ornithischia: Ankylosauria) from the Lower Cretaceous of Liaoning Province, China. Journal of Vertebrate Paleontology, 45(4). https://doi.org/10.1080/02724634.2025.2566325

© 2025 Informa UK Limited (Tayor & Francis).
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.

What makes this such a neat example of the scientific method in action is that the original interpretation was not treated as sacred and untouchable, but as a provisional conclusion to be tested against new evidence. When additional specimens were found and the old assumptions no longer fitted the growing body of data, palaeontologists did what science requires: they re-examined the fossils, compared alternative explanations, and changed their minds. That is not a weakness in science but one of its great strengths. Science moves closer to the truth precisely because it is willing to discard ideas that no longer survive contact with the evidence.

Creationism, by contrast, works the other way round. Its conclusions are fixed in advance by religious dogma, and the evidence is then forced to fit, ignored, or explained away with ad hoc excuses whenever it proves inconvenient. Where science welcomes correction, creationism fears it; where science follows the evidence, creationism demands obedience to mythology. The reassessment of Liaoningosaurus paradoxus is therefore about much more than one small fossil animal from Cretaceous China. It is another reminder that reliable knowledge comes from questioning, testing and revising, not from clinging to ancient stories and refusing to let facts get in the way.

And, to add insult to injury for creationists, these baby dinosaurs were from about 150 million years before 'Creation Week'.

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