Creationists love so-called ‘living fossils’ because they imagine they show evolution has not happened and that Earth is only a few thousand years old. Of course, by the twisted logic of creationism, the vast number of species that have changed over time somehow do not prove the opposite: that evolution does happen and that Earth is vastly older than a few thousand years.
Their argument also ignores the scientific definition of evolution: change in allele frequencies in a population over time. Without DNA from earlier members of the same lineage, it is impossible to say whether evolution has or has not occurred within that lineage. Superficial resemblance is not genetic stasis. But then, the creationist ‘definition’ of evolution is not the scientific one. It is a childish straw man parody, designed to be easier to attack.
So this latest ‘living fossil’, reported in Proceedings of the Royal Society B by a team led by Dr Jason D. Pardo of the Field Museum, Chicago, is bound to set up cognitive dissonance in creationists. That will probably result in their usual coping strategy: ignoring it altogether, or blaming scientists for trying to make them change their minds.
The fossil belongs to a new species, Tanyka amnicola, an archaic stem tetrapod from the Early Permian of Brazil, about 275 million years ago. It belonged to a lineage that had been thought to have disappeared much earlier, making it a “living fossil” even in its own time. The fossils were found in a dry riverbed in north-eastern Brazil, in the Pedra de Fogo Formation, one of the few windows scientists have into Gondwanan animal life during this period.
What the team found was not a complete skeleton but a set of fossil lower jaws — nine in all — each showing the same extraordinary feature: the jaw was twisted, with some teeth pointing sideways, while the inside of the jaw was lined with numerous small denticles that appear to have formed a grinding surface. Since all the jaws show the same structure, this was not a deformity or fossilisation artefact, but part of the animal’s normal anatomy.
The researchers suggest that this strange arrangement may have allowed Tanyka to process food in a highly unusual way. The Field Museum describes it as probably eating aquatic plants, while the paper itself leaves open the possibility that the jaw was adapted either for processing plant material or for specialised feeding on small invertebrates. Either way, this was not a static remnant of a bygone age, but a member of an ancient lineage still exploring new ecological possibilities in Permian Gondwana.
Background^ What Were The Early Stem Tetrapods? Tetrapods are the group of vertebrates that includes amphibians, reptiles, birds and mammals. Although the word literally means “four-footed”, not all living tetrapods have four feet; snakes, whales, birds and humans are all tetrapods because they descend from the same four-limbed ancestry.
The early stem tetrapods were extinct relatives close to the base of this great evolutionary branch. They were not modern amphibians, reptiles or mammals, but members of ancient lineages that lived before the main living groups had fully separated. They evolved from lobe-finned fish-like ancestors during the Devonian Period, roughly 390–360 million years ago, when vertebrates were beginning to exploit shallow-water, swamp, river-margin and occasionally land-based habitats.
This transition was not a sudden leap from fish to land animal. It was a long, branching evolutionary process in which features appeared in stages. Flattened skulls, eyes positioned more towards the top of the head, stronger ribs and vertebrae, air-breathing capacity, limb-like fins, digits, neck mobility and stronger connections between the limbs and backbone all evolved as part of life in shallow, vegetation-rich, oxygen-poor or unstable aquatic environments.
Some famous fossils illustrate this mosaic pattern. Tiktaalik roseae, about 375 million years old, still had fins and scales, but also had a flattened head, a neck, robust ribs and limb-like fin bones. Later forms such as Acanthostega and Ichthyostega had limbs with digits, but were still strongly tied to water; their limbs may originally have been useful for pushing through shallow water, clambering through vegetation or bracing against the bottom, rather than for walking confidently on dry land.
This is why the old cartoon image of evolution as a fish deciding to crawl out of a drying pond is misleading. Early tetrapod evolution was not a ladder, and it was not a straight march towards humans. It was a branching radiation of related forms, many of them aquatic or amphibious, with different combinations of fish-like and tetrapod-like features. Some branches led eventually to modern amphibians, reptiles, birds and mammals; many others died out.
Tanyka amnicola fits into this broader story because it belonged to one of these archaic stem-tetrapod lineages, yet was still alive about 275 million years ago, long after more modern tetrapod groups had evolved. That is what makes it a “living fossil” in the meaningful scientific sense: not an organism unchanged since creation, but a late-surviving member of an ancient lineage.
