Triamyxidae, Qvarnström & Fikáček & Vikberg Wernström & Huld & Beutel & Arriaga-Varela & Ahlberg & Niedźwiedzki, 2021

Family Triamyxidae fam. nov.

Type genus

Triamyxa gen. nov.

Differential diagnosis

Characters of the new family are put in contrast to [ x] other myxophagan families: dorsal body surface without tubercles or ridges ( x Lepiceridae ); eyes strongly protruding ( x Sphaeriusidae , most Hydroscaphidae ); head anterior of eyes prolonged and distinctly narrowing ( x Hydroscaphidae , Sphaeriusidae ); antennal bases exposed dorsally between eyes ( x Hydroscaphidae , Lepiceridae ); antennal scapus and pedicel distinctly separated from each other ( x Torridincolidae , Lepiceridae ), exposed in dorsal view ( x Lepiceridae , modern Hydroscaphidae ); terminal maxillary palpomere long, longer than penultimate ( x Hydroscaphidae , Sphaeriusidae ); mentum large, narrowing anteriad ( x modern Hydroscaphidae ); prosternum long, with very short prosternal process ( x Hydroscaphidae , Lepiceridae ); propleuron wide, without posterior projection ( x all modern families); mesoventrite only slightly shorter than metaventrite ( x Hydroscaphidae , Sphaeriusidae , Torridincolidae ); mesoventrite with wide subpentagonal elevation ( x modern Hydroscaphidae , Torridincolidae ); elytra only slightly shortened, exposing 1 to 2 terminal abdominal tergites ( x all modern families), truncated posteriorly ( x Sphaeriusidae , Torridincolidae , Lepiceridae ); metanepisternum moderately wide anteriorly ( x Sphaeriusidae , Torridincolidae , Lepiceridae ); metacoxal plates present, narrow ( x Sphaeriusidae , Torridincolidae , Lepiceridae ); abdomen with 5 to 6 exposed ventrites ( Figure 4 View Figure 3 ; x Sphaeriusidae , some Torridincolidae ); all abdominal segments with separate tergite and sternite ( x Hydroscaphidae ). For more details, see Table S1. From its habitus, Triamyxidae is similar to Hydroscaphidae but differs from this family in a series of characters listed above, most notably the lack of fused tergites and sternites of abdominal segments III–VI. This abdominal configuration, a very uncommon shared derived feature and synapomorphy of extant Hydroscaphidae and the Triassic Leehermania , is clearly absent from Triamyxa , where tergites and sternites of all abdominal segments are distinctly separated ( FigureS1 View Figure 1 ).