A technical note that may be of interest for the marine mammal science community: "Complete mitochondrial genomes and phylogeny of two rare whale species: True’s (Mesoplodon mirus: True 1913) and Sowerby’s (Mesoplodon bidens: Sowerby 1804) beaked whales" Beaked whales of the genus Mesoplodon are rarely encountered and information on their basic biology is lacking. We sequenced the complete mitochondrial genomes of True’s (Mesoplodon mirus) and Sowerby’s (Mesoplodon bidens) beaked whales to high depth (>120X). The length of the de novo assembled genomes was 16,342 bp (M. mirus) and 16,347 bp (M. bidens), with GC compositions of 37.7 and 39.2%, respectively. A maximum-likelihood phylogeny supports the hypotheses that M. mirus is most closely related to Mesoplodon europaeus, and that M. bidens is the basal species of the genus. These data provide molecular resources that will aid in further understanding population genetics and evolution in this rare and poorly understood group of cetaceans. Anthony L. Einfeldt, Ian G. Paterson & Laura J. Feyrer (2019) Complete mitochondrial genomes and phylogeny of two rare whale species: True’s (Mesoplodon mirus: True 1913) and Sowerby’s (Mesoplodon bidens: Sowerby 1804) beaked whales, Mitochondrial DNA Part B, 4:1, 275-276, DOI: 10.1080/23802359.2018.1541719 Available at: https://www.tandfonline.com/doi/full/10.1080/23802359.2018.1541719 Cheers, Laura Feyrer @deepdivewhales Whitehead Lab Biology Dept. Dalhousie University Halifax, NS