Pakistatyrus Hlaváč, 2006

Yin, Zi-Wei, 2022, Discovery of mysterious Pakistatyrus in Tibet (Coleoptera: Staphylinidae: Pselaphinae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 62 (1), pp. 129-135 : 130-133

Genus Pakistatyrus Hlaváč, 2006

Chinese common name: Ẳ山ẅḎƤƂ

Pakistatyrus Hlaváč, 2006: 171 .

Type species. Pakistatyrus ater Hlaváč, 2006 ( Figs 2B, C ) (by original designation).

Diagnosis. In the original description (Hඅൺඏගඹ 2006), Pakistatyrus was suggested to be most closely related to the Australian Hamotulus Schaufuss, 1887 , and was compared with and separated from the latter genus. However, a list of characters that are diagnostic for Pakistatyrus was not given. The diagnosis is provided here based on the examination of the holotype of P. ater and two Tibetan species:

Tyrine of medium to large size, body length ranging from 3.0– 3.8 mm. Head elongate-trapezoidal, with apex truncate; with small asetose vertexal (dorsal tentorial pits) and large setose frontal fovea; area between antennal tubercles longitudinally sulcate; frontal rostrum broad and prominent; antennal insertions on ventral side of rostrum; with setose postantennal foveae and large ocular canthi; gula with foveae (posterior tentorial pits) widely separated, lacking median carina; eyes in both sexes small; maxillary palpi with palpomere 1 small, 2 elongate and curved, 3 and 4 pedunculate at base and broadening apically, 4 with distinct apical cone. Pronotum with well-marked median and lateral antebasal foveae connected by shallow transverse antebasal impression/sulcus, areas anterior to foveae impressed, medial impression may extend anteriorly to form shallow longitudinal sulcus. Prosternum with widely separated lateral procoxal foveae. Elytra strongly shortened and fused, trapezoidal, truncate at bases, each elytron with two large, setose basal foveae; discal stria represented by broad, shallow impression. Metathoracic (hind) wings lacking. Mesoventrite with moderately separated median foveae in transverse setose impression, large, setose lateral foveae forked internally. Metaventrite with large, setose lateral mesocoxal foveae and single setose median metaventral fovea, with postero-admedial areas conspicuously projecting/ridged. Legs elongate; pro- and mesofemur broadened, profemur with two large, widely separated ventral spines strongly divergent from shared base, protibia with two rows of spinose setae along mesal margin; mesotrochanter with distinct spine on ventral margin; tarsi with short tarsomere 1 and elongate tarsomeres 2 and 3, 2 slightly longer than 3, each tarsus with two subequal pretarsal claws. Abdomen with tergites 1–3 (IV–VI) subequal in length in middle and broadly sulcate at bases; corresponding paratergites of tergites 1–3 complete, protruding laterally, paratergite of tergite 4 (VII) triangular. Male sexual characters present on antennae and legs, or inconspicuous; aedeagus elongate, dorso-ventrally slightly asymmetric, with elongate parameres and weakly developed endophallus.

Comparative notes. Members of Pakistatyrus are usually large in size (3.0– 3.8 mm) and possess characters that may be related to their high-altitude lifestyles, e.g., shining surface of the body, small eyes, greatly reduced elytra, and well-developed spines of the legs. Using Hඅൺඏගඹ & CH ൺඇൽඅൾඋ (2005) Pakistatyrus is keyed out at couplet 13 with Palimbolus Raffray, 1890 , a fairly large group comprising 23 described species and some 50 undescribed ones in Australia ( CH ൺඇൽඅൾඋ 2001). Pakistatyrus shares with Palimbolus the presence of frontal and vertexal foveae of the head, distinct median and lateral antebasal foveae of the pronotum, ovoidal fourth segments of the maxillary palpi, and relatively short first visible tergites. Aside from the aforementioned characters, Pakistatyrus clearly differs from Palimbolus in more elongate antennomeres, lack of anteroprosternal foveae (foveae present and large in Palimbolus ), tergite 1 (IV) approximately as long as 2 (V) (tergite 1 distinctly shorter than 2 in Palimbolus ), and the presence of well-developed parameres of the aedeagus (parameres lacking in Palimbolus ).

