Would a single insect wing be able to change the history of the prehistoric past? In the Dinosaur Provincial Park, also known as a treasures trove of fossils of the mighty dinosaurs, a McGill University student crushed a rock slab and found something that had never been found in Canada before a dragonfly fossil from the time of the Mesozoic era. A species named Cordualadensa acorni, with a partial hind wing, was 75 million years old, from the Late Cretaceous Period.
This discovery is not only an extraordinary find due to its rarity, being the first of its kind discovered in Canada, but also an important find in terms of filling a gap within evolution. Cordualadensa acorni belongs to a now-extinct family of dragonflies known for their unique method of reproduction, known as Cavilabiata, which has been missing for 30 million years from the record of dragonflies. “We were taken by surprise as we were not expecting to find any insects there,” said study author André S. Mueller. The wing measured about as wide as a human hand.
The fossilization of this fossil alone is grounds for scientific celebration. While it was unusual for fossils of insects suspended in amber to be discovered in such formations, such as the case of a minute aphid, the Cordualadensa acorni fossilized as an impression fossil. It occurs when the specimen leaves an imprint in sediment, which hardens to become a fossil. The Vein patterns of the fossilized wing enabled scientists to determine its aerodynamic shape. The presence of elongated cells at the base of the wing suggests it was colony-born, characteristic of gliding specialist dragonflies. Such wing morphology is efficient during gliding, facilitating extensive searches of ponds and rivers.
Paleoentomologists used sophisticated imaging and morphological comparison to unlock the secrets of the fossil’s flight system. Dragonflies, like all insects, use their veins to provide the right balance between stiffness and flexibility to their wings. The hind-wing foot loop with a high density of square cells, which was unique among dragonflies, indicates an experimentation stage in the evolution of wing physiology that would provide additional lift to this apex predator to survive in a world where aerial quickness spelled the difference between life and death.
The ecological setting in which the discovery was made is just as interesting. During the late Campanian period in the Cretaceous era, the Dinosaur Park Formation had a landscape of interlinked river systems and ponds. Moreover, it was full of life hadrosaurs, ceratopsians, crocodilians, and turtles. There also exist now recognized insect top predators. Dragonflies are apex predators in their ecosystems as they prey on other flying insects. It would provide a food source for vertebrate predators and raptorial small dinosaurs. In Mueller’s view, the Cordualadensa acorni dragonflies would make a very appetizing raptor meal.
From an evolutionary biology context, this fossil provides a unique opportunity for calibrating the timescales on which dragonfly lineages existed. Such connections from earlier Cavilabiata species to living relatives would make it possible to understand the evolution of differences in the shape of wings, reproductive systems, and patterns of flight. Such observations support what was experienced in Mesozoic eras among flying species, in which cases predator-prey interactions, including the aerial arms race between birds and insects, stimulated advancements in morphologies.
It also widens the range known forpreserve methods for insects within the park. According to Alexandre Demers-Potvin, the discovery that impression fossils exist leads research down new avenues for searching for ancient insects. While the usual target is the dinosaur bonebeds, new research into old quarries for plants and sediments leads to finding a more diverse range of insects that exist much more extensively than was known before.
Artistic renditions, now based on the vein pattern found on the fossil, finally provide a visual glimpse into what a Canadian Cretaceous dragonfly may have looked like. As a specimen, Cordualadensa acorni would have made a swift and gliding predator of a quiet lake surface, and its appearance would have meant a complex, well-integrated system was in place. For people who love science and paleontology, a single wing is more than a curiosity, it is a connection to a world filled with insects and dinosaurs.
