Antarctopelta (ann-TARK-toh-PEL-tə; meaning 'Antarctic shield') is a genus of ankylosaurian dinosaur, a group of large, quadrupedal herbivores, that lived during the Maastrichtian stage of the Late Cretaceous period on what is now James Ross Island, Antarctica.

The fossils were later described in 2006 by paleontologists Leonardo Salgado and Zulma Gasparini, who named the type species A. oliveroi after Olivero.

It was a medium-sized ankylosaur, reaching 4 meters (13 feet) in length or more, and showed characteristics of two different families, making more precise classification difficult for many years.

It was discovered in rocks of the Gamma Member of the Snow Hill Island Formation, which bears a variety of other fossils, many of them unique as they evolved in the isolation of Antarctica after the breakup of Gondwana.

During an expedition to James Ross Island off the coast of Antarctica, an incomplete skeleton of an ankylosaur was discovered by Argentine geologists Eduardo Olivero and Robert Scasso in January 1986.

Olivero and Scasso had found the specimen in strata from the Gamma Member of the Snow Hill Island Formation, which dates to the Maastrichtian age of the Late Cretaceous period.

[2] The holotype (specimen used as the basis for the taxon) MLP 86-X-28-1 is the only known examplar of this genus and species, and was the first dinosaur ever found in Antarctica.

[3][4] Although the material had been known for decades and written about in three separate publications, Antarctopelta oliveroi was not named until 2006, by Argentine paleontologists Leonardo Salgado and Zulma Gasparini.

The single known species, A. oliveroi, is named after Eduardo Olivero, who discovered the holotype, first mentioned it in print, and has worked in Antarctica for decades.

[4] Like other ankylosaurs, Antarctopelta oliveroi was a stocky, herbivorous quadruped protected by armor plates embedded in the skin.

Although a complete skeleton has not been found, the species is estimated to have reached a maximum length of 4 meters (13 feet) from snout to tail tip.

The leaf-shaped teeth are asymmetrical, with the majority of the denticles on the edge closest to the tip of the snout and large furrows on the cingula.

Seven to eight mesial denticles are found on each Antarctopelta tooth, the highest number known from Parankylosauria, a trait distinguishing it from the related Stegouros.

[7] A fragment from the left dentary (lower jaw bone) preserving these teeth was recovered, which has a curved tooth row like other ankylosaurs'.

[9][1][4] Six different types of osteoderms were found along with the skeletal remains of Antarctopelta, but very few were articulated with the skeleton, so their placement on the body is largely speculative.

A few examples of this fifth type were found ossified to the ribs, suggesting that they ran in rows along the flanks of the animal, a very typical pattern among ankylosaurs.

The following cladogram is reproduced from the phylogenetic analysis of Soto-Acuña et al. (2021):[3] Lesothosaurus Scutellosaurus Emausaurus Scelidosaurus Huayangosaurus Stegosauridae Kunbarrasaurus Antarctopelta Stegouros Nodosauridae Liaoningosaurus Gobisaurus Shamosaurus Ankylosaurinae In their 2024 redescription of Antarctopelta, Vargas & Kaluza updated the phylogenetic matrix of Soto-Acuña et al. (2021) and recovered similar parankylosaurian relationships, with the Argentinian Patagopelta also found in this clade.

[1][12] However, a 2019 histological analysis by Argentine paleontologist Ignacio Cerda and colleagues found that the holotype individual was sexually mature.

Samples from three osteoderms, a bone shaft, a metapodial, several undetermined fragments, ossified tendons, and dorsal ribs were used in the study.

[13][14] The holotype skeleton was collected about 90 m (300 ft) from the base of the Gamma Member of the Snow Hill Island Formation.

[17] During the time in which Antarctopelta lived, Earth's climate was much warmer and more humid than it is today and as a result Antarctica was without ice.

[19][20][21] The Antarctic Peninsula, including James Ross Island, was connected to South America throughout this time period, allowing interchange of fauna between both continents.