Ictinogomphus engelorum, Nel & Poschmann & Wedmann, 2020

Nel, André, Poschmann, Markus J. & Wedmann, Sonja, 2020, New dragonflies and damselflies (Odonata) from the late Oligocene of Enspel (Rhineland-Palatinate, SW Germany), Palaeontologia Electronica (a 59) 23 (3), pp. 1-24 : 14-16

Ictinogomphus engelorum sp. nov.

Figures 9–10

zoobank.org/ EE23E6B8-F66E-4465-9B46-D743CCDDC312

Type material. Holotype PE 2000 /5006- LS a, b (part and counterpart of a nearly complete hind wing with extreme apex and base missing), paratype PE 2003/5040- LS (part only, basal two-third of a forewing), paratype PE 2003/5039- LS a, b (part and counterpart of distal half of a wing), stored at the State Collection of Natural History of Rhineland-Palatinate.

Diagnosis. Wing characters only. A broad area between posterior branch of IR2 and RP3/4 with three rows of cells in the narrowest part: broad area between two branches of IR2 with three rows of cells basal of secondary longitudinal vein; a long well-defined secondary vein between branches of IR2; hind wing subtriangle free; forewing one probably two-celled; forewing discoidal triangle fivecelled, with costal side distinctly longer than basal side; in hind wing, one row of cells between IR2 and RP2 below pterostigma.

Etymology. Named after Carmen Engel and the entire Engel family from Enspel, for their continuous interest in and support of the excavations.

Description. Holotype PE 2000 /5006- LS a, b ( Figures 9.1-2 , 10.1 ): Hind wing, hyaline, 46.7 mm long, wing 13.3 mm wide; pterostigma 7.1 mm long, 1.1 mm wide, covering six cells; pterostigmal brace strong and oblique; 12 postnodals; distance between nodus and pterostigma 15.6 mm, between nodus and arculus 15.6 mm; Ax2 at level of distal angle of discoidal triangle; possibly one crossvein in hypertriangle; discoidal triangle elongate, crossed by a vein, with distal side MAb slightly angled at base of trigonal planate tspl; tspl rather weak and short; 4–5 crossveins in area between RP and MAa basal of RP3/4; probably numerous antenodals, but many are not preserved; 4–5 Bqs crossveins; oblique crossvein ‘O’ four cells distal of subnodus; IR1 basally zigzagged, and straight in distal part; base of RP2 aligned with subnodus, RP2 regularly curved without marked concavity; main branch of IR2 parallel to RP2; posterior branch of IR2 well-defined with four rows of cells and a well-defined secondary longitudinal vein between it and main branch; three rows of cells between posterior branch of IR2 and RP3/ 4 in narrower part; RP3/4 smoothly curved but with a more pronounced curve apically; one row of cells between RP3/4 and MAa, but near their apices a zigzagged vein and two rows of cells in-between; MAa smoothly curved; a posterior branch of MAa similar to that of IR2; postdiscoidal area with two rows of cells basally and distally greatly broadened; mostly one row of cells between MP and CuAa, but two rows near posterior wing margin; cubito-anal area broad with 6–7 rows of cells between CuAa and posterior wing margin and 4–5 posterior branches of CuAa; anal area poorly preserved, anal loop apparently subdivided into four cells; subtriangle free; PsA well-defined and oblique; median area free; submedian crossed by CuP and another vein.

Paratype PE 2003 /5039- LS a ( Figures 9.3 , 10.2 ): As the basal third is missing, it is not possible to determine if it is a fore- or a hind wing. Preserved parts are very similar to those of specimen PE 2000/5006-LS. Only IR1 is slightly shorter than in PE 2000/5006-LS, only four rows of cells between the branches of IR2, and 11 postnodals. Pterostigma 6.7 mm long, 1.1 mm wide, distance between nodus and pterostigma 10.5 mm.

Paratype PE 2003 /5040- LS ( Figures 9.4 , 10.3 ): Forewing, hyaline; length of fragment 38.6 mm; wing ca. 9.8 mm wide; distance from base to arculus 4.5 mm, from arculus to nodus 19.8 mm, from base to Ax 1 2.7 mm, from Ax1 to Ax2 6.3 mm; Ax2 slightly basal to distal angle of discoidal triangle; five crossveins between Ax1 and Ax2, 15 secondary antenodal crossveins distal of Ax2; 14 preserved postnodals; 12 crossveins between RP and MAa basal of RP3/4; seven Bqs veins; oblique vein ‘O’ five cells distal of subnodus; hypertriangle with two crossveins; discoidal triangle subdivided into five cells, with costal side 3.2 mm long, basal side 2.5 mm long, distal side MAb 3.2 mm long, MAb with a slight angle at base of tspl; RP3/4 and MAa weakly curved and parallel in preserved parts, with one row of cells in-between; three rows of cells in basal part of postdiscoidal area, broadened distally; a distinct posterior branch of MAa, with four rows of cells between it and MAa; median area free; submedian area crossed by CuP and two other veins; PsA strong and oblique; subtriangle possibly crossed by a vein (fragment visible).