Among the Asian genera of Tyrina Pakistatyrus appears to be most similar to the genus Tyrinasius Kurbatov, 1993 with seven species found in Central Asia ( Kyrgyzstan, Uzbekistan) and China (Ningxia, Yunnan, Sichuan). Tyrinasius likewise has all members with small eyes and reduced elytra, and the male sternite 7 (IX) is composed of three plates (Nඈආඎඋൺ 1999). Tyrinasius can be readily separated from Pakistatyrus by small body size (1.6–2.5 mm), suboval head, sub-globose pronotum that lacks foveae, the absence of spines on the profemora, and by short parameres of the aedeagus. Pakistatyrus is also similar to Tibetyrus from Tibet in general appearance, but the latter genus has tufted setae on temporal angles, the apical cone of the maxillary palpomere 4 and the femoral spines are lacking, parameres of the aedeagus are short, and ecologically, the adults were found in association with Formica ants.

Ecology. According to Hඅൺඏගඹ (2006) the two males of P. ater were collected from Malam Jabba ( Fig. 2C ) in May at an altitude between 2300 to 2600 m, where the area is dominated by temperate coniferous forests and with temperature varying from −4.7°C in January to 21.9°C in June (Aඍඍൺ- ඎඋ- RൺHආൺඇ & Dൺඐඈඈൽ 2017). Similarly, the two Tibetan species were collected from rather high-altitude areas, where the other pselaphine groups, except for a few Brachyglutina, are poorly represented. Three males of P. inconspicuus sp. nov. were found, one was collected by sifting a mixed litter sample of fern leaf and wood debris at an altitude of 3750 m ( Figs 3A, B ), and the other two males were taken by sifting fern leaves lying on the ground on a steep, rocky slope at a slightly lower area of approximately 3600 m. The single female of Pakistatyrus sp. ( Fig. 3E ) was collected by sifting leaf litter and debris on the ground in a Rhododendron dominant forest ( Figs 3C, D ), at an altitude of 4100 m with rather low temperature (<15℃). An examination of the Tibetan species revealed that the elytra of all four individuals are fused (cannot be open separately), and the hind wings in both sexes are lacking, which suggests that these species are probably locally endemic and have limited abilities of dispersal. This was further reinforced by the small, reduced eyes of the male, which is often corelated to wing development, indicating trade-offs related to flight capability, reproductive output, and longevity of life span (Gඎൾඋඋൺ 2011) may exist for the male sex. The presence of two rows of spinose setae along the inner margin of the protibia of Pakistatyrus appears to be a highly distinctive character that is rarely found among the other tyrine genera. These spinal structures and the projecting ocular canthi may be involved in a specialized, previously unknown prey mechanism in pselaphine beetles, and future behavioral observation is desired to confirm such a hypothesis.

It is interesting to note that all three specimens of P. inconspicuus sp. nov. were thought to be female during initial checks using a magnifier in the field, because it was assumed that the male antennae of these beetles may present modifications as in P. ater . The members of Pakistatyrus are difficult to collect due to their high-altitude habitats which are hard to access, as well as the minimum dispersal capabilities of the beetles. It is clear that additional collecting efforts are needed to further determine the diversity of the genus along the Himalayan range.

Figures

Fig. 2. Dorsal habitus (A, B) and distribution (C) of Pakistatyrus. A – Pakistatyrus sp.; B – holotype of P. ater, with type labels (upper) and sketch of aedeagus (lower, from Hඅൺඏගඹ 2006); C – circle: P. ater, triangle: Pakistatyrus sp., square: P. inconspicuus sp. nov. Scale bars: 1.0 mm.

Fig. 3. Environment and habitat of P. inconspicuus sp. nov. (A, B) and Pakistatyrus sp. (C, D), and a living individual of Pakistatyrus sp. in situ (E).