10.5061/DRYAD.8594
Gerber, Sylvain
University of Chicago
Data from: Comparing the differential filling of morphospace and
allometric space through time: the morphological and developmental
dynamics of early Jurassic ammonoids
Dryad
dataset
2011
Early Jurassic
2011-02-15T20:32:07Z
2011-02-15T20:32:07Z
en
https://doi.org/10.1666/10005.1
72118 bytes
1
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
The evolutionary history of shell geometry of Early Jurassic ammonoids
during the Pliensbachian–Toarcian second-order mass extinction is explored
at both adult and ontogenetic levels. The ontogenetic approach builds on
the concept of allometric space to get insights into the developmental
aspects of morphological evolution. Investigation of the deployment of
taxa in adult morphospace and allometric space allows the appraisal of the
temporal evolution of morphological and allometric disparities. Curves of
taxonomic diversity, adult morphological disparity, allometric disparity,
and average adult size are contrasted. Results show that during the
Pliensbachian–Toarcian interval, ammonoids underwent two successive and
drastic declines in taxonomic diversity. Patterns of morphospace and
allometric space occupancy suggest nonselective extinction at both
morphological and developmental levels. Another measure of allometric
disparity suggests the occurrence of two heterochronic trends, a
peramorphocline followed by a paedomorphocline, during the Toarcian. These
trends are concomitant with changes in average adult size that compensate
for the heterochronic effects and explain the striking stability of
morphological disparity despite changes in diversity. The results also
emphasize the existence of two contrasted evolutionary dynamics in
Pliensbachian and Toarcian ammonoids. Methodologically, the allometric
disparity approach appears to be a fruitful tool to analyze the rather
understudied clade-wide ontogenetic aspects of morphological evolution.
Combining multiple approaches to describe clade morphological dynamics
leads to a better characterization and understanding of the
diversity-disparities relationships and a better distinction of the
potential processes driving these macroevolutionary patterns.
Morphological data of early Jurassic ammonoidsThe following table provides
the list of the 164 species used as representative of the 164
Pliensbachian-Toarcian genera, their stratigraphic occurrences, their
values for Raup’s (1966, 1967) parameters WR (whorl expansion) and DR
(distance of the generating curve to the coiling axis), their relative
warp coordinates (RW1, RW2) and their scores on the two principal
components of the allometric space (PC1, PC2). Chronostratigraphic
abbreviations are as follows: 1, Jamesoni; 2, Ibex; 3, Davoei; 4,
Margaritatus; 5, Spinatum; 6, Tenuicostatum; 7, Falciferum; 8, Bifrons; 9,
Variabilis; 10, Thouarsense; 11, Dispansum; 12, Pseudoradiosa; 13,
Aalensis.Appendix.xls