Two new early balognathid conodont genera from the Ordovician of Oman and comments on the early evolution of prioniodontid conodonts

Reports of Ordovician conodonts from the Arabian region of the Gondwanan margin are extremely rare. Here we provide a description of the apparatus of two new conodont genera and species, Aldridgeognathus manniki and Omanognathus daiqaensis, based on discrete elements recovered from the Am5 Member of the Amdeh Formation, Darriwilian, Ordovician of the Sultanate of Oman. The apparatuses contain 17 and 15 elements, respectively, and both possess three pairs of P elements. The apparatus structure of Omanognathus is similar to the bedding plane assemblage-defined genus Notiodella (= Icriodella) but differs in that as yet only 15 elements rather than 17 have been identified. Aldridgeognathus has similar P elements to the early Silurian apparatus Pranognathus but differs in the possession of a geniculate M element and a Baltoniodus-like S element array. Aldridgeognathus does not easily fit with either the 17-element Notiodella (Icriodella) or the 19-element Promissum templates and suggests that there may be othe...