Evolution Icon Evolution
Paleontology Icon Paleontology

Fossil Friday: Are Ediacaran “Fishing Hooks” a Breakthrough Discovery of Precambrian Animals?

December 6, 2024, 6:57 AM
Photo credit: Citronnel, CC BY-SA 4.0 , via Wikimedia Commons.

This Fossil Friday shows the famous Ediacaran fossil beds at the Nilpena National Park in the Flinders Ranges of South Australia, which are dated to a Late Precambrian age of about 555 million years. These outcrops recently yielded fossils that allegedly shed light on the origin of animals in general and so-called ecdysozoans in particular. Ecdysozoa is a controversial clade of metazoan animals that clusters arthropods with nematelminth worms (e.g., nematode roundworms) and thus comprises the majority of Earth’s biodiversity. All these animals share a cuticle that is moulted by a process of hormonally controlled ecdysis. A press release said that “paleontologists have hypothesized for decades that a major animal group called Ecdysozoa must be older than the Cambrian period, but until now its origins have remained enigmatic” (News Staff 2024), but this has now changed with a “big evolutionary discovery” (Nightingale 2024). So, let’s have a look at the newest edition of the Precambrian animal guessing game.

During ongoing excavations at the Ediacaran site, the distinguished paleoecologist Mary Droser from the University of California Riverside and her son Ian Hughes, a paleontology grad student at Harvard University, discovered strangely curved impressions of 6-31 mm length in the ancient sediments. They initially did not recognize these structures as very significant and jokingly called them “fishing hooks.” After detailed studies with 3D laser scans, the supposed fossils were recently described by Hughes et al. (2024) in an article in the journal Current Biology, and named Uncus dzaugisi, because uncus means hook in Latin language. But just a hook-like structure would not have been very remarkable, so what did the study find that explains the massive global media coverage of the discovery (e.g., Barras 2024, News Staff 2024, Pennisi 2024). This is what the highlights of the study are described by the authors:

  • A new, motile bilaterian is described from the Ediacaran of South Australia
  • Features including morphology and movement suggest an ecdysozoan affinity
  • This discovery firmly places ecdysozoans in the Precambrian

The press release from the UC Riverside (UCR 2024) calls this a “Breakthrough Fossil” that “sheds light on the dawn of diverse animal life.” It confidently reports that the “scientists have identified Uncus dzaugisi, the oldest ecdysozoan fossil from the Precambrian period, confirming long-held assumptions about the ancient origins of this major animal group.” It also quotes the lead author Mary Droser as triumphantly claiming that “this discovery reconciles a major gap between predictions based on molecular data and the lack of described ecdysozoans prior to the rich Cambrian fossils record.”

The popular science journal New Scientist even educates their audience that allegedly the “worm-like fossil is the oldest ancestor of spiders and crustaceans” (Barras 2024). That would be surprising news to the authors of the actual study, who make no such specific claim, and perfectly know that direct ancestors are almost never positively identified in paleontology (see Bechly 2024). The journal Science clarifies that “the species was probably not the common ancestor to all ecdysozoans” (Pennisi 2024). But let’s focus on the more important issues.

Are the “Fishing Hooks” Ecdysozoan Worms?

What evidence does the new study present that the fossils really represent ecdysozoan worms? Indeed, it is only the unspecific elongate cylindrical worm-like shape of the impressions and the fact that “the depth of relief of Uncus is unique among Ediacara fossils and consistent with a rigid outer cuticle.” Well, many things are consistent, but this is not in anyway positive evidence for the presence of a cuticle. The abstract also says that “ecological relationships and associated trace fossils demonstrate that Uncus was motile. Body morphology and the inferred style of movement are consistent with Nematoida, providing strong evidence for at least an ecdysozoan affinity.” So again it is just fuzzy inference and mere consistency with the interpretation but no positive evidence.

None of the crucial diagnostic characters of Ecdysozoa has actually been found in these fossils. Given the dismal track record of scientific misinterpretations of Ediacaran and Cambrian fossils, the attribution of these curved impressions as bilaterian animals and even ecdysozoan nematode-like worms is preposterous and at best a very tentative wild guess. But it is not humbly presented as such, but the authors boldly conclude that their discovery “validates the Precambrian origin of Ecdysozoa, reconciling a major gap between predicted patterns of animal evolution and the fossil record.” This is about as bad science as the silly claim that only because the shape and trajectory of the cosmic object Oumuamua is consistent with an extraterrestrial spaceship, we have finally proven the existence of aliens visiting our solar system (Billings 2021). Unfortunately, this seems to be the poor state of modern scientific inquiry in various disciplines, where any fluff is perfectly acceptable as long as it does not challenge the ruling materialist paradigm.

