Paleobiota of the Cañadón Asfalto Formation

The Cañadón Asfalto Formation is a geological formation which dates to the Toarcian age of the Early Jurassic period of Argentina. The rocks of the formation preserve a diverse biota, including plants, dinosaurs, invertebrates, mammals and pterosaurs, among others. The formation is divided into two members: the lower Las Chacritas Member, and the overlying Puesto Almada member, though the latter has also been assigned to the overlying Cañadón Calcáreo Formation by some authors. The members are typically composed of fluvial-lacustrine deposits consisting of sandstones and shales, with a limestone carbonate evaporitic sequence also being present in the lower of the two.

Insecta
Insect eggs of unknown affinity were reported from several layers of the Estancia Fossati locality.

Theropods
During a campaign conducted in early 2021, remains of a large theropod dinosaur were found near the town of Las Chacritas. In 2020 a new fossil locality was found, named Cañadón de las Huellas due to the large number of sauropod, and probably theropod, footprints on one of the canyon walls. In the same locality in 2021, articulated remains where recovered and represent at least one sauropod and one large theropod. At least four theropod morphotypes, including one with ceratosaur and another with Piatnitzkysauridae affinities, are known from the Cañadón Bagual.

Sauropodomorphs
A sediment tubular shaped mass enriched in organic matter, closely associated within the ventral area of articulated remains of a sauropod, was recovered at Cerro Condor, composed of a high concentration of pollen grains & cuticular fragments, mainly leaves of two morphotypes (Araucariaceae and Cheirolepidaceae), probably representing the gut contents of the sauropod, inferring a conifer-based diet.

Plants
According to a palynological study the dominant pollen was produced by the conifer families Cheirolepidiaceae (Classopollis) and Araucariaceae (mainly Araucariacites and Callialasporites), suggesting that warm-temperate and relatively humid conditions under highly seasonal climate prevailed during the depositional times of the unit. The abundance of Botryococcus supports the presence of a shallow lake with probably saline conditions. Locally, the Cañadón Asfalto represents a more poor record of the floras seen in the undeliying Lonco Tapial Formation, with its closest floras found on the Antarctic Peninsula Sweeney Formation at Potter Peak, sharing Brachyphyllum spp. and Elatocladus confertus.

Phytoplankton
Possible freshwater "calcareous algae", associated with conifer shoots and acuatic invertebrates, have been reported from Cerro Caracoles.