Cretolixon, Lohrmann & Zhang & Michalik & Blaschke & Müller & Jeanneau, 2020

Lohrmann, Volker, Zhang, Qi, Michalik, Peter, Blaschke, Jeremy, Müller, Patrick & Jeanneau, Laurent, 2020, † Cretolixon - a remarkable new genus of rhopalosomatid wasps (Hymenoptera: Vespoidea: Rhopalosomatidae) from chemically tested, mid-Cretaceous Burmese (Kachin) amber supports the monophyly of Rhopalosomatinae, Fossil Record 23 (2), pp. 215-236 : 228-229

Cretolixon and its implication for the biology of early rhopalosomatids

Lohrmann and Engel (2017) showed that the ectoparasitoid larval habit of rhopalosomatids has not changed since the Cretaceous, and the discovery of enlarged ocelli in Eorhopalosoma ( Engel, 2008; Boudinot and Dungey, 2020) indicates that early members of the family may have had crepuscular or nocturnal habits similar to those of recent rhopalosomatids. In contrast to Eorhopalosoma and most species of Paniscomima and Rhopalosoma (similar to Fig. 9g ), Cretolixon has moderately small ocelli ( Figs. 4b , 5b , 6b ); i.e., the size is similar to those found in Liosphex ( Fig. 9i ). Otherwise, only Paniscomima seyrigi ( Berland, 1951) has ocelli of a similar size ( Fig. 9h ). While this is surely the plesiomorphic character state within the family, it does not allow any conclusion with respect to the biology of the species.

The two previously described Burmese rhopalosomatid taxa are known from males only. Thus, C. alatum gen. et sp. nov. represents the first Cretaceous rhopalosomatid species known from both sexes and thus allows for investigations of sexual dimorphism. As known from recent Rhopalosomatidae , Cretolixon shows only moderate sexual dimorphism. Apart from the reproductive organs, the visible differences are limited to the number of visible metasomal tergites and the morphology of the antennae and legs.

Figures

Figure 4. Cretolixon alatum gen. et sp. nov., male, holotype (MB.I 6500; ZMB). (a) Habitus in lateral view. (b) Head in slightly oblique frontal view.(c) Mesosoma in lateral view.(d) Partial right antenna.(e) Wings.Abbreviations:ab – apical bristle; FI, FII, FIII – flagellomere 1, flagellomere 2, flagellomere 3; lo – lateral ocellus; oc – occipital carina; p – pedicel; sc – scape. The arrowheads indicate the apical bristles on third maxillary palpomeres (c) and basal flagellomeres (d).

Figure 5. Cretolixon alatum gen. et sp. nov., female, paratype (VL-Bu-04, UMB). (a) Habitus in lateral view. (b) Head and basal halves of antennae in oblique lateral view. (c) Mesosoma in lateral view. (d) Right protibia and protarsus. (e) Wings. The arrowheads indicate the apical bristles on second labial and third maxillary palpomeres (b).

Figure 6. Cretolixon alatum gen. et sp. nov., male and female, paratypes (male: SNSB-BSPG 2020 XCIII 25, SNSB; female: NIGP173865, NIGP). (a, c, d) Male. (a) Habitus in lateral view. (c) Base of right antenna. (d) Base of left antenna. (b, e) Female. (b) Habitus in slightly oblique dorsal view. (e) Partial right antenna (apex of FI to base of FIV). The arrowheads indicate the apical bristles on basal flagellomeres.

Figure 9. Some characters of Rhopalosomatidae. (a) Rhopalosomatidae, gen. et sp. indet., Burmese (Kachin) amber (ZMB; MB.I 6501), basal section of hind wing. (b) Liosphex boreus Lohrmann (in Lohrmann and Ohl, 2010), basal section of hind wing. (c) Rhopalosoma nearcticum Brues, 1943, basal section of hind wing. (d) Olixon banksii (Brues, 1922), mouthparts. (e) Liosphex longicornis Lohrmann (in Lohrmann and Ohl, 2010), mouthparts. (f) Paniscomima kilombero Lohrmann, 2011, mouthparts. (g) Paniscomima opposita Guidotti, 2007, male, paratype, head in dorsal view. (h) Paniscomima seyrigi (Berland, 1951), female, head in dorsal view. (i) Liosphex varius Townes, 1977, female, holotype, head in dorsal view. Abbreviations: ab – apical bristle; lp1,..., lp4 – labial palpomere 1,..., labial palpomere 4; mp1,..., mp6 – maxillary palpomere 1,..., maxillary palpomere 6. Panel (i) is reproduced with permission from copyright holder and was first published in Zootaxa (Lohrmann and Ohl, 2010); photo by David Wahl.