Is There Any Evidence for Motility?

One piece of alleged ecological evidence for motility is the fact that some of the Uncus fossils were found on top of other fossils, but this could as well be explained with passive transport. But, what about the associated meandering sinusoidal trace fossils? Even though they arguably occur only in the same layers and there is no other candidate that would qualify the criteria as possible maker, there simply is no direct association of maker and trace. There is not a single fossil that documents that Uncus is the maker of these so-called Multina traces, which were previously recorded from Early Cambrian to Tertiary localities but generally considered to be produced by an unknown maker and almost never connected to roundworms. The only exceptions are Parry et al. (2017) who also considered Multina traces to be consistent with a nematode vermiform trace maker, and McIlroy (2022) who speculated in a half-sentence that nematodes or foraminiferan protists could be the makers of Multina-like traces, as well as eventually Baliński et al. (2013) who associated other sinusoidal traces with burrowing nematodes. None of these studies provided any empirical proof for this association beyond mere speculation.

Here Are Some Critical Questions

Why in 82 found fossils of Uncus none of the bodies left a trace behind, so how did they even get there? Why has none of the Multina trace fossils a body fossil of a nematode worm preserved at its end? Which modern roundworms produce Multina traces? Why are these obvious questions not even asked? Where has critical thinking gone? The answer arguably seems to be the desperate need to find this result to reconcile the conflicting data of molecular clocks and fossil record. This quote by the lead author Ian Hughes shows this motivation quite clearly (UCR 2024):

We know they didn’t just appear out of nowhere, and so the ancestors of all ecdysozoans must have been present during the preceding Ediacaran period. [Emphasis added.]

The new study by Hughes et al. (2024) opens with this admission: “Molecular clocks and Cambrian-derived metazoans strongly suggest a Neoproterozoic origin of many animal clades. However, fossil bilaterians are rare in the Ediacaran, and no definitive ecdysozoan body fossils are known from the Precambrian.” Indeed, several previous studies (e.g. Howard et al. 2022) had suggested that “the Ediacaran divergence of Ecdysozoa occurred at least 23 myr before the first potential ecdysozoan trace fossils” and even much more earlier than the oldest body fossils from the mid-Cambrian. This conflict between molecular clock estimates and the fossil record is a well known general problem (e.g., Cunningham et al. 2017) and readily acknowledged as such by mainstream science, which emphasises that “a precise timeline of animal evolution cannot be obtained with current methods” and therefore “attempts to build evolutionary narratives of early animal evolution based on molecular clock timescales appear to be premature” (dos Reis et al. 2015).

By the way: Another recent study by Carlise et al. (2024) also suggested an Ediacaran age of bilaterian animal phyla, but the article again has zero fossil evidence for this. It actually uses the Early Cambrian mollusc Aldanella as calibration point for its molecular clock estimates, and in the supplementary materials it explicitly acknowledges the doubtful status of several alleged Ediacaran bilaterian animals and thus confirms a position that I advocated in several critical articles here at Evolution News. The authors for example say that “possible sponge biomarkers … can also be produced by bacteria”, that “vermiform microstructures” could be “cyanobacteria or algae”, that the alleged stem-mollusc Kimberella could have a coelenterate affinity, and that for the alleged lophotrochozoan Namacalathus “there have been numerous other interpretations for this animal, ranging from cnidarian to stem eumetazoan, and this uncertainty makes it an unsuitable calibration.” They also unambiguously corroborate my view that “the Lantian Biota also has extensive macrofossils without any definitive metazoans.” Maybe somebody should tell know-it-all “Professor” Dave from the prestigious YouTube University.

In light of all these issues, you may judge yourself wether the fossil “fishing hook” qualifies as a breakthrough evolutionary discovery or should it rather be considered as a “brainfart” discovery, motivated by the need to reconcile conflicting data to protect the evolutionary narrative from empirical falsification. So, what might be the true identity of the Ediacaran “fishing hooks”? They could be almost anything, including poop of Precambrian rabbits (just kidding).

References