An abnormal enamel pattern of the first lower molar (M1) in a field vole (Microtus agrestis) from the province of Zeeland, the Netherlands

Abstract: In barn owl (Tyto alba) pellets, a skull from a field vole (Microtus agrestis) was found with an abnormal dental pattern. The enamel ridge of the first right lower molar displayed a ‘capital M’ outline. The rim of the rootwas thin (as in a regular M1 molar), without irregularities or thickenings. Other morphs described in field voles and even the 22 morphotypes of other European and Asian arvicoline species within the genera Alexandromys and Microtus do not bear any resemblance to this specimen. The very rare abnormality in this field vole can be described as the ‘syndrome of the unilateral missing lingual re-entrant angles of the anterior cap complex of M1’. It is hypothesized that the form wasn´t caused by an infection, abnormal growth after an accident or tumour growth but most probably by an epigenetic condition.