Late Triassic (Norian) Conodont Apparatuses Revealed by Conodont Clusters from Yunnan Province, Southwestern China

Almost all aspects of conodont research rely on a sound taxonomy based on comparative analysis. This is founded on hypotheses of homology which ultimately rest on knowledge of the location of elements in the apparatus. Natural assemblages—fossils that preserve the articulated remains of the conodont skeletal apparatus—provide our only direct evidence for element location, but very few are known from the Late Triassic. Here we describe fused clusters (natural assemblages) from the late Norian limestone beds of the Nanshuba Formation in Baoshan, Yunnan Province, southwestern China. Recurrent arrangements and juxtaposition of S and M elements in multiple clusters reveal the composition of the apparatus of Mockina and, probably, Parvigondolella. They indicate that these taxa had a standard 15 elements ozarkodinid apparatus, and provide new insights into the morphology of the elements occupying the P2, M and S locations of the apparatus. The apparatus comprised a single alate (hibbardelliform) S0 element, paired breviform digyrate (grodelliform) S1 and (enantiognathiform) S2 elements, paired bipennate (hindeodelliform) S3 and S4 elements, paired breviform digyrate (cypridodellifrom) M elements, paired, modified-angulate P2 elements (with reduced or lacking ‘posterior’ process) and segminiplanate (mockiniform and parvigondolelliform) P1 elements. Our results will allow testing of the hypothesis that Mockina, Parvigondolella and Misikella—critical taxa in Late Triassic biostratigraphy—are closely related and possessed morphologically similar elements in homologous locations

Reconstruction, composition and homology of conodont skeletons – a response to Agematsu et al. 2018

[First paragraph] AGEMATSU et al. (2018) commented on our recent paper about testing hypotheses of element loss and apparatus stability in the apparatus composition of complex conodonts (Zhang et al. 2017). They take issue not with our approach, but with our specific hypothesis concerning the skeletal apparatus of Hindeodus parvus. We proposed that,in marked contrast to the remarkable anatomical conservatism exhibited by ozarkodinid conodonts, which seem not to vary their 15 element ‘dental formula’ over a period in excess of 250 million years, H. parvus had only 13 elements, lacking 2 elements from the posterior P domain of the apparatus.Our paper presents an hypothesis of homology for the skeletal elements of H. parvus that Agematsu et al. (2018) argue is incorrrect, based on three lines of reasonin