A distinctive Late Triassic microvertebrate fissure fauna and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia) from Woodleaze Quarry, Gloucestershire, UK

During the Late Triassic and Early Jurassic, diverse terrestrial vertebrates were preserved in fissures formed in Carboniferous Limestone on an island archipelago spanning from the south of Wales to the north and south of Bristol. Here we report the faunas of two new fissures in Woodleaze quarry, near to Tytherington quarry, where the vertebrate fauna is already well known. The new site extends the lateral distribution of fissures in this vicinity to over 900. m, and fissures sampled along that transect show a southerly change in the dominant species and a reduction in diversity. The Woodleaze fissure fauna is nearly monofaunal, comprising >98% of a new Clevosaurus species, as well as some Diphydontosaurus fragments, a possible undescribed lepidosaur and a few fish fossils. The new clevosaur is distinguished from the type species Clevosaurus hudsoni by its dentition, and by being smaller (average long bones are 40-80% the length of C. hudsoni). In addition, the collection also includes individual skeletal elements that were not previously well described, thus expanding our knowledge of clevosaur anatomy. The Woodleaze bones are preserved as black or dark grey, rather than white, and this preservation mode and single-species dominance occurs elsewhere only inthe Windsor Hill fissure where Oligokyphus predominates. Together with Tytherington, this location offers an exceptional opportunity to study a Triassic terrestrial biota across an extended distance, and to compare near-littoral niches with more inland island habitats.