The Cambrian Fossils of Chengjiang, China The Flowering of Early Animal Life / Кембрийские окаменелости из Чэнцзяна, Китай Расцвет ранней животной жизни

The base of the Cambrian Period is one of the great watersheds n the history of life. In the earlier half of the nineteenth century, Charles Darwin had already recognized the startling change that happens in the fossil record at this horizon, when the fossil remains of metazoans appear in abundance for the first time in many localities around the world. The dawn of the Cambrian marks the appearance of mineralized shells, which apparently originated independently in several animal groups shortly after the beginning of the period. A century or more of careful collecting has only reinforced the distinctiveness of this seminal phase in the story of marine life. Initially, paleontologists concentrated on documenting the sequence of shelly fossils through the interval, in order to establish a basis for the correlation of marine strata. Trilobites – now supplemented by microfossils, like acritarchs – have proved to be of particular importance in stratigraphy for all but the lowest part of the Cambrian, and for a while our picture of early life was colored by the kind of shelly fossils that could be recovered from collecting through the average platform sedimentary rock sequence. However, there was another world that the usual fossil record did not reveal, a world of softbodied, or at least unmineralized, animals that lived alongside the familiar snails and trilobites, but which usually left no trace in the fossil record. <...>