Allonnia nuda lived more than half a billion years ago and could be related to sponges

Allonnia Nuda (Image courtesy Derek Siveter/Tom Harvey/Peiyun Cong. All rights reserved)
Allonnia Nuda (Image courtesy Derek Siveter/Tom Harvey/Peiyun Cong. All rights reserved)

An article published in the journal “Proceedings of the Royal Society B: Biological Sciences” describes the discovery of an organism that shows similarities with sponges dating back to more than half a billion years ago which was named Allonnia nuda. A team of researchers examined the fossils discovered in China and classified it within the chancelloriid family, whose relationship with other animals is controversial.

The chancelloriid (Chancelloriidae) family is composed of simple animals that lived in the Cambrian period of which various fossils of different shapes and sizes are available with few characteristics in common such as the lack of traces of internal organs. Often the fossils are fragmentary, rigid mineralized parts called sclerites jargon. In 1920, paleontologist Charles Doolittle Walcott described these organisms for the first time as the most primitive group of sponges but over the decades their classification has been the focus of a lot of arguments.

The genus Allonnia was classified in the chancelloriid family and the new species discovered in the Chengjiang deposits of the Chinese province of Yunnan was attributed to this genus even if it’s much larger than the other species, perhaps up to 50 centimeters. Scientists from the British Universities of Leicester and Oxford and the Chinese University of Yunnan examined the fossils and believe they found connections with sponges that could bring new clues to confirm the old Walcott hypothesis.

Dr. Tom Harvey of the University of Leicester emphasizes in particular the growth of the body of Allonnia nuda as a link with the sponges. However, he shows caution regarding the classification of the chancelloriid family as he’s aware of the fact that this is still an open question. If his team’s hypothesis is correct, it would provide new information on the diversification of early sponges.

A better knowledge of early sponges would also offer new information regarding the controversy concerning the first animals appeared on Earth. Sponges are one of the major candidates and various research, the most recent published in December 2017 in the journal “Current Biology”, are the oldest, but in the field of paleontology new fossil discoveries can change things.

Dr Peiyun Cong, one of the authors of the study of Allonnia nuda, stressed the fact that the Chengjiang deposits keep on revealing surprising new fossils. They can offer new information that is sometimes crucial to better understand the Cambrian explosion, one of the most important periods for life on Earth due to the extraordinary diversification that occurred in a relatively short time.

Strange organisms lived during that period such as Allonnia nuda, an animal with a tube-shaped body and with spines, although few of them and small compared to other species of the genus Allonnia. Such a creature can be difficult to recognize so it’s possible that other specimens, perhaps only partial, exist in fossil collections but have not been recognized because they haven’t been adequately studied yet. These are the reasons why the study of Cambrian organisms is so complex and fascinating at the same time.

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