Remarks. The preserved parts of these three wings are very similar, and the forewing and the hind wing fit well with a Gomphidae of the genus Ictinogomphus Cowley, 1934. Probably all wings are of the same species. The attribution to the family Gomphidae is suggested by the following synapomorphies: distinct PsA; slight angle in the posterodistal side of the discoidal triangle caused by the presence of the tspl; anterior side of the hypertriangle distinctly curved; straight arculus (Bechly, 1996, 2003). Ictinogomphus engelorum sp. nov. shows an elongated discoidal triangle with a distinct tspl, which is a feature only known within Gomphidae from the Hageniinae and Lindeniinae. The Hageniinae have the veins MP and CuAa strongly divergent towards the wing margin in their hind wings; IR1 is secondarily elongated in both wings; costal margin and RA is not widened along pterostigmata. All these characters are not present in Ictinogomphus engelorum sp. nov. Also, the Hageniinae have the discoidal triangles distinctly longitudinal elongate in both pairs of wings, which is not the case for the forewing. The Lindeniinae are characterized by the following synapomorphies: secondary branch of IR2 very distinct, therefore IR2 appears to be dichotomously forked distal of the lestine oblique vein; hind wing discoidal triangle longitudinal elongate with a strongly sigmoidal and angulated distal side, caused by the development of a distinct tspl in the postdiscoidal area; discoidal triangles divided into more than two cells in both pairs of wings; in forewings the basal part of the subdiscoidal cell (between CuP-crossing and pseudo-anal vein PsA) is traversed by supplementary cubito-anal-crossveins; pseudo-anal vein PsA is less distinct in the hind wing, correlated with the elongated hind wing discoidal triangle; hypertriangle divided by at least two or more crossveins.

Among the Recent lindeniine genera, Diastatomma Burmeister, 1839 , has a pronounced angle in the forewing distal side (MAb) of discoidal triangle, strongly curved distal halves of main longitudinal veins, and many more cells covered by the pterostigmata, unlike Ictinogomphus engelorum sp. nov. (Schouteden, 1934; Dijkstra and Clausnitzer, 2014). Lindenia De Haan, 1826 , has also a pronounced angle of MAb, a more elongate discoidal triangle of forewing, and a narrower apical part of the area between RP3/4 and MAa than Ictinogomphus engelorum sp. nov. Gomphidictinus Fraser, 1942 , differs from Ictinogomphus engelorum sp. nov. in the absence of the pterostigmal brace, in numerous small cells covered by the pterostigmata and in the three-celled hind wing subtriangle (Carle, 1986; Zhang et al., 2017). The venation of Gomphidia Selys, 1854 (incl. Mitragomphus Needham, 1944 ), resembles that of Ictinogomphus engelorum sp. nov., but the pterostigmal braces are reduced, and the forewing discoidal triangle is more equilateral than in Ictinogomphus engelorum sp. nov., although subject to some variation (Needham, 1944; Garrison et al., 2015; Zhang et al., 2017; Babu and Subramanian, 2019). Cacoides Cowley, 1934 shares with Ictinogomphus engelorum sp. nov. the presence of three rows of cells between RP3/4 and posterior branch of IR2, several crossveins in the area between RP and MAa basal of RP3/4, but it differs from Ictinogomphus engelorum sp. nov. in the equilateral forewing discoidal triangle, a marked concavity of the vein RP2, and a longer pterostigma, covering much more cells (Schmidt, 1935: pl. 17, fig. 5; Garrison et al., 2010). Melanocacus Belle, 1986 , also differs from Ictinogomphus engelorum sp. nov. in the equilateral forewing discoidal triangle and a longer pterostigma, covering many more cells (Belle, 1986).

