APPARATUS OF YAOXIANOGNATHUS SP., CONODONTA, FROM THE VIOLA FORMATION, FORT WORTH BASIN, UPPER ORDOVICIAN (MID MOHAWKIAN)

A drill core sample containing a high abundance, low diversity conodont fauna dominated by Yaoxianognathus sp. that also included elements of Drepanoistodus suberectus and Panderodus sp. from the Viola Formation, Fort Worth Basin, central Texas, within the Belodina compressa Zone (mid Mohawkian) enabled reconstruction of the multielement apparatus, consisting of P₁, P₂, M, and five S elements, including a symmetrical S₀. The P₁ element is carminate, differing from Y. abruptus (Branson and Mehl) by longer anterior and posterior processes, and the absence of a pronounced gap between the posteriorly inclined cusp and the nearly erect denticles of the anterior process. The P₂ is a short, moderately arched angulate element. The M element is dolobrate, the S elements, for the most part fragmented and covered with apatite overgrowths, are bipennate (S₄ and S₃), digyrate (S₂ and S₁), and alate (S₀). Notable on the P₂, M, and S elements are longitudinal striations on the cusp and larger denticles.