Rosa Rubicondior: Refuting Creationism - The Evolution of Our Ancestral Fish

Illustration of the Paleolophus swimming in ancient Asian seas.

Credit: Dr Brian Choo (Flinders University)

New pieces link fish puzzle – News

Today we have not one but two papers which together help fill a gap between the bony fishes and the first fish to venture onto land and evolve into the terrestrial tetrapods from which all land vertebrates subsequently evolved. It is a gap that presents creationists with a dilemma: it would have been a perfect god-shaped gap into which to insert their designer; however, it dates to some 410 million years ago, far too distant for their preferred timeline of 6,000–10,000 years, into which they need to try to compress the entire history of the universe.

One of these papers, just published in Canadian Journal of Zoology, is by a team from Flinders University, led by Dr Alice Clement, who have reassessed a mysterious fossil from the Late Devonian Gogo Formation in Western Australia using the latest technology, including CT scanning and computed tomography.

This work adds to our understanding of lungfish evolution from a key Australian fossil site that contains a diversity of lungfish fossils, including some poorly preserved specimens.

Meanwhile, Flinders University researcher Dr Brian Choo and colleagues at the Chinese Academy of Sciences, led by the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, have described a new fossil, Paleolophus yunnanensis (‘old crest from Yunnan’). This team's work has just been published in Current Biology.

Paleolophus helps fill the gap between ancestral lungfish and their diversification a few million years later; in other words, it is one more example of the sort of transitional form that creationists insist does not exist: yet another so-called 'missing link'.

The Origins and Diversification of Lungfish. Lungfish (subclass Dipnoi) are among the closest living relatives of tetrapods, the group that includes amphibians, reptiles, birds, and mammals. Along with the coelacanths, they belong to the Sarcopterygii, or lobe-finned fishes, a lineage characterised by muscular, limb-like fins supported by internal bones. These anatomical features provided the evolutionary foundation for the limbs of the first land vertebrates.

Devonian Origins

Lungfish first appear in the fossil record during the Early Devonian, more than 410 million years ago, a period often called the “Age of Fishes” because of the extraordinary diversification of vertebrates in aquatic environments. Early forms already show many distinctive lungfish characteristics, including:

Tooth plates rather than individual teeth, adapted for crushing hard food such as molluscs and crustaceans.
Paired lungs, derived from a modified swim bladder, allowing them to breathe atmospheric oxygen.
Lobed fins, supported by internal skeletal elements.

These early lungfish inhabited freshwater lakes and rivers as well as coastal marine environments.

Rapid Devonian Diversification

During the Middle and Late Devonian, lungfish diversified dramatically. Dozens of genera are known from fossil deposits worldwide, including famous Devonian species such as Dipterus, Chirodipterus, and Rhinodipterus. Fossil sites such as the Gogo Formation in Western Australia have yielded exceptionally preserved specimens, including three-dimensional skulls and even soft-tissue structures revealed by modern CT scanning.

Many Devonian lungfish show transitional combinations of features, reflecting experimentation in feeding strategies and body plans. Some retained primitive cranial bones similar to other lobe-finned fishes, while others evolved more specialised skulls and powerful tooth plates.

Adaptations to Harsh Environments

One key innovation in lungfish evolution was the ability to survive in oxygen-poor or seasonally drying habitats. Their lungs allowed them to breathe air when water oxygen levels were low. In some later lineages, especially African and South American species, this adaptation went further: they evolved the ability to aestivate—burrowing into mud and entering a dormant state during droughts.

These adaptations may explain why lungfish survived environmental crises that eliminated many other Devonian fish groups.

Decline and Survival

Although lungfish were diverse during the Devonian and Carboniferous, their diversity declined later in the Paleozoic and Mesozoic. Today only six living species remain, distributed in three lineages:

Australian lungfish (Neoceratodus forsteri)
African lungfishes (Protopterus species)
South American lungfish (Lepidosiren paradoxa)

Despite their low diversity today, modern lungfish retain many ancient anatomical features, making them important “living fossils” that help scientists understand the evolutionary steps leading to tetrapods.

Why Lungfish Matter to Evolutionary Biology

Genetic and anatomical studies consistently show that lungfish are the closest living relatives of tetrapods, even closer than coelacanths. Their anatomy—especially the structure of their fins, lungs, and skull—provides valuable clues about how vertebrates made the transition from water to land during the Devonian.

Fossils such as those from the Gogo Formation and newly described transitional forms help fill the evolutionary sequence linking early lobe-finned fishes with the ancestors of terrestrial vertebrates.

The two teams' research is the subject of a Flinders University news item:

New pieces link fish puzzle
New pieces have been added to the puzzle of the evolution of some of the oldest fish that lived on Earth more than 400 million years ago.
In two separate studies, experts in Australia and China have found new clues about primitive lungfishes, the closest living relatives of land vertebrates.

