Eastern rim of the Tyndall Glacier (Cretaceous to of Chile)

Also known as Ichthyosaur graveyard

Where: Ultima Esperanza, Chile (51.1° S, 73.3° W: paleocoordinates 50.7° S, 34.1° W)

• coordinate stated in text

• small collection-level geographic resolution

When: Zapata Formation, Valanginian to Valanginian (139.8 - 129.4 Ma)

• group of beds-level stratigraphic resolution

Environment/lithology: deep-water; siltstone and claystone

• This oceanic basin reflects the early extensional phase of proto-Andean

•evolution and developed as a consequence of the initial breakup of southern Gondwana and formation of the South Atlantic Ocean basin

• The ichthyosaur-bearing unit of the Zapata Formation is ~80 m thick and consists of thin to medium-bedded sandstone alternating with siltstone and claystone (mudstone). CaCO3 contents are generally low. Lenticular chaotic breccia units, up to several tens of meters thick, are interlayered within this monotonous sequence

Size class: macrofossils

• 46 articulated ichthyosaur skeletons

Preservation: soft parts, replaced with pyrite

Collection methods: quarrying, mechanical

• Ichthyosaur remains are mostly exposed in polished sections due to the

•glacier abrasion but are principally preserved in three dimensions. Due to the exceedingly hard matrix, an extraction was extremely difficult and only achieved for five specimens. Therefore, most data were collected in the field. The outlines of bones exposed on the surface were traced 1:1 on transparent foil. The data set comprises field number, GPS value, biometric

•data, the directions of skull and belly, and taphonomic or anatomic specialties if present. In addition, photos were taken of each specimen, especially of diagnostic body areas, i.e., fins and skull. For extraction we used a high-performance diamond disc mounted on a fuel-driven rock cutter, and complemented the extraction with a pneumatic hammer drill, placing lines of bore holes under the specimens and then removing the sediment between them with hammer and chisel. Mechanical preparation with air abrasive and hand tools was initiated at the laboratory of Heidelberg University, Germany, but was impossible due to the exceedingly hard sediment and relatively soft bone. Chemical preparation of these specimens with acetic acid was not possible due to paucity of carbonate in the matrix.

Primary reference: W. Stinnesbeck, E. Frey, L. Rivas, J. P. PĂ©rez, M. L. Cartes, C. S. Soto, and P. Z. Lobos. 2014. A Lower Cretaceous ichthyosaur graveyard in deep marine slope channel deposits at Torres del Paine National Park, southern Chile. Geological Society of America Bulletin [P. Mannion/J. Tennant]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 164882: authorized by Philip Mannion, entered by Jonathan Tennant on 29.12.2014

Creative Commons license: CC BY (attribution)

Taxonomic list

Bivalvia
 Myalinida - Inoceramidae
Inoceramus cf. anomiaeformis Feruglio 1936 clam
Neocomiceramus curacoensis Weaver 1931 clam
Cephalopoda
 Ammonitida - Crioceratitidae
 Ammonitida - Neocomitidae
 Ammonitida - Aegocrioceratidae
Aegocrioceras sp. Spath 1924 ammonite
 Belemnitida - Belemnopseidae
Reptilia
 Ichthyosauria - Ophthalmosauridae
Ophthalmosauridae indet. Andrews 1910 ichthyosaur
Platypterygius sp. von Huene 1922 ichthyosaur
Platypterygius hauthali von Huene 1927 ichthyosaur
Platypterygius cf. hauthali von Huene 1927 ichthyosaur
Actinopteri
 Pycnodontiformes - Gyrodontidae
Gyrodus sp. Agassiz 1833