Oblatopyrochroa bellula, 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 Oblatopyrochroa gen. nov. are also discussed but appear difficult to resolve.

Fire-colored beetle, taxonomy, Tibet

Pyrochroinae Latreille, 1807 is the most speciose subfamily of Pyrochroidae Latreille, 1807 and is widely distributed in the Holarctic Region, especially in temperate areas of Asia. This subfamily includes more than 120 recent species in 14 genera (Young 1975, 2002; Young et al. 2020; Pan et al. 2021; Molfini et al. 2022): Dendroides Latreille, 1810 (8 species), Dendroidopsis Young, 2004b (4 species), Eupyrochroa Blair, 1914 (1 species), Frontodendroidopsis Young, 2004b (3 species), Hemidendroides Ferrari, 1869 (4 species), Himalapyrochroa Young, 2004a (2 species), Neopyrochroa Blair, 1914 (4 species), Phyllocladus Blair, 1914 (5 species), Pseudodendroides Blair, 1914 (7 species), Pseudopyrochroa Pic, 1906 (ca 70 species), Pyrochroa Geoffroy, 1762 (5 species), Pyroghatsiana Young, 2016 (1 species), Schizotus Newman, 1838 (5 species), and Sinodendroides Young, 2005 (2 species). However, most of the abovementioned genera include only few species, the only world revision was admittedly preliminary (Blair 1914), and no comprehensive taxonomic revision including phylogenetic hypotheses has been published for this subfamily. The taxonomic validity of some genera has been debated (e.g. Eupyrochroa, Pseudopyrochroa, etc.; Gao et al. 2024).

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.

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).

$\mathrm{OI}=\frac{\mathrm{Minimum} \mathrm{dorsal} \mathrm{distance} \mathrm{between} \mathrm{compound} \mathrm{eyes} }{\mathrm{Maximal} \mathrm{dorsal} \mathrm{width} \mathrm{across} \mathrm{compound} \mathrm{eyes} }\times 100$.

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.

Figure 3. 

Head of two pyrochroine species, males, dorsal view A Eupyrochroa insignita (Fairmaire, 1894) B Pseudopyrochroa carinifrons Kôno, 1929. Scale bars: 1 mm.

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.

Figure 4. 

Tegmen of pyrochroine species, dorsal view A Eupyrochroa insignita (Fairmaire, 1894) B Frontodendroidopsis pennyi Young, 2017 C Pseudopyrochroa carinifrons Kôno, 1929 D Phyllocladus grandipennis (Pic, 1906). Scale bars: 1 mm.

Flagellar rami III–IX of Oblatopyrochroa are short and thin, similar to Himalapyrochroa (Gao et al. 2023; Young 2004a, 2005), not long and almost thread-like, 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.

We wish to thank Mr Quan-Yu Ji (Hebei University, Baoding, China) who collected the specimen in the field. Thanks are also extended to Prof. Darren A. Pollock (Eastern New Mexico University, Portales, USA) and Dr Dmitry Telnov (Natural History Museum, London, UK) for constructive comments.