Ancient dates or accelerated rates? Morphological clocks and the antiquity of placental mammals.

ABSTRACT: Analyses of a comprehensive morphological character matrix of mammals using 'relaxed' clock models (which simultaneously estimate topology, divergence dates and evolutionary rates), either alone or in combination with an 8.5 kb nuclear sequence dataset, retrieve implausibly ancient, Late Jurassic-Early Cretaceous estimates for the initial diversification of Placentalia (crown-group Eutheria). These dates are much older than all recent molecular and palaeontological estimates. They are recovered using two very different clock models, and regardless of whether the tree topology is freely estimated or constrained using scaffolds to match the current consensus placental phylogeny. This raises the possibility that divergence dates have been overestimated in previous analyses that have applied s

SUBMITTER: Beck RM 

PROVIDER: S-EPMC4173679 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature