In paleontology, how things die can matter just as much as how they lived. In a new study published last week, Smyth and colleagues investigate injuries in 150-million year old baby pterosaurs. The Pterosaurs were recovered from the famous Solnhofen limestone beds of Germany.
The paper finds that many of these juveniles met their end through accidents, not predators. Or at least that the fossil record is strongly biased in preserving such mishaps.
Could accidental death preserve better in Solnhofen than predation death?
The researchers examined a collection of Solnhofen pterosaur fossils, focusing on tiny, delicate skeletons of neonatal or very young individuals. They documented healed and unhealed trauma, such as fractures, dislocations, and other damage, especially in wing bones and joints. Injuries were caused by the storms that buried these and numerous other small pterosaurs.
“Catastrophic storms played a primary role, preferentially sampling small, immature pterosaurs“, the scientists wrote. “Storms caused these pterosaurs to drown and rapidly descend to the bottom of the water column. Where they were quickly buried in storm-generated sediments, preserving both their skeletal integrity and soft tissues.“
Scientists examined two tiny pterosaurs caught in a storm
Among these storm-sampled individuals, we document two highly immature specimens of Pterodactylus exhibiting similar oblique humeral fractures. These fractures are consistent with excessive wing loading during flight, providing compelling evidence of super-precocial flight capabilities in immature pterosaurs.
The frequency and pattern of these injuries led them to propose a bimodal taphonomic model. Small pterosaur remains are either lost entirely, or preserved only if they experienced fatal injuries that left them immobilised and thus more likely to be buried and fossilised.
What stands out is that many of the juveniles show damage in places one would expect from flight mishaps. This includes wing overextension, joint failure, or broken bones consistent with falls.
Some injuries appear to have happened at or near death, without signs of healing, supporting the idea that accidents were common causes of death in the young. The authors interpret this as a natural hazard of early flight, when wing membranes, bones, and muscles were still developing.
Examples of different taphonomic classes in Pterodactylus antiquus photographed under UV light
How preservation can influence sampling selection
Moreover, the team uses simulations and comparisons across size ranges to argue that selective sampling significantly skews our view of pterosaur juvenile mortality. Because the smallest, intact bodies are unlikely to survive fossilization unless aided by additional damage, the fossils we find disproportionately represent individuals that died catastrophically or with visible injury.
They further suggest that similar biases may affect other fossil assemblages of delicate animals, meaning paleontologists must consider that what we see is as much about how fossils were preserved as about biology itself. Catastrophic storm sampling explains marked juvenile preservation bias in Solnhofen.
Accidents likely played a significant role in the mortality of baby pterosaurs, and that our fossil record overrepresents those that died violently.