Pantostictus hirsutus, Jan & ºimon-Pražák & Yamamoto & Lackner & Fikáček & Prokop & Michael & Caterino, 2024

Simon-Pražák, Jan, Yamamoto, Shûhei, Lackner, Tomáš, Fikáček, Martin, Prokop, Jakub & Caterino, Michael S, 2024, A bonanza of Cretaceous fossils provides insights into the evolution of antennal protection in clown beetles (Coleoptera: Histeridae), Zoological Journal of the Linnean Society (zlae 137) 202 (3), pp. 1-28 : 10

Pantostictus hirsutus sp. nov.

( Fig. 7 )

Material: Kachin amber (c c. 99 Mya). Amber piece dimensions: 12 × 7 × 1 mm. Amber clear with several insect fragments and air bubbles. Deposited at HUM ( SEHU-121212 ) .

Measurements: Head width: 0.25 mm; width between anterior pronotal angles: 0.35 mm; width between posterior pronotal angles: 0.55 mm; pronotal length: 0.35 mm; sutural elytral length: 0.35 mm; elytral width (in pair, across widest point): 0.65 mm.— Body: Oval with a densely and coarsely punctuated cuticle. Dorsal surface with sparse short setation.— Head: Frons and clypeus flat, coarsely punctuate, without striae. Labrum short and wide, rounded apically, plurisetose. Left mandible appearing bidentate. Antennal club flat and triangular (most likely deformed).— Thorax: Pronotal disc coarsely punctuate, broadly rounded basally, anterior angles pointed. Lateral margin finely crenulate. Scutellar shield hidden. Elytra expanded laterally in basal third, surface of elytral disc coarsely punctuate and finely setose, without striae. Epipleura punctate, but not striate. Prosternum short and wide. Prosternal process widely rectangular anteriorly, coarsely punctuated with crenulate margin and lateral fissures for antennal passage. Antennal clubs rest in shallow cavities located in anterior prosternal angles. Prosternal lobe not distinct. Meso- and metaventrite coarsely punctuated. Metaventrite with recurved postcoxal striae.— Legs: Profemur flattened, with a groove for protibial reception. Protibia slightly expanding apically, outer margin rounded in apical half, bearing few short spines; protibial apex with a small tibial spur. Protarsomeres short, terminal as long as 3–4 combined. Middle leg similar to front leg. Metafemur swollen with setae dorsally, metatibia slightly expanded apically, with several small setae along outer margin increasing in size apically and with a tibial spur. Tarsomeres short, terminal tarsomere as long as tarsomeres 3–4 combined; tarsomeres 1–4 bearing single pair of apicoventral spines.— Abdomen: First abdominal ventrite punctuated with the same coarseness as metaventrite. Other visible abdominal sclerites (incl. pygidium) with finer punctuation. Propygidium short and wide, largely concealed by elytra.

Taxonomic assignment: We assign this new species to the genus Pantostictus (in the monotypic Pantosticini; Zhou et al. 2020) based on the ventrally flat and oval body shape, broad and rectangular apex of prosternal process, and the coarse punctuation. The genus was further characterized by Poinar and Brown (2009) as having an acute, triangular-shaped antennal club, and by lacking postmesocoxal and ventral abdominal striae. Despite appearing somewhat similar in the sole specimen of this new species, we believe that the odd antennal club shape is a postmortem deformity caused by collapse of a poorly sclerotized structure, as its exact shape varies considerably among available specimens (compare, e.g. Poinar and Brown’s figs 2 vs. 3). Further, although the tribal separation of Pantostictini from Plegaderini is well justified on several characters ( Zhou et al. 2020), the alleged absence of postcoxal striae (on the lateral metaventrite and on abdominal ventrite 1) should be disregarded. Their absence is difficult to assess in the specimens of P. burmanicus , and the postmesocoxal striae, at least, are visible in P. hirsutus (see Fig. 7F ).

Differential diagnosis: The species appears to be closely related to Pantostictus burmanicus Poinar and Brown, 2009 . It is similar in overall appearance, but there are significant differential characters. The elytral punctuation is coarser in P. burmanicus . The lateral pronotal margins are finely crenulate in P. hirsutus ( Fig. 7E ), whereas in P. burmanicus they are smooth. In P. hirsutus , the pronotum is wider basally and lateral margins are simply rounded and parallel-sided in the posterior half ( Fig. 7A ), while the lateral pronotal margins of P. burmanicus are sinuate. Furthermore, P. hirsutus displays a setose dorsal cuticle ( Fig. 7D ). Setation presence in P. burmanicus cannot be determined based on the original description and published photographs ( Poinar and Brown 2009).

Etymology: The name of this species was chosen to point out its hirsute cuticle.

Figures

Figure 7. Pantostictus hirsutus sp. nov.. A, dorsal view. B, ventral view.C, lateral view. D, elytral setation, E, dorsal view. F, metaventrite, abdomen.Abbreviations:ac, antennal club; as, antennal scape; ls, labral setae; pl, prosternal lobe; pmss, postmesocoxal stria.