Science. 1977 Feb 18;195(4279):676-9. doi: 10.1126/science.195.4279.676.
Carbonaceous shales of the late Precambrian Chuar Group of the Grand Canyon, Arizona, contain abundant and well-preserved chitinozoans. The occurrence of these distinctive, tear- and flask-shaped microfossils, the oldest chitinozoans now known and the first to be reported from the Precambrian, seems to suggest that heterotrophic protists (or primitive metaozoans) were extant at least as early as about 750 +/- 100 million years ago.
亚利桑那州大峡谷晚前寒武纪 Chuar 群的碳质页岩中含有丰富且保存完好的几丁虫。这些独特的、撕裂状和瓶状的微体化石的出现，是目前已知最古老的几丁虫，也是首次在前寒武纪报道的几丁虫，似乎表明异养原生生物（或原始后生动物）至少在约 7.5 亿年前就已经存在了。
