Updated diagnoses for the cricket family Trigonidiidae (Insecta: Orthoptera: Grylloidea) and its subfamilies (Trigonidiinae, Nemobiinae), with a review of the fossil record

Abstract Morphological diagnoses are given for the cricket family Trigonidiidae and its two monophyletic subfamilies, the Trigonidiinae and the Nemobiinae. Owing to their morphological characters, we transfer the extant genus Lissotrachellus Hubbell, 1838 from the Gryllidae: Pentacentrinae to the Trigonidiidae: Nemobiinae. Lissotrachellus was the type genus of Lissotrachelini including also Trigonidomimus Caudell, 1912 and Tohila Hubbell, 1938 which are here transferred to Pentacentrinae incertae sedis. The fossils currently attributed to the Trigonidiidae and its subfamilies are reviewed, in order to facilitate future phylogenetic studies. Few fossils can actually be classified in Nemobiinae or Trigonidiinae, and most are Cenozoic: the oldest nemobiine is the Eocene Baltonemobius fossilis Gorochov, 2010 (37.2–33.9 Ma), while the oldest representatives of the crown group Trigonidiinae date from the Miocene (20.43–13.65). The early Cretaceous Liaonemobius tanae Ren, 1998, originally described in the Trigonidiinae, and currently listed in the Gryllidae, proved an Elcanidae. The mid-Cretaceous Birmaninemobius hirsutus Xu et al., 2020, described in the Nemobiinae, is here transferred to the stem group Trigonidiinae.