Maimetshidae Rasnitsyn 1975
Creators: name: Rasnitsyn, Alexandr P.
name: Brothers, Denis J.
Publisher: name: Zenodo
Year: 2009
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Maimetshidae

description: Family Maimetshidae Rasnitsyn, 1975
Maimetshidae: Rasnitsyn 1975: 73; 1988: 124; Ronquist et al. 1999: 33.
Megalyridae (Dinapsinae): Shaw 1988: 109.
Megalyridae (Dinapsini): Shaw 1990: 578; 2007.
Type genus: Maimetsha Rasnitsyn, 1975 (monobasic).
Diagnosis: Head without ocular carina, without subantennal groove accommodating antennal base.Vertex with (in type genus) or without longitudinal median sulcus.Antenna filiform, with scape not elongate, flagellomeres variable in number (known as at least 14 to 17). Mandible with four teeth (mandibles perhaps rarely asymmetrical, with 4 and 3 teeth). Pronotum short medially, mesoscutum with notauli and medial sulcus, axillae meeting anterior to scutellum or separated by prescutellar impression. Propodeum areolate. Forewing with costal space moderate to wide; vein C and pterostigma present; basal sections of RS and M subequal in length, not continuously aligned (not forming smooth basal vein); marginal cell closed, wide (not triangular), moderately short to moderately long; cells 2rm and/or 3rm closed; cell 1mcu closed, small, distant from 2rm (by at least 0.7× length of 1m –cu); cell 2mcu open (at most delimited by spectral 2m –cu crossvein); 1cu–a antefurcal. Hind wing with no posterobasal lobe; with 4 or 5 distal hamuli; basal cell (1rm) closed; free apex of RS stub-like, short; free apices of M and Cu short or absent, that of A absent. Legs unmodified, with trochantelli, spurs 1-2- 2, tarsomeres 5-5-5, claws with preapical tooth. Metasoma rather short, compact, not much sculptured, attached low on propodeum, with first segment forming small articulatory ring, second segment the longest, apical sternum of female elongate, nearly reaching metasomal apex. Ovipositor external but not long, sheaths shorter than metasoma, not fitting tightly to ovipositor (often preserved loose).
Genera included: Maimetsha Rasnitsyn, 1977 (type genus) from the Santonian of northern Siberia; Andyrossia Rasnitsyn & Jarzembowski, 2000 (= Arossia Rasnitsyn & Jarzembowski, 1998, nom. preocc.) from the Barremian of the Weald Clay (southern England); Guyotemaimetsha Perrichot, Nel & Néradeau, 2004 from the Albian of southwestern France (based on their figures and description), and the three new genera described below from the Turonian of Botswana, all mid- and late Cretaceous in age. The undescribed fossil from the Albian Álava amber in Spain (misidentified as Trigonalidae in Delclòs et al. 2007, fig. 4F) also belongs here. Furthermore, based on the available characters, the incompletely preserved Cretogonalys Rasnitsyn, 1977 from the Cenomanian of northern Siberia (Rasnitsyn 1977) also may be a member of Maimetshidae. Its asymmetrical mandibles with 3 and 4 teeth are more characteristic of Trigonalidae, but the venation as far as is known is more typical of Maimetshidae. Unfortunately, the metasomal base is insufficiently preserved to reveal the presence or absence of a small ring-like basal segment. If a genus of Maimetshidae, Cretogonalys can be distinguished from the other genera in having both 2rm and 3rm cells enclosed (the former not petiolate) and in its slender stature.
Taxonomic position: The small ring-like first metasomal segment limits attribution of the family either to the superfamily Stephanoidea s.l. (including Ceraphronoidea s.str.) or to the infraorder Proctotrupomorpha; this is additionally supported by the low metasomal articulation (excluding Evanioidea), distinct costal space (excluding Ichneumonoidea) and external ovipositor (excluding Aculeata). The wide, but not triangular, marginal cell excludes Proctotrupomorpha, which additionally differs in having either the hind wing with no enclosed cells (all but Mesoserphidae), or a normal (not ringlike) first metasomal segment (Mesoserphidae). In the superfamily Stephanoidea s.l., only the families forming the Ceraphronoidea s.str., viz., extant Ceraphronidae and Megaspilidae and extinct (Cretaceous) Stigmaphronidae (Engel & Grimaldi 2009), are similar in having the first metasomal segment small and ring-like. All of those differ, however, in having the wing venation far more reduced (with no veins preserved beyond R and no enclosed cells), two foretibial spurs, and internal ovipositor. Of the remaining stephanoid families, Maimetshidae is most similar (except in the form of the first metasomal segment) to Trigonalidae (except that the latter has the forewing with cell 2rm close to 1mcu and vein 2m –cu tubular, the ovipositor rudimentary and internalized, and several other modifications related to reproductive biology; see e.g. Carmean & Kimsey 1998) and Megalyridae (particularly to its archaic Mesozoic subfamily Cleistogastrinae, sometimes considered as a separate family, e.g., by Shaw 1988). In comparison with the two subfamilies of Megalyridae, Maimetshidae shares with Cleistogastrinae well developed notauli, more complete venation (forewing with 2rm enclosed and M+Cu tubular, hind wing with enclosed cells) and variable flagellomere number (14–17 or more, in contrast to always 12 in Megalyrinae; 8–19 in Cleistogastrinae). In addition to the form of the first metasomal segment, Maimetshidae differs from all Megalyridae in having the 1cu–a crossvein antefurcal.Although Maimetshidae is generally most similar to Megalyridae and particularly to Cleistogastrinae, all the similarities are of a plesiomorphic nature, while its own putative synapomorphies, and particularly the form of the first metasomal segment, link it to the Ceraphronoidea s.str. That is why we consider Maimetshidae as forming a morphological and possibly phylogenetic transition between Cleistogastrinae and Ceraphronoidea s.str.
