Fatal Accidents Encountered by Juvenile Pterosaurs
- 演化之聲
- Mar 10
- 4 min read
Updated: Apr 11
Pterosaurs were a group of reptiles that lived during the Mesozoic Era. They exhibited a wide diversity of forms and species, and they were also the first vertebrates to evolve powered flight. Because of this, the study of pterosaur flight has long attracted the attention of scientists. Recent studies suggest that pterosaurs were capable of flight from the moment they hatched, although their body structures at that stage appear to have been relatively fragile. In 2025, a study describing juvenile pterosaur fossils from the Solnhofen Limestone provided a concrete example supporting this view.
Solnhofen Limestone
The Solnhofen Limestone (Solnhofener Plattenkalk) is a famous quarry deposit located in southern Germany. It was formed during the Late Jurassic, when the depositional environment consisted of a series of lagoons connected to shallow seas but relatively enclosed. These lagoons had high salinity and oxygen-poor bottom waters, conditions that prevented most scavengers from inhabiting them. Combined with very fine sediments and minimal disturbance, organisms that fell into these lagoons could avoid severe decomposition for a short time and were subsequently rapidly buried and mineralized. As a result, the area is renowned for producing exceptionally well-preserved fossils, including all known specimens of Archaeopteryx. In addition, fossils of fishes, ichthyosaurs, pterosaurs, invertebrates, and plants have also been discovered there.
Among these finds are more than 500 pterosaur fossils. Consequently, pterosaur specimens from the Solnhofen Limestone have long served as important material for scientists studying pterosaur anatomy, evolution, and flight. Notably, most of these pterosaur fossils are juvenile individuals, and these juvenile specimens are often more complete.
The Specimens
The study describes two juvenile specimens of Pterodactylus dating to approximately 153–148 million years ago. The two fossils are MBH 250624-07 from the Tithonian stage and SNSB-BSPG 1993 XVIII 1508 from the Kimmeridgian stage.
These two specimens are nearly identical in size. Their skulls measure only 2.5 to 3.3 cm in length—about one-eighth the size of the largest known individuals—and their wingspans range from about 18 to 22 cm. They are also the smallest among nearly 50 known specimens of Pterodactylus. Analysis of their ontogenetic stage indicates that they were newly hatched individuals only a few days to a few weeks old.
Both specimens show injuries to the humerus of the forelimb. In MBH 250624-07, the left humerus is fractured at the distal third, whereas in SNSB-BSPG 1993 XVIII 1508 the fracture occurs at the distal third of the right humerus. In both specimens, the fracture surfaces are very clean and show no signs of remodeling, and the bones display no additional deformation. When fractures occur after death due to external forces, bones are usually distorted. Therefore, these fractures likely occurred while the pterosaurs were still alive, and the individuals probably died shortly after the injuries.
Cause of Death
In modern animals such as bats and birds, fractures of the humerus in the forelimb occasionally occur during flight in severe weather conditions such as storms. This is because the humerus bears most of the mechanical stress exerted on the wings. When a storm strikes, the stress on the humerus can exceed its load-bearing capacity, causing it to break and leading to the animal's fall and death.
Based on this comparison, the researchers propose that these juvenile Pterodactylus encountered a powerful storm while flying over the Solnhofen lagoons. Because their wings were not strong enough to withstand the stress, their humeri fractured, causing them to fall onto the water surface. Storm-driven waves then forced large amounts of seawater into their lungs, reducing buoyancy and causing them to sink directly to the lagoon floor. There they were rapidly buried by sediment, eventually becoming fossils preserved to the present day.
Correspondence with the Depositional Pattern of the Solnhofen Limestone
This process may represent the primary source of many pterosaur fossils found in the area. It could explain why most of these pterosaur fossils are relatively complete juvenile individuals, while adult specimens are rarer and often fragmentary.
Juvenile individuals may have fallen directly to the lagoon floor due to sudden disasters, whereas adult deaths likely resulted from other causes. If adult bodies fell onto the water surface, their bones—containing many hollow spaces—would give them relatively high buoyancy, allowing them to float for a long time. Only after decomposition and disarticulation would parts of the skeleton sink to the lagoon floor and eventually become fossilized.
However, this hypothesis still has limitations. Another common pterosaur from the locality, Rhamphorhynchus, is typically preserved in partially disarticulated condition regardless of body size, suggesting that it was less affected by climatic disasters.
This study is important for understanding the ecology and evolution of pterosaurs, not only in terms of explaining the flight capabilities of juvenile individuals. It also highlights the presence of strong taphonomic bias in the formation of pterosaur fossils. Similar biases may also occur in other regions, suggesting that the pterosaur fossils we have discovered may not accurately reflect the true size range of adult pterosaurs at the time.
In short, fossil records must be interpreted with caution, especially when dealing with fossil assemblages formed through different preservation pathways. Otherwise, taphonomic bias may be mistakenly interpreted as an evolutionary trend.
（Author: Bai Leng）
Reference：
Smyth, R. S. H., Belben, R., Thomas, R., Unwin, D. M. (2025). Fatal accidents in neonatal pterosaurs and selective sampling in the Solnhofen fossil assemblage. Current Biology.
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