And far from showing that evolution had stopped, Tanyka shows the opposite. Its twisted jaw, sideways-facing teeth and grinding denticles reveal a specialised animal adapted to its own ecological niche in Early Permian Gondwana. In other words, even this ancient lineage was still changing, still diversifying and still being shaped by natural selection.
The paper by Dr Pardo's team is accompanied by a news release from the Field Museum:
This ancient plant-eater had a twisted jaw and sideways-facing teeth
Even for its time, Tanyka was a “living fossil” from a lineage that scientists thought had already gone extinct
Illustration showing Tanyka amnicola in life, eating underwater plants.Vitor Silva
In a dry riverbed in Brazil, in a dense forest near the Amazon, a team of paleontologists found a fossilized jawbone from an ancient animal. Over the course of their fieldwork, they found eight similar bones, each around six inches long—but no other bones that they could confidently use to complete a skeleton for one of these mystery animals. However, the jawbones alone were enough to reveal that they belonged to a species that would have been a “living fossil” for its time, 275 million years ago when it lived. What’s more, the jawbones were oddly twisted, with some teeth pointed out and to the sides, and numerous smaller teeth lining the inside of the jaws—a sign that these strange creatures were among the first of their kind to grind up plants for food.
In a new paper published in the journal Proceedings of the Royal Society B, the researchers described the new species, giving it the name Tanyka amnicola. Tanyka is from the local Indigenous Guaraní language, meaning “jaw,” and amnicola means “living by the river.”
Tanyka is from an ancient lineage that we didn’t know survived to this time, and it’s also just a really strange animal. The jaw has this weird twist that drove us crazy trying to figure it out. We were scratching our heads over this for years, wondering if it was some kind of deformation. But at this point, we’ve got nine jaws from this animal, and they all have this twist, including the really, really well-preserved ones. So it’s not a deformation, it’s just the way the animal was made.
Dr. Jason D. Pardo, lead author
Negaunee Integrative Research Center
Field Museum of Natural History
Chicago, IL, USA.
Tanyka is part of a much larger group of animals called tetrapods. Tetrapods are four-legged animals with backbones; modern tetrapods include reptiles, birds, mammals, and amphibians. The oldest tetrapod lineage, called the stem tetrapods, eventually split into two groups—ones that laid eggs outside of water, and ones that laid their eggs in the water. Today’s reptiles, birds, and mammals are all descendants of the branch that laid watertight eggs on land; modern amphibians like frogs and salamanders are the relatives of the tetrapods whose eggs needed to remain moist.
But even after the tetrapod family split into these new groups, some of the stem tetrapods remained. Tanyka was one of them.
New members of an older lineage can evolve alongside their more “advanced cousins”—the mammal family is a good example. The first mammals laid eggs, but some mammals evolved the ability to give birth to live young. While most of the mammals alive today, whether marsupials like kangaroos or placental mammals like humans, reproduce this way, there are still a couple mammals, like platypuses, that are members of the older, egg-laying lineage.
In the sense that Tanyka was a remaining member of the stem tetrapod lineage, even after newer, more modern tetrapods evolved, Tanyka is a little like a platypus. It was a living fossil in its time.
Dr. Jason D. Pardo.
Pardo… is now a research associate at the Field Museum while working on a postdoctoral fellowship through the University of Vilnius in Lithuania.
There’s a lot about Tanyka that remains a mystery: namely, its body. “We found these jaws in isolation, and they're really weird, and they're very distinctive. But until we find one of those jaws attached to a skull or other bones that are definitively associated with the jaw, we can't say for sure that the other bones we find near it belong to Tanyka,” says Ken Angielczyk, a curator of paleomammalogy at the Field Museum in Chicago, who served as Pardo’s advisor during his post-doctoral fellowship there, and a co-author of the paper.
We can say, by comparison with close relatives, that Tanyka might have looked kind of like a salamander with a slightly longer snout.
Dr. Jason D. Pardo.
The researchers aren’t sure how big Tanyka would have been, but they estimate that it might have been up to three feet long, and it probably lived in lakes, based on the kind of rocks in which the fossils are found.
But Tanyka’s jawbone alone was enough to show scientists what an unusual animal it was.
