3D laser scans enable the researchers to study the fossils’ shape and curvature.
Droser Lab/UCR
Researchers Scott Evans (left) and Ian Hughes examine a fossil bed at Nilpena Ediacara National Park.
Droser Lab/UCR.
The refutation of creationism continues today with news of another one of those 'non-existent' transitional species that turn up with monotonous regularity only to be dismissed by creationists as 'not transitional but fully formed' with now two gaps in the record where there was originally one, or by simply dismissing the dating method as unreliable and coincidentally wrong by an order of magnitude sufficient to make 6-10,000 years look like x-million years.
Another big disappointment for creationists is the fact that this one is from before the Cambrian when their traditional disinformation claims lots of species popped into existence without ancestors by magic in a single event called the 'Cambrian explosion'. The Cambrian 'explosion' was of course a period of some 6-10 million years during which many of the basic body plans of multicellular organisms evolved.
This fossil however was before then and was clearly the ancestral stem species from which a whole range of Cambrian organism, collectively known as Ecdysozoa evolved. These are a group of organisms with an outer cuticle which is shed periodically as the organism grows. The vast group includes nematode worms and arthropods such as insects, spiders, crustaceans like crabs, shrimps, lobsters, and the horseshow crab. So, this discovery, which the palaeontologists have named
Uncus dzaugisi sits at the base of this branch of the evolutionary tree. It resembled a nematode worm.
Tell me all about the Ecdysozoa, please.
Ecdysozoa is a major clade of animals within the larger group known as Protostomia, distinguished by their unique mode of growth, which involves periodic moulting of an external cuticle. The term "ecdysozoa" comes from the Greek word ecdysis, meaning "to strip off" or "to shed," referring to this moulting process.
Characteristics of Ecdysozoa
- Moulting (Ecdysis):
- The defining feature of Ecdysozoans is the shedding of their cuticle—a tough, non-living outer layer made of proteins, polysaccharides (like chitin), or collagen. This process allows them to grow, as the rigid cuticle limits continuous size increase.
- After moulting, a new, larger cuticle is secreted, which hardens over time.
- Body Structure:
- Many have a hydrostatic skeleton, relying on fluid pressure in their body cavity for movement and structure.
- Most lack cilia or flagella in their adult form, distinguishing them from other protostomes.
- Diversity:
- The group includes some of the most diverse and abundant organisms on Earth, ranging from microscopic species to large, visible ones.
- Nervous System:
- Typically, they have a ventral nerve cord and a dorsal brain, with varied sensory adaptations.
Major Groups Within Ecdysozoa
Ecdysozoa includes eight phyla, with two of the most well-known being Arthropoda and Nematoda:
- Arthropoda
- The largest and most diverse group of animals, including insects, arachnids, crustaceans, and myriapods.
- They have segmented bodies, jointed appendages, and a hard exoskeleton.
- Examples: Butterflies, crabs, spiders, centipedes.
- Nematoda (Roundworms)
- Microscopic to macroscopic worms with a cylindrical, unsegmented body.
- Found in nearly every habitat on Earth, often as parasites in plants and animals.
- Examples: Caenorhabditis elegans (a model organism), Ascaris (a human intestinal parasite).
- Tardigrada (Water Bears)
- Microscopic, water-dwelling animals known for their extreme resilience to harsh environments.
- They can survive desiccation, radiation, and even the vacuum of space.
- Onychophora (Velvet Worms)
- Segmented, soft-bodied terrestrial animals with slime glands used for capturing prey.
- Priapulida
- Marine worms with a tubular body, often found burrowing in sediment.
- Kinorhyncha
- Tiny, segmented marine animals often referred to as "mud dragons."
- Loricifera
- Microscopic animals inhabiting marine sediment, with a complex, retractable body.
- Nematomorpha (Horsehair Worms)
- Parasites as larvae, often controlling the behaviour of their insect hosts.
