In the quarries of Bavaria, fossil slabs hold a record of sudden and violent events that took place 150 million years ago. Among them are two of the smallest pterosaurs ever found, preserved almost completely intact, their skeletons so fragile that the chance of survival in stone should have been nearly zero. They are hatchlings of Pterodactylus antiquus, a species already famous as the first pterosaur described by science. What makes these two stand out is not only their size but the condition of their bones. Each shows the same cleanly fractured humerus, broken in a way that reveals how they died. The study describing them shows that the cause was not disease, predation, or postmortem damage, but storms powerful enough to snap their wings mid-flight and drive them into the water.
The fossils, now kept in German collections, measure less than twenty centimeters in wingspan. Their skulls are only a few centimeters long, their forelimbs thinner than a matchstick. Examination under ultraviolet light revealed fractures in the upper wing bone, angled and sharp, with no sign of healing. The pattern is consistent with torsional stress, the kind of break that happens when a wing is twisted violently while airborne. Modern birds and bats sometimes suffer similar injuries during storms, and in both cases the bone that fails most often is the humerus, because it bears the greatest load as the wing attaches to the body. The fact that these pterosaurs show exactly this type of fracture confirms that they were flying when the storm overtook them.
The Solnhofen deposits where they were found are already known for exceptional preservation. The region in the Late Jurassic was a series of shallow carbonate basins fringed by reefs and dotted with small islands. Fine lime mud accumulated in layers, sometimes during quiet periods, sometimes during storms. When storms swept across the archipelago, they stirred up enormous flows of suspended carbonate mud that spread across the seafloor in thin sheets. These deposits buried plants, insects, fish, reptiles, and even the feathers of Archaeopteryx. For flying animals, the same storms that caused their deaths also provided the only conditions that could preserve them.
The researchers reconstructed the sequence of events. Juveniles of Pterodactylus were aloft during a storm. A sudden gust or wind shear twisted the wing and snapped the humerus. Flight became impossible, and the hatchlings fell into the lagoon. Once in the water, they inhaled fluid, which reduced buoyancy and made their bodies sink. At the seafloor, storm-driven carbonate mud quickly buried them before decay or scavenging could destroy the remains. The result was two neonates preserved with almost complete skeletons, their broken bones recording the exact cause of death.
This case study provides a direct explanation for one of the longest-standing puzzles of Solnhofen: why the fossil beds are dominated by juveniles. Out of more than forty examined specimens of Pterodactylus, the majority are immature individuals preserved in full articulation. Adults appear only rarely, and when they do they are incomplete, often reduced to fragments of skull or jaw. Smyth and his team compared these patterns across other Solnhofen pterosaurs. The same trend emerged among ctenochasmatoids, close relatives of Pterodactylus. Juveniles were preserved whole, while larger animals broke apart before burial. The only major exception was Rhamphorhynchus muensteri, which shows a different profile, more consistent with accumulation over time from animals that actually lived in the lagoons rather than being swept in by storms.
The model that explains these differences is called the catastrophic and attritional taphonomic pathway, or CATT. In catastrophic events, small and inexperienced fliers were caught in storms, drowned, and entombed quickly, producing complete articulated fossils. In attritional scenarios, larger animals that died outside of storms floated, decayed, and sank only after days, resulting in fragmentary remains. In Solnhofen, catastrophic preservation was the dominant process for pterodactyloids, while attritional preservation shaped the record of Rhamphorhynchus. The bias is clear. The seeming abundance of juveniles is not a reflection of the true population structure but a result of how storms decided which animals entered the rock record.
The two neonates, referred to as MBH 250624-07 and SNSB-BSPG 1993 XVIII 1508, were confirmed as hatchlings through osteological study. Their bones showed incomplete ossification, unfused joints, and proportions typical of the earliest growth stage. The skulls were only about twenty-five to thirty millimeters long, and the humeri about eleven millimeters. Yet their wing membranes and skeletal proportions matched those of larger juveniles, consistent with the ability to fly immediately after hatching. Debate over pterosaur development has gone on for decades, but the broken wings of these neonates serve as direct evidence that they were already airborne. Animals that never flew could not have sustained such fractures.
