Rosa Rubicondior: Refuting Creationism Again - Now A 500-Million-Year-Old Fossil Worm From Greenland

Wednesday, 27 August 2025

Refuting Creationism Again - Now A 500-Million-Year-Old Fossil Worm From Greenland

The holotype specimen of Nektognathus from Sirius Passet

Image credit: Tae Yoon Park

2025: Ancient squid-like creatures are not squid after all, study finds | School of Biological Sciences | University of Bristol

The bad day for those creationists who haven't yet closed their minds to contrary information continues. Close on the news of a 220-million-year-old fossil ichthyosaur from Japan comes the discovery of a 500-million-year-old fossil worm from Greenland.

The identification of this Cambrian fossil, Nectocaris, as an ancestor of arrow worms rather than an early squid, as once thought, is a fine example of something creationists pretend to find incomprehensible: scientists changing their minds when new evidence demands it. Wedded to simple certainties, right or wrong, creationists insist that science must be either wholly right or wholly wrong. If a conclusion is shown to be mistaken, they assume the entire scientific enterprise collapses into a cloud of vacuous uncertainty. In their black-and-white world of false dichotomies, that somehow means their evidence-free superstition wins by default.

About 15 years ago, a study of fossils from the Burgess Shale concluded that Nectocaris was a cephalopod mollusc. But that classification posed problems since what could be discerned of its anatomy did not match that of cephalopods. That difficulty has now been resolved by a detailed examination of the ventral ganglion – part of the nervous system – which is revealed to consist of paired structures consistent with being ancestral to arrow worms.

This breakthrough was made possible by the exceptional preservation of fossils at Sirius Passet in northern Greenland, a remarkable Cambrian fossil site.

Sirius Passet^ A Glimpse into the Early Cambrian.

Beautifully preserved stem-group trilobitomorph, Arthroaspis (left); specimen approximately 200 mm in length, photo taken in the field under low Arctic light (Photo by David Harper). Pelagic predator Isoxys (right); scale bar 5 mm. (Photo by Arne Thorshøj Nielsen).

The main section in Sirius Passet, showing the white carbonate rocks of the Portfjeld Formation, faulted against the dark, metamorphosed muddy siltstones of the Buen Formation; the main section is in the brown strata in the centre of the photograph (Photo: Paul Smith).

Geological section through the exposure of the Buen Formation in Sirius Passet (From Harper et al. 2019).

Base camp at the Sirus Passet fossil site

Location & Discovery

Situated in Peary Land, northernmost Greenland, along the eastern shores of J.P. Koch Fjord, within the Buen Formation. It comprises six primary localities. [1.1]
Discovered in 1984 by geologist A. Higgins during mapping by the Geological Survey of Greenland; first described in 1987 by Simon Conway Morris and colleagues. [1.1]

Age & Regional Significance

The site dates to Cambrian Series 2, Stage 3, making it approximately 10–15 million years older than the Burgess Shale and roughly contemporaneous with the Chengjiang fauna. [1.1]

Fossil Preservation & Environment

A Lagerstätte known for exceptional soft‑tissue preservation—covering aspects such as guts, muscles, nervous systems, and the rare preservation of delicate features. [2.1]
Initially preserved via silicification (“death masks”) and later altered by low‑grade Devonian metamorphism (~409 ± 50 °C). [1.1]
Geological and geochemical analyses indicate deposition in a deep‑water slope setting near the shelf–slope break, within low‑oxygen or intermittently anoxic conditions, akin to modern oxygen‑minimum zones. [3.1]

Faunal Diversity

One of the oldest metazoan‑dominated fossil ecosystems, with a moderate but notably diverse assemblage. [4.1]
The fossil collection includes arthropods (e.g., Buenaspis forteyi, Aaveqaspis inesoni, Tamisiocaris), lobopodians (Kerygmachela, Pambdelurion), halkieriids (Halkieria), worms, sponges, vetulicolians (Ooedigera), and others. [1.1]
Many specimens offer insights into anatomical evolution and phylogeny of early animal phyla. [3.1]

