MOVE over, Dickinsonia. This 558-million-year-old creature was named the earliest known animal last year, but 快猫短视频 can now exclusively reveal one that existed even earlier 鈥� by more than 40 million years.
This previously unknown animal comes from 600-million-year-old rocks in China and doesn鈥檛 have a name yet. While Dickinsonia was an Ediacaran 鈥� a primitive group of organisms that went extinct about 541 million years ago 鈥� the unnamed animal seems to have belonged to a group of animals that still exists today: comb jellies.
It was discovered by Zhenbing She at the China University of Geosciences, Wuhan. 鈥淭he origin and earliest evolution of animals is a fascinating question that has puzzled scientists for many decades,鈥� said She as he unveiled his findings at a meeting of the Geological Society of London in London last week.
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The fossils were found in a drill core taken from the Doushantuo Formation in southern China. These beds have already yielded exquisitely preserved fossils from as far back as 631 million years ago. These mysterious fossils are only visible through microscopes, and may be algal cells, developing animal embryos or something else entirely.
Among these rocks, She鈥檚 team has found fossils visible to the naked eye, measuring about 0.7 millimetres across. The first clue to their identity was their jellyfish-like shape. Microscopic analysis revealed what appear to be tentacles, muscle tissue, nerve cells, gonads, mucous layers and clusters of hairlike-structures called cilia.
True jellyfish belong to the Cnidaria phylum of animals, but She said these features are reminiscent of the comb jelly phylum Ctenophora. The cilia clusters in particular look like structures called ctenes that comb jellies use to swim. The fossils most closely resemble the living genus of comb jellies called Pleurobrachia, or sea gooseberries, She told the meeting.
鈥淚t was a very interesting talk 鈥� it seems like they have some very interesting biological creatures preserved,鈥� says Emily Mitchell at the University of Cambridge, who attended the conference.
鈥淚f these fossils are comb jellies, they may have been part of a surprisingly complex ecosystem鈥�
As a rule, comb jellies are more primitive than jellyfish, says Dominic Papineau of the London Centre for Nanotechnology, whose laboratory helped to analyse the fossils. They have a simpler life cycle and are anatomically less advanced.
Nonetheless, comb jellies would be remarkably advanced for 600 million years ago, says Tim Lenton at the University of Exeter, one of the meeting organisers. Living comb jellies have a gut connecting their mouth and anus, a feature not present in many other primitive groups including the Cnidarians.
If the new fossils are comb jellies, more discoveries may yet be to come. The vast majority of living comb jellies today are predators, feeding on small marine organisms. If the 600-million-year-old fossil was a carnivore too, then it must have been part of a food web and hence a surprisingly complex ecosystem. 鈥淭here are many other creatures in the deposit, but we are not sure what they are,鈥� She told 快猫短视频.
Ancient carnivores
Papineau confirmed that the deposits contain other, unidentified fossils that the comb jellies could have eaten. They resemble algae, he says.
The discovery has yet to be peer-reviewed or published in a journal but has been seen by other scientists, said She.
Some have doubts about the discovery. Maoyan Zhu of Nanjing Institute of Geology and Palaeontology, who was also at the meeting, says he doesn鈥檛 accept She鈥檚 interpretation. The comb-jelly-like structures could be artefacts or bacterial contamination, he says.
If it does check out, the discovery won鈥檛 radically alter our knowledge of life before the Cambrian explosion 鈥� the sudden appearance of many kinds of animal fossils about 541 million years ago. We know that the ancestors of modern species must have appeared long before this time, says Zhu 鈥� it is just that nobody has found them yet.
Zhu presented his own evidence of early, non-Ediacaran animal life from Doushantuo at the same conference, but revealed that his work has been rejected by some leading journals.