The conditions that led to their burial are well understood from sedimentology. Solnhofen limestones alternate between hard thin beds rich in calcium carbonate, the Flinze, and softer laminated beds with higher clay and organic content, the Fäulen. Flinze represent rapid storm-driven sedimentation, while Fäulen represent slower deposition during calm intervals. Most of the articulated pterosaur fossils, including the neonates, come from the base of Flinze beds. This confirms that they were buried by storm muds, not by ordinary background sedimentation.
The same forces affected many other animals. The majority of tetrapod fossils from Solnhofen are volant species. Pterosaurs make up more than sixty percent of recorded specimens. Birds and insects are also common. By contrast, marine reptiles and terrestrial animals are much less abundant. Storms acted directly on flying creatures, pulling them from the sky, while also mixing surface waters with deeper hypersaline layers that suffocated fish and invertebrates. For those that sank quickly, the oxygen-poor bottom waters suppressed decay and scavenging, creating ideal conditions for fossilization.
The neonatal specimens also help refine how pterosaur mortality in storms compared to modern analogs. Mass die-offs of birds during hurricanes often involve hundreds of thousands of individuals. Most victims show no skeletal trauma, dying instead from exhaustion or drowning. A small percentage display wing fractures, often caused by turbulent winds or wave action. The Solnhofen neonates match this rare pattern. They are not the rule but the exceptions that show how storm forces could physically break wings. Most juvenile pterosaurs preserved in the beds probably died from drowning or wing membrane damage that left no skeletal trace. The fractured bones of MBH 250624-07 and SNSB-BSPG 1993 XVIII 1508 provide the clearest case where the chain of events can be reconstructed from flight to fracture to burial.
The pattern of juvenile dominance has shaped paleontology for more than a century. For decades, scientists described Solnhofen as a community of small pterosaurs. Textbooks illustrated it as a landscape where tiny fliers outnumbered larger species. The new study shows that this was a distortion. The apparent abundance of small forms was created by selective preservation. Larger adults existed but rarely entered the fossil record intact. Other Upper Jurassic deposits elsewhere confirm the presence of large pterosaurs with wingspans exceeding two meters. Solnhofen simply failed to record them.
The broader lesson is that the fossil record cannot be read as a simple census of ancient life. It is a filtered archive shaped by environmental accidents. In Solnhofen, storms preserved the small and erased the large. In other deposits, the reverse is true. The Lower Cretaceous Crato Formation of Brazil, for example, is dominated by adults, with juveniles rare. Each site reflects a different balance of processes. Without recognizing these filters, interpretations of growth, ecology, or diversity risk being skewed.
What makes “Lucky I” and “Lucky II,” as the juveniles have been nicknamed, so valuable is the precision of their story. Most fossils leave little evidence of cause of death. Here, the clean fractures and perfect articulation capture the moment of accident. These specimens do not just confirm that hatchling pterosaurs could fly. They show exactly how dangerous that flight was when storms swept across Jurassic lagoons.
The Solnhofen limestones remain one of the most iconic fossil sites in the world, but the new work demonstrates that its record is shaped by catastrophe rather than calm accumulation. The baby pterosaurs of Bavaria did not die quietly. They were torn from the air by sudden gusts, drowned in turbulent waters, and entombed in storm-driven muds. The fact that we can hold their skeletons today is the result of the same violence that ended their lives. The slabs of limestone may look serene, but every perfect skeleton inside is a record of disaster.
Source:
Smyth, R.S.H., Unwin, D.M., & Martill, D.M. (2025). Storm-induced mortality and preservation bias in Late Jurassic Pterodactylus hatchlings from the Solnhofen limestones of Bavaria, Germany. Current Biology, 35(19), 4303–4312. https://doi.org/10.1016/j.cub.2025.07.058
