A new tribe of Diamesinae (Diptera: Chironomidae) from the Lower Cretaceous of Mongolia

• New tribe of Diamesinae is described based on pupa from Early Cretaceous of Mongolia.
• It is the earliest fossil record of the subfamily.
• New taxon is distinguished by numerous branched lateral setae on abdominal segments.

A new tribe of Diamesinae, Eugenodiamesini tr. nov. (Diptera: Chironomidae), is described based on a single pupa from Khutel Khara (lower part of the Tsagan Tsab Formation, Lower Cretaceous of Mongolia). The most distinctive characters of the new taxon are numerous multibranched lateral setae on tubercles along entire margins of abdominal segments II–VIII, and a unique setation of the anal lobes, with two multibranched anal macrosetae on each side and one simple near the apex. The fossil is the oldest known member of Diamesinae.