The new research builds on long-running work by Flinders University and other palaeontologists in the fossil-rich Gogo site in Western Australia’s far north, and with the Chinese Academy of Sciences.

The study of living and fossil lungfish provides anatomical clues into the evolutionary development of tetrapods, backboned animals with limbs including humans, that first left the water to live on land.

The mysterious fossil from the Late Devonian Gogo Formation in WA has been further analysed using the latest technologies including CT scanning and computed tomography, with the results published in the Canadian Journal of Zoology.
Lead author Dr Alice Clement, from Flinders University’s Palaeontology Lab, says new research is slowly adding to the story of the key Australian fossil site’s rich diversity of lungfishes – including re-examining poorly preserved specimens. One such damaged specimen has yielded valuable new clues. It comes from Australia’s first ‘Great Barrier Reef,’ the Devonian-age reef in the Kimberley region of northern WA.

Fossil fish imprint from the Gogo field.

The unusual specimen was so enigmatic, the authors who first described it in 2010 considered it could be a whole new type of fish never before seen in science. Using high-tech scanning, this time we were able to create comprehensive new digital images of the external and internal cranium, showcasing the complexity of the brain cavity of this fascinating lungfish. In fact, we were also able to confirm that previous impressions were probably viewed upside down and back to front.

Dr Alice M. Clement, senior author
College of Science & Engineering
Flinders University
Adelaide, SA, Australia.

Coauthor Hannah Thiele, with support from multiple museums and facilities such as Australian Nuclear Science and Technology Organisation (ANSTO), was able to use the advanced technologies to put a new lens on this most enigmatic specimen.

We were able to compare its most preserved inner ear area with other Gogo lungfish. This is an extra data point in the amazing collection of lungfish and early vertebrate species. It adds to the wider understanding of the evolution of these earliest lobe-finned fishes, both in Gondwana and across the world.

Hannah S. Thiele, co-author
College of Science & Engineering
Flinders University
Adelaide, SA, Australia.

3D print of Chirodipterus australis skull, a lungfish from the Gogo Formation, which shares close similarities to Cainocara enigma.

Meanwhile in the journal Current Biology, another reconstruction of an early fish skull has described a species called Paleolopus – a lungfish that swam in the South Chinese seas 410 million years ago. Flinders researcher Dr Brian Choo and colleagues at the Chinese Academy of Sciences, led by the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, have called the new fossil, Paleolophus yunnanensis (‘Old crest from Yunnan’).
Paleolophus gives us an unprecedented look at a lungfish from a time between their earliest appearance and their great diversification a few million years later. It was a time when the group was just starting to develop the distinctive feeding adaptations that would serve them for the remainder of the Devonian and onwards to the present day. [Lungfish are an incredibly ancient lineage] including the still living Australian lungfish from Queensland, that have long fascinated researchers due to their close relationship to the tetrapods, or backboned animals with limbs, including humans. The exceptional lungfish skull unearthed in 410 million-year-old rocks in Yunnan gives us major insights into the rapid evolutionary diversification between the early-, mid- and late Devonian.

Dr Brian Choo, co-author.
College of Science & Engineering
Flinders University
Adelaide, SA, Australia.

Dr Brian Choo at the Flinders University Palaeontology Lab.

Dr Choo adds that the new specimen had similar and divergent features compared to the earliest and most primitive Diabolepis fossil in southern China, and species such as Uranolophus from Wyoming in the US and other forms like Australia’s Dipnorhynchus.

Publications:
Hannah S. Thiele, John A. Long, Joseph J. Bevitt, and Alice M. Clement. 2026.
Deciphering Cainocara enigma from the Late Devonian Gogo Formation, Australia.
Canadian Journal of Zoology. 104: 1-13. https://doi.org/10.1139/cjz-2025-0109

Qiao, Tuo; Cui, Xindong; Zhao, Wenjin; Liu, Chengxi; Li, Maokun; Lu, Jing; Choo, Brian; Zhu, Min (2026)
A new fossil fish sheds light on the rapid evolution of early lungfishes
Current Biology 36(1) 243-251.e3 https://doi.org/10.1016/j.cub.2025.11.032

