# Wrestler of the Pampas: South America's Saber-Toothed Predator That Outlived Its Own Supposed Extinction *Postcranial remains from Miramar, Argentina, extend the thylacosmilid record into the early Pleistocene and suggest overlap with North American carnivores arriving in South America.* By Sandee Oster · Published 6 October 2026 Source: https://archaeologyteahouse.com/stories/wrestler-of-the-pampas-south-america-s-saber-toothed-predator-that-outlived-its-own-supposed-extinction Primary source: [A new sabre-toothed thylacosmilid (Thylacosmilidae, Metatheria) from the Pliocene–Pleistocene of Southern Buenos Aires Province, Argentina](https://doi.org/10.1080/03115518.2026.2727509) Subjects: [Thylacosmilidae](https://www.wikidata.org/entity/Q5493808), [Southe America](https://www.wikidata.org/entity/Q18), [Paleontology](https://www.wikidata.org/entity/Q7205) --- ![](https://archaeologyteahouse.com/media/01a0fd8d-5171-7690-a283-06e0280de39c/1600.webp) *P. calibar after a successful hunt. Credit: Illustration by Sebastián Rozadilla courtesy of E. del Campo* Have you ever heard of the thylacosmilids? Perhaps you have, or perhaps you accidentally mistook them for saber-toothed cats; while I will give you that some of their features are similar, they are, in fact, saber-toothed predatory metatherians. In other words, they belong to the group that includes marsupials. I will concede that when I read saber-toothed and marsupial, my first thought was a saber-toothed kangaroo, or maybe a dagger-toothed wombat, which is quite funny. But this isn't quite either. For a long time, it was thought these ancient predators went extinct in South America by the mid-to-late Pliocene, leaving behind an open niche for predators from North America to move in and take over. But a recent discovery of a new thylacosmilid species may change that. *Pampaluctor calibar*, an estimated 100-kg ambush hunter, may have survived beyond the point when these creatures supposedly went extinct, meaning it may have shared its home with the first predators coming in from North America. And why would it matter? Simple: because knowing who survived and who didn't helps us understand how the animals we see living in these regions now got there. ### The Ancient Carnivores of South America ![](https://archaeologyteahouse.com/media/01a0fd8f-e90d-7c62-92ed-1957c366cf13/960.webp) *Retrieving the fossil from the seaside cliff. Courtesy E. del Campo* Sparassodonts were a group of carnivorous mammals closely related to modern marsupials that lived in South America for much of the Cenozoic era. Their fossilized remains are all that is left to us today, and they have turned up across the continent from Venezuela to Chile, though they are most commonly found in Argentina. The oldest confirmed fossils date to the early Eocene epoch, and bits and pieces of these creatures would continue to pop up until the mid-to-late Pliocene, when the last of these animals were thought to have gone extinct. There are over 50 known species, some weighing less than 3 kg, which is lighter than your average house cat, while others were lumbering giants coming in at over 100 kg, heavier than a male jaguar. Among the sparassodonts, one of the most remarkable groups was the thylacosmilids, which lived in South America from the middle Miocene to the early Pliocene epochs. They sported saber-like upper canines, short skulls with sturdy snouts, strong front legs and a stiff lower back. In many ways, they looked a lot like saber-toothed cats despite not being closely related. Over their long history, sparassodonts shared their South American home with giant snakes, land-dwelling crocodile-like creatures, and the so-called "terror birds." For the past century, researchers have debated how to classify them, and how many species there actually are. Today the general consensus is three: one from Colombia, one from Patagonia and one from Argentina and perhaps Uruguay. In most cases, these fossils are skulls and teeth, with the only fairly complete skeleton coming from *Thylacosmilus atrox*. But then, while reviewing the collections of a small museum in Miramar, Argentina, the researchers came across some bones. Since sparassodonts were thought to have been extinct by the time these rocks formed, the species the bones belonged to was unknown, but the researchers had a creeping suspicion they may have been thylacosmilids. To figure that out, they took a closer look. ### Built to Hunt ![](https://archaeologyteahouse.com/media/01a0fd91-30c1-721a-bd38-53f43e1b5661/1600.webp) *Neck vertebrae, courtesy of E. del Campo* The remains had been dug out of a seaside cliff just north of Miramar on the south coast of Buenos Aires Province. Based on the rock layers of nearby sites and a small fossil rodent, the remains came from the Vorohué Formation, making them late Pliocene to early Pleistocene in age. The surviving skeleton included the atlas and axis, four more neck vertebrae, a shoulder blade (scapula), an upper arm bone (humerus), a forearm bone (radius), a thigh bone (femur), a shin bone (tibia), two tail bones and a few unidentified fragments, one possibly from a hand or foot. To figure out what it was and where it fit in the evolutionary family tree, they compared 30 features from its neck, front legs and hind legs to those of 48 other species, both living and extinct. They then used computer analysis to find the best match. The atlas (no, not the map) and axis are the two bones just below your skull. These vertebrae were large and sturdy, with prominent ridges and spines meant to support powerful muscles. The shoulder blade and humerus also showed large muscle attachments, especially around the elbow area, consistent with strong front legs suited for pinning down and holding prey. When the researchers ran their family tree analysis, the fossil consistently matched closest with *Thylacosmilus atrox*, but it wasn't a perfect match. So they compared the bones to other related predators and found the fossil was similar but had its own distinct characteristics. It had an especially muscular elbow region with unusually deep hollows on the arm bone, a sturdier atlas, and a differently shaped knee end of the thigh bone. Its tibia was