A new marsh beetle from mid-Cretaceous amber of northern Myanmar (Coleoptera: Scirtidae)

As one of the earliest-diverging lineage of the megadiverse beetle suborder Polyphaga, marsh beetles (Scirtidae) are crucial for reconstructing the ancestor of all polyphagan beetles and the ecomorphological underpinnings of their remarkable evolutionary success. The phylogeny of marsh beetles has nonetheless remained challenging to infer, not least because of their fragmentary Mesozoic fossil record. Here we describe a new scirtid beetle genus and species, Varcalium lawrencei gen. et sp. nov., preserving internal tissue, from Albian-Cenomanian Kachin amber (ca 99 Ma), representing the second member of this family known from the deposit. Based on a formal morphological phylogenetic analysis, Varcalium is recovered within the crown-group of Scirtinae, forming a clade with other genera that possess subocular carinae. The finding suggests that the crown-group of Scirtinae has already diversified by the mid-Cretaceous.

Automated summary

Marsh beetles play a crucial role in understanding the evolutionary success and ecological morphology of Polyphaga beetles, but their phylogeny has been challenging due to limited fossil records. A new scirtid beetle genus and species, Varcalium lawrencei gen. et sp. nov., has been discovered in Albian-Cenomanian Kachin amber, suggesting the diversification of Scirtinae crown-group in the mid-Cretaceous.