Longing Gap, plesiosaur (Jurassic of Antarctica)

Where: Antarctica (64.4° S, 59.0° W: paleocoordinates 54.9° S, 35.5° W)

• coordinate based on unpublished field data

• hand sample-level geographic resolution

When: Longing Member (Ameghino Formation), Early/Lower Tithonian (150.8 - 145.0 Ma)

Environment/lithology: marine; lithified, massive, tuffaceous, black mudstone

• Anoxic conditions prevailed especially in the Longing Member; this is indicated by the often lacking bioturbation and rare horizons with benthonic fossils. In the Ameghino Member moderately intense bioturbation (Zoophycos, Chondrites, Planolites) and a consequent destruction of lamination indicate dysaerobic conditions. Doyle and Whitham (1991) attribute this environmental change to an uplift of the depositional environment above a permanent pyknocline. The submarine relief was very low and a simple hemipelagic sedimentation was dominant.
• At Longing Gap locality, the Ameghino Formation consists of laminated or massive black mudstones and gray tuffs with abundant calcitic concretions (Kiessling et al., 1999). The tuff beds increase from the stratigraphically lower Longing Member to the overlying Ameghino Member (Whitham and Doyle, 1989) and reflects hemipelagic sedimentation close to an active volcanic arc (Kietzmann et al., 2009; Scasso, 2001). The complete

•sequence is about 580 m thick (Longing Member: 420 m and Ameghino Member: 160 m, according toKiessling et al.,1999).

Size class: macrofossils

• IAA-Pv 354, five articulated dorsal vertebrae, fragments of at least two additional dorsal vertebrae, dorsal ribs and indeterminate fragments; IAA-PV 355; one dorsal vertebra, a fragment of dorsal rib and one indeterminate vertebral fragment.

Preservation: concretion

Collection methods: bulk, mechanical, sieve,

• Radiolarians only. Additional faunal elements are sponge spicules and very rare foraminifera.

Primary reference: J. P. O'Gorman, S. Gouiric-Cavalli, R. A. Scasso, M. Reguero, J. J. Moly and L. Acosta-Burlaille. 2018. A Late Jurassic plesiosaur in Antarctica: Evidence of the dispersion of marine fauna through the Trans-Erythraean Seaway?. Comptes Rendus Palevol 17(3):158-165 [E. Vlachos/F. Aspromonte]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 232340: authorized by Evangelos Vlachos, entered by Franco Aspromonte on 09.11.2023

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names
Reptilia
 Plesiosauria -
Plesiosauria indet.
Plesiosauria indet. plesiosaur
IAA-Pv 354, five articulated dorsal vertebrae, fragments of at least two additional dorsal vertebrae, dorsal ribs and indeterminate fragments, IAA-PV 355; one dorsal vertebra, a fragment of dorsal rib and one indeterminate vertebral fragment