Fossil of oldest flying insect ... or not?

The fossil that was thought to be the oldest flying insect (and has been used to interpret and date the origins of flight) may not even be an insect at all! In an interesting turn, a recent publication asserts that the fossil Rhyniognatha hirsti is not the mandible of a flying insect, but is in fact a fragment of a myriapod: specifically, an immature centipede. 

In an article published May 30, 2017 in the journal PeerJ, Haug & Haug present evidence that the Devonian fossil R. hirsti (>400 My old) is not a flying insect... or an insect... or even closely related to insects... It is a centipede. The fossil is fragmentary, mainly mandibles and some other rather ambiguous parts connected to it. However, the shape of these mandibles was similar to those of dragonflies and neopterans, which prompted Engel and Grimaldi (2004) to tentatively assign it as a fragment of a flying insect. Now, Haug & Haug use 3D imaging and show remains of what they hypothesize is a myriapod-like head capsule. Also, the putative apodemes are deemed to be glands of ectodermal origin. 

Engel & Grimaldi 2004

Haug & Haug 2017

The potential misplacement of this fossil has some pretty big implications. The next oldest fossils of flying insects are from the late Carboniferous -- about 80 My after this fossil! That is a huge time difference and affects our interpretation of the origins and evolution of insect flight. Also, many molecular phylogenetic studies have used this as a fossil calibration. For instance, the hexapod dated phylogeny of Misof et al. 2014 incorporated this fossil as a stem calibration for Dicondylia (winged insects + their sister group Diplura), with an age of 411.5 Mya. The reinterpretation of this fossil, if it is accepted, will have wide effects on future work on insect evolution and dating.

As of September 23, there were ~1500 views of the article and no papers citing it, so we'll have to stay tuned for a response!

references:
Engel, M.S. & Grimaldi, D. (2004) New light shed on the oldest insect. Nature  427, 627-630.
​Haug, C. & Haug, J.T. (2017) The presumed oldest flying insect: more likely a myriapod? PeerJ, 5, e3402.
Misof, B., Liu, S., et al. (2014) Phylogenomics resolves the timing and pattern of insect evolution. Science, 346, 763-767.