Rosa Rubicondior: Refuting Creationism - Cambrian Fossils Confirm The Bible Is Wrong.

Interbedded fine-grained clastic and carbonate strata of the lower Illtyd Formation, Wind River, Yukon, Canada, that locally contain Salterella.

A skeleton and a shell? Ancient fossil finally finds home on the tree of life | Virginia Tech News | Virginia Tech

As though fossils from half a billion years before their mythical “Creation Week” weren’t awkward enough for creationists, this latest find slips neatly into the tree of life and closes a small but meaningful gap in our understanding of how protective shells evolved. In doing so, it undermines more creationist claims than they might care to consider.

A research team led by Prescott J. Vayda of Virginia Tech has shown that the enigmatic fossils Volborthella and Salterella, long puzzling palaeontologists, are in fact early cnidarians — members of the group that includes corals, jellyfish, and sea anemones. These organisms are united by their stinging cells, which they use to subdue prey. Even more troublesome for creationists, the structure of the earlier Volborthella shell strongly suggests a transitional relationship with the more complex shell of Salterella, hinting at an evolutionary sequence between the two.

The team’s findings have just been published in the Journal of Paleontology.

The Cambrian period was defined by the emergence of mobility and, with it, true predation. These new ecological dynamics sparked evolutionary “arms races”, driving rapid diversification in both offensive and defensive strategies: sensory structures, spines, shells, and behaviours such as burrowing. These early cnidarians provide an important glimpse into how some of the earliest protective shells came to be.

Such evolutionary arms races also offer yet another reason to dismiss the notion of an intelligent designer. No competent designer would turn yesterday’s solution into today’s problem — yet that is precisely what we see in nature, where improvements in predators prompt improvements in prey, and vice versa. It’s exactly what one would expect from an unguided evolutionary process with no foresight, driven solely by differential survival and reproduction.

Background^ Early Shelled Life in the Cambrian. The fossils: Volborthella and Salterella are tiny, cone-shaped fossils that have puzzled researchers for more than a century. Their unusual shells made them difficult to classify, leading to debates over whether they belonged to molluscs, annelids, or something else entirely.

New classification: Recent research demonstrates that both fossils are early cnidarians. This places them among one of the earliest branching groups of animals, helping resolve a long-standing mystery.

Shells before armour: Early animals lacked hard parts and were exposed to predation. As predators evolved sharper tools and greater mobility, their prey faced intense pressure to develop new defences.

Why these fossils matter: The structural differences between Volborthella and Salterella capture an early stage in the emergence of mineralised protective shells. Their shells show how defensive armour evolved incrementally rather than appearing fully formed, offering a valuable window into the earliest stages of biomineralisation.

The team’s work and its broader significance are also highlighted in Virginia Tech News.

A skeleton and a shell? Ancient fossil finally finds home on the tree of life
Picky, pragmatic, and enigmatic — a tiny fossil found in Southwestern Virginia eluded classification for more than 514 million years. Now, Virginia Tech geoscientists have restored this unique organism into its evolutionary lineage.

Prescott Vadya, geosciences graduate student, has taken a deep dive into Salterella, an ancient and unusual organism that sported both a shell and a skeleton.

Photo by Spencer Coppage for Virginia Tech.

Skeleton season may be just around the corner, but the skeleton age dawned with the early Cambrian Period, about 538 million to 506 million years ago.

In this time span, most major animal groups independently evolved methods to build mineral skeletons or shells, usually in one of two ways: They either built up mineral tissues using an organic scaffolding, like how we grow our bones and teeth, or they gathered materials from their environment and “glued” them together in a protective coating.

Then they stuck with that technique for the next 540 million-plus years — hey, if it ain’t broke...

One notable exception can be found in the fossilized remains of Salterella, a tiny creature that thrived in the early Cambrian and is so common in rocks from that time that paleontologists use it as an index fossil to orient themselves in time.

Salterella bucked the “either-or” trend by growing a conical shell around its body and then packing the shell’s cavity full of carefully selected minerals to form a snug inner lining. Scientists have rarely observed this type of doubling up in any other animal group.

“It makes Salterella difficult to place on the tree of life,” said Prescott Vayda, a geosciences graduate student who authored a study of the enigmatic Salterella published in the Journal of Paleontology.

Scientists first classified Salterella with squids and octopuses, said Vayda. Then they were categorized with creatures closely related to sea slugs. Later, they were grouped with ancestors of jellyfish. Then with worms. Finally, in the 1970s, a researcher created a new classification for Salterella, along with a slightly older fossil with similar construction called Volborthella.

And there they languished, disconnected and misunderstood.

Until Vayda, working with University Distinguished Professor Shuhai Xiao, started tracking down connections.

Salterella fossils from Canada. This sample is on loan from the First Nation of Na-Cho Nyäk Dun in collaboration with Yukon Government Heritage. It was sourced from their traditional territory with their permission.
Photo by Spencer Coppage for Virginia Tech.

Finding the right place for these fossils is important for our understanding of how animals evolved skeletons and shells.

Prescott J. Vayda, first author
Department of Geosciences
Virginia Tech
Blacksburg, VA, USA.

Vayda spent the past four years collecting fossil samples from places such as Death Valley and Yukon, Canada, as well as from much closer to home in Wythe County, Virginia.

Working with colleagues at Virginia Tech, Johns Hopkins University, Dartmouth College, the University of Missouri, and the Denver Museum of Nature and Science, he studied the shape, mineral composition, and crystal structure of these organisms in hopes of finding them a context.

Salterella was a scrappy creature, as Vayda found, but was selective about its building materials.

No clays, for instance, ew. Quartz was acceptable, but not ideal. Titanium was choice, of course. Who wouldn’t like a Titanium skeleton?

The variety of minerals selected led researchers to believe that the internal structure served a distinct purpose, likely something to do with feeding or enhanced stability. The findings also imply that the creatures must have had some sort of appendage to pick and grab.

We’re starting to get an image of their biology and where they fit in the larger web of life.

Prescott J. Vayda.

Based on the combined evidence of morphology, ecology, and shell structure, the research team suggested that Volborthella and Salterella belong with cnidarians, a group made up of more than 9,000 living species, including corals, jellyfish, and sea anemones.

Reconnecting this unique and long missing fragment of evolutionary lineage may lead to new answers about why and how creatures formed shells and skeletons.

And for Vayda? It’s all about
...truly learning where we come from and the history of life on Earth, which is an amazing and beautiful thing.

Prescott J. Vayda.
Publication:
Vayda PJ, Xiao S, Keller ND, et al.
A Cnidarian affinity for Salterella and Volborthella: implications for the evolution of shells.
Journal of Paleontology. Published online 2025:1-24. doi:10.1017/jpa.2025.10164

Abstract
The Cambrian Explosion saw the widespread development of mineralized skeletons. At this time, nearly every major animal phylum independently evolved strategies to build skeletons through either agglutination or biomineralization. Although most organisms settled on a single strategy, Salterella Billings, 1865 employed both strategies by secreting a biocalcitic exterior shell that is lined with layers of agglutinated sediments surrounding a central hollow tube. The slightly older fossil, Volborthella Schmidt, 1888, shares a similar construction with agglutinated grains encompassing a central tube but lacks a biomineralized exterior shell. Together these fossils have been grouped in the phylum Agmata Yochelson, 1977, although no phylogenetic relationship has been suggested to link them with the broader metazoan tree, which limits their contribution to our understanding of the evolution of shells in early animals.

To understand their ecology and place them in a phylogenetic context, we investigated Salterella and Volborthella fossils from the Wood Canyon and Harkless formations of Nevada, USA, the Illtyd Formation of Yukon, Canada, and the Shady Formation of Virginia, USA. Thin-section petrography, acid maceration, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray tomographic microscopy were used to provide new insights into these enigmatic faunas. First, morphological similarities in the aperture divergence angle and ratio of central tube diameter to agglutinated layer thickness suggest Salterella and Volborthella are related. Second, both fossils exhibit agglutinated grain compositions that are distinctive from their surrounding environments and demonstrate selectivity on the part of their producers. Finally, the calcitic shell composition and simple layers of blocky prismatic shell microstructure in Salterella suggest a possible cnidarian affinity. Together these data point to these organisms being sessile, semi-infaunal filter or deposit feeders and an early experimentation in cnidarian biomineralization chronicling a hypothesized transition from an organic sheath in Volborthella to a biomineralized shell in Salterella.

