New research has shown that Australia is the “last stronghold on Earth” for four out of five threatened species of sawfish. With their serrated snouts, these predatory fish are one of the ocean’s most unusual and endangered animals.They have a snout, or rostrum, that looks like a hedge-trimmer or a chainsaw. Small electromagnetic sensors help the sawfish detect the heartbeat and movement of buried prey. They are generally unassuming creatures, but when threatened, the saw also serves as a weapon. They can grow up to 7 meters in length and …

The top public health agency in the U.S. said Friday that in-person schooling could resume safely with masks, social distancing and other strategies but that vaccination of teachers, while important, was not a prerequisite for reopening.The Centers for Disease Control and Prevention released its long-awaited road map for getting students back to classrooms in the middle of the coronavirus pandemic. But its guidance is just that — the agency cannot force schools to reopen, and agency officials were careful to say they were not calling for a mandate that all …