DOI: 10.15468/684uec
title: The first Stylogaster Macquart, 1835 (Diptera: Conopidae) fossil, from Oligo-Miocene Dominican amber, and some phylogenetic and biogeographic considerations

description: This dataset contains the digitized treatments in Plazi based on the original journal article Rocha, L. S. G., Burt, T. O., de Mello-Patiu, C. A., Skevington, J. H. (2015): The first Stylogaster Macquart, 1835 (Diptera: Conopidae) fossil, from Oligo-Miocene Dominican amber, and some phylogenetic and biogeographic considerations. Fossil Record 18 (2): 119-125, DOI: 10.5194/fr-18-119-2015, URL: http://dx.doi.org/10.5194/fr-18-119-2015Abstract. Stylogaster Macquart, 1835 has been unknown in the fossil record until now, the only fossil conopid genus being Palaeomyopa Meulnier, 1912. Two Stylogaster specimens in amber from the American Museum of Natural History collection were studied and are described here. Both specimens, male and female, belong to a new species, S. grimaldii sp. nov., that is probably basal to at least the New World species with a short ocellar triangle. Photos and drawings of the new species are provided. The relationship with other Stylogaster species and ancient distributional patterns are briefly discussed.1 IntroductionConopidae, or thick-headed flies, are an interesting and understudied group of flies with a nearly worldwide distribution. They are only absent from Antarctica and the islands of Pacific. The adults are nectarivorous and the larvae are obligatory parasitoids of other insects. About 800 extant species of conopids in 58 genera are known, and one fossil genus with two species has been recorded from Baltic amber (Stuke, 2005; Gibson and Skevington, 2013).Stylogaster Macquart, 1835 is a peculiar genus of Conopidae, with 118 valid species described so far, distributed amongst all biogeographic regions except for the Palaearctic (Papavero, 1971; Camras and Parrillo, 1985; Smith and Peterson, 1987; Yang, 1995; Camras and Parrillo, 1996; Stuke, 2006; Rocha and Mello-Patiu, 2009; Schneider, 2010; Rocha and Mello-Patiu, 2012; Stuke, 2012; Pape and Thompson, 2013, Burt et al., 2014). The genus (thus the subfamily) can be diagnosed by the following characters: a pronounced facial keel, elongated prementum and labella, medial ommatidia larger than all other conopid genera, females with an elongated tube-like terminalia, formed by the segments VI, VII and VIII and dart-like eggs with a hard and scaled chorion and barb-shaped spines (Kotrba, 1997). Stylogaster are parasitoids like all other Conopidae but unlike the others, which are mostly parasitoids of Hymenoptera, Stylogaster ’s preferred hosts are cockroaches (Blattaria) and grasshoppers and their relatives (orthopteroids). Records of oviposition on calyptrate flies have been described from Africa, but no evidence of development in dipteran hosts has been found (Rettenmeyer, 1961; Couri and Pont, 2006; Couri and Barros, 2010, Couri et al., 2013). In the New World and Africa, many species are associated with army and driver ants, (Hymenoptera: Formicidae: Ecitoninae), with Stylogaster attacking in the insects that run from the swarms, but not the ants themselves (Lopes, 1937; Smith and Peterson, 1987; Skevington et al., 2010).Recent phylogenetic analyses give many alternative phylogenetic hypotheses for Stylogaster: one as the sister group of all other conopids, or as sister of the Lauxaniidae, depending on the method of analysis (Gibson et al., 2012; Gibson and Skevington, 2013) or even a paraphyletic Conopidae, inside the Sciomyzoidea, with Stylogaster separated from the other conopids (Wiegmann et al., 2011). The age of Stylogaster has not been proposed before, as the only known fossil conopid genus, Palaeomyopa Meulnier, 1912 is not closely related to Stylogaster (Hennig, 1966; Gibson and Skevington, 2013). The short mouthparts with palps and widely open cell R 4+5 are putative plesiomorphic characters of Palaeomyopa, while the presence of facial foveae and pad-like extensions of sternite 5 of the female are shared with the non-stylogastrine conopids. Evolutionary studies of Conopidae are important because this family is hypothesized to be the sister taxon to all other schizophoran Diptera (Gibson et al., 2010), thus providing insights into the evolution of diet and parasitoidism amongst the enormous radiation of higher flies. The morphology of the mouthparts and female terminalia suggests that ancestral conopids were nectarivorous and parasitoids (Hennig, 1966), and must have evolved after the appearance of the flowering plants. It remains unclear which hosts are plesiomorphic: orthopteroids or hymenopterans, or another group entirely, unknown to date. The estimated divergence from molecular data between schizophoran and non-schizophoran Diptera is Upper Cretaceous (Santonian age), ca. 84.5 Mya (Bertone and Wiegmann, 2009), although there were no conopids in their analysis. A posterior analysis (Wiegmann et al., 2011), including conopids, found that the Schizophora date from the K–T boundary, ca. 66 Mya. The oldest schizophoran fossil is a Cretaceous (ca. 70 Mya, Maastrichtian age) puparium from Alberta, Canada, Cretophormia fowleri McAlpine, 1970, and its family relationships are uncertain. Except for this, all other fossil Schizophora are Cenozoic (ca. 66 Mya) and very common in Baltic amber, although occurring in younger amber (Grimaldi and Cumming, 1999; Grimaldi and Engel, 2005).The early–middle Miocene amber-bearing sediments in the Dominican Republic are associated with lignitic material and were formed in a great variety of depositional environments, from coastal to deep marine. The age of the amber-bearing sediments is estimated to be from Oligo-Miocene boundary (23 Mya) to middle Miocene (14 Mya) (Iturralde-Vinent, 2001). The exact formation of origin for the fossil is not provided on the specimen label, but its age corresponds to the amber-bearing sediments cited by Iturralde-Vinent (2001). This author suggests that those sediments were likely formed from debris produced from active uplift of a highland terrestrial or near-shore area.This paper aims to describe the first known Stylogaster fossils, compare them with the other conopid fossils, and discuss the systematic and biogeographic relevance of this new species.