Pampaluctor is an extinct genus of metatherian mammal in the Thylacosmilidae, a family of carnivorous, saber-toothed sparassodonts. The genus contains a single species, Pampaluctor calibar, known from a partial skeleton. It is known from the Vorohué Formation of Argentina, which is assigned to the Vorohuean subage of the Marplatan South American land mammal age (SALMA), which is correlated to the late Pliocene to early Pleistocene epochs. With an estimated body mass of around , Pampaluctor is among the largest known mammalian predators from South America. It is also the geologically youngest thylacosmilid (and sparassodont), as other members of this clade did not cross the Plio-Pleistocene boundary.
Discovery and naming
The Pampaluctor fossil material was discovered in outcrops of the Vorohué Formation on a coastal cliff north of Miramar in Buenos Aires Province, Argentina. The specimen is housed in the paleontology collections of the Punta Hermengo Municipal Museum in Miramar, where it is permanently accessioned as specimen MPH P0730. It consists of a partial postcranial skeleton, comprising the first six cervical (neck) vertebrae, a partial right scapula, the distal end of the right humerus, the shaft of the right radius, most of the left femur, the shaft of the left tibia, two caudal (tail) vertebrae, and a small unidentified distal limb bone fragment.
In 2026, Eric N. del Campo and colleagues described Pampaluctor calibar as a new genus and species of thylacosmilid mammal based on these fossil remains, designating MPH P0730 as the holotype specimen. The generic name, Pampaluctor, combines a reference to the Argentina Pampas region in which the holotype was found, with the Latin word , meaning . The specific name, calibar, references Calibar, the 19th century thief-tracking gaucho of Central Argentina.
A single humerus and two associated molars (specimen CCA-196) were found in the Argentine El Polvorín Formation, which has been paleomagnetically dated to ~. Given their comparable age, as well as the anatomical similarities of this humerus to that of the P. calibar holotype, it is possible that CCA-196 represents another specimen of this taxon. Notably, these specimens occur comparatively recently in the fossil record (crossing the Pliocene–Pleistocene boundary), making them the youngest known sparassodonts. As such, they may have coexisted with placental carnivores that began entering South America near this time.
Description and paleobiology Though many of the skeletal elements of the only definitive Pampaluctor specimen are incomplete, the atlas (first cervical vertebra) and humerus are notably more robust than the closely related Thylacosmilus. These combined features suggest powerful neck muscles and strong forelimbs. In Pampaluctor, the tibia was likely shorter than the femur, which, combined with the robust neck and arms, is suggestive of an ambush predator ecology capable of grasping and immobilizing prey. The preserved caudal vertebrae are proportionally short compared to other sparassodonts, instead being comparable to the extinct thylacine, a marsupial.
Based on the measurements of the femur, del Campo et al. (2026) estimated the body mass of Pampaluctor at , comparable to or larger than the holotype of Thylacosmilus atrox, which has an estimated body mass ranging from . The only sparassodonts with an estimated larger size are some proborhyaenids, at up to . For comparison, male pumas and jaguars—two extant felids—have body masses of and , respectively. As such, Pampaluctor is not only among the largest sparassodonts known, but also one of the largest mammalian predators known from South America.
Classification To test the affinities and relationships of Pampaluctor, del Campo et al. (2026) included it in an updated version of the phylogenetic matrix of Suarez et al. (2025), a publication that had described the more basal thylacosmiliform Dimartinia. Pampaluctor was recovered as the sister taxon to Thylacosmilus, with the other two named thylacosmilids, Anachlysictis and Patagosmilus, forming their own clade. The result of their analysis using implied weighting (k = 3) are displayed in the cladogram below:
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