Scientific Impact & Recognition

Significant in understanding early animal evolution, the site offers a window onto early Cambrian ecosystems and the diversification of life. [3.1]
In 2022, the International Union of Geological Sciences (IUGS) designated Sirius Passet as one of the first 100 Geological Heritage Sites, underscoring its global significance. [1.1]

The study was led by Associate Professor Jakob Vinther of the University of Bristol, UK, in collaboration with palaeontologists from the Korean Polar Research Institute and the University of Copenhagen. Their findings are published, open access, in Science Advances and are summarised in a University of Bristol news release.

Ancient squid-like creatures are not squid after all, study finds
Remarkable fossils found in North Greenland have helped researchers solve a 500-million-year-old puzzle surrounding squid-like ancestors.
It was previously thought ancient organisms called nectocaridids, which bear a resemblance to squid, were a type of cephalopod – marine molluscs with tentacles and a prominent head. But scientists, co-led by the University of Bristol, have now shown these creatures are actually an early descendent of arrow worms, also known as chaetognaths.

This surprising discovery means the rather simple marine arrow worms had ancestors with much more complex anatomies and a predatory role higher up in the food chain.

The study, in partnership with palaeontologists at the Korean Polar Research Institute and University of Copenhagen, is the culmination of a series of excavation expeditions to Sirius Passet in North Greenland, which began nine years ago. The locality is famous for its extreme exceptional preservation of marine organisms from the Early Cambrian around 518 million years ago.

Sirius Passet is a treasure trove of fossils from the Cambrian Explosion. We not only find delicate soft-bodied fossils but also their digestive systems, musculature and sometimes even their nervous system. Around 15 years ago a research paper, based on fossils from the famous Burgess Shale, claimed nectocaridids were cephalopods. It never really made sense to me, as the hypothesis would upend everything we otherwise know about cephalopods and their anatomy didn’t closely match cephalopods when you looked carefully.

Associate Professor Dr Jakob Vinther, co-lead author
School of Earth Sciences
Palaeobiology Research Group
University of Bristol, Bristol, UK.

The research team’s excitement grew as fossils of the mysterious nectocaridids were unearthed in Sirius Passet for the first time.

By analysing 25 fossil specimens, the researchers were able to pinpoint where nectocaridids fit into the tree of life. The solution came from Sirius Passets’ unique preservation conditions resulting in their nervous systems commonly remaining intact.

We discovered our nectocaridids preserve parts of their nervous system as paired mineralised structures, and that was a giveaway as to where these animals sit in the tree of life.

Associate Professor Dr Jakob Vinther.

Recently, the team uncovered fossils in Sirius Passet belonging to another branch of the animal tree – a small group of swimming worms called arrow worms or chaetognaths.

These fossils all preserve a unique feature, distinct for arrow worms, called the ventral ganglion.

Dr Tae-Yoon Park, co-lead author
Divisions of Polar and Earth Sciences
Korea Polar Research Institute
Incheon, Republic of Korea.

The ventral ganglion is a large mass of nerves situated on the belly of living arrow worms, which is unique to this type of creature. The unique anatomy of the organ combined with the special preservation conditions means it sometimes is replaced by phosphate minerals during decay.

We now had a smoking gun to resolve the nectocaridid controversy. Nectocaridids share a number of features with some of the other fossils that also belong to the arrow worm stem lineage. Many of these features are superficially squid-like and reflect simple adaptations to an active swimming mode of life in invertebrates, just like whales and ancient marine reptiles end up looking like fish when they evolve such a mode of life.

Dr Tae-Yoon Park.

The discovery helps reveal clues about arrow worms and their past.
Nectocaridids have complex camera eyes just like ours. Living arrow worms can hardly form an image beyond working out roughly where the sun shines. So, the ancestors of arrow worms were really complex predators, just like the squids that only evolved about 400 million years later. We can therefore show how arrow worms used to occupy a role much higher in the food chain. Our fossils can be much bigger than a typical living arrow worm and combined with their swimming apparatus, eyes and long antennae, they must have been formidable and stealthy predators.

