Antarctopelta
Antarctopelta (/ænˌtɑːrktoʊˈpɛltə/ ann-TARK-toh-PEL-tə; meaning 'Antarctic shield') was a genus of ankylosaurian dinosaur with one known species, A. oliveroi, which lived in Antarctica during the Late Cretaceous Period. It was a medium-sized ankylosaur, reaching no more than 4 meters (13 ft) in length, and showed characteristics of two different families, making more precise classification difficult. The single known fossil specimen was discovered on James Ross Island in 1986, constituting the first dinosaur remains ever discovered on Antarctica, although it is the second dinosaur from the continent to be formally named.
The holotype (specimen used as the basis for the taxon) is the only known example of this genus and species, and was the first dinosaur ever found in Antarctica. It consists of three isolated teeth, part of the lower jaw with another tooth in situ, some other skull fragments, vertebrae (neck, back, hips and tail), some partial limb bones (scapula, ilium and femur), toe bones (five metapodials and two phalanges), and numerous pieces of armor, representing approximately 15% of the skeleton. This specimen was initially located in January 1986 on James Ross Island, off the Antarctic Peninsula. It was discovered by Argentine geologists Eduardo Olivero and Roberto Scasso, but excavation was not completed for almost a decade due to the frozen ground and harsh weather conditions. The material was collected from an area of 6 square meters (64.5 sq ft) over several field seasons but is assumed to have belonged to a single individual. Much of the skeleton is in poor condition, as many of the bones nearest to the surface were subjected to years of fragmentation by freeze-thaw weathering.[1]
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. It was therefore the second named genus of dinosaur from Antarctica after Cryolophosaurus in 1993, despite being discovered first.[2] The genus name refers to its location on the continent of Antarctica and its armored nature. Antarctica is derived from the Greek words αντ/ant- ('opposite of') and αρκτος/arktos ('bear' referring to the constellation Ursa Major, which points north).[1] The Greek πελτη/pelte ('shield') is commonly used to name genera of ankylosaurs (Cedarpelta and Sauropelta, for example). 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.[1]
Earlier work suggested that the James Ross Island ankylosaur was a juvenile.[3][4] More recent research indicates that the different parts of the vertebrae are completely fused together, while a juvenile would be expected to have visible sutures between the neural arch and body (centrum) of the vertebrae. A preliminary histological analysis of several bones also indicates a level of remodeling that would not be seen in newly formed bone.[1]