Non-technical Summary
During the early Cambrian (~538–506 million years ago) nearly every major group of animals (e.g., mollusks, arthropods, echinoderms, and so on) independently evolved ways to build a mineral skeleton. Some strategies involved controlling the growth of minerals with an organic scaffolding (called biomineralization) while others utilized the minerals existing in the surrounding sediment to build a protective coating (called agglutination). Most organisms settled on a single method of skeleton building, and that preference has been retained in their lineage to the present day. One unique fossil from the early Cambrian, called Salterella Billings, 1865, incorporates both a biomineralized shell and agglutinated sediments, a strategy that has not been observed in almost any other animal group throughout history. This distinctive morphology makes Salterella difficult to place on the tree of life but important for our understanding of how animals evolved skeletons. The slightly older fossil Volborthella Schmidt, 1888 shares a similar agglutinated skeleton but lacks the biomineralized shell.

In this research, we investigated the morphology of these fossils from multiple localities across North America to characterize their shape, mineral composition, and mineral crystal structure to understand the biology and ecology of these organisms and place them on the tree of life. Through this work, we document that these organisms were selective in the types of minerals they incorporated into their skeletons, suggesting a purpose such as deposit feeding or ballast. We also use the crystal structure of the shell of Salterella to suggest that these fossils are most closely related to the group that includes corals and jellyfish (Cnidaria Hatschek, 1888.1). The unique preservation of related taxa, an older form lacking a biomineralized shell (Volborthella) and a younger form with a biomineralized shell (Salterella), may provide crucial insights into the timing and drivers of the evolution of shells in ancient animals.

Figure 1.
Paleogeographic map of Epoch 2 of the Cambrian showing the occurrences of Volborthella and Salterella. Paleogeographic reconstruction modified from Wu et al. (2024), Lerosey-Aubril and Ortega-Hernández (2024), Golonka (2007), and Google Earth. References for occurrences of Salterella and Volborthella are provided in Supplementary Figure 1 and Supplementary Table 1.

Figure 2.
Simplified stratigraphic sections of Cambrian strata at the four localities where Salterella or Volborthella specimens were collected and utilized in this study, showing chronostratigraphy, lithostratigraphy, and fossil occurrences: Shady Formation (Byrd et al., 1973; Pfeil, 1977; Willoughby, 1977; Barnaby and Read, 1990); Illtyd Formation (Fritz, 1991); Harkless Formation (Hagen et al., 2024); Wood Canyon Formation (Hagadorn and Waggoner, 2000, 2002).

Figure 3.
Volborthella from the Wood Canyon Formation in southern Salt Spring Hills, California. (1) Field photo showing occurrence of Volborthella in the upper member of the Wood Canyon Formation. Measuring stick marks strata where Volborthella specimens were collected. (2) VMNH 211625, hand sample showing abundance of Volborthella in a fossiliferous bed. (3–7) Thin-section photomicrographs of Volborthella in longitudinal (3, 4, 7) and transverse (5, 6) sections showing agglutinated material (red arrows) and central tube (yellow arrows); (7) size, sorting, and layering of the agglutinated grains. Thin-section numbers: (3, 5) VMNH 211625 (thin section SSSH-1A); (4, 6) VMNH 211625 (thin section SSSH-U2); (7) VMNH 211625 (thin section SSSH-U1).

Figure 4.
Salterella from the Harkless Formation near Gold Point, Nevada. (1) Field photo showing shales of the Harkless Formation with rare limestone beds containing Salterella (white arrows) and archaeocyath reefs at the top of the section. (2) VMNH 211623, hand sample showing abundance of Salterella in a fossiliferous layer. (3–10) Thin-section photomicrographs of Salterella in longitudinal (3–6) and transverse (7–10) sections, showing biomineralized shell (blue arrows), agglutinated material (red arrows), and central tube (yellow arrows); white arrow in (5) marks intergrowth between the biomineralized shell and the agglutinated material. (6) A micritized shell; note the lack of distinction between the layers of the shell. (10) Transverse section showing the grain size and sorting of the agglutinated layer. Thin-section numbers: (3) VMNH 611624 (thin section HS22BF1-2); (4, 6) VMNH 211623 (thin section M2137B-2); (5, 7, 8) VMNH 211623 (thin section M2137B); (9, 10) VMNH 211624 (thin section HS22B-F1(29)).