Associate Professor Dr Jakob Vinther.

As further evidence for nectocaridids being swimming carnivores, the researchers found several specimens with the carapaces of a swimming arthropod, called Isoxys, inside their digestive tract.

The fossil is named Nektognathus evasmithae. The species name honours Professor Eva Smith, the first female professor of law in Denmark and renowned human rights advocate.
My decision to name our fossil after Eva, is that this animal was a smart and stealthy fighter just like she is.

Associate Professor Dr Jakob Vinther.

Publication:
Jakob Vinther et al.
A fossilized ventral ganglion reveals a chaetognath affinity for Cambrian nectocaridids.
Sci. Adv.11, eadu6990 (2025). DOI:10.1126/sciadv.adu6990

Abstract
Nectocaridids are enigmatic Palaeozoic animals with a controversial phylogenetic position. Previous hypotheses have placed them in their own phylum, chordates, molluscs (specifically cephalopods), or radiodont panarthropods. We describe here a nectocaridid, Nektognathus evasmithae gen. et sp. nov. from the early Cambrian (~519 million years) Sirius Passet Lagerstätte of North Greenland. Key specimens preserve paired, phosphatized arcuate structures consistent with preservation of a ventral ganglion, a feature characteristic of extant and fossil chaetognaths, including the amiskwiid Timorebestia koprii also from Sirius Passet. Nektognathus shares a gnathostomulid-like jaw apparatus, lateral fins, subterminal anus, and large antennae with Timorebestia and Amiskwia, placing nectocaridids in the chaetognath stem lineage. The complex sensory anatomy of nectocaridids, which is partially shared with other extinct amiskwiids, highlights a more dynamic predatory lifestyle much higher in the trophic food chain during early chaetognath evolution.

INTRODUCTION
While most animal phyla had originated by the Cambrian (~541 to 485 million years ago) (1–4), the tree of life has been extensively pruned by subsequent extinctions, with stem lineages of different phyla sometimes having unexpected character combinations that could not be predicted from extant species. This has left some fossils in taxonomic limbo as they preserve ambiguous character combinations inviting competing hypothesized phylogenetic placements.

S. J. Gould took the many peculiar looking “weird wonders” from the Burgess Shale as evidence for the Cambrian explosion having given rise to unique and bizarre body plans that were short lived (mostly or entirely extinct by the end of the Cambrian) and that contingency played a fundamental role in determining evolutionary outcomes through time (5). However, the discovery of additional Burgess Shale type localities, new specimens, and an ever increasing array of imaging techniques, together with a wider appreciation of the principles of stem and crown groups (2) and the application of phylogenetic analysis (6–9) many of these weird wonders have instead been placed on the stem lineages of phyla or supra-phyletic groups. These fossils therefore showcase unexpected morphologies deep in the ancestry of several animal clades and have provided key insights into how the diverse body plans of the animal phyla were assembled. The iconic Burgess Shale taxa Anomalocaris and Hallucigenia are key examples, being placed in the arthropod stem lineage and panarthropod total group (or Onychophoran stem) respectively (10–12), revealing unexpected combinations of features in the early evolution of panarthropods. Other weird wonders that have a more resolved affinity due to subsequent discoveries or through revisiting old material include Odontogriphus and Wiwaxia (stem molluscs) (7, 13, 14), Dinomischus (stem ctenophores) (8), Opabinia (stem arthropod) (15, 16), and Amiskwia (stem chaetognath) (17). Today, very few of Goulds’ weird wonders remain relegated to their own unknown lineage but are considered part of some known (extant) phylums’ total group, while their exact placement may still be debated in the literature.

The Cambrian nectocaridids (18–21) are another of Goulds’ weird wonders (5). Nectocaridids were adapted for swimming, having lateral fins, a head region with stalked camera eyes, and paired cephalic tentacles (19, 22). While originally described from an incomplete specimen in lateral view from the middle Cambrian Burgess Shale (18), nectocaridids have since been documented from the early Cambrian of Chengjiang (20) and possibly also in the Late Ordovician (21). Previous hypotheses placed them in a crustacean-like new phylum (18), chordates (23), molluscs (20) [specifically cephalopods (19, 21, 22)], or radiodont panarthropods (24), but each has been subject to criticism (24–27). The hypothesis that has received most attention is a placement among cephalopods (14, 19, 21, 22, 27). These studies drew attention to the remarkable similarity between nectocaridids and coleoids, such as cuttlefish and squid, due to the presence of extensive lateral fins, well-developed eyes, and head appendages in Nectocaris pteryx, comparable to the cephalopod arm crown as well as a funnel-shaped structure on the head, possibly functionally similar to the cephalopod hyponome. This hypothesis would have substantial implications for understanding cephalopod evolution, as the fossil record documents a more gradual evolution of the coleoid body plan with the shell becoming internalized and eventually reduced throughout the Palaeozoic and Mesozoic (26). Cephalopod affinities for nectocaridids have therefore also drawn criticism due to its incongruence with evidence from both fossils, development, topology of specific anatomical characters, and molecular clocks (26). However, alternative phylogenetic positions suggested in studies criticizing the cephalopod hypothesis, such as radiodont panarthropods (24), are similarly incongruent (27). Ultimately, this leaves the taxonomic status of nectocaridids in limbo.

A fundamental issue in placing nectocaridids confidently in the animal tree of life is identifying unequivocal synapomorphies shared with any living phylum. Recent discoveries have shown that the previous similarly problematic amiskwiids belong to the chaetognath stem lineage and bridge the morphology displayed in chaetognaths and their closest sister taxon, the gnathiferans (17, 28, 29). Amiskwiids exhibited a broadly chaetognath-like bodyplan, with lateral fins and a distinct head region, but with an internal jaw apparatus with bilateral elements and a symmetric basal plate that is present in the gnathiferan phylum Gnathostomulida (17, 28, 30). A key discovery from the Early Cambrian Sirius Passet in North Greenland is the preservation of the ventral ganglion in a very large-bodied amiskwiid, Timorebestia koprii. Preserved by phosphatization, the lateral neuron somata is enriched in nuclei that provided a source of phosphate to mineralize this part of the ventral ganglion along with adjacent musculature. This study also documented a phosphatized ventral ganglion in a taxon that has external grasping spines and is therefore an unequivocal member of the chaetognath total group (28). Preservation of phosphatized internal organs is commonplace in Sirius Passet, with preservation of digestive systems, muscle systems, or both in different taxa (31–33). However, the preservation of paired arcuate structures in the mid-trunk, sometimes in association with adjacent musculature is unique to the chaetognaths and amiskwiids documented from Sirius Passet (28). Such an enlarged ventral ganglion is unique to extant chaetognaths among extant phyla (34, 35), strongly suggesting a chaetognath affinity for amiskwiids (28) to the exclusion of the other gnathiferan phyla, contra (30).

Here, we report the first nectocaridids from Sirius Passet and show that they preserve paired arcuate phosphate mineralizations, otherwise unique to chaetognaths including amiskwiids also reported from Sirius Passet (28). This provides evidence for the systematic placement of nectocaridids in the chaetognath stem group. Nectocaridids share a number of characteristics with amiskwiids and chaetognaths that explain their otherwise peculiar bodyplan and highlight aspects of the ecology and trophic role stem group chaetognaths had during the Cambrian explosion.

