Chacaico Sur, Lajas (Jurassic of Argentina)

Where: Neuquen, Argentina (39.3° S, 70.3° W: paleocoordinates 36.5° S, 31.7° W)

• coordinate stated in text

• small collection-level geographic resolution

When: Lajas Formation, Early/Lower Callovian (164.7 - 161.2 Ma)

• Uppermost part of the middle Lajas Formation (early Callovian)

• bed-level stratigraphic resolution

Environment/lithology: deltaic; sandstone

• Tidally-influenced delta
• The intermediate section of the Lajas Formation contains the plesiosaurs remains near the top. This section includes about 2/3 the thickness of the formation. It is characterized by large sandstone bodies of cosets (sandwaves) tens of metres thick, that can be traced for considerable distances. The sandstones are cross-bedded as amalgamated tridimensional sets (dunes). SIgmoidal foresets, numerous reactivation surfaces, and alternating tractional (sandy) and fall-out laminae (rich in fine carbonized vegetal detritus) in the foresets, are conspicuous features of these sandstones. Some bipolar or herringbone cross-bedding is also present. According to their sedmintary attributes, these sandstone bodies represent extensive fields of tidal sand bars developed in shallow marine environments.

Size class: macrofossils

• ...dismemberment of cadavers occured rapidly...the most common material include vertebrae centra without neural arches, fragments of ribs, humeri and femora. Some epipodial, carpals, tarsals and phalanges have also been found

Collected by Gasparini, Spaletti, and paleobotanists of the Museo de La Plata in 1991

Collection methods: surface (in situ),

• MOZ, Museo Olsacher, Zapala, Neuquén, Argentina

Primary reference: Z. Gasparini and L. Spaletti. 1993. First Callovian plesiosaurs from the Neuquen Basin, Argentina. Ameghiniana 30(3):245-254 [R. Benson/R. Benson]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 140300: authorized by Philip Mannion, entered by Jonathan Tennant on 07.03.2013, edited by Roger Benson

Creative Commons license: CC BY (attribution)

Taxonomic list

Reptilia
 Sauropterygia - Cryptoclididae
cf. Cryptoclidus sp. Seeley 1892 plesiosaur
MOZ 6006, 1011 (cervical vertebrae), 6007 (radius)
cf. Muraenosaurus sp. Seeley 1874 plesiosaur
Cervical vertebrae: MOZ 6003, 6004, 6010; and a radius (MOZ 6005)
 Sauropterygia - Pliosauridae
Pliosauridae indet. Seeley 1874 plesiosaur
MOZ 6002, cervical centrum