A new Cretaceous genus of xyelydid sawfly illuminating nygmata evolution in Hymenoptera.

Mei Wang,Chungkun Shih,Alexandr P Rasnitsyn,Dong Ren

doi:10.1186/1471-2148-14-131

Mei Wang, Chungkun Shih + Show 2 more

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https://doi.org/10.1186/1471-2148-14-131

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Abstract

BackgroundNygmata are prominent glandular structures on the wings of insects. They have been documented in some extant insects, including several families of Neuroptera and Mecoptera, the majority of Trichoptera, and a few of the hymenopteran Symphyta. However, because nygmata are rarely preserved in compression fossils, their early development and evolution are still enigmatic. For example, the only documented nygmata in the Hymenoptera are on the forewings of the Triassic xyelids Asioxyela paurura and Madygenius primitives.ResultsThis study describes and illustrates a new genus and species from the family Xyelydidae, Rectilyda sticta gen. et sp. nov., from the Early Cretaceous Yixian Formation of Duolun County, Inner Mongolia, China. This genus has 1-RS reclival and linearly aligned with 1-M, which is different from all other genera in the Xyelydidae. In addition, R. sticta gen. et sp. nov. has clearly preserved nygmata: four symmetrical nygmata on each forewing and two on each hind wing.ConclusionPrevious reports of nygmata on the forewings of Triassic xyelids and extant sawflies, together with this new fossil record of nygmata, provide rare insights into their developmental trends, as well as into the evolution of hymenopterans and insects in general.

Highlights

Nygmata are prominent glandular structures on the wings of insects
Xyelydidae is an extinct family known from compression fossils ranging in age from the later Early Jurassic to Early Cretaceous
Very few Xyelydidae fossils have been reported from China and only three species have been described from the Jiulongshan Formation of Daohugou, Inner Mongolia, China [8]: Ferganolyda Rasnitsyn, 1983, F. scylla Rasnitsyn, Zhang & Wang, 2006; F. charybdis Rasnitsyn, Zhang & Wang, 2006; and F. chungkuei Rasnitsyn, Zhang & Wang, 2006

Summary

Introduction

Nygmata are prominent glandular structures on the wings of insects. They have been documented in some extant insects, including several families of Neuroptera and Mecoptera, the majority of Trichoptera, and a few of the hymenopteran Symphyta. Xyelydidae is an extinct family known from compression fossils ranging in age from the later Early (or earlier Middle) Jurassic to Early Cretaceous. This family, considered to be the most primitive of the Pamphilioidea, plays an important role as an ancestral group in the evolution of the superfamily [1-4]. Novalyda cretacica is the only record reported from the Early Cretaceous, representing the youngest record of this family to date [10]

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