﻿Oblatopyrochroabellula, an enigmatic new genus and species of Pyrochroinae (Coleoptera, Pyrochroidae) from Xizang, China

﻿Abstract Oblatopyrochroabellula, a new genus and species of Pyrochroinae Latreille, 1807 from Xizang, China, is described and illustrated. The antennae, cranial apparatus, and genitalia of the new genus form a truly unique set of characters not observed in any other pyrochroid genus. The taxonomic position and phylogenetic relationships of Oblatopyrochroagen. nov. are also discussed but appear difficult to resolve.

In May 2023, a unique species of fire-colored beetle was discovered in Xizang, China.The antennae, cranial apparatus, and male genitalia form a truly unique set of characters not observed in any other described pyrochroid genus.Therefore, we propose it as a new pyrochroine genus, which is described and illustrated below.

Material and methods
The male holotype is deposited at the Museum of Hebei University, Baoding, China (MHBU).The specimen was studied using a Nikon SMZ1500, and the images were taken using a Canon EOS 5D Mark III (Canon Inc., Tokyo, Japan) with a Laowa FF 100 mm F2.8 CA-Dreamer Macro 2× or Laowa FF 25 mm F2.8 Ultra Macro 2.5-5× (Anhui Changgeng Optics Technology Co., Ltd, Hefei, China).The figure of the antenna was drawn by hand using a Nikon SMZ1500 with a camera lucida.Label data are presented verbatim.Line breaks on labels are denoted by a double slash (//); metadata and notes (not written on the labels, themselves) are presented in square brackets ([ ]).Scientific names are uniformly presented in italics.
Most of the terms in the description are from previous literature (e.g.Young 1975).The ocular index (OI) was first used to quantify the relative distance between the compound eyes of Alleculinae Laporte, 1840 (Campbell and Marshall 1964).

OI
Minimum dorsal distance between compound eyes Maximal dorsal width across compound eyes 100.Diagnosis.This new genus is easily distinguished from other pyrochroine genera by the combination of following characters: frons with a single, large transverse concavity between compound eyes (Fig. 1B); eyes of moderate size, transverse width of an eye less than width between eyes, dorsally (Fig. 1B); antennal pedicel long, approximately 0.8× length of scape, dorsal face slightly concave (Fig. 1D); parameres of a male genitalia fused along approximately basal 2/3 and lacking recurved apical hooks (Fig. 1F, G).
Etymology.From the Latin root "oblat-" for "spread out" and Pyrochroa, in reference to the single, large transverse concavity on the frons, putatively diagnostic for the genus.This generic name is feminine.
Distribution.China: SE Xizang.Diagnosis.This species, the only known member of Oblatopyrochroa, can be recognized by the generic diagnosis given above.Description.Male: body (Fig. 1A) orange-yellow, except labial palpi, antennae, and legs black; mandibular apices dark brown.Body densely covered with short, fine, orange-yellow setae; dorsal surface of head sparsely setose except for patch of moderately long, mostly retrorse setae along meson of frons and along anterior rim of cranial excavation.Body length: 19.8 mm; humeral width: 4.8 mm.

Oblatopyrochroa bellula
Head (Fig. 1B) with dense, small punctures, diameter of punctures less than spacing of punctures, each inside with a very fine, medium-length seta.Dorsal distance between compound eyes wide (OI = 49.4).Clypeus and labrum flattened; labrum with anterior margin slightly emarginate.Frons with widely U-shaped, sub-reniform concavity, shallowly excavate mesally and more deeply so on sides near compound eyes, posterior margin complete, anterior margin obsolete mesally.Antennae (Fig. 1D) extending back to near middle of elytra; flagellomere I shortest; II-IV subequal in length, approximately as long as pedicel.
Pronotum (Fig. 1C) widest in middle, approximately as wide as head, length 0.87× width; disc shining, densely covered with small punctures, each side of base with inconspicuous protuberance; basal marginal bead complete.Scutellar shield densely covered with small punctures.Leg slender; prothoracic tarsomere V longest, I second longest, II-IV gradually shorter; mesothoracic tarsomere I subequal in length to V, II-IV gradually shorter; metathoracic tarsomere I longest, IV second longest, II-III gradually shorter.
Posterior margins of abdominal sternites III-VII subparallel, VIII with posterior margin shallowly, acutely emarginate mesally (Fig. 1E).In dorsal view, parameres subequal in length to phallobase, basal 2/3 of parameres fused (Fig. 1F).Penis broadly flattened, proximal part abruptly narrowed toward apex, apex nodular-shaped and curved ventrally (Fig. 1H, I Etymology.The specific epithet comes from the Latin adjective root "bellula-" meaning "pretty" or "elegant", in reference to the beauty of the species. Collecting habitat.The holotype was collected in May on the side of a stretch of road from Pai Town to Mêdog County, at a relative low elevation compared to the average elevation in Xizang, with cool temperatures but moist air (Fig. 2A).Specifically, it was found on a dying tree, parts of which had decayed and died (Fig. 2B, C).

