Geological Society of America

T220 Celebrating Advances in Conodont Studies—134 Years of North American Conodonts

Tuesday, 29 October 2013
8:00 AM - 12:00 PM
Mile High Ballroom 1CD

NEW EVIDENCE FOR A LAMPREY-LIKE MOTION OF THE GRASPING ELEMENTS OF OZARKODINID CONODONTS

Paper number: T220-12
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Nicolas Goudemand Presenting Author
Stanford University, Stanford, CA
Guido Roghi
IGG / University of Padua, Padua, N/A
Manuel Rigo
University of Padova, Padova, N/A
Morgane Brosse
Universität Zürich, Zürich, N/A
Maximiliano Meier
University of Zurich, Zürich, N/A
Paul Tafforeau
European Synchrotron Radiation Facility, Grenoble, N/A
Séverine Urdy
University of California San Francisco, San Francisco, CA

Abstract

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.