Pseudochironomini SAETHER 1977
- Dataset
- Wanted, tracked down and identified: Mesozoic non-biting midges of the subfamily Chironominae (Chironomidae, Diptera)
- Rank
- TRIBE
Classification
- kingdom
- Animalia
- phylum
- Arthropoda
- class
- Insecta
- order
- Diptera
- family
- Chironomidae
description
In adult Chironomidae, the lack of the wing vein MCu is the synapomorphy for Chironominae + Orthocladiinae, a clade comprising the two largest, most diverse and probably youngest chironomid subfamilies, considered sister to the remaining Chironomidae combined (e. g. Saether, 2000; Cranston et al., 2012). A character state common to all the Chironominae concerns the gonostylus that is backward-directed and connected rigidly with the gonocoxite in most Chironominae, although able to flex slightly in a few taxa (Cranston et al., 1989; Tang & Cranston, 2019). Within four Chironominae tribes (Chironomini, Pseudochironomini, Tanytarsini and the recently erected Xiaomyiini), the character state best separating the tribe Pseudochironomini is the dark comb on the apex of the foreleg tibia, similar to that on mid- and hindlegs (a probable tribal synapomorphy) and the pars ventralis, the structure being, however, weakly developed or absent in most genera. Following reports on a distinct heteromorphy within the Pseudochironomini, especially with respect to the adult genital morphology, as highlighted recently by Krosch et al. (2020), the significance of diagnostic characters or character combinations of a tribe should be treated with the highest caution. The wing anal lobe usually well-developed (vs. anal lobe weak or absent in the Tanytarsini, but also in some Pseudochironomini genera), the vein RM oblique (vs. RM parallel to M and R 4 + 5 in the Tanytarsini or transverse to M and R + 4 5 in most other Chironominae) and the foreleg ratio (LR 1 = ta 1 / ti) usually close to, or less than 1 (vs. higher than 1 in most Chironominae) are the character states in Pseudochironomini that may support the tribe definition. However, these features, and the presence of the pars ventralis, rarely appear as a full set, hence their proper interpretation usually requires a reference to taxa of other Chironominae that may display character combinations or some character states similar to those listed above. Owing to the difficulty in establishing a clear diagnosis based on a set of synapomorphies for the tribe (in the current taxa composition), its monophyly is still being tested but not confirmed (Cranston et al., 2012; Cranston 2019 a, b; Tang & Cranston, 2019; Krosch et al., 2020). To date, the following six extant genera are included in the tribe Pseudochironomini (Andersen, 2016; Krosch et al., 2020): Aedokritus Roback, 1958, Manoa Fittkau, 1963, Madachironomus Andersen, 2016, Pseudochironomus Malloch, 1915, Riethia Kieffer, 1917, and Megacentron Freeman, 1961, the latter with Megacentron eocenicus Doitteau & Nel, 2007 – the sole Pseudochironomini known from the fossil record (Eocene Oise amber) (Doitteau & Nel, 2007). Descriptions of two further genera, based on unique characters found in specimens preserved in the Cretaceous ambers, are presented below.