Revision of fossil species of Deinodryinus, with description of a new species (Hymenoptera, Dryinidae)

Abstract Deinodryinus velteni sp. n. is described from middle Eocene Baltic amber. The species differs from other fossil Palaearctic species of Deinodryinus Perkins owing to the shape of the antenna (clavate, with distal part very thickened), the large compound eyes, and the distal part of the stigmal vein much longer than the proximal part. A revision and a key to the fossil Palaearctic species of Deinodryinus Perkins, 1907 is presented.


Introduction
Dryinidae (Hymenoptera, Chrysidoidea) are parasitoids of Auchenorrhyncha (Guglielmino and Olmi 1997, 2006, 2007. The genus Deinodryinus Perkins, 1907 is present in all zoogeographical regions and a member of the subfamily Anteoninae. One hundred and forty-eight species of Deinodryinus have been described from throughout the world, of which only two are fossil species (Olmi 1984(Olmi , 1999Olmi et al. 2010;Ponomarenko 1975): D. areolatus (Ponomarenko, 1975), from Baltic amber, and D. ? aptianus Olmi, Rasnitsyn & Guglielmino, 2010, a compression fossil from Early Cretaceous marl of the Khurilt rock unit (Mongolia). The latter species is tentatively placed within Deinodryinus given that it is uncertain whether the attribution of this Early Cretaceous species to a modern genus is justified. Insufficient characters were preserved in D.? aptianus to support its placement in a new generic taxon.
Recently we have discovered an additional new fossil species of Deinodryinus from Baltic amber, and the taxon is described herein.

Material and methods
The descriptions follow the terminology used by Olmi (1984Olmi ( , 1994aOlmi ( , 1999. The measurements reported are relative except for the total length (head to abdominal tip, without the antennae) and the length of some parts of the body, which are expressed in millimetres.
The redescriptions of D.? aptianus and D. areolatus, respectively by Olmi et al. (2010) and Ponomarenko (1975), are provided for the sake of completeness. Information on the fossil deposits under consideration are provided by Rasnitsyn and Quicke (2002).

Diagnosis.
Female: macropterous or micropterous; palpal formula 6/3; in macropterous specimens forewing usually with distal part of stigmal vein longer than proximal part, less frequently as long as, or shorter than proximal part; occipital carina complete; vertex frequently with two strong oblique keels connecting posterior ocelli to occipital carina; pronotum with distinct anterior collar and posterior disc; foreleg chelate; enlarged claw with inner proximal prominence not bearing bristles, with 1-2 bristles or peg-like hairs located further distally than proximal prominence; tibial spurs 1/1/2. Male: always macropterous (even if female micropterous); palpal formula 6/3; forewing usually with distal part of stigmal vein longer than proximal part, less frequently as long as, or shorter than proximal part; forewing usually with pterostigma four or more than four times as long as broad; antennal hairs usually much longer than breadth of segments, less frequently shorter than breadth of segments; vertex frequently with two strong oblique keels connecting posterior ocelli to occipital carina; paramere without dorsal process, usually with more or less large inner branch wrapping penis, less frequently with reduced inner branch; tibial spurs 1/1/2. Distribution. Worldwide.

Species. Presently with 152 living and fossil species.
Key to the fossil species of Deinodryinus Females 1 Antenna filiform (Fig. 1); compound eye shorter than one-half length of head ( Fig. 1)  Remarks. This fossil is only visible in ventral aspect and is difficult accordingly to place within a particular genus. In addition, the legs are partly missing and the chela is hardly visible. However, it is possible to identify tentatively this specimen as a species of the extant genus Deinodryinus given the shape of the pterostigma and stigmal vein and for the presence in the forewing of three basal cells completely enclosed by pigmented veins. Among Anteoninae, the above characters may also place this specimen in Lonchodryinus Kieffer, 1905, but Lonchodryinus has the hypostomal bridge much shorter than in Deinodryinus. Given that the fossil exhibits the condition in the latter genus the authors placed the species in Deinodryinus. Among Dryinidae, the above characters of the forewing may also place this specimen in Dryininae and Gonatopodinae but because the occiput is less excavated in Dryininae and Gonatopodinae than in Deinodryinus, and in D.? aptianus, attribution to Deinodryinus is more justified. Another unusual character of D.? aptianus is the shape of the antennae: they are filiform, as in males of Dryinidae, whereas in females usually they are clavate (Olmi et al. 2010 Diagnosis. Female with antenna clavate and compound eye large (Fig. 2); distal part of stigmal vein about as long as proximal part (Fig. 2).

Hosts. Unknown.
Remarks. In the holotype the sculpture of the vertex, face, and pronotum is hardly visible; the scutellum and metanotum are not visible.

Discussion
With 152 species, the genus Deinodryinus is present in all zoogeographical regions: six species are Palaearctic; 22 Afrotropical; nine Oriental; three Nearctic; 110 Neotropical; and two Australian. The only known fossil species have been found in the Palaearctic region, and all have been summarized in the present paper. Because of its geographic distribution, Deinodryinus is considered a 'Pangean' genus (Olmi 1994b). The genus perhaps originated in Central and South America, where the greatest number of extant species are present (110), although centres of origin do not always reside in areas today harboring the greatest species diversity and so this hypothesis requires phylogenetic testing. Almost all species live in tropical or subtropical countries. Very few are the species living in temperate countries: two in the Palaearctic region [Deinodryinus biroi (Olmi, 1984) and D. hispanicus (Olmi, 1991)], and one in the Nearctic region [Deinodryinus atriventris (Cresson, 1872)]. The presence of fossil species in Baltic amber and Early Cretaceous Mongolia marl perhaps indicates that these areas had relatively warm climates in the past, conclusions supported by other faunal and floral elements in these deposits, and that the genus had a much wider distribution.
From a morphological standpoint, D. areolatus and D. velteni do not exhibit significant differences from extant species of the genus. This is common with many fossil dryinids. By contrast, D.? aptianus, visible only in ventral aspect, with legs partly missing and the chela hardly distinct, is difficult to interpret. As mentioned above, attribution to Deinodryinus is only tentative and based on the shape of the pterostigma and stigmal vein and by the presence in the forewing of three basal cells completely enclosed by pigmented veins. However, the presence of filiform antennae, a character present in very few females of dryinids and rare in Deinodryinus (only the females of D. benoiti Olmi, 1984, from Madagascar, andD. colombianus Olmi, 1984, from South America, have filiform antennae), makes this attribution somewhat suspect. Accordingly, our assignment of this species to Deinodryinus remains speculative and we hope for the eventual discovery of more completely preserved material so as to clarify the generic status of this ancient taxon.