Antarctopelta
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| Antarctopelta oliveroi Salgado & Gasparini, 2006 |
Antarctopelta (ant-ARK-to-PEL-ta; "Antarctic shield") was a late Cretaceous genus of medium-sized ankylosaurian dinosaur that reached no more than than 4 meters (13 feet) in length. The specimen was recovered from James Ross Island in 1986, making it the first dinosaur ever discovered on Antarctica, though it is the second dinosaur from the continent to be formally named.[1][2]
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[edit] Taxonomy and naming
Antarctopelta was named by Argentine paleontologists Leonardo Salgado and Zulma Gasparini in 2006. The name is derived from the continent of Antarctica and the Greek word pelta (meaning 'shield'), referring to the location of its discovery and its armored nature. Antarctica itself comes from the Ancient Greek words anti- (meaning 'opposite of') and arktos (meaning 'bear': the meaning 'north' came via "the direction of Ursa Major and Ursa Minor – the Great Bear and Little Bear"). There is one named species (A. oliveroi), which honors Argentine geologist Eduardo Olivero, who discovered the holotype and has worked in Antarctica for decades.
Antarctopelta shares several features with both ankylosaurids and nodosaurids, making assignment to a specific family difficult and it has been designated as Ankylosauria incertae sedis (Salgado & Gasparini, 2006; p. 133). Earlier work suggested that the James Ross Island ankylosaur represented a juvenile (Olivero et. al., 1991; Gasparini et al., 1996). However, this may be refuted by the fact that the vertebrae of Antarctopelta show complete fusion of the neural arches and vertebral centra. A juvenile would be expected to have visible sutures between the bones or even complete separation. Also, preliminary histological analysis of several ribs and toe bones shows internal bone structures which a juvenile animal should not have formed yet, indicating that the holotype specimen is of adult age or very close to it (Salgado & Gasparini, 2006).
[edit] Known fossil material
The holotype and only known specimen (MLP 86-X-28-1, Museo de La Plata) was collected over an area of 6 square meters, over several field seasons but is assumed to have belonged to a single individual. This specimen consists of an incomplete left dentary (with one tooth in situ), a number of skull fragments, cervical (neck) vertebrae, fragments of eight ribs, two dorsal (thoracic) vertebrae from the presacral rod, eight fragmentary caudal (tail) vertebrae, fragments of the left scapula, right ilium, and left femur, five metapodials (foot bones), two phalanges (toe bones) and osteoderms representing six distinct types of dermal armor.
[edit] History
The holotype skeleton was collected about 90 meters from the base of the Gamma Member of the Santa Marta Formation (late Campanian, about 78 to 74 million years ago), which was deposited in a shallow marine environment and also preserves marine fossils such as shark teeth, remains of the mosasaur Lakumasaurus antarcticus, pelecypods, gastropods, and ammonites.
This specimen was initially located in January 1986 on James Ross Island, off the Antarctic Peninsula and was the first dinosaur ever found in Antarctica. Despite this, its remains were not formally named and described until 2006, making it the second named dinosaur genus from Antarctica (the first was the theropod Cryolophosaurus, in 1993). Harsh Antarctic weather conditions made collecting and identifying its remains difficult and fieldwork proceeded over more than a decade.
[edit] Footnotes
[edit] References
- Hammer, William R. "Antarctic Dinosaurs". Encyclopedia Prospectus. Department of Geology, Augustana College.
- Gasparini, Z., Olivero, E., Scasso, R., & Rinaldi, C. 1996. New data on the ankylosaurian dinosaur from the Late Cretaceous of the Antarctic Peninsula. Memoirs of the Queensland Museum 39: 583-594.
- Olivero, E., Gasparini, Z., Rinaldi, C., & Scasso, R. 1991. The first record of dinosaurs in Antarctica (Upper Cretaceous, James Ross Island): paleogeographical implications. In: Thomson, M.R.A., Crame, J.A., & Thomson, J.W. (Eds.). Geological Evolution of Antarctica. Cambridge: Cambridge University Press. Pp. 617-622.
- Salgado, L. & Gasparini, Z. 2006. Reappraisal of an ankylosaurian dinosaur from the Upper Cretaceous of James Ross Island (Antarctica). Geodiversitas 28(1): 119-135.
