Mathesia Mainelli (Hippuritoidea, Monopleuridae) from the Late Aptian-Albian of the Mediterranean Region: A Revision

Agria darderi Astre and Mathesia terticolloquiirudistarum Mainelli represent a single taxonomic entity: Mathesia darderi (Astre). Mathesia is characterized by an erect posterior myophoral plate and an anterior myophoral crest in the LV, the RV myophores being on the shell wall. A peculiar shell structure is observed in the RV: the junction between the outer calcitic shell layer and the inner formerly aragonitic shell layer is scalloped or festooned and usually includes longitudinal tubes. The overall morphological traits and myocardinal organisation of Mathesia are similar to those of Debrunia, although the latter lacks the scalloped or tubular inner shell features of the former. Debrunia is regarded as the ancestor of Mathesia. The palaeobiogeographical distribution of Mathesia darderi includes the southern and northern margins of the Mediterranean Tethys, and its maximum geographical extent coincides with the late Aptian-Albian.