Remarks: Shaw (1988, 1990, 2007; see also Grimaldi & Engel 2005) synonymised Maimetshidae (based on Maimetsha only) under Megalyridae: Dinapsini. His only positive arguments were that “ Maimetsha is characterized as having a more reduced pattern of forewing venation (Rasnitsyn 1975), which is in fact very similar to that of some modern megalyrids, such as Ettschellsia. In particular, Maimetsha has Rs curving towards the wing margin to form a short radial cell, very similar to the short radial cell that characterizes the Dinapsis + Ettschellsia lineage of dinapsine megalyrids. This indicates that Maimetsha should be classified in the Megalyridae. … In Maimetsha the Rs of the hindwing is reduced to a short stub (Rasnitsyn 1975); therefore, the genus can be assigned to the Dinapsinae [later Dinapsini] on the basis of this character.” (Shaw 1988: 109). Both observations are correct but not very convincing because both characters represent a part of the miniaturization syndrome. This is a set of modifications resulting in the formation of a wide vein-free zone along the outer and posterior margins of the functional wing (joined fore- and hind wings in the case of the hymenopterons) which commonly accompanies evolutionary reduction of body size in winged insects (Rasnitsyn 1980). Both characters emphasised by Shaw (1990) as placing Maimetsha in Dinapsini (his characters 9 and 10) appear to us as possibly wrongly polarised, with the putative derived states involving development of veins otherwise lost; if so, the shared states would be symplesiomorphies. Opposed to these is a set of characters implying a possible sister-group relationship between Maimetshidae and Megalyrinae (= Megalyridae excluding Cleistogastrinae). This set includes a number of synapomorphies of Megalyrinae for characters which are plesiomorphic in Maimetshidae, e.g., the head with subocular groove (absence of the groove demonstrated in Maimetsha (Rasnitsyn 1975, fig. 87a, c, d), in Guyotemaimetsha (Perrichot et al. 2004, fig. 2), and inferred in the new taxa described below), reduced and stabilized number of flagellomeres (12) (variable in Maimetshidae), lost notauli (present in Maimetshidae), forewing with M+Cu lost as a tubular vein and 2r–m and 3r–m both lost (M+Cu tubular, 2r–m and 3r–m present in ground plan and never both lost in Maimetshidae), and hind wing with M+Cu and A lost and no closed cells (M+Cu and A present, and cells rm and cua closed in Maimetshidae). Furthermore, there is a potential synapomorphy of Maimetshidae and Ceraphronoidea s.str. in having the first metasomal segment reduced to a small articulatory ring (best described by Perrichot et al. 2004: 161, and visible in their photo, fig. 1B) (not so modified in Megalyridae s.l.). This makes the proposal by Shaw (1988, 1990) to synonymise Maimetshidae under Dinapsini in Megalyridae s.str. inappropriate. Shaw’s (1990) cladistic analysis included only characters relevant to his concept of Megalyridae (incidentally, there are three errors in his coding for Maimetsha, which should be 100?002021?12?0??212). If the matrix were expanded in taxa and characters to include Cleistogastrinae and Ceraphronoidea, as well as the other genera now assigned to Maimetshidae, we are confident that the results would differ; such an analysis is beyond the scope of this paper, however. Meanwhile, we prefer to retain Maimetshidae as a family in its own right, for the reasons outlined above.
description: Published as part of Rasnitsyn, Alexandr P. & Brothers, Denis J., 2009, New genera and species of Maimetshidae (Hymenoptera: Stephanoidea s. l.) from the Turonian of Botswana, with comments on the status of the family, pp. 191-204 in African Invertebrates 50 (1) on pages 192-193, DOI: 10.5733/afin.050.0108, http://zenodo.org/record/7668179