Run your tongue over the teeth on your lower jaw. Feel how the tops of your teeth are facing up, towards the roof of your mouth? In Tanyka, the lower jaw was twisted, so that instead of facing up, the teeth pointed out to the sides. Meanwhile, the part of its jawbone that, in us, faces the tongue, in Tanyka is facing up towards the roof of its mouth. This surface of Tanyka’s jawbone is covered in a series of smaller teeth called denticles, which form a grinding surface sort of like a cheese grater.
Scientists have yet to find the bones that would make up Tanyka’s upper jaw, but they imagine its top teeth and denticles were oriented similarly to the ones on the lower jaw.
We expect the denticles on the lower jaw were rubbing up against similar teeth on the upper side of the mouth. The teeth would have been rasping against each other, in a way that’s going to create a relatively unique way of feeding.
Dr. Jason D. Pardo.
In general, teeth that are able to grind against each other are used for crushing up plant material.
Based on its teeth, we think that Tanyka was a herbivore, and that it ate plants at least some of the time.
Juan Carlos Cisneros, co-author of the paper.
Centro de Ciências da Natureza
Universidade Federal do Piauí
Teresina, Brazil.
The researchers say that it’s surprising that a stem tetrapod like Tanyka would have evolved to eat plants, since most of its fellow stem tetrapods only ate meat.
Finding out that a stem tetrapod like Tanyka was living when and where it did helps scientists fill in big gaps in the paleontological record. When Tanyka was alive, 275 million years ago, the area that’s now Brazil was part of a supercontinent called Gondwana. It included much of modern South America, Africa, Australia, and Antarctica, but compared with areas in the Global North, very few of its fossil animals from this time period have been discovered in Gondwana.
The Pedra de Fogo Formation in Brazil is one of the only windows we have into Gondwana’s animals during the early Permian Period of Earth history, and Tanyka is telling us about how this community actually worked, how it was structured, and who was eating what.
Kenneth D. Angielczyk, so-author
University of the Witwatersrand Johannesburg
Johannesburg, South Africa.
The following scientists co-authored this study: Jason Pardo (Field Museum, University of Vilnius), Claudia Marsicano (Universidad de Buenos Aires, CONICET), Roger Smith (Iziko South African Museum, University of the Witwatersrand Johannesburg), Ken Angielczyk (Field Museum), Jörg Fröbisch (Museum fur Naturkunde - Leibniz-Institut fur Evolutions- und Biodiversitatsforschung), Christian Kammerer (North Carolina Museum of Natural Sciences), and Martha Richter (Natural History Museum, London).
Publication:
So, far from being a problem for evolution, Tanyka amnicola is another beautiful example of what evolution predicts: ancient lineages can persist, sometimes for tens of millions of years, while still changing, adapting and occupying new ecological niches. A “living fossil” is not a creature frozen in time, nor evidence that evolution has stopped. It is simply a surviving representative of an old branch on the tree of life — and, like every living population, still subject to mutation, selection, drift and environmental change.
Creationists, of course, will try to turn this into evidence against evolution by pretending that superficial continuity means biological stasis. But that only works if they first replace the scientific definition of evolution with their own cartoon version of it. Evolution is not defined as one “kind” turning into another in a single dramatic leap. It is the change in inherited variation within populations over time. By that definition, even a lineage that retains a broadly familiar body plan can still be evolving — and Tanyka, with its specialised twisted jaw, sideways-facing teeth and grinding denticles, was plainly not just sitting around unchanged waiting to embarrass palaeontologists.
What this fossil actually shows is a world far older, richer and more complex than creationist mythology allows: a 275-million-year-old Permian ecosystem in what is now Brazil, populated by animals descended from earlier tetrapod radiations, still experimenting with new ways to feed and survive. There is no hint here of a recent creation, no evidence of separately created “kinds”, and no need for magic to explain what we find. There is only the ordinary, cumulative, evidence-based story of descent with modification.
Once again, science has taken a few fragments of fossil jaw from ancient rocks and used them to reconstruct a lost animal, a lost ecosystem and a lost chapter in the history of life. Creationism, by contrast, has nothing to offer except denial, word-games and a refusal to understand the thing it claims to refute. Fossils such as Tanyka amnicola do not rescue creationism from the evidence; they add yet another branch to the vast, branching tree that creationism insists is not there.
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