I do not see any reason you could call that a ctenophore
Long before the Cambrian explosion gave rise to the animal world we recognize, the Ediacaran period left behind a fossil record that scientists are still learning to read — and misread. A recent paper in Science claimed to have found early animal fossils in those ancient rocks, but independent paleontologist Joseph Botting and a separate team of researchers are urging caution, arguing that many of the specimens are more likely algae, bacteria, or already-known organisms than the pioneering animals the authors envisioned. The episode reflects a deeper truth in paleontology: the closer we look at the origins of complex life, the more we must resist the temptation to see what we hope to find.
- A high-profile Science paper claimed to push the known record of animal life deeper into the Ediacaran, but the evidence is now being picked apart fossil by fossil.
- The paper's most dramatic claim — a newly identified ctenophore from before the Cambrian — may actually be a cnidarian already well known from that era, collapsing the count of new animal phyla from one to zero.
- Supposed worm-like bilaterians show biological inconsistencies, poor preservation, and structural features that look more like algae than animal tissue.
- A parallel study of Brazilian microfossils once read as worm traces reidentifies them as fossilized bacterial-algal communities, reinforcing the pattern of overclaiming animal origins in ambiguous material.
- Even if some Ediacaran animals are confirmed, scientists warn this would not explain the Cambrian explosion — the sudden proliferation of body plans remains its own unsolved mystery.
A paper published in Science recently made sweeping claims about early animal fossils from the Ediacaran period, predating the Cambrian explosion. The scientific community has responded with pointed skepticism, led by Joseph Botting, an independent paleontologist and Honorary Research Fellow at the National Museum Wales.
Botting's sharpest challenge targets the paper's identification of a ctenophore — a structurally distinctive marine animal — in Ediacaran rock. He argues the fossil is not a ctenophore but a cnidarian, a group already documented in Precambrian deposits. The transverse structures the original authors treated as diagnostic of a ctenophore, Botting contends, are consistent with a conulariid cnidarian instead. If he is right, the paper's claim of identifying a new Cambrian animal phylum in Ediacaran rocks falls entirely.
His critique of the paper's bilaterian fossils — early worm-like organisms — is equally thorough. One specimen shows supposed gut structures appearing in multiple versions within a single fossil, which makes little anatomical sense; Botting suspects the features are algal, not animal. Another specimen's preservation is too poor to confirm a gut at all. A third resembles a known organism but may share only superficial features. Even the strongest candidate, compared to Cambrian cambroernids, falls short: its tentacles are short and barely branched, unlike the elaborate structures of true cambroernids, and its branching stalk suggests a colonial organism — something cambroernids were not. Botting also notes that the fossils' precise age remains uncertain, and they could sit just below the Cambrian boundary rather than firmly within the Ediacaran.
Support for this skepticism comes from a separate study in Gondwana Research, which reexamined 540-million-year-old Brazilian microfossils previously interpreted as traces left by tiny worm-like animals. The new analysis identifies them instead as fossilized microbial consortia — communities of bacteria and algae with cells and organic material still preserved — organized into at least three distinct size classes representing different species.
Together, these challenges illuminate a persistent difficulty in paleontology: distinguishing genuine early animal fossils from other organic structures in ancient rock. Botting himself calls the fossil assemblage "wonderful and interesting" even as he disputes its interpretation, and he acknowledges that some specimens may yet prove to be animals. But the field will need better preservation and more rigorous analysis before these Ediacaran rocks yield confident answers about the true dawn of animal life.
A paper published in Science last month made bold claims about finding early animal fossils in rocks from the Ediacaran period, before the Cambrian explosion. But the scientific community is pushing back hard. Joseph Botting, an independent paleontologist and Honorary Research Fellow at the National Museum Wales, has posted a detailed analysis that dismantles many of the paper's central assertions — and in several cases, his skepticism runs even deeper than that of other critics.
The most striking challenge concerns what the Science paper identified as a ctenophore, a type of marine animal with a distinctive body structure. Botting argues it is not a ctenophore at all, but rather a cnidarian, a group already well documented in Precambrian rocks. He points to the transverse structures in the fossil that the original authors took as diagnostic of a ctenophore, suggesting instead they match a cnidarian type called a conulariid, which is common in Ediacaran deposits. "I do not see any reason you could call that a ctenophore," Botting wrote, calling it the "least convincing" of the paper's examples. If he is correct, the number of newly identified Cambrian animal phyla in Ediacaran rocks drops from one to zero.
