Elsevier

Palaeoworld

Volume 32, Issue 4, December 2023, Pages 709-715
Palaeoworld

The first fossil Parascleroderma (Hymenoptera: Bethylidae): a new species in mid-Miocene Zhangpu amber

https://doi.org/10.1016/j.palwor.2022.01.009Get rights and content

Abstract

The recently discovered amber biota from Zhangpu, China, offers a unique window into the tropical ecosystem of an Asian rainforest during the Mid-Miocene Climatic Optimum (MMCO). Here, the first flat wasp (Bethylidae) from this deposit is documented: Parascleroderma palaeosinica n. sp. is described and figured from a single male, and is the first fossil Parascleroderma known to date. The new extinct species is characterized by its minute size, the pedicel longer than the flagellomeres, the posterior ocelli inserted much posteriad on head, the notauli not impressed on anterior third of anteromesoscutum, and the hypopygium simple, with posterior margin slightly incurved medially. Parascleroderma is a cosmopolitan genus within the Pristocerinae and it is therefore not surprising to find its record in the Zhangpu biota, simultaneously with the northern expansion of the southeastern Asian tropical forest during the MMCO.

Introduction

With up to 3000 current species arranged in 96 valid genera (Azevedo et al., 2018), the Bethylidae form the largest family among the Chrysidoidea. This family of wasps displays its greatest diversity in tropical regions but is cosmopolitan in its global distribution. Bethylid wasps are generally considered to be external parasitoids of lepidopteran and coleopteran larvae that they paralyze and drag into cracks (Evans, 1964, Rubink and Evans, 1979).

Within Chrysidoidea, Bethylidae are generally retrieved as the sister-group of Chrysididae in phenotypic studies (Brothers and Carpenter, 1993, Carpenter, 1999, Brothers, 2011, Brothers and Melo, 2021), but sister to Plumariidae in phylogenomic studies (Branstetter et al., 2017, Peters et al., 2017). Grimaldi and Engel (2005) indicate that the narrowly transverse and nearly completely hidden metanotum would be the synapomorphy of the clade (Bethylidae + Chrysididae). However, in the bethylid subfamily Pristocerinae, the metanotum is developed medially and tends to overlap the mesoscutellum (Azevedo et al., 2018). Bethylids are recognizable by the prognathous head, the antennae with the same number of antennomeres in males and females (11 or 10, rarely 8 or 7 flagellomeres), the pronotum with anterior flange, the prosternum small, transverse, and the six or seven exposed metasomal terga (Finnamore and Brothers, 1993). The flattened body, evolved to sneak into their host habitats, is also retained as a characteristic feature of the family, hence their nickname ‘Flat wasps’. Nine subfamilies were recently recognized in the Bethylidae (Colombo et al., 2020): the extant Bethylinae, Epyrinae, Mesitiinae, Pristocerinae and Scleroderminae, and the extinct Elektroepyrinae, Holopsenellinae, Lancepyrinae and Protopristocerinae. Since then, however, Holopsenella Engel et al., 2016, type genus of the Holopsenellinae, has been removed from Bethylidae and elevated to a family left as incertae sedis in the Aculeata (Lepeco and Melo, 2022).

With more than 90 species in seven of the eight subfamilies (no fossil Mesitiinae has been described yet), the fossil record of Bethylidae spans nearly 130 million years from the Lower Cretaceous to the Holocene (see Martynova et al., 2019; and the posterior discoveries of: Engel, 2019, Falières and Nel, 2019a, Falières and Nel, 2019b, Falières and Nel, 2019c, Falières and Nel, 2020, Colombo et al., 2020, Colombo et al., 2021a, Colombo et al., 2021b, Jouault et al., 2020, Jouault et al., 2021, Colombo and Azevedo, 2021, Jouault and Brazidec, 2021, Tribull et al., 2021). Despite this relatively high richness compared to other chrysidoid lineages (e.g., Chrysididae), lots of new species are likely to be described from Cretaceous or Cenozoic deposits, particularly from the recently discovered Miocene amber of Ethiopia and China (Bouju and Perrichot, 2020, Wang et al., 2021). Even from long-surveyed deposits such as Baltic amber, new taxa may be recovered, as exemplified by the recent discovery of a new pristocerine genus (Tribull et al., 2021).

Here, we report the first Bethylidae from the rich mid-Miocene amber biota of Zhangpu, in Fujian Province, China, and we discuss its taxonomic affinities.

Section snippets

Material and methods

Zhangpu amber is found with plant impressions in two layers of sandy mudstone interbedded with coal seams that belong to the Fotan Group, a geological unit that occurs widely in Zhangpu County, Fujian Province, southeastern China (Wang et al., 2021, fig. 1). Under- and overlying basalt layers allow constrained dating of the amber between 14.8 ± 0.6 Ma and 14.7 ± 0.4 Ma, which corresponds to the middle Miocene (Langhian; Zheng et al., 2019).

This study is based on a complete male specimen kindly

Systematic palaeontology

  • Superfamily Chrysidoidea Latreille, 1802

  • Family Bethylidae Haliday, 1839

  • Subfamily Pristocerinae Mocsáry, 1881

  • Genus Parascleroderma Kieffer, 1904

  • Parascleroderma palaeosinica n. sp.

  • (Fig. 1, Fig. 2)

  • LSID: urn:lsid:zoobank.org:act:1E0E3362-9053-47AA-A6A2-457880270E5E.

  • Etymology: The species name combines ‘palaiós’, meaning ‘ancient’ in Greek and ‘sinica’, in reference to the geographic origin of Zhangpu amber.

  • Material: Holotype male, NIGP178180.

  • Type locality: Zhangpu County, Zhangzhou Prefecture,

Discussion

Following the key to the subfamilies of Bethylidae of Azevedo et al. (2018), the new fossil keys out in Pristocerinae because of the following characters: macropterous species, forewing with Rs+M vein absent, metanotum developed medially and overlapping mesoscutellum posteriorly. This last character is usually considered as a synapomorphy of the Pristocerinae.

Following the keys to pristocerine genera of Azevedo et al. (2018), the new fossil keys near Parascleroderma because of the following

Acknowledgments

We warmly thank the guest editor Prof. Bo Wang for its invitation to contribute this special issue of Palaeoworld and for its precious comments on the manuscript. We are grateful to the reviewers, Prof. Celso O. Azevedo, Prof. Massimo Olmi and an anonymous reviewer for valuable comments and remarks on the earlier manuscript. Research on the Zhangpu amber was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB26000000) and National Natural Science

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