The four Recent genera Ictinogomphus , Austrictinogomphus Fraser, 1940 , Sinictinogomphus Fraser, 1939 , and Indictinogomphus Fraser, 1939 , can be accurately separated on the basis of the genitalia only (Fraser, 1939). Carle (1986: 320) indicated that Austrictinogomphus , Cinitogomphus Pinhey, 1964 , Indictinogomphus , and Sinictinogomphus could be subgenera of Ictinogomphus . Only this group of genera would greatly resemble Ictinogomphus engelorum sp. nov. Nevertheless, Ictinogomphus engelorum sp. nov. differs from the African genus Cinitogomphus in the forewing discoidal triangle with the costal side longer than the basal side, not right angled isosceles (Pinhey, 1964, 1970). In Ictinogomphus engelorum sp. nov., this triangle is isosceles in having costal and distal sides of the same lengths, not the basal and costal sides. The monotypic genus Austrictinogomphus has only two rows of cells in the postdiscoidal area, but the variability of this character remains unknown (Fraser, 1940). It is not possible to discriminate among the three other genera Ictinogomphus , Sinictinogomphus , and Indictinogomphus . We can only indicate that Ictinogomphus engelorum sp. nov. corresponds to an Ictinogomphus sensu lato. The presence of three rows of cells in area between RP3/4 and posterior branch of IR 2 in Ictinogomphus engelorum sp. nov. seems to be unusual in the genus Ictinogomphus . At least Cinitogomphus dundoensis , Ictinogomphus alaquopterus , I. angulosus , I. australis , possibly I. distinctus , I. kishori and I. celebensis , I. decoratus , I. dobsoni , I. ferox , I. fraseri , I. paulini , I. pertinax , I. pugnovittatus , I. rapax , I. regis-alberti , and I. tenax have only two rows of cells in this area (Schmidt, 1935; Ram, 1985).

Among the fossil Lindeniinae , the oldest representative Cratolindenia knuepfae Bechly, 2000 , is from the Early Cretaceous of Brazil. It strongly differs from Ictinogomphus engelorum sp. nov. in a more distal position of the posterior branch of IR2, in a strongly oblique pterostigmal brace and in having a very broad area between RP2 and RP1 below the pterostigma. Schädel and Bechly (2016) described Burmalindenia imperfecta based on the basal parts of hind wings from the ‘mid’-Cretaceous Burmese amber, and attributed it to the ‘subfamily cf. Lindeniinae’. It differs from Ictinogomphus engelorum sp. nov. in the strongly curved veins AA1b and CuAb.

Hagen (1863) described Ictinogomphus fur from the Oligocene of Rott am Siebengebirge ( Germany), on the basis of the basal third of a wing. The elongate vein CuAb would suggest it is a hind wing; but if this is correct, the presence of three cells in the subdiscoidal area does not fit with an Ictinogomphus in which this area is unicellular (Frazer, 1957). Indeed, the shape of the discoidal triangle better corresponds to that of a forewing. Nel and Paicheler (1994a) already indicated that it is an Anisoptera of uncertain family that should be revised.

Nel and Paicheler (1994a) described an undetermined Lindeniinae from the latest Oligocene of Bes-Konak ( Turkey). Also Prokop et al. (2016) described an? Ictinogomphus species indet. from the early Oligocene of Seifhennersdorf (Saxony, Germany) on the basis of the distal two-third of a forewing. Ictinogomphus engelorum sp. nov. differs from these two fossils in the broader area between posterior branch of IR2 and RP3/4 with three rows of cells in the narrowest part, instead of two, the broader area between the two branches of IR2 with three rows of cells basal of the secondary longitudinal vein instead of two, and the longer and better defined secondary vein between the branches of IR2.

Schädel and Lechner (2017) described Ictinogomphus hassleri from the early Miocene of Carinthia ( Austria), on the basis of the distal two-third of a hind wing. Ictinogomphus engelorum sp. nov. differs from I. hassleri in the presence of three rows of cells between RP3/4 and posterior branch of IR2 instead of two, and in the presence of only one row of cells between IR2 and RP2, instead of two, below the pterostigma.

Schädel and Lechner (2017: 157) indicated that Ictinogomphus hassleri can be separated from the other lindeniine genera, except Ictinogomphus and Sinictinogomphus Fraser, 1939 , by the ‘shape of the triangulum and the position of the Tspl-origin’, without being more precise. But the preserved parts of the wing of I. hassleri are nearly identical to those of the Recent Gomphidia podhigai Babu and Subramanian, 2019 , without perceptible differences in the discoidal triangle, position of the angle of MAb and shape of the trigonal planate (Babu and Subramanian, 2019: fig. 9).

Yasuno (1990) attributed an abdomen with characteristic lateral expansions from the Miocene of Japan to the genus Ictinogomphus . It is not possible to compare it to Ictinogomphus engelorum sp. nov., and its attribution to a lindeniine genus is not possible.

Figures

FIGURE 9. Ictinogomphus engelorum sp. nov. 1, Holotype PE 2000/5006-LS a, hind wing; 2, Counterpart of holotype, PE 2000/5006-LS b; 3, Paratype, PE 2003/5039-LS a, distal part of wing; 4, Paratype, PE 2003/5040-LS, part of forewing. Scale bars are 10 mm.

FIGURE 10. Ictinogomphus engelorum sp. nov., interpretative drawings of wings. 1, Holotype PE 2000/5006-LS a, hind wing; 2, Paratype, PE 2003/5039-LS a, distal part of wing; 3, Paratype, PE 2003/5040-LS, part of forewing. Scale bars are 10 mm.