Lagerstätte may not be a word that many people run into in their daily lives, but for geologists it’s an extremely exciting term. A lagerstätte is an area were rocks have preserved evidence of ancient life—with extraordinary fidelity and in great numbers. Unlike most fossils, which are generally only reflect bones and shells—the ‘hard parts’ of vanished organisms—the remains found at a lagerstätte may include the delicate sweep of a brush-stroke-thin antenna, dangling representations of a jellyfish’s tendrils, even the internal organs of tiny creatures.
What we know about ancient life is heavily dependent on just a few such areas. The most famous is Canada’s Burgess Shale, whose fine dark stones not only showcase somewhat familiar characters from 507 million years ago, such as the trilobite, but a squadron of genuine oddities, such as the aptly-named Hallucigenia or the early predator Anomalocaris. The Burgess even preserves the first known example of a chordate, a tiny proto-fish named Pikaia whose fingernail-sized form may be the ancestor of every animal with backbone alive today—including us.
Creating a deposit that preserves creatures with this kind of detail requires very special conditions, thus lagerstätte are exceedingly rare. But now it seems that a new one has been discovered in China, and the fossils that it offers are simply stunning.
In a report this week in Science, researchers from a pair of Chinese universities report on discoveries at a site named Qingjiang in South China. This site is actually older than the Burgess Shale by more than ten million years, making it an even better window into the early days of complex life, and the view through the window contains some spectacular details. Not just jellyfish, but other soft-bodied creatures, such as sponges and sea anemones, have been preserved with “sub-millimeter” accuracy, thanks to the dust-fine particles from which the stones at Qingjiang are made.
That fine detail means that the stones don’t just record the adults of the species discovered. The find includes both juvenile and larval forms of some of the organisms—preserving not just details of their form, but stages in their life history. This information is critical to determining how these creatures relate to modern forms and how they fit into what we already know about the beginnings of animal life on Earth.
The Cambrian Period begins not long before the deposits at Qingjiang were laid down, and it begins with a “bang.” Previous to this period, large organisms — organisms larger than the period at the end of this sentence — are relatively rare. And many of those that have been discovered, like the Ediacaran fauna first found in Australia, which date to around 545 million years ago, remain largely mysterious both in determining how they lived and how they relate to modern organisms.
Then … bang! In a few million years at the beginning of the Cambrian, every major branch of life that exists today appears. Sponges. Jellyfish. Mollusks. Arthropods. Some of these ancestral creatures look wildly different than their descendants, and some of the creatures from these rare lagerstätte may not be related to anything still around, but this period seems to represent evolution at its most fecund, spinning of experiments at a blistering rate as the Earth turns from a place populated mainly by a soup of microscopic creatures, to one in which larger, more complex forms dominate the seas.
Assembling a full image of the tree of life will always remain impossible. Too much is invisible to us. Too much is never preserved. But sites like Qingjiang offer moments of startling clarity, a still image captured against the filmstrip of evolution, that stands out starkly from the grainy background and offers to answer questions that have puzzled scientists for decades.
Already the information from Qingjiang has put to bed speculation over the evolution of Ctenophores, the lovely “comb-jellies” whose iridescent forms are so often the stars of documentaries showcasing the inhabitants of the deep ocean. And the specimen seem to be indicating that some of those currently unrepresented “experiments” found in the Burgess were part of much larger and more diverse groups.
But perhaps the most interesting information in the published paper is an indication that Qingjiang is not one site. In fact, the fossils that have been recovered in only a few months of field work represent deposits that may be “widespread” around South China. Which indicates that our image of life in the early Cambrian may go from black and white to technicolor over the next few years.