Sponges are often considered to be the most basal and primitive metazoan phylum. Early sponge fossils may provide important clues to the origin and early evolution of animals. Molecular clock estimates and controversial biomarker data suggest that sponges should have appeared around 700 million years ago. Enigmatically, however, no unambiguous sponge fossils have been found before the Cambrian Period. Therefore, a 160-million-year gap exists in the sponge fossil record, a period in early sponge evolution known as the “lost years.”
A research team from NIGPAS discovered a late Ediacaran crown-group sponge, Helicolocellus, from the Shibantan Biota in Hubei Province—a fossil biota dating to about 550 million years ago. This finding, which fills an important gap in the early evolution of sponges, was published in Nature on June 5th, 2024.
The discovery of Helicolocellus indicates that non-biomineralizing sponges did exist in the Precambrian. It suggests that modern sponges should not be used as the sole guide for finding Precambrian sponge fossils, as early sponges may not have had biomineralized spicules and may not have had all the features of modern sponges. Moreover, early hexactinellid sponges first laid out the reticulate skeletal blueprint using organic material, and later added siliceous biominerals to the recipe for skeletal formation in the Cambrian.
Download：