Bioluminescent beetles of the superfamily Elateroidea (fireflies, fire beetles, glow-worms) are the most speciose group of terrestrial light-producing animals. The evolution of bioluminescence in elateroids is associated with unusual morphological modifications, such as soft-bodiedness and neoteny, but the fragmentary nature of the fossil record discloses little about the origin of these adaptations. We report the discovery of a new bioluminescent elateroid beetle family from the mid-Cretaceous of northern Myanmar (ca99 Ma), Cretophengodidae fam. nov.Cretophengodes azarigen. et sp. nov. belongs to the bioluminescent lampyroid clade, and would appear to represent a transitional fossil linking the soft-bodied Phengodidae + Rhagophthalmidae clade and hard-bodied elateroids. The fossil male possesses a light organ on the abdomen which presumably served a defensive function, documenting a Cretaceous radiation of bioluminescent beetles coinciding with the diversification of major insectivore groups such as frogs and stem-group birds. The discovery adds a key branch to the elateroid tree of life and sheds light on the evolution of soft-bodiedness and the historical biogeography of elateroid beetles.

The cryptic slime mold beetles, Sphindidae, are a moderately diverse cucujoid beetle family, whose members are obligately tied to slime molds throughout their life. The fossil record of sphindid beetles is sparse; stem-sphindids and crown-group members of uncertain systematic placement have been reported from Cretaceous ambers. Here we review the Mesozoic fossil record of Sphindidae and report a new sphindid genus and species, Trematosphindus newtoni gen. et sp. nov., from Albian/Cenomanian amber from northern Myanmar (ca. 99 Ma). Trematosphindus is set apart from all other sphindids by the presence of distinct lateral cavities on the anterior pronotal angles. Our phylogenetic analysis identifies Trematosphindus as an early-diverging genus within Sphindidae, sister to the remainder of the family except Protosphindus, or Protosphindus and Odontosphindus. The new fossils provide evidence that basal crown slime mold beetles begun to diversify by the mid-Cretaceous, providing a valuable calibration point for understanding timescale of sphindid co-evolution with slime molds.

Beetles have a remote evolutionary history dating back to the Carboniferous, with Mesozoic fossils playing a pivotal role in elucidating the early evolution of extant families. Despite their exceptional preservation in amber, deciphering the systematic positions of Mesozoic trogossitid‐like beetles remains challenging. Here, we describe and illustrate a new trogossitid‐like lineage from mid‐Cretaceous Kachin amber, Foveapeltis rutai Li, Kolibáč, Liu & Cai, gen. et sp. nov. Foveapeltis stands out within the Cleroidea due to the presence of a significant large cavity on each hypomeron. While the exact phylogenetic placement of Foveapeltis remains uncertain, we offer a discussion on its potential affinity based on our constrained phylogenetic analyses.

A new genus of malachiine Melyridae, Platyintybiagen. nov., is described based on several male-specific characters, along with description of its type species, Platyintybia zhongshanensissp. nov., from China. A new combination, Platyintybia sarawakensis (Champion, 1921), comb. nov., is proposed after examining the type specimen; this species is newly recorded from China. A key to the genera of Chinese Apalochrini is provided for the first time.

A new species of the extinct genus Brochocoleus Hong, Brochocoleus zhiyuani sp. nov. is described based on two well preserved fossils embedded in the mid-Cretaceous amber originating from Myanmar. The species is deposit to B. caseyi Jarzembowski, Wang et Zheng, 2016 described from the same deposits but differs in having not an elongated head, long antennae and rounded prothorax.

Helotidae is a small and morphologically uniform family in Nitiduloidea. In this study, we report an unusual form of helotids, represented by Lobatihelota lescheni Li, Liu & Cai gen. nov., sp. nov. and L. iridescens Li, Liu & Cai sp. nov. from mid-Cretaceous Burmese amber. Lobatihelota is unique within the family in having a leg morphology typical of some Nitidulidae and Kateretidae (tibia widened distally, tarsomeres 1–3 bilobed, tarsomere 4 shortened). Additionally, new diagnostic characters are suggested for Trihelota from the same deposit (prosternum and mesoventrite with paired carinae, metanepisterna short, metacoxae meeting elytra laterally), and the morphological divergence of representative genera of the superfamilies Erotyloidea, Nitiduloidea and Cucujoidea is visualised using a phylomorphospace approach. ZooBank: urn:lsid:zoobank.org:pub:FE0E4D6A-8157-4E14-9240-7B87F285AEA5