Fig. 1. Nektognathus evasmithae gen et sp. nov. holotype, MGUH34956.
(A) Image with low-angle lighting illuminated from top left, coated with magnesium oxide smoke. (B) Illuminated submerged in water under high-angle illumination. (C) EPMA carbon elemental map. (D) Interpretative drawing. (E to G) Close-up of anterior trunk region preserving the jaw apparatus. (E) Carbon elemental map featuring the outline of the jaw apparatus due to splitting of the specimen. (F) Low-angle lighting illumination coated with magnesium smoke. (G) Low-angle illumination coated with magnesium smoke with outline of jaw apparatus superimposed. (H and I) Specimen of Isoxys in the anterior section of the digestive tract, outlined in (I). (J and K) Preservation of ventral ganglion with superimposed striated musculature outlined in (K). (L and M) Digestive tract preserved by modest relief in the posterior trunk and caudal region, outlined in (M). Colors in interpretative drawing represent gut (green), ventral ganglion and nervous system (blue), jaw apparatus (red and mustard yellow), eyes (light yellow), Isoxys specimen (pink) and body outline (gray). a, antennae; cr, caudal region; fr, fin rays.

Fig. 2. N. evasmithae gen et sp. nov. additional specimens.
Each specimen illuminated in high-angle lighting submerged in water on the left. Image is a high dynamic range (HDR) image made from several images with different high-angle illuminations. Each right-hand panel is an EPMA carbon map. (A and B) MGUH34957, smallest studied individual. (C and D) MGUH34958, small individual. (E and F) MGUH34959. (G and H) MGUH34960. (I and J) MGUH34961, EPMA carbon map in (J) is a composite with anterior region from counterpart superimposed on to the EPMA map from the main part, outlined with a stippled line. (K and L) MGUH34962.

Fig. 3. Jaw apparatus in N. evasmithae gen. et sp. nov.
(A to E) MGUH34962. (A) Overview image, low-angle illumination from upper left and coated with magnesium oxide, and with subsequent panels denoted with squares. (B) Right lateral jaw element, outlined in (C). (D) Basal plate, outlined in (E). (F to J) MGUH34963. (F) Overview image, low-angle illumination from upper left and coated with magnesium oxide, and with subsequent panels denoted with squares. (G) Left lateral jaw element, outlined in (H). (I) Basal plate, outlined in (J). (K) Schematic outline of N. evasmithae gen. et sp. nov. with the proportions of the jaw apparatus relative to overall body dimensions highlighted. Colors: Lateral jaw elements (mustard yellow) and basal plate (red).

Fig. 4. Phosphatized ventral ganglion in N. evasmithae gen. et sp. nov.
(A) MGUH34964, very large individual, imaged with polynomial texture mapping (PTM) specular enhancement (low angle from NW). Ventral ganglion highlighted in blue. (B and C) Close-up of ventral ganglion in counterpart imaged in low-angle illumination and with magnesium oxide smoke. (D) MGUH34960 imaged with PTM specular enhancement. Ventral ganglion highlighted in blue. (E and F) Close-up of ventral ganglion, imaged with PTM specular enhancement. (G) Extant chaetognath, sagittid sp. that have been histochemically labeled for nuclei [blue, previously figured (28)] highlighting the presence of the lateral neuron somata of the ventral ganglion enriched in nuclei, giving rise to phosphatization of ventral ganglia in total group chaetognaths in Sirius Passet (28).

Fig. 5. Nervous system in N. evasmithae gen. et sp. nov.
(A and B) MGUH34956 holotype. (A) EPMA carbon map. (B) Outline of preserved nervous system. (C and D) MGUH34960. (C) EPMA carbon map. (D) Outline of preserved nervous system. (E) Schematic outline of possible nervous system trajectory based on available material. (F and G) MGUH34957. (F) EPMA carbon map. (G) Outline of preserved nervous system. (H and I) MGUH34962. (H) EPMA carbon map. (I) Outline of preserved nervous system. (J) Schematic nervous system in living chaetognaths, modified from Figure 2a and b in Harzsch and Müller ((34) under CC BY 2.0 license (https://creativecommons.org/licenses/by/2.0/).

