| Caveasphaera Temporal range: | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Genus: | † Caveasphaera |
Caveasphaera is a multicellular organism found in 609-million-year-old rocks laid down during the Ediacaran period in the Guizhou Province of South China. The organism is not easily defined as an animal or non-animal. [1] [2] [3] [4] [5] The organism is notable due to the study of related embryonic fossils (measuring about a half-millimeter in diameter) [1] which display different stages of its development: from early single-cell stages to later multicellular stages. [1] [2] [3] [4] Such fossil studies present the earliest evidence of an essential step in animal evolution – the ability to develop distinct tissue layers and organs. [1] According to researchers, fossil studies of Caveasphaera have suggested that animal-like embryonic development arose much earlier than the oldest clearly defined animal fossils [1] and may be consistent with studies suggesting that animal evolution may have begun about 750 million years ago. [2] [6] Nonetheless, Caveasphaera fossils may look similar to starfish and coral embryos. [1] Still, researchers have concluded, "Parental investment in the embryonic development of Caveasphaera and co-occurring Tianzhushania and Spiralicellula , as well as delayed onset of later development, may reflect an adaptation to the heterogeneous nature of the early Ediacaran nearshore marine environments in which early animals evolved." [4]