Data from: How to date a crocodile – estimation of neosuchian clade ages and a comparison of four time-scaling methods

Clade ages within the crocodylomorph clade Neosuchia have long been
debated. Molecular and morphological studies have yielded remarkably
divergent results. Despite recent advances, there has been no
comprehensive relative comparison of the major time calibration methods
available to estimate clade ages based on morphological data. We used four
methods (cal3, Extended Hedman [EH], smoothed Ghost-Lineage-Analysis
[sGLA] and the Fossilised Birth-Death model [FBD]) to date clade ages
derived from a published crocodylomorph supertree and a new neosuchian
phylogeny. All time-scaling methods applied here agree on the origination
of Neosuchia during the Late Triassic/Early Jurassic, and the presence of
the major extant eusuchian groups (Crocodyloidea, Gavialoidea,
Alligatoroidea, and Caimaininae) by the end of the Late Cretaceous. The
number of distinct lineages present before the K/Pg boundary is less
certain, with support for two competing scenarios in which Crocodylinae,
Tomistominae and Diplocynodontinae either: 1) diverged from other
eusuchian lineages before the K/Pg boundary; or 2) evolved during a
‘burst’ of diversification after the K/Pg event. Cal3 and FBD are
identified as the most suitable methods for time-scaling phylogenetic
trees dominated by fossil taxa. Extended Hedman estimates are
substantially older than the others, with larger standard deviations and a
strong vulnerability to taxon sampling and topological changes. sGLA has
similar problems and cannot be recommended either. We conclude that a
detailed understanding of phylogenetic relationships, tree reconstruction
methods, and good taxonomic coverage (in particular the inclusion of the
oldest taxon in each clade) is essential when evaluating the results of
such dating analyses.