A single fossilized footprint present in volcanic mud on a distant Antarctic island is the primary recognized trackway from a mammal in Antarctica, and the earliest proof anyplace on the continent of a carnivorous mammal.
Observe-bearing slab T-373 from King George Island, Antarctica. Sclae bar – 10 mm. Picture credit score: Mansilla-Vera et al., doi: 10.1007/s00300-026-03539-1.
The brand new specimen, a partial hand-and-foot (manus-pes) print set, dates again to the Eocene epoch, some 55 million years in the past.
Labeled T-373, it was collected from the Fossil Hill Formation on King George Island’s Fildes Peninsula.
This paleontological web site is so wealthy in preserved vegetation, feathers and animal traces that it’s protected as an Antarctic Specifically Protected Space.
“Though the oldest mammalian or mammal-like footprints date from the Late Triassic, a outstanding enhance within the range and abundance of their file happens in direction of the tip of the Mesozoic, along with direct proof within the type of enamel and skeletal stays,” stated Dr. Héctor Mansilla-Vera from the Instituto Antártico Chile on the Museo Colección Paleontológica de Antártica y Patagonia and his colleagues from Chila and Argentina.
“Following the Cretaceous-Paleogene mass extinction occasion, the fossil file of land mammals, together with bones, enamel, and ichnological proof, comparable to footprints, turns into markedly extra ample worldwide.”
“The mammalian fossil information from South America, that are phylogenetically linked to these from the Antarctic continent, clearly distinction with the a lot scarcer file documented there.”
“The entire land-mammal fossil file from Antarctica is represented primarily by remoted enamel and, to a lesser extent, by skeletal stays.”
“Notably, all these supplies are restricted to Eocene-Oligocene layers on Seymour (Marambio) Island, West Antarctica, highlighting the sturdy geographic bias of the Antarctic Paleogene mammalian file in a continent the place terrestrial mammals are actually solely absent.”
The T-373 print itself is small — concerning the dimension of a giant coin — however its form gives clues to who made it.
The specimen exhibits three rounded toe pads organized in an arc, a triangular heel pad, and no claw marks, options according to a cat-sized mammal strolling on its toes.
Utilizing a formulation that estimates physique mass from footprint space, the authors calculated that the animal weighed solely about 1.3 kg.
These dimension and form carefully match a gaggle of extinct South American predators known as sparassodonts, pouched, weasel-like mammals associated to opossums that have been widespread in Patagonia throughout the identical period.
“T-373 represents the pure solid of a small, partially preserved manus and pes imprint, characterised by a rounded triangular metapodial pad impression, a minimum of three round digit impressions organized in an anterior arch, and a digitigrade posture,” the paleontologists stated.
“The estimated physique mass for the T-373 trackmaker aligns exactly with the dimensions vary of small Hathliacynidae sparassodonts, e.g., Pseudonotictis.”
No fossilized bones or enamel from a sparassodont have ever been present in Antarctica.
However the researchers argue the footprint is the strongest proof but that these animals crossed into Antarctica over a land bridge that after related the continent to South America, earlier than the 2 landmasses drifted aside and Antarctica’s local weather turned frigid.
Till now, palentologists believed the one land predators in Antarctica’s Eocene forests have been small ancestors of right now’s falcons and flightless terror birds.
The brand new discover suggests mammals additionally occupied a predatory area of interest in that ecosystem, including a beforehand unknown layer to the Antarctic meals net.
“The T-373 footprint constitutes the primary direct ichnological proof of a land mammal within the Eocene ecosystems of Antarctica,” the scientists concluded.
“The invention helps the concept these endemic South American predators had reached excessive southern latitudes by the early Paleogene.”
“It additional refines the reconstruction of the trophic construction of the West Antarctic ecosystem by revealing a extra complicated meals net integrating herbivores, small mammals, birds, and now a mammalian apex predator inside a transitional coastal surroundings.”
The invention is reported in a paper revealed this month within the journal Polar Biology.
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H. Mansilla-Vera et al. 2026. First mammal tracks from the Eocene of Antarctica. Polar Biol 49, 101; doi: 10.1007/s00300-026-03539-1
