Arkadiserphus leleji Rasnitsyn, gen. et sp. nov., is described from the Upper Jurassic deposits of Karatau (Kazakhstan) in the proctotrupoid family Peleserphidae hitherto known solely from the mid-Cretaceous Burmese (Kachin) amber. Taxonomic position of the genus and past distribution of the family are briefly discussed.

Fossil insects, Proctotrupomorpha, new taxa, Upper Jurassic

The family Peleserphidae is established in the superfamily Proctotrupoidea based on three fossil wasps in the Burmese (Kachin) amber arranged in three species and two genera (Zhang et al. 2018). The family was treated as aberrant within Proctotrupoidea primarily because of the modified wing venation, with RS+M extending far distally to diverge only beyond 2r-rs, so as free M mimics ‘RS₂’ of Pelecinidae. Enlarged head with prognathous mouthparts and very long female hypopygium are claimed synapomorphic for Peleserphidae as well. Along with some others, the family was listed as endemic of the mid-Cretaceous tropical biota of the West Burma plate (Rasnitsyn and Öhm-Kühnle 2018; Zhang et al. 2018).

A far older wasp fossil from the well-known Upper Jurassic insect site in the Range Karatau (southern Kazakhstan) (cf. Rohdendorf 1968) was long waiting for proper identification among other strange wasp fossils kept at the Paleontological Institute in Moscow until recently it is identified as a member of Peleserphidae. The fossil is described herein as a new genus and species.

The holotype specimen under description was collected in the Upper Jurassic deposits of Karabastau Formation near Mikhailovka village, southern Karatau Range, Kazakhstan (43.0°N, 70.0°E: paleocoordinates 41.1°N, 73.3°E according to the Fossilworks Database, http://fossilworks.org/bridge.pl?a=collectionSearch&collection_no=30231, accessed Feb. 26, 2021) in 1967 by the field team of the Borissiak Paleontological Institute, Russian Academy of Sciences (further referred to as PIN), led by Alexander G. Sharov. The material is kept at PIN.

The holotype is photographed at PIN by Dmitry V. Vasilenko using a Leica M165C stereomicroscope with a Leica DFC 420 camera. Line drawings were made with CorelDRAW 2019 Graphic software based on the photographs.

The new genus is attributed to the family Peleserphidae based on RS extended distally up to 2r-rs or beyond it. Putatively this character represents a synapomorphy of the family which is unique of all Proctotrupomorpha, if not Hymenoptera in general. Otherwise, Arkadiserphus and Peleserphidae as a whole are most similar to Mesoserphidae, the basal family of Proctotrupomorpha, in having ovipositor external and metasomal segmentation more or less homonomous (with no petiolar segment and no terga strongly enlarged or fused together). In respect to other known genera of Peleserphidae, namely Peleserphus and Peleproctus, Arkadiserphus displays both putative synapomorphies (antenna oligomerous and crossvein 1m-cu totally lost) and plesiomorphies (head orthognathous but not large, rudimentary 1–RS+M present, Cu with rudimentary kinks at 1cu-a and 2cu-a, 1cu-a postfurcal, and hypopygium moderately long). In spite of these differences, it seems to be premature to set a distinction of the subfamily level within a family embracing only three genera and four species as well as four specimens.

Concerning its biology, morphology of the new genus gives little evidence of that kind, so it is possible only to repeat what was earlier suggested for the Peleserphidae in general based on the hitherto known material: “these wasps had a host, possibly a holometabolous larva, concealed within a substrate, perhaps wood or the like” (Zhang et al. 2018: 71). Unlike this, the very finding of the new genus in Angaraland adds considerably to our knowledge about the distribution of Peleserphidae in time and space. The family has evidently originated at least in the Late Jurassic and reached the West Burma plate in the midst of the Tethys Ocean not later than mid-Cretaceous. Unfortunately, nothing can be concluded at present about particular routes of migration, whether these insects spread directly overseas, or from Angaraland via the Gondwana continent (the West Burma plate has separated from the Australian part of Gondwana some 156 Ma ago; Seton et al. 2012). Or else Peleserphidae might originate in the Gondwana and then migrate independently to the West Burma plate and to the Angaraland not after Late Jurassic. An evidence of the latter version could be a record of Peleserphidae in Jurassic deposits of Gondwana.

I am thankful to the editors of the Special Issue of JHR dedicated to the 75^th anniversary of Arkady S. Lelej for their invitation to participate. This work was partially supported by the Presidium of the Russian Academy of Sciences Program “Origin of the Biosphere and Evolution of Geobiological Systems”.