Chalscelio, Rasnitsyn & Brothers, 2007

Rasnitsyn, Alexandr P. & Brothers, Denis J., 2007, Two new hymenopteran fossils from the mid-Cretaceous of southern Africa (Hymenoptera: Jurapriidae, Evaniidae), African Invertebrates 48 (1), pp. 193-202 : 193-196

Family Jurapriidae Rasnitsyn, 1983 Genus Chalscelio gen. n.

Figs 1, 2

Etymology: The genus name combines the names Chalcis and Scelio , alluding to the combination of characters both of Chalcidoidea and Scelionidae in the new genus; gender masculine.

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Type species: C. orapa sp. n., by present designation.

Diagnosis: General appearance as in Scelionidae (Scelioninae) , including female antenna clavate with 5 claval segments, geniculate and doubly angled (at apex of scape and before clava), and no anellus apparent; body elongate with long, fusiform, non-petiolate metasoma having 6 apparent segments and no sign of external ovipositor. Forewing venation generally typical of Scelionidae except for angular Cu, and combination of retained M (even if incomplete) and RS apparently lost beyond 2r–rs. Unlike Scelionidae and Platygastroidea in general, but highly reminiscent of Chalcidoidea , pronotum long medially but apparently shortened laterally and possibly not reaching tegula; forewing Cu distinctly angular at fork with M; number of antennal segments (13 evident, but 14 or even 15 possible because of imperfect preservation) low. (Position of antennal attachment (close to clypeus vs. far above it) unknown.)

Species included: Type species only.

Phylogenetic position: As far as the characters available permit judgement, the fossil looks essentially like a scelionid, including the double-geniculate antenna, with only three but important anomalous characters, supposedly apomorphies of either Chalcidoidea or ( Serphitoidea + Chalcidoidea ) as interpreted by Rasnitsyn et al. (2004). One of these, putatively synapomorphic for ( Serphitoidea + Chalcidoidea ), is Cu distinctly bent posteriorly at its junction with M, a state never observed in Platygastroidea or Proctotrupoidea unless combined with cu–a displaced distal of the M+Cu junction (which is not the case here).

Another anomalous character is the medially long pronotum; this state is found in no Platygastroidea and is characteristic of Chalcidoidea . It was probably either independently gained, or independently inherited, by Chalscelio and Chalcidoidea directly from the predominantly Jurassic family Mesoserphidae ( Rasnitsyn 1980, 1986).

The third character state, the pronotum short enough laterally not to reach the tegula, is tentatively inferred from extrapolation of the direction of the preserved forewing toward the mesosoma. The pronotum does not extend to the tegula in most Chalcidoidea because of the presence of an external prepectus between the two. If the pronotum truly does not reach the tegula in Chalscelio , this might imply a large, external prepectus, a feature only of Chalcidoidea . Otherwise, if it is the mesopleuron rather than a prepectus intervening between the pronotum and tegula, this might be a synapomorphy or, more likely, a homoplasy with Microserphites Kozlov & Rasnitsyn, 1979 (Serphitidae) and several fossil Palaeomymar Meunier, 1901 (Mymarommatidae) (cf. Kozlov & Rasnitsyn 1979, figs 7, 8, 10, 11).

