Stempellina, Thienemann & Bause, 1913

Zakrzewska, Marta, Singh, Hukam, Wagner-Wysiecka, Ewa & Giłka, Wojciech, 2020, Minute and diverse in fossil sticky stuff: Tanytarsini (Diptera: Chironomidae) from early Eocene Indian Cambay amber, Zoological Journal of the Linnean Society 189, pp. 1398-1425 : 1417-1421

In Tanytarsini , the median volsella is an appendage of the male gonocoxite, consisting of a stem that bears lamellae of highly diverse shapes ( Saether, 1980). The median volsellae, with a couple of exceptions (i.e. when reduced, cf. Ekrem & Reiss, 1999), are thus the most important diagnostic structures in Tanytarsini . In T. ramus , the MVo is simple, consisting of a twig shaped stem, branched into two lamellae ( Fig. 5E, F). If we treat T. ramus as one of the oldest known tanytarsines,

19. Ultimate palpomere with strong, stiff apical seta; anal tergite with longitudinal crest-like hump bearing median setae ( Giłka, 2011: figs 1, 2) ................................ Tanytarsus fereci (Baltic region: Gulf of Gdańsk) Ultimate palpomere without stiff apical seta; anal tergite without longitudinal hump, median setae absent ( Giłka et al., 2013: fig. 7; Zakrzewska & Giłka, 2015a: fig. 8; Zakrzewska et al., 2016: fig. 5) ......20 20. Gonostylus straight, with long seta on apex; superior volsella finger like, distinctly curved at mid-length and directed medially; median volsella sickle shaped, with slender arcuate lamellae ( Zakrzewska et al., 2016: fig. 5) ..................................................................... Tanytarsus crocota (Baltic region: Gulf of Gdańsk) Gonostylus curved at mid-length or boomerang like, with subapical tooth-like process at most; superior volsella bean shaped or with nipple-like apical extension, straight, directed posteromedially or posteriorly; median volsella never sickle shaped, bearing leaf shaped (foliate) lamellae ( Giłka et al., 2013: fig. 7; Zakrzewska & Giłka, 2015a: fig. 8; Zakrzewska et al., 2016: fig. 6).............................................................21 21. Stem of median volsella bulb shaped ( Giłka et al., 2013: fig. 7) ...................................................................... ............................................................................................. Tanytarsus congregabilis (Baltic region: Rovno) Stem of median volsella elongated, straight ( Zakrzewska & Giłka, 2015a: fig. 8) ........................................ ........................................................................ Tanytarsus PROTOGREGARIUS (Baltic region: Gulf of Gdańsk) 22. Gonostylus distinctly longer than gonocoxite ( Fig. 8; Seredszus & Wichard, 2007: fig. 18)

Stempellina … 23

Gonostylus shorter than or as long as gonocoxite ( Fig. 10; Seredszus & Wichard, 2007: fig. 19; Zakrzewska & Giłka, 2014: fig. 4; Zakrzewska & Giłka, 2015a: fig. 4; Zakrzewska et al., 2016: fig. 8) .... Stempellinella ........................................................................................................................................................................ 24 23. Anal point spinulae absent; superior volsella twig shaped, strongly elongated: length/width ratio nearly ten ( Seredszus & Wichard, 2007: fig. 18) ..................... Stempellina exigua (Baltic region: Gulf of Gdańsk) Anal point spinulae present; superior volsella cylindrical, apically rounded, slightly elongated: length/ width ratio nearly two ( Fig. 8) ........................................................... Stempellina stebneri ( India: Cambay) 24. Inferior volsella with stout process on median margin ( Fig. 10) .................................................................... ............................................................................................................. Stempellinella pollex ( India: Cambay) Inferior volsella without process on median margin ...................................................................................25 25. Gonostylus with apical nipple-like process; anal point with spinulae; superior volsella directed posteriorly; inferior volsella with beak-like protrusion ( Zakrzewska & Giłka, 2014: fig. 4) .............................................. .................................................................... Stempellinella ivanovae (Baltic region: Gulf of Gdańsk, Rovno) Gonostylus without apical nipple-like process; anal point without spinulae; superior volsella directed medially; inferior volsella without beak-like protrusion ( Seredszus & Wichard, 2007: fig. 19; Zakrzewska & Giłka, 2015a: fig. 4; Zakrzewska et al., 2016: fig. 8) ................................................................................ 26 26. Antennal flagellum consisting of ten flagellomeres; median volsella shorter than superior volsella ( Seredszus & Wichard, 2007: fig. 19) ...................... Stempellinella bicorna (Baltic region: Gulf of Gdańsk) Antennal flagellum consisting of 13 flagellomeres, flagellomeres 11–13 or 12–13 partly fused ( Zakrzewska & Giłka, 2015a: fig. 3; Zakrzewska et al., 2016: fig. 7); median volsella longer than superior volsella ( Zakrzewska & Giłka, 2015a: fig. 4; Zakrzewska et al., 2016: fig. 8) ......................................................... 27 27. Median volsella (stem + lamellae) distinctly shorter than gonostylus, bearing wide pectinate and foliate lamellae ( Zakrzewska & Giłka, 2015a: fig. 4) ......... Stempellinella electra (Baltic region: Gulf of Gdańsk) Median volsella (stem + lamellae) and gonostylus of similar length, bearing slender foliate lamellae, single lamella with strongly elongated filiform tip ( Zakrzewska et al., 2016: fig. 8) ..................................... ....................................................................................... Stempellinella fibra (Baltic region: Gulf of Gdańsk)

we then assume that this type of volsella might display one of the simplest/oldest types of MVo structure in Tanytarsini (plesiomorphy), comparable to that known from the extinct genus Archistempellina Giłka

& Zakrzewska, 2013 described from Baltic amber (cf. Giłka et al., 2013; Zakrzewska & Giłka, 2014).