Minute members of Baissinae (Insecta: Hymenoptera: Gasteruptiidae) from the upper Mesozoic of China and limits of the genus Manlaya Rasnitsyn, 1980

Abstract

A brief review and discussion of baissine wasps of Gasteruptiidae, Hymenoptera is given. Eight fossil specimens of wasps from the Laiyang Formation in Laiyang, Shandong, China are described. One new genus, Mesepipolaea, and four new species, M. nanligezhuangica, Humiryssus specialis, H. cancellatus and H. vulgatus are established, and two new combinations are proposed: Humiryssus laiyangensis (Hong and Wang, 1990) (originally Aulocopsis laiyangensis Hong and Wang , 1990), H. oculatissimus (Rasnitsyn and Jarzembowski, 1998) (originally Manlaya oculatissima Rasnitsyn and Jarzembowski, 1998). Sinowestratia communicata Zhang and Zhang, 2000 is a junior synonym of Manlaya flexuosa (Ren et al.,1995) (originally Manlaya flexuosus Ren et al.,1995). Stratigraphic inferences from these finds are briefly discussed.

Introduction

The subfamily Baissinae represents a basal group in the family Gasteruptiidae (s.l.) within Evanioidea, Hymenoptera, and is possibly ancestral to both of the subfamilies Aulacinae and Gasteruptiinae (Rasnitsyn, 1980, Rasnitsyn, 2002). Baissine fossils are widespread in possible latest Jurassic and undoubted Early Cretaceous insect-bearing deposits of Eurasia from China to Spain but are unknown from deposits that are unquestionably Late Jurassic and Late Cretaceous in age. They represent a key group in latest Jurassic–Early Cretaceous or Early Cretaceous insect assemblages. As a result, the hymenopteran assemblages typical of that epoch have been named the baissine type (Rasnitsyn et al., 1998, Rasnitsyn and Martínez-Delclòs, 2000). Currently the Baissinae includes four genera: Baissa Rasnitsyn, 1975, with three described species (Rasnitsyn, 1991); Manlaya Rasnitsyn, 1980, with 21 species (Rasnitsyn, 1980, Ren et al., 1995, Rasnitsyn et al., 1998, Rasnitsyn and Martínez-Delclòs, 2000); and monotypic Humiryssus Lin, 1980 and Aulocopsis Hong and Wang, 1990. Rasnitsyn et al. (1998) suggested that the last two genera deserve to be placed in synonymy under Manlaya but did not provide formal synonymization.

The fact that the Baissinae represents a stratigraphically and, possibly, biogeographically important element of the latest Jurassic–Early Cretaceous insect assemblages means that it deserves detailed analysis, especially since the internal structure of Manlaya is rather obscure and reliable identification of its species is sometimes problematic (Rasnitsyn et al., 1998). Chinese non-marine sedimentary deposits of latest Jurassic/Early Cretaceous age have yielded many fossils belonging or related to Manlaya. These have been considered in four publications to date (Hong and Wang, 1990, Lin, 1980, Ren et al., 1995, Zhang and Zhang, 2000). As a first step towards a better understanding of the group we have selected a rather clear-cut collection of the smallest fossils. Their study has unexpectedly indicated some apparent subdivisions within what one of us (APR) has regarded as Manlaya. This permits the definition of additional genera in the subfamily Baissinae, so making it easier handle the group.

The fossils described here were collected by JZ from two well-known localities in the villages of Nanligezhuang and Tuanwang, Laiyang, Shandong, in the uppermost Jurassic–lowermost Cretaceous deposits of the Laiyang Formation (originally recorded as Upper Jurassic; Zhang, 1992). These eight specimens are separated into four new species, one of which represents a new genus. Three other new species are referred to the genus Humiryssus Lin, 1980 (originally Aulocopsis Hong and Wang, 1990), which is not considered to be a synonym of Manlaya. Besides the type species, Humiryssus leucus Lin, 1980 from the Laocun Formation at Laocun in Jiande, Zhejiang, and the three species described here, there are two species originally referred to other genera, viz. Humiryssus laiyangensis (Hong and Wang, 1990), the type of Aulocopsis, from the Laiyang Formation in the village of Tuanwang and H. oculatissimus (Rasnitsyn et al., 1998), originally Manlaya oculatissima, from the Durlston Formation (Middle Purbeck) of Durlston Bay in southern England. Another taxon, Sinowestratia communicata Zhang and Zhang, 2000, which was based on a single female wasp from the Yixian Formation at Huangbanjiegou, Beipiao, Liaoning, is regarded as a junior synonym of Manlaya flexuosa (Ren et al., 1995) (originally Manlaya flexuosus Ren et al., 1995) based on a male wasp from the same locality and horizon (new synonymy).

As a result, 18 described species are now left in Manlaya, viz. M. mongolica Rasnitsyn, 1980 (type species) from the Mogotuin Formation of south-west Mongolia; M. caudata, M. corrugata, M. gurvanica, M. laevinota, M. obscura, M. pallida, M. pinguis, and M. ventricosa, all described by Rasnitsyn (1986) from the Gurvan-Eren Formation of west Mongolia, M. ghidarina Rasnitsyn, 1990 from the Ghidara Formation, and M. pachyura Rasnitsyn, 1990 from the Turga Formation, both in East Transbaikalia; Manlaya undurgensis (Rasnitsyn, 1975) (originally Cretocleistogaster undurgensis Rasnitsyn, 1975) from deposits in West Transbaikalia that possibly correlate with the Turga Formation; M. flexuosa (Ren et al., 1995) from the Yixian Formation of north-east China; M. anglica Rasnitsyn and Jarzembowski, 1998 from the Lulworth Formation of southern England, M. ockleyensis Rasnitsyn and Jarzembowski, 1998 and M. capelensis Rasnitsyn and Jarzembowski, 1998, from the Upper Weald Clay of southern England, and M. lacabrua Rasnitsyn and Ansorge, 2000 and M. ansorgei Rasnitsyn and Martínez-Delclòs, 2000, from the locality of La Cabrua in Spain. This rather diverse assemblage badly deserves closer study, which will probably result in further splitting into more natural genera. The position of M. lacabrua is particularly questionable (see below).