Have you ever considered the life of a paleoentomologist? Studying fossil insects is a great gig, but it does present its share of difficulties.

Foremost among those difficulties: finding ancient insects is not nearly as easy as unearthing dinosaurs. Their small size and lack of hard bone make them ill suited to preservation. Dating back 125 million years, insects can be found encased in amber, but before that, there are far fewer to be found.

When scientists do stumble upon insect fossils outside of amber, there's often not much to work with, maybe just a thorax, a head embedded into rock, or rarely, a wing. The incomplete remains leave much open to interpretation.

Such was the case back in 2004, when Michael Engel and David Grimaldi reported in Nature the discovery of Rhyniognatha hirsti, the world's oldest insect. Found in a layer of chert from Aberdeen, Scotland dating to around 400 million years old, the fossil consisted only of a well-preserved head, but according to the duo, the fossil's mandible structure clearly placed the centimeter-sized critter in the category of winged insects.

A recent study published to PeerJ challenges this assertion.

Researchers Carolin Haug and Joachim T. Haug, based out of Ludwig-Maximilians University in Munich, re-examined the fossil with the latest microscope technology and sophisticated imaging techniques. The advancements granted a new perspective with finer detail.

A sharper view of Rhyniognatha hirsti's mandibles did not reveal the uniquely insect structures that Engel and Grimaldi observed. On the other hand, when the Haugs zoomed in on the critter's head and other mouthparts, they found them to be more like those of ancient myriapod centipedes.

Like insects, centipedes and millipedes are arthropods. They date back as many as 430 million years. In fact, the oldest-known animal to live on land is a millipede.

If the Haugs' interpretation holds up, the title of oldest insect will fall to a wingless insect dating back 379 million years.

"In summary we cannot fully exclude an insect affinity of R. hirsti, as the specimen is very incomplete and the supposed key characters of the mandible are at best difficult to observe," the Haugs write. "Yet given the observable characters of the structures surrounding the mandible, a myriapod interpretation is in our view better supported."

Source: Haug and Haug (2017), The presumed oldest flying insect: more likely a myriapod? PeerJ 5:e3402; DOI 10.7717/peerj.3402