This is what the small mammal that left its mark in Antarctica might have looked like.
Credit: Álvaro Medina
Sometimes, a small footprint exposes an enormous problem for creationism. In this case, it is a partial impression preserved in approximately 55.5-million-year-old volcanic sediment on what is now King George Island, Antarctica. Its age alone places it far outside the few thousand years allowed by a literal reading of Genesis. But its setting tells an equally significant story: an Antarctic landscape capable of supporting terrestrial mammals, profoundly different from the frozen continent we know today.
The discovery, described by Héctor Mansilla-Vera and colleagues in Polar Biology, comprises a partial forefoot-and-hindfoot impression. The researchers interpret its maker as a small carnivorous mammal, possibly a sparassodont—an extinct relative of marsupials otherwise known from South America. That identification remains tentative: the incomplete trace cannot establish a particular species or confidently identify the group. Nevertheless, it records a mammal walking across an Antarctic substrate, providing evidence of its presence where it lived, rather than bones or teeth transported after death. Javier Gelfo’s account of the research explains both the interpretation and its limitations.
This animal inhabited a warmer, forested Antarctica that retained land connections with South America. Antarctica was already at high southern latitudes; its subsequent transformation cannot simply be explained as a warm continent drifting towards the pole. The larger story involves the breakup of Gondwana, the loss of connections between continents, changing ocean circulation and a changing atmosphere.
As tectonic movements opened and deepened southern ocean gateways, they altered the movement of water and heat around Antarctica. Falling atmospheric carbon dioxide also played a major role in the cooling that culminated in extensive Antarctic glaciation around 34 million years ago. Geography and climate interacted over geological time to transform the conditions under which life could survive. Scientific Committee on Antarctic Research.
The challenge to creationism is therefore more precise than simply showing that Earth has changed. Biblical literalists themselves invoke catastrophic change through their Flood narrative. What confronts them here is evidence belonging to a much longer, independently reconstructed history: continents separating, connections disappearing, climates shifting and ecosystems being transformed over tens of millions of years. An appeal to an originally “perfect” creation explains none of those details.
This tiny trace offers a glimpse of life on a planet whose geography and habitability have never been permanent fixtures. Understanding it requires geology, palaeontology and climate science working together—and the willingness to distinguish what the evidence demonstrates from what it merely suggests.
An account and discussion of this research by Antonio García was published in La Brújula Verde. His article is reprinted here under a Creative Commons licence, reformatted for stylistic consistency:
First Terrestrial Mammal Footprint Discovered in Antarctica
A team of paleontologists has discovered on King George Island, in the South Shetland Islands, the first fossil footprint unequivocally attributable to a terrestrial mammal in the Eocene of Antarctica. It is a specimen barely two centimeters long, preserved as a natural mold in fine-grained volcanic sediment, providing direct evidence of the presence of a small carnivore in an ecosystem that until now had only yielded transported or fragmentary bone and dental remains, almost always from Seymour Island (Marambio).
The research, published in the journal Polar Biology, places the finding in the Fossil Hill Formation, within Antarctic Specially Protected Area 125a, a locality already known for its exceptional preservation of lower Eocene fossils, including plant remains, feathers, bird ichnites, and invertebrates. The age of the layer containing the footprint has been estimated at about 55.5 million years, a time when the southern continent still maintained land connections with South America and hosted temperate forests at high latitudes.
The specimen, cataloged as T-373, consists of a partial set of a footprint and a hand impression, preserved as natural molds that allowed researchers to reconstruct its morphology in detail through three-dimensional surface models. The small footprint shows a digitigrade posture, a compact plantar or metapodial pad, and at least three digital impressions arranged in a forwardly convex arc.
From the preserved area, the authors estimated a minimum body mass of approximately 1.3 kilograms for the animal that produced it. This figure, though modest, places the likely trackmaker in a size range notably larger than the smallest known mammals in the Antarctic Eocene fossil record, bringing it closer to the dimensions of small haltliacinid sparassodonts, an extinct group of South American metatherians that occupied predatory niches throughout much of the Cenozoic.
