br According to Rolling Stone, Mastodon and Dinosaur Jr. have canceled their upcoming September tour due to an unspecified "critical situation."br The band said in a statement, “Mastodon regrets to inform fans that due to a critical situation of a member of the Mastodon family, their upcoming tour with Dinosaur Jr. will be cancelled.”br Dinosaur Jr. shared a statement on Twitter that noted, as a result of the tour cancellation, their own August 31st gig in Missoula, Montana would also be canceled.