straight compared to the curved one seen in *Thylacosmilus*. It also may have had a shorter, less flexible tail, with tail bones similar to those of the extinct Tasmanian tiger, aka the thylacine. So its tail may have had only a limited range of movement, unlike your neighbor's overly excited Labrador, which whips its tail in every direction out of sheer enthusiasm. The fossil seemed to belong to its own species. While teeth and skulls may support that claim, lead author Eric del Campo explains: > "There is a strong bias towards dental and cranial taxonomy in mammalian paleontology (both due to teeth having high preservation potential and diagnostic features)." He adds, "…within Thylacosmilidae, only *Thylacosmilus atrox* has ample overlapping material with *Pampaluctor*. Finding dental or cranial remains would surely improve the support of *Pampaluctor*'s position in the tree." As with any new species, it needed a name. The researchers first considered *Pampasmilus*, using *smilus* from the ancient Greek smīlē (σμίλη), meaning knife or sharp. But as the fossil lacked a skull and teeth, the authors wanted to focus more on the bones that were present. They considered references to Sleepy Hollow and the Dullahan but ultimately discarded them. Instead, they focused on what the fossils did tell them. The creature was strong; it could grip its prey and probably would have wrestled it to the ground. *Luctor*, Latin for "to wrestle," seemed a fitting name, paired with *Pampa* for the Argentine Pampas. As for *calibar*, well, that was a reference to a famous 19th-century gaucho who tracked thieves and rescued lost individuals in central Argentina. They named it *Pampaluctor calibar*. ### A New Saber-Toothed Predator ![](https://archaeologyteahouse.com/media/01a0fd91-de17-7f3d-a4c3-0334624a98a3/960.webp) *Size comparison. Credit: del Campo et al. 2026* *P. calibar* would have been a heavyweight, possibly around 100 kg, making it likely heavier than its relative *T. atrox* and bigger than a male jaguar. This would also have made it one of the largest mammalian predators known from South America and the top predator of its time, with the only other known large carnivore from its time being a 25-kg scavenging relative of raccoons. It wasn't fast, so it didn't chase prey; instead, its anatomy suggests it was an ambush hunter, lying in wait for the right moment to strike, seizing prey with powerful forelimbs, pinning it down, and delivering a precise killing bite with what were presumably saber-like canines. > As for what it ate, del Campo explains, "During the start of the Pleistocene, the Argentine pampas were inhabited by giant armadillos (such as *Eutatus*), ground sloths, glyptodons (such as *Neosclerocalyptus*, which was found in the same levels), equids, and camelids (such as *Lama*). All of them could be probable prey for *Pampaluctor*." But there is still one problem, regardless of whether this was a new species or not: sparassodonts, thylacosmilids included, were supposed to have gone extinct before this point, so how could this individual have been prowling around in the late Pliocene or early Pleistocene? Simple: at least some of them didn't go extinct when we thought they did. That may also help explain something South American paleontologists had long found odd. If the sparassodonts had already died out, South America would have gone without any large mammalian predators for a long stretch of time, until the northern carnivores showed up to fill the gap. But if *P. calibar* and possibly other thylacosmilids were still around at that time, that means they may have encountered some of these North American predators. --- The story of South America's predators is anything but clear-cut. For a long time, it was thought that the North American saber-toothed cats outcompeted South America's saber-toothed carnivores. But more recent studies suggested those same carnivores were already extinct by the time the North American fauna arrived, which made that scenario unlikely. Now the story may have another rewritten chapter: thylacosmilids may not have been extinct, at least not yet. *P. calibar* is one of the geologically youngest thylacosmilids and sparassodonts ever recorded. It may very well have lived alongside some of these North American newcomers, yet its sheer size likely meant it was the top predator of its time. And why did it go extinct? That remains a mystery. Whatever the cause, *Pampaluctor* was one part of a major evolutionary puzzle that shaped the South American fauna we see today. I find one part of this discovery especially sweet. The bones weren't identified during a large-scale excavation; members of the Miramar museum found them in 2014 and retrieved them in 2016, but they sat in the collection unidentified, since no one expected a sparassodont in rocks that young. That makes the name calibar even more fitting; Calibar was a 19th-century gaucho famous for tracking thieves and rescuing people who had gone missing. This time, it was no missing person, but perhaps a gap in the fossil record, unidentified and now found. Had you heard of thylacosmilids before, and what do you think eventually led to their extinction? *Let me know what you think, and if you'd like to support this blog and the person writing it, you can *[*chip in once, monthly, or yearly.*](https://archaeologyteahouse.com/support)* Only if you'd like to.* ### Reference del Campo, E. N., Agnolín, F. L., Chimento, N. R., Boh, D., Magnussen, M., & De Cianni, F. (2026). A new sabre-toothed thylacosmilid (Thylacosmilidae, Metatheria) from the Pliocene–Pleistocene of Southern Buenos Aires Province, Argentina. *Alcheringa: An Australasian Journal of Palaeontology*, 1–32. [https://doi.org/10.1080/03115518.2026.2727509](https://doi.org/10.1080/03115518.2026.2727509) ## Common questions **How did they estimate its weight?** They used equations based on living carnivores, applied to the thigh bone's shaft circumference and knee joint area. The two methods gave about 100 kg and 96 kg. **Are there other fossils of this animal?** Possibly. A humerus from the El Polvorín Formation near Olavarría, described in 2023 as Thylacosmilus, is very similar and may belong to Pampaluctor.