Abstract
The Late Devonian Gogo Formation, Western Australia, preserves a diverse collection of Frasnian vertebrates, including the most diverse assemblage of lungfishes (Sarcopterygii, Dipnoi) from any geological period or locality. One enigmatic Gogo fossil known from a single specimen was originally dubbed Cainocara enigma Campbell and Barwick, 2011, interpreted as having osteichthyan affinity but otherwise considered not to belong to “any known described major systematic order”. Original interpretation of the specimen was hampered by its poor state of preservation, but thanks to increasing application of computed tomography, we can now use a more comprehensive comparative dataset, elucidating both internal and external anatomy, to study and visualise fossils more thoroughly than previously possible. Herein we show that the original orientation of the specimen was wrong, identify a kite-shaped parasphenoid and pterygoid bones that meet in their midline. We also reconstruct a partial digital cranial endocast, including portions of the inner ears, for comparison with other known endocasts from Gogo taxa, including the first cranial endocast of a holodontid lungfish (Holodipterus gogoensis Miles, 1977). We now recognise Cainocara enigma, as a lungfish (order Dipnoi) based on anatomy revealed via CT, but concede that this enigmatic specimen most likely remains a nomen nudum and nomen dubium.

Hannah S. Thiele, John A. Long, Joseph J. Bevitt, and Alice M. Clement. 2026.
Deciphering Cainocara enigma from the Late Devonian Gogo Formation, Australia.
Canadian Journal of Zoology. 104: 1-13. https://doi.org/10.1139/cjz-2025-0109

© 2026 Canadian Science Publishing.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.

Highlights

New Pragian fossil from China reveals early lungfish anatomy
Lungfish key feeding traits evolved rapidly within ∼4 million years
Cranial specialization for durophagy drove early lungfish diversification
Analysis suggests Early Devonian biogeographic link between China and North America

Summary
Lungfishes, the closest living relatives of land vertebrates, have a long and conservative evolutionary history that began over 415 million years ago (mya) in the Early Devonian.^1,2,3 Morphological gaps between the earliest known and most primitive lungfish, Diabolepis, and the more derived members of the group (Eudipnoi) hinder a comprehensive understanding of key evolutionary transformations near the onset of this lineage.¹ A few early eudipnoans from the Pragian (∼410 Ma),^4,5,6,7 such as Uranolophus from Wyoming, USA,^8,9 have been thought to fill this gap, but their fossils are too flattened to reveal internal structures like the braincase.^8,9,10,11 Here, we describe a new eudipnoan from the Pragian of China, whose skull is exceptionally well preserved, allowing us to study the inside of the head in detail for the first time in such an early lungfish. The new species has a palate similar to Uranolophus but also retains several features seen in Diabolepis. Phylogenetic and tip-dating Bayesian analyses place it at the base of the eudipnoan lineage, suggesting that lungfishes evolved rapidly during their early history. The discovery also points to connections between South China and North America during the Early Devonian. Altogether, this find helps clarify how early lungfishes developed key features that later shaped the group known today as the “living fossils.”^12,13,14

Qiao, Tuo; Cui, Xindong; Zhao, Wenjin; Liu, Chengxi; Li, Maokun; Lu, Jing; Choo, Brian; Zhu, Min (2026)
A new fossil fish sheds light on the rapid evolution of early lungfishes
Current Biology 36(1) 243-251.e3 https://doi.org/10.1016/j.cub.2025.11.032

© 2026 Elsevier B.V.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.

These discoveries add yet more detail to one of the most important transitions in the history of life on Earth—the evolution of vertebrates capable of living on land. Far from appearing suddenly, as creationist mythology would require, the fossil record shows a long sequence of intermediate forms, each contributing another piece to the evolutionary puzzle. Lungfish, tetrapodomorph fishes, and the earliest tetrapods together document a gradual transformation that took place over tens of millions of years during the Devonian.

The new fossils described in these papers help fill what was once perceived as a gap in that record, linking early lungfish with their later diversification and clarifying their relationship to other lobe-finned fishes. These are precisely the sorts of transitional forms that creationists have spent decades claiming do not exist. Yet palaeontologists continue to uncover them, again and again, from fossil deposits all over the world. Each discovery further confirms the branching evolutionary history predicted by the Theory of Evolution.

Equally telling is the way these discoveries are made. Scientists predicted that such transitional fossils should exist because evolutionary theory indicates that complex anatomical innovations—such as lungs, limb-like fins, and modified skulls—must have evolved through a series of intermediate stages. Guided by that framework, researchers examine the rocks of the right age and environment, apply modern imaging technologies such as CT scanning, and repeatedly find exactly the sorts of organisms the theory predicts.

So once again we see the stark contrast between science and creationism. Evolutionary biology continues to generate testable predictions and to uncover new evidence that fills in the history of life in ever greater detail. Creationism, meanwhile, relies on supposed “gaps” in our knowledge—gaps that steadily disappear as the evidence accumulates. Each new fossil discovery, like the ones reported here, pushes the origin of modern biodiversity deeper into Earth’s ancient past and further beyond the narrow confines of creationist mythology.

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