Where were the first animals? Scientists discovered rare fossil<\/figcaption><\/figure>\n<\/div>\nA 550-million-year-old sea sponge fossil discovered in China is helping scientists resolve a 160-million-year gap in the early history of animal life. The discovery provides extraordinary physical evidence that scientists believed had been missing from the fossil record of this bygone era until new evidence emerged about the evolution of ancient sponges. <\/p>\n
The discovery, published in Nature by Virginia Tech researchers and Shuhai Xiao, establishes a definitive connection between the fossil and the period that scientists refer to as the “lost years” of sponge evolution. <\/p>\n
After a colleague sent Xiao an image, the fossil first appeared along the Yangtze River in China. The unusual composition of the object led to several institutions investigating the case, including the University of Cambridge and the Nanjing Institute of Geology and Paleontology. <\/p>\n
The researchers exhausted all possibilities that the specimen resembled sea squirts, anemones, and corals before determining that it was an ancient sponge. The specimen is approximately 15 inches across and displays a complex conical structure with a unique grid pattern covering its surface.<\/p>\n
This structure suggests a close relationship to modern glass sponges, but its size and complexity surprised scientists. Researchers expected that early sponges would be very small and simple in shape.<\/p>\n
One of the main theories explaining the long interval without fossil evidence is that the first sponges did not form any skeletal parts from minerals. Thus, they would hardly be able to preserve themselves within fossils due to their softness.<\/p>\n
This research reinforces previous studies that showed that the growth of sponge spicules was characterized by increased mineralization throughout the process. Therefore, if only soft-bodied sponges were present in the early stages, few specimens would remain preserved within the rocks.<\/p>\n
Modern scientists say that early animal evolution may be underestimated because of the paucity of fossils due to preservation bias, not because of their absence.<\/p>\n<\/p><\/div>\n