Phylogenomic resolution of lampreys reveals the recent evolution of an ancient vertebrate lineage

Jawless vertebrates once dominated Paleozoic waters, but just two lineages persisted to the present day: lampreys and hagfishes. Living lampreys are a relatively small clade, with just over fifty species described, but knowledge of their evolutionary relationships has always been based on either a few mitochondrial genes or a small number of taxa. Biogeographers have noted the disjunct antitropical distribution of living lamprey families. Here we present a comprehensive phylogenomic analysis of living and fossil lampreys, sampling 36 species with phylogenomic data and 46 in total with genetic data. We present new divergence time estimates based on comprehensive nuclear data and analysis of their diversification dynamics. Our analysis indicates a central role for extreme global warming during the Late Cretaceous Cenomanian-Turonian Boundary Event as a likely cause for the antitropical distribution of living lampreys, and a notable increase in lineage diversification in northern hemisphere lampreys during the Miocene corresponding with a period of global cooling.