First occurrence of a Silurian linguloid brachiopod with soft tissue preservation in Wales

The lingulide brachiopod Mergliella sp. aff. M. bechei, with an exceptionally preserved three-dimensional pedicle, is described from the upper part of the Cae’r mynach Formation (Silurian, late Ludfordian) in Wales, UK, where it occurs with a limited shelly fauna and fine plant debris. The shells of Mergliella were probably exhumed locally by a thin storm sand sheet reaching into a subtidal delta-front environment and were transported little. Microbial mats developing in the fairweather environment, limited bioturbation and a sparse shelly fauna suggest an anachronistic taphonomic environment where the soft tissue became preserved. Fossilisation in dysaerobic or euxinic conditions resulted in replacement of organic tissues by platelets of clay minerals and fine pyrite crystal growth around the shell. Soft tissue preservation in this taphonomic environment is rare in shallow subtidal environments after Proterozoic-early Cambrian times except after ecosystem disruption such as extinction events. This is the only example of soft tissue preservation in a linguliform brachiopod from the Silurian Period.