Botting's critique extends to the purported bilaterian fossils — the organisms the paper presented as early worms or worm-like creatures. For one specimen found in multiple copies, he notes that the supposed gut structure appears in multiple versions within the same fossil, which makes little biological sense. He suspects the black lines interpreted as guts represent something else entirely, possibly algae rather than animal tissue. For another specimen, he questions whether a gut is even present, given the poor quality of preservation. A third tubular fossil resembles a known organism called Margaretia, but Botting raises the possibility that the similarity could be coincidental rather than evidence of true relationship. Even the specimen he considers the strongest candidate — one compared to cambroernids, a Cambrian animal group — receives skeptical scrutiny. The tentacles on this fossil look nothing like the long, highly branched tentacles of true Cambrian cambroernids; instead they are short and barely branched. The stalk itself is also branched, suggesting it might be a colonial organism, but cambroernids were not colonial. Botting notes that far better-preserved fossils have faced doubts about cambroernid assignment, so these specimens deserve similar caution.
Another complication Botting raises concerns the age of the fossils themselves. The Science paper assigns them an age of 554 to 546 million years ago, placing them firmly in the Ediacaran. But Botting points out that the geological stratigraphy at the site could allow these fossils to sit just below the base of the Cambrian, which in that region dates to 539 million years ago — a difference that would change their significance entirely.
Botting's skepticism finds support in a separate study published in Gondwana Research, which reexamined 540-million-year-old microfossils from Brazil that had been interpreted as trace fossils left by tiny worm-like creatures. The new analysis concludes they are not animal traces at all, but rather fossilized communities of bacteria and algae, some with remarkably preserved cells and organic material still intact. The researchers identified at least three distinct size classes of these structures, suggesting different species living together in a microbial consortium. The largest populations resemble benthic algae, while the smallest could be algal, cyanobacterial, or sulfur-oxidizing bacteria. The three-dimensional preservation of these pyritized structures points to microbial consortia, not the burrows of small animals.
These challenges underscore a recurring problem in paleontology: the difficulty of distinguishing between early animal fossils and other organic structures preserved in ancient rock. The original Science paper may have interpreted ambiguous evidence too generously in favor of animal origins. Yet even if some Ediacaran fossils do represent early animals, that finding would not resolve the central mystery of the Cambrian explosion — the sudden appearance of most major animal body plans in a geologically brief window. The presence of a few Ediacaran animals would not explain why so many diverse animal forms emerged so rapidly in the Cambrian. Botting himself concludes that while some of the paper's interpretations lean too far toward animal classification, the fossil assemblage remains "wonderful and interesting." The work ahead will require more careful analysis and better preservation to settle what these ancient rocks are actually telling us.
Notable Quotes
Some of it has been interpreted more towards the animals than it should be, but others, yeah, consider me intrigued.— Joseph Botting, paleontologist
Even if some relatives of sponges, cnidarians, stem metazoans, and maybe even stem bilaterians should be present in the Ediacaran, this would do absolutely nothing to explain the sudden appearance of the many different bilaterian animal body plans in the Cambrian explosion.— Günter Bechly, paleontologist
The Hearth Conversation Another angle on the story
Why does it matter whether a 550-million-year-old fossil is a ctenophore or a cnidarian? Aren't they both animals?
They are, but the point is whether we're finding something genuinely new in the Ediacaran. Cnidarians were already known from that time. A ctenophore would have been a different animal group appearing earlier than we thought. If Botting is right, we've found nothing new.
What makes it so hard to tell what these fossils actually are?
Preservation is often poor, and the structures are ambiguous. A black line in rock could be a gut, or it could be a mineral vein, or algal filament. When you see multiple black lines in one specimen, you have to ask whether that makes biological sense. It usually doesn't.
The paper found many specimens of one organism. Doesn't that strengthen the case?
Not necessarily. If they're all the same species, why do they look different? Botting suggests some may have been misidentified or represent different organisms entirely. More specimens can actually complicate the picture.
What about the tentacles on that cambroernid-like fossil?
The real problem is that they don't look like cambroernid tentacles at all. True cambroernids have long, highly branched tentacles. These are short and barely branched. It's like saying something is a giraffe because it has a long neck, but ignoring that the neck is actually short.
Does this mean there were no animals in the Ediacaran?
No. We know some animals existed then. The question is how many, how diverse, and how early. These papers suggest we should be more cautious about what we're claiming. Better preservation and more evidence are needed before we rewrite the textbooks.
What does this tell us about the Cambrian explosion?
It tells us that finding a few Ediacaran animals doesn't solve the mystery. The explosion is still an explosion — most animal body plans still appear suddenly in the Cambrian, not gradually before it.