Evolution and Phylogeny
- Ecdysozoa was proposed as a clade in 1997, based on molecular evidence (notably studies of ribosomal RNA).
- They share a common ancestor with other protostomes but diverged early to adopt their unique moulting strategy.
- Their evolutionary success is evident in their sheer numbers and adaptability, especially in arthropods.
Ecological and Economic Importance
- Ecological Roles:
- Many ecdysozoans are key components of ecosystems as decomposers, predators, prey, and parasites.
- Insects, a subgroup of arthropods, are critical for pollination and nutrient cycling.
- Economic Impact:
- Beneficial: Insects (e.g., bees) aid in agriculture, while nematodes play a role in soil health.
- Harmful: Some ecdysozoans are pests or parasites causing diseases in humans, animals, and crops.
Fun Facts
- Tardigrades can enter a state called cryptobiosis, surviving for decades without water or food.
- Arthropods are the most successful phylum, with over a million described species, and likely many more undiscovered.
- Nematodes may account for about 80% of individual animals on Earth.
The discovery was made by a team from University of California, Riverside (UCR), led by Professor Mary Droser a distinguished professor of geology. The have explained their findings in the journal,
Current Biology, and in a UCR press release:
Tiny worm makes for big evolutionary discovery
UC Riverside scientists have described ‘Uncus,’ the oldest ecdysozoan and the first from the Precambrian period
Everyone has a past. That includes the millions of species of insects, arachnids, and nematode worms that make up a major animal group called the Ecdysozoa.
Until recently, details about this group’s most distant past have been elusive. But a UC Riverside-led team has now identified the oldest known ecdysozoan in the fossil record and the only one from the Precambrian period. Their discovery of Uncus dzaugisi, a worm-like creature rarely over a few centimeters in length, is described in a paper published today in Current Biology.
Scientists have hypothesized for decades that this group must be older than the Cambrian, but until now its origins have remained enigmatic. 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 and adds to our understanding of the evolution of animal life.
Mary L. Droser, co-author
Earth and Planetary Sciences
University of California, Riverside
Riverside, CA , USA.
The ecdysozoans are the largest and most species-rich animal group on Earth, encompassing more than half of all animals. Characterized by their cuticle — a tough external skeleton that is periodically shed — the group comprises three subgroups: nematodes, which are microscopic worms; arthropods, which include insects, spiders, and crustaceans; and scalidophora, an eclectic group of small, scaly marine creatures.
Like many modern-day animal groups, ecdysozoans were prevalent in the Cambrian fossil record and we can see evidence of all three subgroups right at the beginning of this period, about 540 million years ago. 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.
Ian V. Hughes, first author
Organismic and Evolutionary Biology
Harvard University, Cambridge, MA, USA.
DNA-based analyses, used to predict the age of animal groups by comparing them with their closest living relatives, have corroborated this hypothesis. Yet ecdysozoan fossil animals have remained hidden among scores of animal fossils paleontologists have discovered from the Ediacaran Period.
Top:
Uncus fossil from Nilpena Ediacara National Park. The numbers correspond to the coordinates of this fossil on the fossil bed surface. Bottom: 3D laser scans enable the researchers to study the fossils’ shape and curvature.
Droser Lab/UCR.
This excavation process has only been done at Nilpena Ediacara National Park in South Australia, a site Droser and her team have been working at for 25 years that is known for its beautifully preserved Ediacaran fossils.
Nilpena is perhaps the best fossil site for understanding early animal evolution in the world because the fossils occur during a period of heightened diversity and we are able to excavate extensive layers of rock that preserve these snapshots. The layer where we found Uncus is particularly exciting because the sediment grains are so small that we really see all the details of the fossils preserved there.
Assistant Professor Scott Evans, co-author
Earth, Ocean, and Atmospheric Sciences
Florida State University, Tallahassee, FL, USA.
