Sesquithrips rostratus, Ulitzka, 2022

Ulitzka, Manfred R., 2022, New genera and species of Rohrthripidae (Thysanoptera: Tubulifera) from Burmese Cretaceous amber, Zootaxa 5162 (1), pp. 1-36 : 23-24

Sesquithrips rostratus gen. et sp. n.

( Figs 21–23 )

Female. Body ( Fig. 21 ) fully distended, head and thorax partially concealed by a vertical crack, basal abdominal segments deformed; left wings spread, right wings for the most part overlapping body; right hind leg and tarsus of left fore leg folded under body.

Colour ( Fig. 21 ) uniformly light brown to brown, including antennae and legs; wing veins and fringes dark as well as anal setae; major body setae, however, almost translucent and therefore difficult to see; fore wings shaded brownish, paler from the middle towards base; hind wings brownish, slightly paler than fore wings.

Head broad, wider than long; dorsally sculptured with transverse reticulations. Cheeks broadened behind eyes, converging slightly rounded towards base; laterally with spine-like setae arising from small tubercles. Ocellar setae difficult to assess; one short pair visible close to fore ocellus, one pair just before hind ocelli; postocular setae far behind compound eyes, pointed. Eyes small, about as wide as long, not prolonged ventrally. Ocelli large; hind ocelli close to compound eyes and far apart from each other; fore ocellus between antennal insertions, directed forwards. Antennal bases close together. Antennae nine-segmented; segment I conically shaped; II inversely conical, apically with a small sensorium; III–VII basally with a pedicle, then inverse conically shaped and tapering distally, somewhat oval in appearance but rather short; VIII with a pedicel, distally broadly joined to IX, giving the impression of one single segment. Sense cones not preserved, only some large attachment points visible. Mouth cone long and pointed, protruding to middle of mesosternum ( Fig. 21 ). Maxillary palps two-segmented. Pronotum wider than long. Major pronotal setae pointed; epimeral and posteroangular setae longer than others; anteromarginal setae vestigial. Mesonotum and metanotum reticulate. Fore wings narrow, somewhat broadened in basal half and bluntly rounded at tip; anterior vein complete, bearing six stout setae in distal two-thirds; second vein ending with a distinct stout terminal seta in the middle of the wing ( Fig. 22 ); wing membrane without microtrichia. Clavus with paired setiform processes at tip, their length not assessable. Fringe cilia straight; embedded into wing membrane, except at posterior distal margin of hind wings, where the wing margin is serrate into small teeth, each carrying a fringe cilium at tip attached on a tiny socket ( Fig. 23 ). Fore wing with nine duplicated cilia from tip along distal part of posterior margin, running parallel to normal wing fringes, and one single duplicated cilium on fore margin. Fore legs with femora not enlarged, apically with external margin sharply curved into a tooth-like protuberance; fore tibiae not clearly assessable; tarsi without tooth but with a recurved hamus. Mid and hind legs slender; tibiae each with a long dorsal seta; mid and hind tarsi two-segmented. Abdominal tergites without wing-retaining setae; lateral setae almost straight and pointed. Tergite I not assessable; IV–VII sculptured loose reticulate at anterior margin but with transverse lines posterior to setae s1. Abdominal segment IX conical, sculptured with 5–6 transversal lines; setae s1 blunt, s2 and s3 finely pointed; s1–s3 shorter than tube. Abdominal segment X tubular, with margins parallel; with a terminal crown of anal setae, these much shorter than tube.

Measurements. Female (in microns): Body, length 970. Head, length 109; width 130. Eyes, length 40; width 40. Hind ocelli, diameter 13; distance between the hind ocelli 25. Pronotum, length 133; largest width 177. Pronotal setae (length), anteromarginals 9, anteroangulars 16, mediolaterals 22, posteroangulars 31, posteromarginals 28; epimeral setae 34. Pterothorax, largest width 192 (at level of mesothoracic spiracles). Abdomen, length about 570 (not measurable due to deformed basal segments); width 202 (at segment V, anterior segments broader due to deformation); segment X (tube), length 90; width 28. Setae on tergite IX, length s1 47; s2 56; s3 62. Antennae, length 229; length (largest width) of segment I 25 (25), II 34 (19), III 34 (22), IV 33 (33), V 28 (22), VI 25 (19), VII 25 (16), VIII 19 (9), IX 12 (5). Fore wings, length 485; width at terminal seta of cross vein 40.

Material studied. Holotype female MU-Fos-136/1 ( Figs 21–23 ); inclusion in Burmese amber from Hukawng Valley , Kachin State, Myanmar. The holotype was donated by Patrick Müller and is deposited in the author’s collection.

Syninclusions. Remnants of different insects, stellate plant hairs and particles of plant detritus as well as some small droplets, air bubbles and brownish stains of unknown origin.

Etymology. The species epithet rostratus comes from the Latin word rostrum, meaning “beak”. It refers to the long and pointed mouth cone of this species ( Fig. 21 ).

Differential diagnosis. The two species are already distinguished by their visual appearance. S. markpankowskii gen. et sp. n. is more robust, with a much broader head and shorter pronotum. The most striking difference between the two species, however, is the shape of their mouth cone, which is long and pointed in S. rostratus gen. et sp. n. but short and rounded in S. markpankowskii gen. et sp. n. (see Figs 19–21 ). Furthermore, antennal segments VIII and IX are broadly joined in S. rostratus gen. et sp. n. whereas they are more clearly separated in S. markpankowskii gen. et sp. n.

Figures

FIGURES 21–23. Sesquithrips rostratus gen. et sp. n. holotype female. (21) dorsal view, mouth cone outlined white; (22) left wings, indicated: distinct seta at distal end of second wing vein; (23) serrate hind margin of left hind wing.

FIGURES 19–20. Sesquithrips markpankowskii gen. et sp. n. (19) holotype female, dorsal view, mouth cone outlined white; (20) paratype male, dorsal view, mouth cone outlined white. (Note: The wings of the male are bent upwards and, therefore, longer than visible on the photo).