A new study by Virginia Tech Department of Geosciences researchers may well resolve a long-standing question about the origin of spicules or needle-like structures in sponge animals, an animal group that branched out from all other animals more than 600 million years ago.

Published today in Nature Communications, Professor Shuhai Xiao and Post-Doctoral Associate Qing Tang said the study tackles a long-debated scientific question about where and how to find the oldest sponge fossils and provides a new search image for Precambrian sponge body fossils. How so? Tang said he discovered a transitional animal with weakly biomineralized spicules, a bridge from sponges with spicules and those with none.

In a community blog post for Nature Ecology and Evolution, Tang writes, “Our discovery provides strong evidence supporting the hypothesis that Precambrian sponges may have had only weakly biomineralized spicules or even completely lacked biomineralized spicules. Perhaps Precambrian sponges are not preserved as biomineralized spicules, but as organic remains.”

“Sponges are the most ancient animals but they did not evolve fully mineralized spicules until around 540 million years ago,” Tang said. “Our study will prompt paleontologists to take a second look at those Precambrian fossils that were said to be sponges but were dismissed by some scientists because of the lack of biomineralized spicules.”

Xiao added that the study also has “broader impact on the origin of animal biomineralization, its evolutionary developmental basis, and its ecological and geological consequences.”

Read the full blog post by Tang.