As noted above, Chalscelio looks superficially like a female scelionid, notably in having a double-geniculate antenna with 5-segmented clava, apparently only six visible similar metasomal terga and a fusiform metasoma without evidence of an external ovipositor. Of these features, the antennal form is probably the strongest in possibly indicating a close relationship, the other features perhaps likely to be plesiomorphies. However, Rotoitidae , considered a basal lineage of Chalcidoidea , have a 6-segmented clava in the female (5-segmented in the male; other chalcidoids have a clava of three or fewer segments, rarely four; Gibson & Huber 2000), so the claval form in Chalscelio does not necessarily indicate a close relationship with Scelionidae . A complication is that Rotoitidae have a scelionid-like pronotum, short medially and reaching the tegula laterally because the prepectus is linear and concealed under the hind margin of the pronotum, but it is uncertain whether that condition should be regarded as the groundplan for Chalcidoidea . Another complication is that Khutelchalcis Rasnitsyn, Basibuyuk & Quicke, 2004 from the lowermost Cretaceous of Mongolia, another possible basal chalcidoid ( Rasnitsyn et al. 2004), shows a different combination of features characteristic of Scelionidae and Chalcidoidea : antenna lacking anelli but apparently with long multiporous plate sensilla and without scelionid-like bend; pronotum short medially and with prepectus not extending far dorsad, but with spiracle accommodated into posterodorsal excision of pronotum; venation essentially scelionid-like whilst metasoma chalcidoid-like ( Fig. 3 ).

All the evidence taken together makes Chalscelio a possible sister group of Chalcidoidea . The basal position of Chalscelio with reference to Chalcidoidea is demonstrated by the plesiomorphic (not reduced ring- or tube-like) first metasomal segment, as well as by the wing venation retaining some plesiomorphic details (pterostigma, distal branch of Cu indicating a former connection with A). A sistergroup rather than ancestral position is supported by a few venational autapomorphies in Chalscelio , such as the loss of RS connected with the 2r–rs crossvein, loss of the anal vein, and possibly loss of the costal vein enclosing the costal space (all of these being present in Khutelchalcis ). All these autapomorphies are, however, of rather low phylogenetic importance, being common results of miniaturisation (reduction in body size). Numerous phylogenetically important characters (antennal sensilla, position of the mesothoracic spiracle with respect to the pronotum, external vs. internal ovipositor) are not determinable in Chalscelio because of the imperfect preservation of the unique fossil. Nevertheless, the available information leads to the conclusion that Chalscelio may be morphologically similar to the true chalcidoid ancestor. This characterises the fossil as a relict, because Chalcidoidea are now known from at least the earliest Cretaceous, that is they predate Chalscelio by some 40 to 50 million years.

Taxonomic position: This fossil is not a chalcidoid by any current definition, and yet it may be monophyletic with Chalcidoidea . However, to attribute Chalscelio formally to Chalcidoidea (naturally as a family of its own) would result in only a single character, the pronotum long medially and shortened laterally, as diagnostic of the resulting assemblage (except for Rotoitidae and Khutelchalcididae ). This is impractical, particularly because knowledge of the fossil is incomplete. This is why, until more information is accumulated, we prefer to consider Chalscelio formally as a genus of questionable taxonomic position, tentatively grouped together with another such genus, Jurapria Rasnitsyn, 1983 , for which the family name is already available (Rasnitsyn 1983; Rasnitsyn et al. 2004). Jurapria differs from Chalscelio in the antenna and general appearance, being less strikingly scelionid- or chalcidoid-like ( Fig. 4 ), and in having the wing venation far more complete. Other important characters are hardly comparable because of the different preservation states of the two fossils: the pronotum form is unknown for Jurapria , while the position of the ovipositor, short and not tightly enclosed in Jurapria , is unknown for Chalscelio , although it may be similar or internal (but not long and exerted). The two genera are similar in two other important characters: both are synapomorphic with Serphitoidea + Chalcidoidea in having Cu arching or angular at the fork with M, and both are plesiomorphic with respect to them in having the first metasomal segment not modified into a tube or ring. This provides further justification for the present interpretation of their taxonomic position.

Figures

Figs 1, 2. Chalscelio orapa Rasnitsyn & Brothers, gen. et sp. n.: (1) Holotype, BP/2/26990a and b/6, part and counterpart (slightly different scales); (2) Composite drawing; wing veins labelled conventionally. Scale bars = 1 mm.

Figs 3, 4. (3) Khutelchalcis gobiensis Rasnitsyn, Basibuyuk & Quicke, holotype; drawing based on part