Fig. 6. Jaw apparatus in Nectocaris from Chengjiang and Burgess shale.
(A to F) Nectocaris latus HKMF-50001 illuminated dry with oblique lighting. (A) Close-up of anterior and medial portion of specimen. (B) Close-up of anterior region preserving jaw apparatus, lateral jaw elements, and basal plate highlighted in (C). [(D) to (F)] N. latus ANSK-20001 illuminated dry with oblique lighting. (D) Close-up of anterior and medial portion of specimen. (E) Close-up of anterior region preserving jaw apparatus, lateral jaw elements highlighted in (F). (G to I), N. pteryx ROM 59660 (counterpart) illuminated with oblique lighting while dry. (G) Overview of entire specimen. (H) Close-up of jaw apparatus in anterior region, highlighted in (I). (J to N) N. pteryx ROM 59661 counterpart, laterally compressed specimen illuminated while submerged in water and using high-angle cross-polarized lighting. (J) Closeup of anterior and medial region of specimen. (K) Jaw apparatus highlighted in close-up view. (L) Close-up of anterior region, the same view as in (K). (M) Close-up of putative basal plate preserved in laterally compacted view, highlighted in (N). (O and P) Schematic outline of Nectocaris pteryx and N. latus with the proportions of the jaw apparatus relative to overall body dimensions highlighted. Colors: Lateral jaw elements (mustard yellow) and basal plate (red). Images of N. latus from (22). jw, jaw; bp, basal plate.

Fig. 7. Phylogenetic analysis.
(A) Majority (50%) rule consensus tree from a Bayesian analysis (228 characters and 58 taxa), placing nectocaridids on the chaetognath stem as a sister taxon to Timorebestia (support low, 56). (B) Schematic summary phylogeny with major body plans shown and the position of the jaw apparatus highlighted.

Fig. 8. Reconstruction of N. evasmithae gen. et sp. nov.
(A) Oblique ventral view. (B) Lateral view. (C) Dorsal view. (D) Ventral view, musculature removed. (E) Ventral view.

Jakob Vinther et al.
A fossilized ventral ganglion reveals a chaetognath affinity for Cambrian nectocaridids.
Sci. Adv.11, eadu6990 (2025). DOI:10.1126/sciadv.adu6990

Copyright: © 2025 The authors.
Published by the American Association for the Advancement of Science. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

What emerges strongly from this study is that, with more Cambrian fossil sites than the Burgess Shale and with improved imaging techniques, what Stephen J. Gould once presented as evidence of a sudden “explosion” of unique but short-lived body plans was in fact a transitional stage in the evolution of multicellular organisms. Several species once thought to represent wholly distinct taxa are now recognised as stem-members of existing groups, their distinctive features showing that these traits evolved surprisingly early in their lineages.

What the Burgess Shale represents is a snapshot of that process frozen in time. What Gould saw as an “explosion” was really an artefact of geology, like trying to work out the plot of a film from a single frame. Science is now recovering many more frames, and examining them under different lighting, so that a clearer picture of the story is emerging. Creationists, however, insist on treating that single frame as if it tells the whole story — and then, when the details don’t quite fit, they declare the entire film incoherent and demand we replace it with a fairy tale instead.

It is becoming increasingly clear that the so-called “Cambrian Explosion” that creationists like to parade as proof of the sudden appearance of complex life — conjured in an instant by divine fiat, while quietly ignoring the actual geological timescale — is in reality evidence of evolutionary processes unfolding over tens of millions of years. It reflects the transition from the Ediacaran biota to the Ordovician, driven by the evolutionary arms race between predators and prey unleashed by the development of motility.

Far from supporting creationism, this discovery pulls the Cambrian Explosion rug from beneath their feet and replaces it with solid support for evolution. The 500-million-year age of the fossil renders the Biblical timeline not just implausible but absurd. More importantly, the study exemplifies the scientific embrace of uncertainty in the pursuit of truth and the readiness to revise conclusions in light of new evidence — an approach that steadily drives science closer to reality, while the theistic craving for simple certainties, even at the expense of truth, drives religion ever further from it.

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