Classifying fossil Darwin wasps (Hymenoptera: Ichneumonidae) with geometric morphometrics of fore wings

Abstract

Linking fossil species to the extant diversity is often a difficult task, and the correct interpretation of character evidence is crucial for assessing their taxonomic placement. Here, we make use of geometric morphometrics of fore wings to help classify five fossil Darwin wasps from the Early Eocene Fur Formation in Denmark into subfamilies and often tribes. We compile a reference dataset with 342 fore wings of nine extant subfamilies and nine relevant fossil species. Since geometric morphometrics was mostly ignored in the past in Darwin wasp classification, the dataset is first used to examine differences and similarities in wing venation among subfamilies. In a next step, we used the reference dataset to inform the classification of the fossil species, which resulted in the description of one new genus and five new species, Crusopimpla weltii sp. nov., Ebriosa flava gen. et sp. nov., Entypoma? duergari sp. nov., Lathrolestes? zlatorog sp. nov., and Triclistus bibori sp. nov., in four different subfamilies. Carefully assessing data quality, we show that the fore wing venation of fossil Darwin wasps is surprisingly suitable to assign them to a subfamily or even lower taxonomic level, especially when used in conjunction with characters from other parts of the body to narrow down a candidate set of potential subfamilies and tribes. Our results not only demonstrate a fast and useful approach to inform fossil classification but provide a basis for future investigations into evolutionary changes in fore wings of ichneumonids. The high informativeness of wing venation for classification furthermore could be harvested for phylogenetic analyses, which are otherwise often hampered by homoplasy in this parasitoid wasp family.

Impact of increasing morphological information by micro-CT scanning on the phylogenetic placement of Darwin wasps (Hymenoptera, Ichneumonidae) in amber

“…Since the first Pimplinae amber fossil was only described very recently (Manukyan, 2023 ), we did not consider Pimplinae as the most likely candidate subfamily at first, but were rather leaning towards it belonging to one of the basal ophioniform subfamilies. This highlights the importance of considering different approaches, such as a combined-evidence phylogenetic analysis as done here, or a fore wing morphometric analysis as in Viertler et al ( 2022a ), for classifying fossil specimens, as these might constitute more objective placement methods.…”

“…Diagnosis : There are two other fossil Triclistus species described, both from sediments, Triclistus ventrator (Khalaim, 2008) from the Biamo assemblage (Russia, late Eocene, or Early Oligocene), and Triclistus bibori (Viertler et al 2022a ) from the Fur formation (Denmark, Early Eocene).…”

Disparification and extinction trade-offs shaped the evolution of Permian to Jurassic Odonata

“…Compared to mouthparts, wings are far more abundant as fossils and easier to document. Moreover, they are a privileged item to compute landmark-based morphometrics analyses 32 , 33 , 34 , 35 , 36 and to elaborate a dataset exploitable with a focus on disparity.…”