Figure 5.
Salterella from the Illtyd Formation at the type section along the Wind River, Yukon, Canada. (1) Interbedded fine-grained clastic and carbonate strata of the lower Illtyd Formation that locally contain Salterella. (2) YG 836.1, hand sample showing abundance of Salterella in a fossiliferous layer. (3–8) Thin-section photomicrographs of Salterella in longitudinal (3–5) and transverse (6–8) sections, showing biomineralized outer shell (blue arrows), agglutinated material (red arrows), and central tube (yellow arrows). White arrows in (4) show the clear boundary between the agglutinated layer and the shell near the apex, which becomes less defined toward the aperture. (5) Zoomed view of the interfingering of the biomineralized shell and agglutinated layers. (8) Transverse section showing the grain size and sorting of the agglutinated layer. Thin-section numbers: (3, 6–8) YG 836.2 (thin section J1212); (4, 5) YG 836.3 (thin section J1212-2).

Figure 6.
Salterella from the Shady Formation at Porters Crossroads near Austinville, Virginia, USA. (1) Field photo showing massive dolomite of the Shady Formation, with white arrow marking fossiliferous bed with Salterella. (2) VMNH 90623, hand sample showing sparse occurrences of Salterella (white arrows). (3–9) Thin-section photomicrographs of Salterella in longitudinal (3–6) and transverse (7–9) sections, showing calcitic biomineralized shell (blue arrows), agglutinated material (red arrows), and central tube (yellow arrows). Note various degrees of recrystallization of the biomineralized shell and agglutinated material (4–6). Thin-section numbers: (3) VMNH 90619 (thin section H8b); (4) VMNH 90621 (thin section H9e); (5, 7) VMNH 90621 (thin section H9b); (6) VMNH 90619 (thin section H8c); (8) VMNH 90621 (thin section H9f); (9) VMNH 90621 (thin section H9c).

Figure 12.
Reconstruction of Salterella on the Cambrian seafloor exhibiting behaviors such as collecting sediment grains to be incorporated into the agglutinated layer and retracting the body into the apertural chamber.
Art by Amy Hagen.

Vayda PJ, Xiao S, Keller ND, et al.
A Cnidarian affinity for Salterella and Volborthella: implications for the evolution of shells.
Journal of Paleontology. Published online 2025:1-24. doi:10.1017/jpa.2025.10164

Copyright: © 2025 The authors.
Published by Cambridge University Press on behalf of Paleontological Society. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

Finds like these are awkward for creationists precisely because they sit so comfortably within an evolutionary framework. Their age alone is enough to cause headaches: these organisms lived around half a billion years before the events described in creationist mythology. That discrepancy isn’t a minor rounding error; it is a fundamental clash between evidence and dogma. The rocks record a world already brimming with complex life at a time when, according to creationism, nothing existed at all.

Equally problematic is how neatly *Volborthella* and *Salterella* fit into the broader story of animal evolution. Rather than appearing suddenly without context—something creationists insist should be common if “kinds” were created fully formed—these fossils instead close a small but meaningful gap. They provide a clear intermediary step in the emergence of early defensive shells, linking simple structures with more complex ones in a way that aligns perfectly with expectations from common descent.

Even the evolutionary sequence implied between the two fossils undermines creationist claims. The gradual refinement from the simpler shell of *Volborthella* to the more sophisticated structure of *Salterella* is precisely the sort of stepwise change creationists say cannot occur. Yet here it is, written unambiguously in the fossil record: not a leap, not a miracle, but a natural progression driven by selective pressures in a world where predation was newly possible and newly dangerous.

Taken together, the age, placement, and transitional nature of these fossils highlight the strength of evolutionary science and the weakness of creationist arguments. Evolution doesn’t need special pleading or ad hoc explanations—it simply accounts for the evidence. Creationism, by contrast, can only accommodate discoveries like this through increasingly strained reinterpretations. The rocks tell a coherent story; the creationist narrative does not.

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