Recent Southern Hemisphere Lamprimine Stag Beetle in Cretaceous Burmese Amber and Its Biogeographic Implications (Coleoptera: Lucanidae)

Simple Summary Lucanidae (stag beetles) is a small family and one of the most ancient groups within the Scarabaeoidea superfamily. Most adult lucanids exhibit clear sexual dimorphism, with males often having impressive mandibles that are used in fierce competition for mates. Fossils of Lucanidae from the Mesozoic era are rare. In this study, we describe a new lucanid fossil, Prostreptocerus burmiticus Yu & Cai gen. et sp. nov., found in mid-Cretaceous Burmese (Kachin) amber, which shares similar features with the modern Lampriminae. This discovery marks the first fossil record of Lampriminae in mid-Cretaceous amber from northern Myanmar and is the oldest reliable record of the subfamily. The well-developed mandibles and curved claws of Prostreptocerus Yu & Cai provide additional evidence for sexual dimorphism and combat behavior in Mesozoic lucanids. This new taxon also enhances our understanding of early biodiversity and the biogeographic implications of stag beetles.Abstract A new stag beetle fossil, Prostreptocerus burmiticus Yu & Cai gen. et sp. nov., is described based on a single male specimen. This is the first representative of the subfamily Lampriminae (Coleoptera: Scarabaeoidea: Lucanidae) from mid-Cretaceous Burmese amber. The new species is distinctive among Lucanidae due to its well-developed, right-angled mandible, frons featuring a pair of large protuberances, a coarse and sparsely punctate elytral disc, and large tubercles on the humeri. Prostreptocerus Yu & Cai is placed within Lampriminae based on several key characteristics. Morphologically, it is most similar to the extant Streptocerus Fairmaire, 1850. The current distribution of Streptocerus and Lampriminae is primarily restricted to the Southern Hemisphere, suggesting that this lineage is ancient and existed on Gondwanaland, which has significant geographical implications. This discovery extends the fossil record of Lampriminae and provides additional evidence for the existence of sexual dimorphism and potential combat behavior in Mesozoic lucanids. Additionally, Electraesalopsis Bai, Zhang & Qiu, 2017, previously placed as Lucanidae incertae sedis, shares many characteristics with Prostreptocerus Yu & Cai and is also assigned to Lampriminae based on a suite of traits.