| Vegasaurus | |
|---|---|
 | |
| Life restoration | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Sauropterygia |
| Order: | †Plesiosauria |
| Superfamily: | †Plesiosauroidea |
| Family: | †Elasmosauridae |
| Genus: | †Vegasaurus O'Gormanet al.,2015 |
| Type species | |
| †Vegasaurus molyi O'Gormanet al., 2015 | |
Vegasaurus is anextinctgenus ofelasmosauridplesiosaur known from theLate Cretaceous (earlyMaastrichtian stage)Snow Hill Island Formation ofVega Island,Antarctic Peninsula. It contains asingle species,Vegasaurus molyi.[1]
Vegasaurus is known solely from theholotype MLP 93-I-5-1, a nearly complete well preservedpostcranialskeleton (lacking the tip of the tail) housed at theLa Plata Museum in La Plata, Argentina. Elements include the whole neck with 54 completecervical vertebrae, threepectoral vertebrae, 17back vertebrae, threesacral vertebrae, the front and middletail vertebrae, pectoral and pelvic girdles, forelimbs and hindlimbs, ribs, and 45gastroliths associated with the dorsal region. MLP 93-I-5-1 was discovered in 1989, by Eduardo Olivero, Daniel Martinioni, Francisco Mussel and Jorge Lusky, at Cape Lamb ofVega Island at the edge of the Antarctic Peninsula ofJames Ross Archipelago (northernmost part ofAntarctica). Excavations took places during three Antarctic summer expeditions in 1993, 1999 and 2005. MLP 93-I-5-1 was collected from an area of 3 square meters in a semi-articulated state, at locality "Assemblage 10", which belongs to the middle section ofCape Lamb Member of theSnow Hill Island Formation, dating to the earlyMaastrichtian stage of theLate Cretaceous, about 72million years ago.
Vegasaurus was first described and named byJosé P. O'Gorman,Leonardo Salgado,Eduardo B. Olivero andSergio A. Marenssi in2015 and thetype species isVegasaurus molyi. Thegeneric name is derived fromVega, in reference to theVega Island where the holotype was found, and fromGreeksaurus, meaning "lizard", a common suffix for genus names of extinct reptile. Thespecific name honors the Argentinepaleontological technicianJuan Jose Moly, for participating in 17 Antarctic field trips and in the collection of the holotype.[1]
Vegasaurus is unique amongelasmosaurids in having 54 neck vertebrae.Callawayasaurus with a similar count of 56 lacks the dumbbell-shaped articular faces that are present on the vertebrae ofVegasaurus. Additional traits rarely seen in other elasmosaurid include: atlas-axis complex with a visible keel on its lower surface, a side ridge that is present on neck vertebrae 8 to about 42, a well developed notch on lower surface in neck vertebrae before the seventh but not in the last five vertebrae, acoracoid with projection from the middle of its lower surface, afemur with strongly convex capitulum (head), the lack of pectoral and pelvic bars, and ahumerus with front facing knee and a strong expansion to the back ending in an accessory back facet (only shared byMorenosaurus andKaiwhekea), among other traits.[1] It was about 6.5 m (21 ft) long.[2]
O'Gormanet al. (2015) tested thephylogenetic position ofVegasaurus using a modified version of the Kuboet al. (2012) data-set. In the resultant topology,Vegasaurus nests with three otherLate CretaceousSouth Pacific elasmosaurids, beingMorenosaurus, and two species from theWeddell Sea region, thearistonectinesAristonectes andKaiwhekea.Vegasaurus differs from the two members of Aristonectinae by having elongated neck vertebrae, yet links them to taxa from the other side of the Pacific, e.g.Futabasaurus fromJapan. Thecladogram below follows their results, showing only the relationships within Elasmosauridae.[1]
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