英发现世界最小化石 长度不到五分之一毫米

　　Scientists at the University of Manchester have discovered what is believed to be the smallest fossil ever found.

　　A 50-million-year-old parasite - hitching a ride on a not-much-bigger spider - was discovered during a scan of Baltic amber.

　　Published in the Royal Society's Biology Letters, the find was made using a computed tomography (CT) scan, which builds up a 3-D image from multiple flat scans.

　　Biologist Dr David Penney wrote in the paper that the arthropod fossil was extremely small - less than two tenths of a millimetre long - and “extremely rare”.

　　Dr Penney wrote that the Faculty of Life Sciences teams would not have been able to identify the mite without the CT scan.

　　He told the BBC: “CT allowed us to digitally dissect the mite off the spider in order to reveal the important features on the underside required for identification.”

　　“The specimen, which is extremely rare in the fossil record, is potentially the oldest record of the living family Histiostomatidae. “

　　“Most amber fossils consist of individual insects or several insects together, but without unequivocal demonstrable evidence of direct interaction. “

　　Fellow biologist Dr Richard Prezoisi added that the team could now date how long species such as the mite had been using larger organisms for transportation.

　　He said it would give “important clues as to how far back in geological time such behaviours evolved”.