Short communicationThe first plumalexiid wasp (Hymenoptera: Chrysidoidea, Plumalexiidae) from the mid-Cretaceous Burmese amber
Introduction
The family Plumalexiidae was previously known only from a single fossil species. It was described and based on two conspecific males from Turonian Raritan amber (New Jersey, USA) and interpreted as a sister-group of Plumariidae in a clade basal in Chrysidoidea, although it could also be interpreted as sister to the remaining chrysidoids or even to the chrysidoids as a whole (Brothers, 2011). The family is relatively plesiomorphic in most of its characters compared to the Plumariidae and hence is important in understanding the ancestry of the enigmatic plumariids (op. cit).
Plumalexiidae differ from all Chrysidoidea other than Plumariidae in having the hind wing with rich venation including two closed cells (vs. few simple veins and no closed cells). Plumalexiidae differ from Plumariidae primarily in their less modified wing venation: fore wing lacking secondary veins and with the 2rm cell only slightly or not at all smaller than the 1mcu cell. Herein, we describe a second species of Plumalexiidae based on a unique fossil discovered recently in the mid-Cretaceous Burmese amber that confirms and broadens our knowledge of the family and adds significantly to its diversity and distribution in space and time.
Section snippets
Material and methods
The specimen described herein was collected in amber mines in the Hukawng Valley of Kachin State, Myanmar (locality in Li et al., 2018: fig. 1). The rocks containing the Burmese amber are radiometrically dated at 98.79 ± 0.62 Ma (Shi et al., 2012). However, since it is well known that amber easily becomes redepositioned, we prefer to refer to the amber informally as being of mid-Cretaceous age. Morphological terminology is the same as in Brothers (2011) except for the wing venation shown on
Systematic paleontology
Order Hymenoptera Linnaeus, 1758
Superfamily Chrysidoidea Latreille, 1802
Family Plumalexiidae Brothers, 2011
Genus Plumalexius Brothers, 2011
Plumalexius ohmkuhnlei sp. nov.
Fig. 1, Fig. 2, Fig. 3.
LSID: urn:lsid:zoobank.org:act:1522AC39-6A67-4A5C-A6E1-8075343D18C1
Diagnosis. Body slender (vs. robust in P. rasnitsyni), scape and pedicel long (scape about as long as eye width) and each bearing long setae (vs. shorter and with long setae only on pedicel), maxillary palp with 3 apical segments as long
Discussion
The current specimen shows several differences from the type species of Plumalexius, P. rasnitsyni, as given above, some of which could possibly be considered as of generic value in other families. Without additional representatives of the family, however, comparison of intrageneric as opposed to intergeneric variation is not feasible. The similarities between the specimens are very striking, and at least some of the apparent differences may result from the differences in preservation and
Concluding remarks
The original description and establishment of a new family of Chrysidoidea based on a single species known only from two specimens in Turonian New-Jersey amber (Brothers, 2011) was somewhat tentative, given the paucity of material and inability to determine various potentially important characters. The discovery of a second fossil species of Plumalexiidae, from a locality extremely remote from eastern North America and a significantly older deposit, has strengthened the validity of the family
Acknowledgements
The authors are deeply obliged to Dr. Christoph Öhm-Kühnle (Herrenberg, Germany) for donation of the holotype to the Paleontological Institute RAS, and to Dr. Dmitry Vorontsov (Moscow, Russia) for precise trimming and polishing and skillful photography of the holotype. We offer our sincere gratitude to the reviewers and editors for their valuable comments. DJB acknowledges the support provided by the University of KwaZulu-Natal.
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