A new species, Mesolepis arabellae, is described from material recently recovered from the shales of the Scottish Lower Coal Measure Formation. Up until now, three British species of Mesolepis have been named: Mesolepis scalaris Young, Mesolepis wardi Young, and Mesolepis micropterus Traquair. A fourth member of the genus, Mesolepis pustulosa Pruvost from the coalfields of Northern France, was named on scale description alone, though the validity of this taxon is uncertain. The new material described here varies from other Mesolepis species in its caudal peduncle morphology and overall body shape. Micro-computed tomography of the new species reveals the presence of teeth on the premaxilla and dentary and a splint-like fused prearticular and coronoid element, with implications for a possible feeding behaviour of Mesolepis. Additional information on the homogeneous Mesolepis wardi is also presented.
