A team of researchers, led by Shuhai Xiao of the Virginia Tech (Virginia Polytechnic Institute and State University), has discovered a marine sponge fossil from 550 million years in Hubei province, China. This finding fills a gap 160 million years in the fossil record and provides new knowledge about the early evolution of these animals. As detailed SciTechDailythe fossil found offers clues that suggest that the first sponges take care of mineral skeletonswhich would have made its preservation difficult.
The discovery was considered revolutionary because molecular clocks indicated that sponges had evolved approximately 700 million yearsHowever, confirmed fossils only dated back to 540 million years, which generated an enigma in paleontology. In a previous study of 2019, Xiao and his team had already proposed that the first sponges would not have developed the characteristic hard structures, known as spicules, making their fossil preservation difficult. According to Xiao: “If this were true, they would not survive fossilization except in very special circumstances.“.
Researchers of the University of Cambridge and the Nanjing Institute of Geology and Paleontology collaborated in the analysis of the fossil, called Helicolocelluswhich was discovered in the sediments of the Shibantan biota. This fossil has a structure reminiscent of modern glass sponges, but without components biomineralized. The surface of the fossil features a distinctive pattern of boxes, subdivided into smaller ones, a rare feature in these ancient sponges.
Alex Liucollaborating researcher of the University of Cambridgehighlighted: “The new fossil measures about 38 centimeters long and has a relatively complex, conical body plan, which defied many of our expectations about the appearance of early sponges.“. This size contrasts with the initial idea that the first sponges would be much smaller and simpler in comparison.
Xiaopeng Wangpostdoctoral researcher at Nanjing Institute of Geology and Paleontology, explained that this pattern suggests that the fossil would be related to a species of modern glass sponge. The confirmation that the first sponges do not contain minerals in their structures shows why it is so rare to find fossils from before the 19th century. Cambrian Period.
A phylogenetic analysis composed of morphological data from extinct and extant animals led to the conclusion that Helicolocellus It belongs to the crown group of sponges, particularly related to the hexactinellids or glass sponges. This suggests that the ancestors of modern sponges possibly used organic materials in their structures before evolving towards siliceous biological components in the Cambrian Period.
These results not only fill a huge gap in the fossil record, but also link the enigmatic biota of Ediacaran with the animals of the Cambrian, demonstrating a continuity between these two evolutionary stages. The findings could encourage us to review other fossil records from the period Ediacaran and explore less studied fossil sites globally.
The importance of the discovery of Helicolocellus It also lies in its impact beyond paleontology. Jorge Ortega, independent paleontologist, commented: “This discovery challenges existing notions about the timing of biomineralization in sponges and other early animals. “. Furthermore, this finding could inspire advances in biomimetic materials, motivating the development of lightweight and durable materials based on early natural designs.
The next investigations, according to the scientists involvedwill continue to seek to understand more about the diversity and complexity of Precambrian lifewhile reviewing new fossil finds that could provide a clearer vision of the planet’s biological heritage.