Discussion
Oblatopyrochroa differs from all known pyrochroine taxa and shows a mixed distribution of character states.The three most diagnostic characters of Oblatopyrochroa are the shape of the male antennal pedicel, the configuration of the male cranial apparatus (sensu Young 2004b), and the male genitalia.The antennal pedicel of male pyrochroines is subject to significant variation at the generic and specific levels.In Oblatopyrochroa, it is elongate and approximately 0.8× the length of the scape, although its shape approached slightly in Phyllocladus kasantsevi Young, 2005 (see Young 2013: fig.13) and Frontodendroidopsis gibbiceps Young, 2006.
The head of male pyrochroines usually bears one or two pits or depressions that represent important diagnostic features of genera and species.Like several genera and species, Oblatopyrochroa has only one cranial pit.However, it is distinctly different from the modifications in Neopyrochroa (see Young and Caterino 2007: figs 1C, 2, 3a, 4) and Phyllocladus (see Young 2013: figs 2, 3, 8, 9, 12, 14, 15).In genera with a single cranial pit, for example Eupyrochroa (Fig. 3A) and Pyrochroa, the temples are prominent and the pit is quite shallow.
The male genitalia of Pyrochroinae have the parameres fused for most of their length, for example Dendroidopsis, Eupyrochroa (Fig. 4A), Pseudopyrochroa  (Fig. 4C), Pyrochroa, and Schizotus, or fused only along the basal half, for example Himalapyrochroa and Phyllocladus (Fig. 4D).In comparison, the parameres of Oblatopyrochroa are fused along the basal 2/3, close to those of Frontodendroidopsis (Fig. 4B) but without apically recurved hooks or teeth.The structure of the parameres in Oblatopyrochroa is most similar to that of Eupyrochroa and Pyrochroa.The shape of the penis of Oblatopyrochroa, conspicuously widening distally then abruptly "nodular" apically, differs significantly from that of other genera.
Flagellar rami III-IX of Oblatopyrochroa are short and thin, similar to Himalapyrochroa (Gao et al. 2023;Young 2004aYoung , 2005)), not long and almost threadlike, as in most males of Dendroides, Frontodendroidopsis, and Sinodendroides.
The temples of Oblatopyrochroa are strongly reduced and not prominent, similar to some species of Dendroidopsis, Frontodendroidopsis, Neopyrochroa, and Pseudopyrochroa (Fig. 3B).However, Dendroidopsis and Frontodendroidopsis usually have large eyes, and the distance between eyes is distinctly less than the dorsal transverse width of each eye in males, which differs from Oblatopyrochroa.
Although the observations above clearly support generic recognition, the relationship between the new genus and other pyrochroine genera remains difficult to determine at this time.We anticipate that the relationships will become better resolved by the discovery of larvae and females of O. bellula.Additional specimens, together with more material of other genera and species, will enable a more robust molecular phylogenetic analysis of Pyrochroinae as well.

Figure 1 .
Figure 1.Oblatopyrochroa bellula, gen.et sp.nov., male, holotype A habitus, dorsal view B head, dorsal view C pronotum, dorsal view D antenna, left E abdominal sternites VII-VIII, ventral view F, G tegmen: F dorsal view G lateral view H, I penis: H dorsal view I lateral view.Scale bars: 5 mm (A); 1 mm (others).

Figure 2 .
Figure 2. Habitat of Oblatopyrochroa bellula A general habitat B specific site (indicated by arrow) C microhabitat (the beetle inside is the holotype of O. bellula).Photographed from China, Xizang, Pai Town-Mêdog County Highway 42 km, elev.1991 m (type locality), by Quan-Yu Ji.