In the separate age categories for the basicranium, temporal, and occipital regions, the older the individuals, the more congruent the patterns between the genetic and morphological datasets, such that AC3 was the most highly correlated, followed by AC2 and then AC1.
Because of the foreseeable exponential increase in digital morphological data in the years to come we nonetheless advocate the fast implementation of a morphological repository, suggesting that initially only datasets that can easily be standardized (e.g. MRI- or μCT-based) should be uploaded, which in turn would force other techniques to adapt to these standards.
The first four calibrations are preferred because they are based on fossil taxa that have had their relationships to extant taxa determined by computer-assisted phylogenetic analyses of datasets that include molecular and morphological data.
While this work shows that it is possible to understand discrepancies between MSU/AMSU datasets there are still important differences between the datasets that need further scrutiny.
Owing to the calcified skeleton found in sea urchins, palaeontologists have access to a rich fossil record permitting thorough ground-truthing of phylogenetic hypotheses that are based upon molecular or morphological datasets [ 34, 35].
Thus simple exclusion of reduced or simplified characters from the morphological dataset yields a tree that can be better reconciled with the molecular phylogenies.
However, the estimated K-scores indicated that the three distance-optimized trees based on the different morphological datasets were almost congruent in topology and branch lengths, implying similar changes on nodes between the trees.
Labeling by intracellular injection has the virtue that the micro-pipette used for cell filling can also be used to characterize the neuron electrophysiologically, thereby generating a dataset that links morphological and physiological properties [e.g. ref. 6].
Due to the low statistical support for many relationships within Pelecaniformes and the waterbird clade, as well as enduring conflicts between datasets, an emerging consensus of recent studies is that additional data and revision are needed for both molecular and morphological datasets.
While novel approaches that directly use fossil data are certainly preferable [ 35, 78], they require high-quality morphological datasets for both fossil and extant taxa which are currently not available for most groups.
