One hundred million years ago, the number and scale of gymnosperms were much higher than angiosperms. Many insect groups were pollinating gymnosperms during this period, Mesopsychoidea was one of them. Mesopsychoid scorpionflies (Mecoptera) are peculiar, conspicuous Mesozoic insects with distinctively elongate proboscides and were presumably a critical group of pollinators, providing insights into the nature of plant-pollinator interactions before the rise of angiosperms.
Aneuretopsychidae from Late Cretaceous Burmese amber（Image by NIGPAS）
Recently, an international research group led by Prof. WANG Bo, which is supported by the "Construction and Application of Paleontology and Paleoenvironment Integrated Database" project within the special "Biodiversity and Ecological Security" project, did a systematic research on three-dimensionally preserved insect fossils in Myanmar amber (100 million years ago). The result reveals the origin of scorpionflies’ long mouthpart. This discovery was reported in Science Advances on March 4.
Figure 1. Proboscis of Aneuretopsychidaeconsisting of one pair of galeaeand one unpairedcentral hypopharynx, the hypopharynxwitha food channel. During feeding,the galeae cometogether temporarily and enclose the hypopharynx,thus forming a functional proboscis.
Mesopsychoid scorpionflies were widely distributed in Chinese Jurassic Yanliao biota, Cretaceous Jehol biota and Myanmar amber biota. Among Mesopsychoidea, Aneuretopsychidae was the first known group of mecopteran insects with a long siphonate proboscis, and has recently been argued to be an extinct sister group of fleas. However, the structures of the new three-dimensionally preserved fossils suggest that neither Aneuretopsychidae nor Mesopsychoidea is a sister group to Siphonaptera. In the Burmese amber forest, at least five families of long-proboscid insects have been discovered, further revealing the variety and complexity of mid-Cretaceous pollinating insects.
Figure 2. Ecological reconstruction of Mesozoic Aneuretopsychidae (Image by Dinghua Yang).
The phylogenetic results based on 38 taxa and 54 discrete characters support the monophyly of Mesopsychoidea, and reveal that the long siphonate proboscis may have originated in the Late Permian. This discovery provides new evidence for us to understand the early evolution of pollinators and blood-sucking insects.
This research was supported by the Big Earth Data Science Engineering Project in Strategic Priority Research Program of the Chinese Academy of Sciences (XDA19050101, first annotation).