Multielement conodont apparatus (Cornudina) from the Lower Triassic of China, revealed by high-resolution X-ray microtomography

The apparatus of the coniform conodont genus Cornudina remains equivocal because the previous results were derived from discrete element collections rather than natural assemblages. Four exceptionally preserved natural assemblages collected from bed 719 of the upper Nanlinghu Formation in Majiashan quarry, Chaohu of Hefei City, Anhui Province, East China, were imaged using high-resolution X-ray microtomography. The consistent and repeated patterns of element juxtaposition suggest an apparatus of 15 elements, conforming to the classical 2M-9S-4P skeletal template that comprises three basic morphologies: two breviform dolabrate elements, nine elongate bipennate elements, and four angulate elements. The angulate P₁ and P₂ elements have a distinct cusp, short anterior and posterior processes and the P₂ element is twisted crescent-shaped, which supports a taxonomic assignment to Cornudina breviramulis sensu stricto Koike. Multielement comparisons among Cornudina, Neostrachanognathus, and Hindeodus apparatuses suggest Cornudina and Neostrachanognathus are closely related and possibly derived from Hindeodus. The multi-element comparison between Ordovician ‘complex’ conodont apparatuses (e.g., Paracordylodus and Phragmodus) and Triassic ‘coniform’ apparatuses (e.g., Cornudina and Neostrachanognathus) suggests that the low variation in the elemental forms of the latter is probably a secondary ‘evolution’.