The most extensive terrestrial biome, drylands cover more than one-third of Earth’s continental surface. The moss genus Syntrichia occurs worldwide in a variety of habitats and is comprised of about 90 species, many of which are dryland specialists. Previous research indicates the presence of a single clade, recently named Borealsyntrichia, containing both the diverse S. ruralis and S. caninervis species complexes and that may represent a rapid radiation. We aim to understand whether the genus Syntrichia contains diversification rate shifts and whether timing of the divergence of Borealsyntrichia coincides with the evolution of Northern Hemisphere deserts. Using a genome skimming approach, we assembled plastomes de novo for 144 samples of Syntrichia and close relatives from around the world. From these assemblies we selected 86 plastid genes to build a phylogeny, estimate divergence times, and test for temporal diversification heterogeneity in a Bayesian framework. We report when Syntrichia diverged from the rest of Pottiaceae as well as an estimated divergence time of Borealsyntrichia from the rest of Syntrichia and whether we find support for association of this divergence with development of Northern Hemisphere deserts. Tests for temporal shifts diversification rate will indicate if, during its evolutionary history, Syntrichia had any drastic diversification rate shifts. Our results will provide context on the dominance of Borealsyntrichia in Northern Hemisphere drylands.