DOI: 10.5061/dryad.fj6q573vq
title: Data from: Ontogeny in the steinmanellines (Bivalvia: Trigoniida): an intra- and interspecific appraisal using the Early Cretaceous faunas from the Neuquén Basin as a case study

description: Despite the paleontological relevance and paleobiological interest of
 trigoniid bivalves, our knowledge of their ontogeny –an aspect of crucial
 evolutionary importance– remains limited. Here, we assess the intra- and
 interspecific ontogenetic variations exhibited by the genus Steinmanella
 Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian –
 late Hauterivian of Argentina, and explore some of their implications. The
 (ontogenetic) allometric trajectories of seven species recognized for this
 interval were estimated from longitudinal data using 3D geometric
 morphometrics, segmented regressions and model selection tools, and then
 compared using trajectory analysis and allometric spaces. Our results show
 that within-species shell shape variation describes biphasic ontogenetic
 trajectories, decoupled from ontogenetic changes shown by sculpture, and
 with a gradual decay in magnitude as ontogeny progresses. The mode of
 change characterizing each phase (crescentic growth and anteroposterior
 elongation, respectively) is conserved across species, thus representing a
 feature of Steinmanella ontogeny; its evolutionary origin is inferred to
 be a consequence of the rate modification and allometric repatterning of
 the ancestral ontogeny. Among species, trajectories are more variable
 during early ontogenetic stages, becoming increasingly conservative at
 later stages. Trajectories’ general orientation allows recognition of two
 stratigraphically-consecutive groups of species, hinting at a potentially
 higher genus-level diversity in the studied interval. In terms of
 functional morphology, juveniles had a morphology more suited for active
 burrowing than adults, whose features are associated with a sedentary
 lifestyle. The characteristic disparity of trigoniids could be related to
 the existence of an ontogenetic period of greater shell malleability
 betrayed by the presence of crescentic shape change.
description: Shell morphology was digitized in three dimensions with a
 HandyScan3D laser scanner and digitally processed in MeshLab to remove
 irregularities from the surface. Longitudinal variation in shell shape and
 size, as well as sculpture shape, were quantified using 3D geometric
 morphometrics (curve and surface semilandmarks). Ontogenetic (allometric)
 trajectories were reconstructed for each species using segmented
 regressions, with the number of segments (i.e., number of ontogenetic
 phases) estimated using model selection methods. Finally, allometric
 spaces were constructed by applying ordination methods (PCA) on
 regression's coefficients.
description: The data uploaded here include:<br> <br> 1)
 <strong>MillaCarmonaetal_FigureS1_1col.pdf</strong>:
 a supplementary figure showing results of a post hoc analysis on shape
 variance. 2.1) <strong>Supplementary materials
 1_meshes.zip</strong>: a zip file containing the 278 meshes used as
 raw material for our analyses. 2.2)
 <strong>Supplementary materials 1_R files and
 data.zip</strong>: a zip file containing 2.2.1) a csv file
 containing data of specimens, 2.2.2-2.2.7) five scripts with the code
 necessary to run all analyses, and 2.2.8-2.2.9) two R objects (to be
 imported directly into the R session) containing the morphometric data
 necessary to run all analyses. 3)
 <strong>Supplementary materials 2_animated
 trajectories.zip</strong>: a folder containing several animations
 intending to aid interpretation of ontogenetic trajectores.
 4) <strong>Supplementary materials 3_extended description
 of changes.doc</strong>: an exhaustive description of our
 species-level findings.