While the team didn’t set out to find an early ecdysozoan during their 2018 excavation, they were drawn to a mysterious worm-like impression that they dubbed “fishhook.”
Sometimes we make dramatic discoveries and sometimes we excavate an entire bed and say ‘hmmm, I’ve been looking at that thing, what do you think?’ That’s what happened here. We had all sort of noticed this fishhook squiggle on the rock. It was pretty prominent because it was really, really deep.
Because it was deep, we knew it wasn’t smooshed easily so it must have had a pretty rigid body. At this point we knew this was a new fossil animal and it belong to the Ecdysozoa.
Ian V. Hughes
After seeing more of the worm-like squiggles the team paid closer attention, taking note of fishhook’s characteristics. Other defining characteristics include its distinct curvature and the fact that it could move around — seen by trace fossils in the surrounding area. Paul De Ley, an associate professor of nematology at UCR, confirmed its fit as an early nematode and ruled out other worm types.
The team called the new animal Uncus, which means “hook” in Latin, noting in the paper its similarities to modern-day nematodes. Hughes said the team was excited to find evidence of what scientists had long predicted; that ecdysozoans existed in the Ediacaran Period.
It’s also really important for our understanding of what these early animal groups would have looked like and their lifestyle, especially as the ecdysozoans would really come to dominate the marine ecosystem in the Cambrian.
Ian V. Hughes
The paper is titled “An Ediacaran bilateran with an ecdysozoan affinity from South Australia.” Funding for the research came from NASA.
Highlights
- 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
Summary
Molecular clocks and Cambrian-derived metazoans strongly suggest a Neoproterozoic origin of many animal clades.1,2,3,4 However, fossil bilaterians are rare in the Ediacaran, and no definitive ecdysozoan body fossils are known from the Precambrian. Notably, the base of the Cambrian is characterized by an abundance of trace fossils attributed to priapulid worms,5,6 suggesting that major divisions among ecdysozoan groups occurred prior to this time. This is supported by ichnofossils from the latest Ediacaran or early Cambrian left by a plausible nematoid,7,8,9 although definitively attributing this inferred behavior to crown-Nematoida remains contentious in the absence of body fossils.10 Given the high probability of the evolution of Ecdysozoa in the Proterozoic, the otherwise prolific fossil record of the Ecdysozoa, and the identification of more than 100 distinct Ediacaran genera, it is striking that no Ediacaran body fossils have been confidently assigned to this group. Here, we describe Uncus dzaugisi gen. et. sp. nov. from the Ediacara Member (South Australia), a smooth, vermiform organism with distinct curvature and anterior-posterior differentiation. The depth of relief of Uncus is unique among Ediacara fossils and consistent with a rigid outer cuticle. 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. This validates the Precambrian origin of Ecdysozoa, reconciling a major gap between predicted patterns of animal evolution and the fossil record.4
I think my favourite quote from one of the scientists is "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", which just about describes the difference between someone who knows the Theory of Evolution is correct because he understands the evidence for it, and a creationists who believes in fully formed living organisms made from nothing, magically popping into existence from nowhere, with magic spells cast by an unproven supernatural deity their mummy and daddy told them about.
The ancestral form, the transitional species, was in exactly for rock formation of exactly the right age which the theory of evolutionary decent with modifiction from a common ancester predicted.
And in case a creationist is tempted to try the 'radiometric dating is flawed/wrong/faked fallacy. The Ediacaran rock formation these fossils were found in was independently dated several different ways that all converged on a 98-million-year span from 635 to 538 million years ago known as the Ediacaran. The Most important being the Uranium-Lead (U-Pb) dating of zircons found in the layers of volcanic ash sandwiched within the rocks. To compress 600 million years of radioactive decay into less than 6-10,000 years would have caused Earth's rocks to melt and the seas to boil away. And the weak nuclear force would have been so weak that atoms could not have formed, let alone life, and there would have been no planet and no universe to fine tune for it either.
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