The taxonomic assignment of the footprint is not straightforward, and the study’s authors have explicitly emphasized the need for caution. The preservation state of T-373 does not allow confident attribution to a specific ichnotaxon or species, and although several types of carnivorous mammal footprints display superficially similar features, the studied specimen differs from established ichnogenera in significant details of proportions, pad morphology, toe arrangement, and posture.
However, the combination of these traits, along with the estimated body mass, offers enough clues to propose a grounded hypothesis. The researchers suggest that the footprint was likely generated by a small sparassodont metatherian, a group of predators widely distributed in South America during the Paleocene and Eocene, which therefore would have had the opportunity to disperse into Antarctica via land bridges that then connected the two continents.
None of these observations, taken in isolation, prove that a sparassodont produced T-373, but the authors stress that together they form the most plausible interpretation among the available alternatives. The footprint’s morphology is consistent with a small mammal, digitigrade, with a body plan similar to that of a mustelid, and the calculated size aligns with the haltliacinids, which were small terrestrial predators.
Moreover, the fact that these animals were already present in South America in the early Eocene reinforces the biogeographic feasibility of their presence in Antarctica, at a time when warmer climates and the continuity of continental blocks allowed faunal exchange.
The importance of the discovery goes beyond the possible identification of its trackmaker. The record of terrestrial mammals in Antarctica is exceptionally scarce and, until now, was almost entirely limited to isolated teeth and a few bone fragments from the La Meseta and Submeseta formations on Seymour Island (Marambio), which implied a severe geographic and anatomical bias.
King George Island now offers a different perspective. The Fossil Hill Formation preserves a complete terrestrial ecosystem, with abundant plant remains and bird traces, and the new footprint adds a faunal component that had not been documented at this locality.
Above all, it represents the first direct ichnological evidence of a terrestrial mammal in the Antarctic Eocene, and it does so under autochthonous conditions: unlike teeth and bones transported post-mortem to marine or estuarine environments, a footprint records the passage of a living animal over a specific substrate, in a precise environment and geological moment.
This circumstance makes T-373 the first autochthonous testimony of a mammal in the Antarctic Eocene, a datum researchers consider exceptional for reconstructing past communities.
The presence of a small terrestrial predator adds a new piece to an ecological puzzle that until now had been revealed in a fragmentary way. The southern continent, 55 million years ago, was very different from today. Despite its high latitude, the warmer climatic conditions and forested landscapes supported diverse terrestrial ecosystems, in which mammals, birds, plants, and other organisms coexisted.
The known mammal community included small metatherians and other groups that occupied insectivorous, frugivorous, folivorous, and granivorous niches, along with larger herbivorous forms like xenarthrans, astrapotheres, and litopterns, representatives of the native South American ungulates.
Predation was already recognized as an important component of these ecosystems, and it had been proposed that large birds, such as the phorusrhacids or terror birds, acted as the main terrestrial predators. The new footprint opens the possibility that a small carnivorous mammal shared that same landscape and occupied a trophic level that until now lacked direct evidence.
The authors of the study stress that a single footprint cannot reconstruct an entire ecosystem, but they underline that, until continental outcrops are found in Antarctica that provide associations of non-transported mammal fossils, this type of indirect evidence gains crucial value.
A footprint does not convey the same as a bone: a bone certifies the existence of an animal, but a footprint attests to its activity and movement in a specific environment. When the direct record of teeth and bones is as sparse as in Antarctica, these traces become one of the missing pieces of the ancient biodiversity puzzle.
The Eocene was also a period of transition in the history of the southern continent. Terrestrial ecosystems persisted while Antarctica was still connected to other southern landmasses, but that configuration changed irreversibly with the final breakup of Gondwana and the consequent progressive isolation of the continent.
