词数:563阅读难度:★★★☆☆建议阅读时间:6分钟They are microscopic artwork:tiny tubes and long fi laments(细丝),strange squiggles(波形短线)etched into some of the most ancient rocks known.On Wednesday,researchers reported that these may be the oldest fossils ever discovered,the remains of bacteria thriving on Earth not long,geologically speaking,after the very birth of the planet.If Word Count: 563 Reading Difficulty: ★★★ ☆☆ Suggested Reading Time: 6 Minutes They are microscopic artwork: tiny tubes and long fi laments (filaments), strange squiggles etched into some of the most ancient rocks known. On Wednesday, researchers reported that these may be the oldest fossils ever discovered, the remains of bacteria thriving on Earth not long, geologically speaking, after the very birth of the planet .If