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Which choice completes the text with the most logical and precise word or phrase? Some scientists have suggested that mammals in the Mesozoic era were not a very ______blank group, but paleontologist Zhe-Xi Luo's research suggests that early mammals living in the shadow of dinosaurs weren't all ground-dwelling insectivores. Fossils of various plant-eating mammals have been found in China, including species like Vilevolodon diplomylos, which Luo says could glide like a flying squirrel.