From the Eocene-Oligocene transition onward, the establishment of the Antarctic Circumpolar Current, progressive cooling, and the development of a large ice sheet profoundly altered the environmental conditions that had sustained those ecosystems and ultimately led to the extinction of Antarctica’s terrestrial mammals.
Today, no native terrestrial mammals or land vertebrates exist in Antarctica, but its fossil record, though scarce and incomplete, is a reminder that deep climatic changes can completely reconfigure the conditions that make life possible. In a time of unprecedented human impacts on climate and the environment, paleontology offers a unique perspective: by reconstructing the puzzle of ancient life from isolated pieces, it allows us to learn from the past and gain insight into the possible paths of the future.
The small footprint from King George Island is, in that sense, much more than a fossil: it is a window into a lost world, and also a warning about the fragility of ecosystems in the face of global transformations.
This is what the small mammal that left its mark in Antarctica might have looked like.
Credit: Álvaro Medina
The specimen, cataloged as T-373, consists of a partial set of a footprint and a hand impression, preserved as natural molds that allowed researchers to reconstruct its morphology in detail through three-dimensional surface models. The small footprint shows a digitigrade posture, a compact plantar or metapodial pad, and at least three digital impressions arranged in a forwardly convex arc.
From the preserved area, the authors estimated a minimum body mass of approximately 1.3 kilograms for the animal that produced it. This figure, though modest, places the likely trackmaker in a size range notably larger than the smallest known mammals in the Antarctic Eocene fossil record, bringing it closer to the dimensions of small haltliacinid sparassodonts, an extinct group of South American metatherians that occupied predatory niches throughout much of the Cenozoic.
Geographic setting of the ASPA 125a Fossil Hill locality on Fildes Peninsula, King George Island, South Shetland Islands, Antarctica. The figure illustrates the location of the Antarctic Peninsula region, the position of King George Island within the South Shetland Islands, and the precise location of the ichnofossil-bearing site within ASPA 125a (star).
Credit: H. Mansilla-Vera et al. 2026
However, the combination of these traits, along with the estimated body mass, offers enough clues to propose a grounded hypothesis. The researchers suggest that the footprint was likely generated by a small sparassodont metatherian, a group of predators widely distributed in South America during the Paleocene and Eocene, which therefore would have had the opportunity to disperse into Antarctica via land bridges that then connected the two continents.
None of these observations, taken in isolation, prove that a sparassodont produced T-373, but the authors stress that together they form the most plausible interpretation among the available alternatives. The footprint’s morphology is consistent with a small mammal, digitigrade, with a body plan similar to that of a mustelid, and the calculated size aligns with the haltliacinids, which were small terrestrial predators.
Moreover, the fact that these animals were already present in South America in the early Eocene reinforces the biogeographic feasibility of their presence in Antarctica, at a time when warmer climates and the continuity of continental blocks allowed faunal exchange.
The importance of the discovery goes beyond the possible identification of its trackmaker. The record of terrestrial mammals in Antarctica is exceptionally scarce and, until now, was almost entirely limited to isolated teeth and a few bone fragments from the La Meseta and Submeseta formations on Seymour Island (Marambio), which implied a severe geographic and anatomical bias.
Track-bearing slab T-373 from ASPA 125a Fossil Hill locality, King George Island, Antarctica. (A) Photograph of the slab showing the preserved track; (B) colour-coded topographic profile generated from the three-dimensional surface model; (C) detailed view of the footprint morphology; (D) interpretative drawing based on the original photograph (A). Scale bars: 10 mm in B–D.
Credit: H. Mansilla-Vera et al. 2026
Above all, it represents the first direct ichnological evidence of a terrestrial mammal in the Antarctic Eocene, and it does so under autochthonous conditions: unlike teeth and bones transported post-mortem to marine or estuarine environments, a footprint records the passage of a living animal over a specific substrate, in a precise environment and geological moment.
This circumstance makes T-373 the first autochthonous testimony of a mammal in the Antarctic Eocene, a datum researchers consider exceptional for reconstructing past communities.
