Taimyraphes gen. nov., the first glandulariine ant-like stone beetle from Santonian Taimyr amber (Coleoptera: Staphylinidae: Scydmaeninae)

Abstract

The Glandulariini includes 78 genera comprising over 70% of the extant nominal species of Scydmaeninae. Extant members of this tribe are ubiquitous in forests of all continents. Because of small size of most species (often below 2 mm), taxonomic problems accumulated over the past 200 years, and scarcity of fossils with exposed ventral structures that are crucial for generic diagnoses, Glandulariini are rarely subjects of palaeontological studies. Consequently, only five Cretaceous genera have been described, mostly those that can be diagnosed by conspicuous, often bizarre autapomorphies. We report a finding of the first Santonian member of Glandulariini, Taimyraphes microscopicus gen. et sp. nov., based on a specimen in Taimyr amber from Yantardakh. This is also the smallest described Cretaceous glandulariine beetle, with the body length merely ∼0.8 mm. The fossil preservation state allows for examination of mesoventral structures, rarely exposed in such small specimens. We conclude that Taimyraphes does not show any novel character states; it is defined, as many extant Glandulariini, by a unique combination of synapomorphies that, separately or in different sets, can be found in its extant relatives. The Santonian Taimyraphes of Taimyr shares a similar body form with the extinct Eocene Rovnoscydmus of Ukraine, and with the extant Neotropical Amimoscydmus and Heteroscydmus, Nearctic Delius and Neladius, cosmopolitan Microscydmus, or Western Palaearctic Leptocharis. As most Cretaceous Glandulariini are known from Cenomanian, and only one from Turonian, the first Santonian fossil is important to fill gaps in our knowledge of the evolution of Scydmaeninae, a group of beetles that apparently diversified into the extant tribes in or before Early Cretaceous.