Palaeocharmon, Belokobylskij & Nel & Waller & Plöeg, 2010

Belokobylskij, Sergey A., Nel, André, Waller, Alain & Plöeg, Gael De, 2010, New fossil non-cyclostome braconid wasps from the lowermost Eocene amber of Paris Basin, Acta Palaeontologica Polonica 55 (3), pp. 519-527 : 520-522

Genus Palaeocharmon nov.

Etymology: After palaios, the Greek for ancient, and the Recent genus Charmon . Gender masculine.

Type species: Palaeocharmon basalis sp. nov., by monotypy.

Description.—Occipital carina fused ventrally with hypostomal carina not far from the base of mandible. Eyes possibly glabrous, distinctly emarginated opposite of antennal sockets. Ocelli almost forming equilateral triangle. Frons and face weakly convex. Clypeus weakly convex ventrally. Mandible large. Palpi long. Scape weakly thickened. First flagellar segment a little longer than second segment (Fig. 2B, E). Mesosoma rather short and high ( Figs. 1B , 2B, C). Notauli complete, rather shallow, wide anteriorly and narrow posteriorly (Fig. 2B, C). Prescutellar depression shallow and wide, with shallow median carina. Scutellum posteriorly without furrow. Prepectal carina absent. Mesopleural pit transformed in shallow elongate furrow. Sternaulus rather wide, sigmoid (Fig. 2C). Metapleural flange distinct and long Propodeum without lateral tubercles and delineated areas. Legs rather long and more or less slender ( Fig. 1B ). Hind basitarsus 0.8 times as long as second to fifth segments combined ( Fig. 1B ). Telotarsus (fifth segment) of hind tarsus short and slender ( Fig. 1B ). Claws simple and weakly curved. Fore wing with radial (marginal) cell not shortened, recurrent vein (m−cu) strongly antefurcal, first radiomedial vein (2−SR) possibly present, second radiomedial vein (r−m) absent, brachial (subdiscal) cell large (Fig. 2G). Hind wing with 3 distal hamuli, submedial (subbasal) cell large, radial vein (SR) unsclerotised, almost parallel to anterior margin of wing, but very weakly divergent posteriorly; recurrent vein (m−cu) rather distinct, weakly sclerotised and almost straight (Fig. 2F). Metasoma distinctly elongate ( Fig. 1A, B ). First tergite short and wide ( Fig. 1A, B ), with narrow but distinct dorsope, with distinct, almost complete and convergent posteriorly dorsal carinae. Second suture indistinct. Spiracles of second tergite situated on the middle of its lateral sides. Tergites behind first one not modified. Ovipositor long ( Fig. 1A, B ).

Discussion.—The presence of the recurrent (m−cu) vein in the hind wing is very common in many groups of cyclostome braconids. This vein is developed in almost all taxa of Rhyssalinae , Doryctinae , Exothecinae sensu lato, and Betylobraconinae (except for some specialised genera), in many taxa of Opiinae and Alysiinae , as well as in some taxa of Rogadinae and in several other small subfamilies. Otherwise, this vein is practically never recorded in the other non−cyclostomate group of subfamilies ( Tobias 1967; Quicke and van Achterberg 1990; van Achterberg 1993).

doi:10.4202/app.2009.1114

This new tribe represents the first member in the helconine phylogenetic group, which either retained, or possibly re−stored, the recurrent vein (m−cu) in the hind wing. In addition to this characteristic feature, the new tribe also displays a set of plesiomorphic wing venation characters, such as a developed first transverse anal vein (2A) in the fore and hind wings and a distinctly petiolate anteriorly discoidal (discal) cell of fore wing. Unfortunately, the medio−anterior half of fore wing is not preserved in this fossil specimen and information about the second radiomedial vein (r−m) and thus presence or absence of the second radiomedial (submarginal) cell cannot be recorded.

If we assume that the second radiomedial vein (r−m) and second radiomedial (submarginal) cell are present, then this genus can be included in subfamily Helconinae and would be similar to Hellenius , although on the basis of mainly plesiomorphic characters, i.e., discoidal (discal) cell is petiolate, the propodeal bridge being absent, the prescutellar depression long, and the second transverse anal vein (2A) in hind wing is present. The new genus differs distinctly from Hellenius , however, and besides the presence of the hind wing recurrent vein (m−cu), also in the following characters: the eyes and ocelli are strongly enlarged, the malar space is very short, the mandible is large, the palpi are long, the third segment of the labial palpus is very short, the prepectal carina is absent, the propodeum is without delineated areas, the nervulus in fore wing is antefurcal, and the eyes are distinctly emarginated opposite the antennal sockets.

On the other hand, the new genus is also similar to Homolobus ( Homolobinae ) in having enlarged eyes and ocelli, a reduced number of labial palpal segments, rather large hind coxae, a spine on the apical segment of antenna, and a well−developed laterope on the first metasomal tergite. Unfortunately, information about such important subfamily character as the antescutal depression is not available for study because of the preservation state of the unique specimen. At the same time, Palaeocharmon gen. nov. differs distinctly from Homolobus in the following features: the spurs of all legs are short, the discoidal (discal) cell is petiolate anteriorly on long distance, the second transverse anal (2A) and recurrent (m−cu) veins of hind wing are present, the radial (marginal) cell of hind wing is very weakly divergent apically, the first metasomal tergite has dorsal carinae and rather distinct laterope, and the ovipositor is very long.

In the case of absence of the second radiomedial vein (r−m) and second radiomedial (submarginal) cell, Palaeocharmon gen. nov. can be compared to the subfamilies Brachistinae and Charmontinae . Differences between this new genus and brachistine genera, especially from the most similar one, Eubazus , are distinct, i.e., the discoidal (discal) cell is distinctly petiolate, the second transverse anal (2A) and recurrent (m−cu) veins of the hind wing are present, the radial (marginal) cell of hind wing is not narrowed apically, the eyes and ocelli are much enlarged, the malar space is very short, the eye has an emargination opposite the antennal socket, the nervulus (cu−a) is antefurcal, and the hind basitarsus is long.

Comparison of the new genus with all aforementioned taxa suggests the placement of the new genus in the subfamily Charmontinae as most reasonable because of the set of following apomorphic and peculiar plesiomorphic features: the eyes and ocelli are enlarged, the labial palpus has the third segment strongly reduced, the areola on propodeum is absent, and the occipital carina is possibly reduced medio−dorsally. Moreover, the shape and proportions of the hind leg in Palaeocharmon are the same as in Charmon , as well as the laterope of the first tergite and the first transverse anal (2A) vein in the both fore and hind wings are present. A number of apomorphic characters (the apical antennal segment with very long apical spine, the rather distinct dorsope and the nervulus [cu−a] of fore wing antefurcal) and the principal plesiomorphic characters (not thickened scape, the narrow and petiolate discoidal [discal] cell, the weakly divergent apically radial [marginal] cell of hind wing, the distinct and long metapleural flange) as well as the presence of recurrent (m−cu) vein in hind wing show an isolated position of this new genus within the Charmontinae . For this reason we erect the new tribe Palaeocharmontini for this genus.

Figures

Fig. 1. Photographs of braconid wasp Palaeocharmon basalis gen. et sp. nov., holotype of female, MNHN A32944, from the French Amber (Farm Le Quesnoy, Oise, France), lowermost Eocene. A. Habitus in dorsal view. B. Habitus in lateral view. C. Part of the body and wing in dorsal view.