Virginia Tech researchers led by Shuhai Xiao revealed a 550 million-year-old sea sponge fossil, showing a 160 million-year gap in the fossil record in South China’s Dengying Formation (551-539 million years ago), in a research paper published at “Nature” recently.
This fossil, which implies that early sponges lacked mineral skeletons, sheds new light on the evolution of one of the first animals and informs paleontologists’ searches for ancient sponges.
At first view, the plain sea sponge appears to be no mysterious creature. No brain. No gut. There’s no trouble dating it back 700 million years. However, credible sponge fossils date back only about 540 million years, leaving a 160-million-year gap in the fossil record.
A geobiologist at Virginia Tech discovered a 550 million-year-old sea sponge from the “lost years” and argued that the earliest sea sponges did not yet have mineral skeletons, providing fresh parameters for the search for the missing fossils.
The riddle of the missing sea sponges revolved on a paradox. Molecular clock estimations, which include calculating the amount of genetic changes that accrue over time, suggest that sponges developed around 700 million years ago. Nonetheless, no credible sponge fossils had been discovered in such ancient strata.
For many years, paleontologists and zoologists debated this problem.