The presumed oldest flying insect: more likely a myriapod?

Abstract

The early fossil record of insects is scarce, with only few finds in the Devonian. All these finds appear problematic and controversial, partly due to incomplete preservation and challenging interpretation of many structures. We provide details of one of these important forms, Rhyniognatha hirsti from the famous Rhynie Chert Lagerstätte with up-to-date 3D imaging techniques. The fossil has been interpreted as the remains of one of the earliest flying insects. The specimen mainly preserves the remains of the head. The structures of the mandibles have been used as a main argument for an interpretation as an insect, but these are in fact less easy to interpret. New observed structures include the remains of a head capsule and an additional pair of mouth parts. Structures formerly suggested to represent remains of the head capsule or apodemes are more likely to be representing glands of ectodermal origin. The newly observed structures do not support an interpretation as an insect. Instead they make the interpretation as a myriapod more likely, possibly as a centipede. Centipede remains from the Rhynie Chert are known from scutigeromorphs. We therefore point out that R. hirsti could be interpreted as an early centipede.

PhanerozoicpO2and the early evolution of terrestrial animals

“…This perspective, along with a recent reexamination of the oldest purported fossil insect [2], has the potential to resolve previous conflicts between the insect fossil record and molecular estimates of the origin of winged insects. Molecular methods have been used to estimate that winged insects originated slightly over 400 Ma [38], an age that corresponds to the fossil mandible that had been interpreted to represent a winged insect [39], but which has now been reinterpreted as representing a myriapod [2]. Though the interpretation presented here contradicts molecular estimates [38], it is not contradicted by any direct evidence in that there are no fossil wings known from the Hexapod Gap or from any preceding intervals.…”

“…Various Devonian fossils have been attributed to the Insecta; however, all but one of these have been subsequently challenged [1,2]. This depauperate Devonian fossil record of insects, which does not contain any direct evidence of wings, is followed by a 62-million-year gap that is completely devoid of insect material.…”

Explaining global insect species richness: lessons from a decade of macroevolutionary entomology

“…Phylogenomic and other evidence tentatively suggests Remipedia as the sister group to hexapods (von Reumont et al., ; Legg et al., ), though there are other posited sister groups (Meusemann et al., ; Regier et al., ), and the date of the split from other Pancrustacea (i.e., the stem age) must be held in doubt until the sister‐group relationship is more certain (Edgecombe, ). Doubt has also been cast on some of the deep hexapod date inferences since a widely used calibration fossil – Rhyniognatha hirsti Tillyard, previously interpreted as a basal pterygote – has recently been tentatively reinterpreted as a centipede (Haug & Haug, ).…”

“…A major use of fossil insect data is also now to time‐calibrate molecular phylogenies (Parham et al., ; Wolfe et al., ), something that had barely been attempted 10 years ago. The need to do this accurately has put a premium on accurate fossil identification and new technologies have begun to impact this (Perreau & Tafforeau, ; Haug & Haug, ).…”

Fossil Insects, Arthropods and Amber: Preface

“…Some of the delegates from land-locked countries confessed that this was the first time they had visited the seaside. The next site was Rhynie, famous for the Rhynie chert, the source of the earliest-known insects and springtails in the world (Ross & York 2004;Fayers & Trewin 2005); however, one of them, Rhyniognatha hirsti, has recently been reinterpreted as a possible centipede (Haug & Haug, 2017). Unfortunately, all that can be seen is a grassy field (the chert lies about 1m below the soil), but pieces of Rhynie chert had been brought along so that the delegates had something to take away with them (Fig.…”