A new species of the extant genus Bulasconotus from mid‑Cretaceous Kachin amber (Coleoptera: Zopheridae: Colydiinae)

. A fossil species of the extant colydiine genus Bulasconotus Ślipiński & Lawrence, B. carinisternus Li, Ślipiński & Cai sp. nov., is reported from mid-Cretaceous Kachin amber of northern Myanmar. The new species shares with extant Bulasconotus the 3-segmented antennal club, externally open procoxal cavities, and similar sculpture on the pronotum and elytra, but could be recognized by the medially carinated prosternal process. The present discovery provides a valuable example of morphological stasis in the cylindrical bark beetles.

Here we describe a new colydiine species from Kachin amber, which could be placed in the extant genus Bulasconotus Ślipiński & Lawrence.As noted by Yamamoto (2024), many beetle taxa with high-level of morphological stasis are likely associated with the "cryptic" microhabitats, such as in leaf litter and soil or under bark (e.g., Cai et al., 2018Cai et al., , 2019;;Liu et al., 2020;Yamamoto, 2021Yamamoto, , 2024;;Li et al., 2024).The current finding offers a valuable example of long-term morphological stasis in the cylindrical bark beetles.

MATERIAL AND METHODS
The Kachin amber (Burmese amber) specimen studied herein (Figs.1-3) originated from amber mines near Noije Bum (26°20′N, 96°36′E), Hukawng Valley, Kachin State, northern Myanmar.The amber specimen is deposited in the Nanjing Institute of Geology and Palaeontology (NIGP), Chinese Academy of Sciences, Nanjing, China.The amber piece was trimmed with a small table saw, ground with emery paper of different grit sizes, and finally polished with polishing powder.
Photographs under incident light were taken with a Zeiss Discovery V20 stereo microscope.Confocal images were obtained with a Zeiss LSM710 confocal laser scanning microscope, using the 488 nm Argon laser excitation line (Fu et al., 2021).Images were stacked with Helicon Focus 7.0.2,Zerene Stacker 1.04 and Adobe Photoshop CC, and were further processed in Adobe Photoshop CC to adjust brightness and contrast.Protibiae apically with two spurs and several smaller spines.Tarsi 4-4-4; tarsomeres 1-3 similar in form, together shorter than tarsomere 4. Pretarsal claws simple, with basal dilation.

Systematic
Abdomen with five ventrites; ventrites 1 to 3 more solidly fused together than 4 and 5. Ventrite 1 with long and acute intercoxal process.Ventrite 5 with deep and narrow preapical groove parallel to apex.

Etymology:
The specific name refers to the medially carinate prosternal process of the new species.
Remaks: Bulasconotus is known in the Recent fauna as two described species living in the Melanesian islands (Ślipiński & Lawrence, 1997;Bernard & Gillett, 2020).The presence of B. scaccarius in Hawaii was thought to be invasive.Extant Bulasconotus can been found among the galleries of ambrosia beetles, and has been suggested as a potential predator of ambrosia beetles (Bernard & Gillett, 2020).

DISCUSSION
According to the keys provided by Lawrence (1980), Ślipiński & Burakowski (1988) and Ivie et al. (2016), the new fossil can be easily ruled out from all other colydiine tribes except Synchitini, based on characters including body surface with recumbent setae, antennae 11-segmented with 3-segmented club, procoxal cavities open, metanepisterna narrow, and tibiae simple.The fossil can be further keyed to the entry of Bulasconotus with the key provided by Ślipiński & Lawrence (1997), although this key was designed for Australo-Pacific taxa only.
In fact, the fossil shows striking similarity with extant members of Bulasconotus.It shares with extant Bulasconotus the absence of antennal grooves, not strongly projected frons, distinctly 3-segmented antennal club, externally open procoxal cavities, and similar sculpture on the pronotum and elytra (Ślipiński & Lawrence, 1997;Bernard & Gillett, 2020).Several synchitin genera also have an overall similar appearance.Among them, however, Bitoma Herbst and Microprius Fairmaire have a 2-segmented antennal club, Paha Dajoz has a 1-seg-mented antennal club, and Lasconotus Erichson has externally closed procoxal cavities (Lord, 2013).Although some species of Bitoma may be described as having a 3-segmented antennal club, their antennomere 9 is usually distinctly smaller than 10 (unlike the fossil which has subequal antennomeres 9 and 10).As such, under the current classification scheme, the fossil can be confidently placed in Bulasconotus.
However, problems remain in the current systematics for Bitoma-like genera.As mentioned above, although Bitoma mostly has a clearly 2-segmented antennal club, some members assigned to Bitoma may have a somewhat 3-segmented antennal club (Lord, 2013).Similarly, although Lasconotus is generally recognized as having  procoxal cavities closed by mesad extension of hypomeron, the procoxal cavities may be narrowly open in a few members assigned to Lasconotus (e.g., Kingsolver et al., 2006).In the phylogeny of New Zealand Zopheridae by Buckley et al. (2020), Bitoma was rendered as paraphyletic.In the phylogenies by Lord (2013), some members within Bitoma and Microprius were even distantly related.Although these studies used only a few gene fragments, they nevertheless indicate that the current generic classification system may require extensive revision.

FUNDING INFORMATION :
Financial support was provided by the National Natural Science Foundation of China (42222201, 42288201) and the Second Tibetan Plateau Scientific Expedition and Research project (2019QZKK0706).Y.-D.L. is supported by a scholarship granted by the China Scholarship Council (202108320010) and the Bob Savage Memorial Fund of the University of Bristol.ACKNOWLEDGMENTS:We are grateful to Keita Matsumoto and Max Barclay (Natural History Museum, London) for providing the photos of Bulasconotus solomon, Rong Huang (Institute of Soil Science, CAS) and Yan Fang (NIGP, CAS) for help with confocal microscopy, and Jing-Jing Tang for help with brightfield microscopy (NIGP, CAS).Vitalii Alekseev and an anonymous reviewer provided helpful comments on the manuscript.