Paper No. 12
Presentation Time: 10:45 AM


GOUDEMAND, Nicolas, Paleobiology Group, Stanford University, 450 Serra Mall, Stanford, CA 94305, ROGHI, Guido, Department of Geosciences, IGG / University of Padua, Padua, 35137, Italy, RIGO, Manuel, Department of Geosciences, University of Padova, Via Giovanni Gradenigo 6, Padova, 35131, Italy, BROSSE, Morgane, Paläontologisches Institut und Museum, Universität Zürich, Karl-Schmid-Strasse 4, Zürich, CH-8006, Switzerland, MEIER, Maximiliano, Paleontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, Zürich, 8006, Switzerland, TAFFOREAU, Paul, European Synchrotron Radiation Facility, 6 rue Jules Horowitz, Grenoble, 38000, France and URDY, Séverine, University of California San Francisco, San Francisco, CA 94107,

Fused clusters of elements of Novispathodus Orchard, an Early Triassic ozarkodinid conodont, led Goudemand et al (2012, Palaeontology) to switch the elements occupying S1 and S2 positions in the feeding apparatus. Goudemand et al (2011, PNAS) also re-interpreted some uncommon bedding-plane natural assemblages as potentially recording rare but alternative living configurations of the elements, and proposed an animated reconstruction of the feeding apparatus at work. The reconstructed movements suggested the presence of a lingual cartilage about which the elements were rotated by pairs of antagonistic muscles, i.e. a pulley-like mechanism also present in extant cyclostomes (hagfishes and lampreys).

One of the predictions of this feeding model is that the unpaired S0 element and the pair of anterior and obliquely pointed M elements performed a synchronized pinching movement. This infrequent configuration appears to be recorded by some bedding-plane natural assemblages. Yet, their preservation renders them somewhat equivocal. In three-dimensional fused clusters either one of the M elements or the S0 element is usually missing.

We have recently imaged some newly discovered and exceptionally preserved fused clusters of elements of the Norian Mockina Kozur using propagation phase-contrast X-ray synchrotron microtomography. The analysis of these almost complete clusters lends further support to the revised hypothesis of S1 and S2 element morphology and to the proposed model. In particular, the recorded positions of the M elements relative to the S elements add new constraints that are compatible with the model and one cluster even shows direct evidence of the predicted pinching configuration.