The presence of a small terrestrial predator adds a new piece to an ecological puzzle that until now had been revealed in a fragmentary way. The southern continent, 55 million years ago, was very different from today. Despite its high latitude, the warmer climatic conditions and forested landscapes supported diverse terrestrial ecosystems, in which mammals, birds, plants, and other organisms coexisted.
The known mammal community included small metatherians and other groups that occupied insectivorous, frugivorous, folivorous, and granivorous niches, along with larger herbivorous forms like xenarthrans, astrapotheres, and litopterns, representatives of the native South American ungulates.
Predation was already recognized as an important component of these ecosystems, and it had been proposed that large birds, such as the phorusrhacids or terror birds, acted as the main terrestrial predators. The new footprint opens the possibility that a small carnivorous mammal shared that same landscape and occupied a trophic level that until now lacked direct evidence.
The authors of the study stress that a single footprint cannot reconstruct an entire ecosystem, but they underline that, until continental outcrops are found in Antarctica that provide associations of non-transported mammal fossils, this type of indirect evidence gains crucial value.
A footprint does not convey the same as a bone: a bone certifies the existence of an animal, but a footprint attests to its activity and movement in a specific environment. When the direct record of teeth and bones is as sparse as in Antarctica, these traces become one of the missing pieces of the ancient biodiversity puzzle.
The Eocene was also a period of transition in the history of the southern continent. Terrestrial ecosystems persisted while Antarctica was still connected to other southern landmasses, but that configuration changed irreversibly with the final breakup of Gondwana and the consequent progressive isolation of the continent.
From the Eocene-Oligocene transition onward, the establishment of the Antarctic Circumpolar Current, progressive cooling, and the development of a large ice sheet profoundly altered the environmental conditions that had sustained those ecosystems and ultimately led to the extinction of Antarctica’s terrestrial mammals.
Today, no native terrestrial mammals or land vertebrates exist in Antarctica, but its fossil record, though scarce and incomplete, is a reminder that deep climatic changes can completely reconfigure the conditions that make life possible. In a time of unprecedented human impacts on climate and the environment, paleontology offers a unique perspective: by reconstructing the puzzle of ancient life from isolated pieces, it allows us to learn from the past and gain insight into the possible paths of the future.
The small footprint from King George Island is, in that sense, much more than a fossil: it is a window into a lost world, and also a warning about the fragility of ecosystems in the face of global transformations.
Publication:
A small mammal’s footprint might seem an insignificant addition to the fossil record, but its implications extend far beyond the animal that made it. Approximately 55.5 million years ago, a mammal walked across ground in an Antarctica that supported forests and terrestrial food webs. That moment belongs to a history thousands of times longer than the entire existence of Earth permitted by young-Earth creationism. Uncertainty about the animal’s precise identity does nothing to rescue that biblical chronology.
The wider geological context also challenges the notion of a world arranged once and for all into an ideal configuration. Continental movements changed Antarctica’s connections with neighbouring landmasses, while changes in ocean circulation and atmospheric composition helped transform its climate. Environments that had supported diverse terrestrial communities eventually became inhospitable to them. What was suitable for life at one stage of Earth’s history offered no guarantee of remaining suitable. Evolution proceeds within those changing circumstances, without foresight or any promise that a successful lineage will survive the next environmental transformation.
There is a revealing contrast, too, in how the evidence is handled. The researchers distinguish the presence of a terrestrial mammal from the more tentative identification of a particular group of predators. They acknowledge what the footprint cannot tell them and leave those questions open to further discoveries. That is how science builds reliable knowledge: explanations remain accountable to evidence, rather than evidence being required to conform to a predetermined conclusion.
The footprint’s maker left no account of its world. Yet the trace it left behind contributes to a coherent history of an ancient, dynamic Earth—a history recoverable through investigation, without invoking magical creation events or compressing millions of years of change into a few thousand.
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