DOI: 10.5061/dryad.mgqnk98xf
title: Patterns of bilateral asymmetry and allometry in Late Devonian Polygnathus conodonts

description: Conodont animals were jawless vertebrates equipped with a feeding
 apparatus composed of several tooth-like elements. The P1 elements, at the
 rear of the apparatus, are well preserved and abundant in the sediments,
 and their temporal evolution constitutes a tracer of ecological
 interactions and/or abiotic changes in the water column. However,
 occlusion occurred in these animals between paired right and left
 elements, occasioning bilateral asymmetry, which, together with allometric
 growth, may obliterate the temporal differences. This study aimed at
 disentangling these different components of morphological variation in
 Late Devonian Polygnathus P1 elements. An extensive 2D geometric
 morphometric analysis of the platform shape was performed and completed by
 a 3D study on a subset of elements. The 2D and 3D morphometric
 quantifications provided highly congruent results, showing that the 2D
 shape provides a good approximation of the element geometry. The 3D
 analysis, however, provides a more complete description of the geometrical
 changes involved in growth and bilateral asymmetry, providing insights on
 the constraints related to occlusion. In complement, the 2D analysis
 allowed a quantitative assessment of the variation between and within
 species, showing that allometry and bilateral asymmetry were differently
 expressed depending on the species considered. This suggests that
 constraints imposed on pairing by the morphology of the elements, and the
 pattern of bilateral asymmetry, varied even among related species. The
 within-species variation was so important that it obliterated temporal
 trends; a relationship of Polygnathus shape and conodont biofacies
 variations through the Famennian suggested an evolution driven by
 ecological interactions between conodonts.
description: <strong>Poly3D_with carina_raw</strong><br>
 .txt file: A first set of landmarks was digitized on 3D models extracted
 from µCT-scans (cubic voxel resolution 1 µm). This dataset includes 34
 <i>Polygnathyus communis</i> and 30 <i>Po.
 glaber</i>. The landmark set comprises three landmarks and 34
 semi-landmarks. The three landmarks described (1) the dorsal extremity of
 the platform, (2) the insertion of the anterior margin of the platform on
 the free blade and (3) the insertion of the posterior margin on the free
 blade. Two curves of 13 equally distributed semi-landmarks correspond to
 the anterior and posterior margins of the platform, from the insertion
 points to the dorsal extremity of the platform. A third curve of 8
 semi-landmarks correspond to the carina. Semi-landmarks are the landmarks
 #4 to 37. Raw 3D coordinates are columns V1 to V111.
 <strong>Polygnathus_2D_CTBU</strong><br> .txt
 file: A second set of landmarks was digitized on 2D pictures of the
 conodont elements, the oral surface facing the camera. This dataset
 includes 1564 conodonts. The landmark set comprises the three landmarks
 and two curves of 13 semi-landmarks described above for the 3D surfaces.
 Semi-landmarks are the landmarks #4 to 29. Aligned 2D coordinates are
 columns V1 to V48; the centroid size is reported in the column
 “Centroid_Size.”
description: <strong>Poly3D_with carina_raw</strong><br>
 .txt file: - 3D morphometric dataset: semi-landmarks along the anterior
 and posterior margins and along the carina; 34 <i>Po.
 communis</i> and 30 <i>Po. glaber.</i>
 <strong>Polygnathus_2D_CTBU</strong><br> .txt
 file: - 2D morphometric dataset: semi-landmarks along the anterior and
 posterior margins; all species through the Famennian (1564
 specimens).
 <strong>SupplementaryTable</strong><br> .xlsx
 and txt files: Number of <i>Polygnathus</i> per level and per
 group in the successive levels in Buschteich (BU) and in Col des Tribes
 (CT). Indet.: indeterminate specimens, <i>lauri</i>.:
 <i>lauriformis</i>, <i>margar</i>.:
 <i>margaretae</i>. Ages are given by the conodont zones after
 Spalletta et al. (2017). The total number of specimens considered for
 morphometric analyses is provided in the column “total” and corresponds to
 the sum of entire elements (“entire”), and those for which only the
 platform was unbroken (“platform”).
 <strong>Supp_Statistics</strong><br> .txt file:
 provide all the statistical results.