Supplementary data from: Contrasting macroevolutionary patterns in pelagic tetrapods across the Triassic–Jurassic transition

The iconic marine raptorial predators Ichthyosauria and Eosauropterygia
co-existed in the same ecosystems throughout most of the Mesozoic Era,
facing similar evolutionary pressures and environmental perturbations.
Both groups seemingly went through a massive macroevolutionary bottleneck
across the Triassic–Jurassic (T/J) transition that greatly reduced their
morphological diversity, leaving pelagic lineages as the only survivors.
However, analyses of marine reptile disparity across the T/J transition
have usually employed coarse morphological and temporal data. We
comprehensively compare the evolution of ichthyosaurian and
eosauropterygian morphology and body size across the Middle Triassic to
Early Jurassic interval and find contrasting macroevolutionary patterns.
The ecomorphospace of eosauropterygians predominantly reflects a strong
phylogenetic signal, resulting in the clustering of three clades with
clearly distinct craniodental phenotypes, suggesting ‘leaps’ towards novel
feeding ecologies. Ichthyosaurian diversification lacks a discernible
evolutionary trend, as we find evidence for a wide overlap of craniodental
morphologies between Triassic and Early Jurassic forms. The temporal
evolution of ecomorphological disparity, fin shape and body size of
eosauropterygians and ichthyosaurians during the Late Triassic does not
support the hypothesis of an abrupt macroevolutionary bottleneck near the
T/J transition. Rather, an important turnover event should be sought
earlier, during times of rapid sea level falls.