New osteological characteristics identify the first stem sleeper goby (Gobioidei, Odontobutidae) from the upper Eocene

Among the Gobioidei, one of the most diverse orders of teleost fishes, the families Odontobutidae (sleeper gobies) and Rhyacichthyidae are considered ‘basal gobioids’ and are therefore particularly interesting for understanding gobioid evolutionary history. However, their fossil record currently consists of only three extinct odontobutid species (two skeleton based, one otolith based). The aim of this study was to investigate the relationship of one of the oldest known gobioid fossils, † Paralates chapelcornerensis from the upper Eocene of southern England, to these families. The material examined comprises newly collected, well‐preserved fossil skeletons, isolated bones, and otoliths from the type strata of † P. chapelcornerensis , as well as specimens of 19 extant species from museum collections representing related groups (both known rhyacichthyid genera, five of the seven recognized odontobutid genera, one genus each of the Eleotridae, Butidae, Gobiidae, Trichonotidae, Apogonidae). Based on micro‐computed tomography of the extant species, comparative morphology and both maximum parsimony and Bayesian inference phylogenetic analyses, our study: (1) elucidates previously unknown osteological characteristics of † P. chapelcornerensis ; (2) identifies the new species † P. simpsoni ; (3) presents an atlas of 17 (15 new) osteological characters that differentiate Odontobutidae and Rhyacichthyidae; and (4) recognizes † Paralates as a stem odontobutid. Previously reported odontobutid fossils originate from southeastern Asia (like present‐day odontobutids) and New Zealand, thus our results extend the palaeobiogeographical range of sleeper gobies to Europe. Furthermore, our fossil stem odontobutid represents the first fossil‐based evidence for the divergence of Rhyacichthyidae and Odontobutidae, indicating a split dating back at least 35–37 myr.