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.
Invertebrates
Demospongiae Genus Species Location Stratigraphic position Material Notes ImagesPalaeospongillaP. chubutensisEstancia Fossati localityLas Chacritas MemberIsolated SpecimensA freshwater (Lacustrine) member of Palaeospongillidae (Spongillida Sponges). Represents the main lacustrine bottom inhabitant of the Chacritas Paleolake
Crustacea Genus Species Location Stratigraphic position Material Notes ImagesCarapacestheriaC. taschiCañadón Asfalto Cañadón Lahuincó Cerro BayoLas Chacritas Member Puesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Eosestheriidae (Spinicaudatan). Originally identified as Cyzicus (Euestheria) taschi. CongestheriellaC. rauhutiSierra de la Manea Estancia El Torito Cañadón Los ChivosPuesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Afrograptidae (Spinicaudatan). It may come from the Cañadón Calcáreo Formation.DarwinulaD. magna D. spp.Cañadón Asfalto Cañadón Lahuincó Cerro Bayo Cañadón Asfalto Quebrada Subsidiaria Estancia el ToritoLas Chacritas Member Puesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Darwinulidae (Ostracod). EosolimnadiopsisE. spp.Cerro Cóndor Estancia FossatiLas Chacritas MemberIsolated ValvesA freshwater (Lacustrine) member of Palaeolimnadiopseidae (Spinicaudatan).EuestheriaE. volkheimeriCerro Cóndor Cerro Bayo Alice Creek Quebrada SubsidiariaLas Chacritas Member Puesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Euestheriidae (Spinicaudatan).LioestheriaC. (Lioestheria) sp. B C. (Lioestheria) sp. CCañadón Las Chacritas Colan Conhué Alice CreekLas Chacritas Member Puesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Fushunograptidae (Spinicaudatan).MandelstamiaM.? spp.Estancia El ToritoPuesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Limnocytheridae (Ostracodan). It may come from the Cañadón Calcáreo Formation.MetacyprisM. sp.Estancia El ToritoPuesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Loxoconchidae (Ostracodan). It may come from the Cañadón Calcáreo Formation.PenthesilenulaP. magna P. sarytirmenensisCañadón de la Angostura Estancia El ToritoLas Chacritas Member Puesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Darwinulidae (Ostracodan). These species are characteristic of the Middle Jurassic of northern China and where used to correlate the age of the bedsPseudestheritesP. sp.Estancia El Torito Cañadón Los ChivosPuesto Almada Member Isolated ValvesA freshwater (Lacustrine) member of Antronestheriidae (Spinicaudatan). It may come from the Cañadón Calcáreo Formation. TheryosinoecumT. barrancalensis minorEstancia El ToritoPuesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Cytheroidea (Ostracodan). It may come from the Cañadón Calcáreo Formation.TimiriaseviaT. sp.Estancia El ToritoPuesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Limnocytheridae (Ostracodan). It may come from the Cañadón Calcáreo Formation.WolfestheriaW. patagoniensis W. smekaliCañadón Asfalto Cañadón Lahuincó Estancia La Sin RumboLas Chacritas Member Puesto Almada MemberIsolated ValvesA freshwater (Lacustrine) member of Fushunograptidae (Spinicaudatan).
Mollusca Genus Species Location Stratigraphic position Material Notes ImagesCorbiculaC. spp.Cerro Cóndor Cerro Bayo Estancia El ToritoLas Chacritas Member Puesto Almada MemberIsolated ShellsA freshwater (Lacustrine) member of Corbiculidae (Bivalve).CyanocyclasC. spp.Cerro Cóndor Cerro Bayo Estancia El ToritoLas Chacritas Member Puesto Almada MemberIsolated ShellsA freshwater (Lacustrine) member of Corbiculidae (Bivalve).DiplodonD. spix D. cf.matildensis D. cf.spix D. spp.Cañadón Asfalto Cerro Caracoles Las Chacritas Cañadón Lahuincó Cañadón Miyanao Cerro Cóndor Cerro Bayo Alice Creek Quebrada Subsidiaria Estancia El ToritoLas Chacritas Member Puesto Almada MemberIsolated ShellsA freshwater (Lacustrine) member of Unionidae (Bivalve). The most abundant Bivalve genus on the Formation. Represents also some of the smallest-sized specimens recorded in the Mesozoic, what can be explained by potential environment stress.Nayadidae indet. IndeterminateCañadón Asfalto Cañadón LahuincóLas Chacritas MemberIsolated ShellsIncertade SedisPalaeomutelaP. spp.Las ChacritasLas Chacritas MemberIsolated ShellsA freshwater (Lacustrine) member of Palaeomutelidae (Bivalve).PotamolithusP.? spp.Cañadón Asfalto Cerro Caracoles Las Chacritas Cañadón LahuincóLas Chacritas MemberIsolated ShellsA freshwater (Lacustrine) member of Tateidae (Snail).Sphaeriidae indet. IndeterminateCañadón AsfaltoLas Chacritas MemberIsolated ShellsIncertade SedisViviparusV. spp.Cañadón Asfalto Cerro Caracoles Cañadón Lahuincó Cañadón Asfalto Quebrada Subsidiaria Estancia El ToritoLas Chacritas Member Puesto Almada MemberIsolated ShellsA freshwater (Lacustrine) member of Viviparidae (Snail).
Insecta Insect eggs of unknown affinity were reported from several layers of the Estancia Fossati locality. Genus Species Location Stratigraphic position Material Notes ImagesChironomidae indet. IndeterminateGan GanPuesto Almada MemberHead capsulesIncertade Sedis, it may come from the Cañadón Calcáreo Formation.Coleoptera indet. IndeterminateCerro Cóndor Estancia Fossati Estancia El Torito Estancia La Sin RumboLas Chacritas Member Puesto Almada MemberElytra and body remainsIncertade SedisConchindusiaC. isp.Cerro Cóndor Gan GanLas Chacritas Member Puesto Almada MemberImprints or compressed moulds of larval casesIndeterminate Trichoptera (Caddisflies) Ichnofossils, associated with lacustrine facies. Larval cases made of conchostracan shellsHeteroptera indet. IndeterminateCerro Cóndor Estancia Fossati Estancia El Torito Estancia La Sin RumboLas Chacritas Member Puesto Almada MemberFragmentary wingsIncertade SedisNeorthophlebidae indet. IndeterminateGan GanPuesto Almada memberWings and parts of bodyIncertade Sedis, it may come from the Cañadón Calcáreo Formation.OstracindusiaO. isp.Cerro Cóndor Gan GanLas Chacritas Member Puesto Almada MemberImprints or compressed moulds of larval casesIndeterminate Trichoptera (Caddisflies) Ichnofossils, associated with lacustrine facies. Larval cases made of ostracodan shellsTerrindusiaT. isp.Cerro Cóndor Estancia Fossati Gan GanLas Chacritas Member Puesto Almada MemberImprints or compressed moulds of larval casesIndeterminate Trichoptera (Caddisflies) Ichnofossils, associated with lacustrine facies. Larval cases made of clasts or terrigenous particlesTrichoptera indet. IndeterminateCerro Cóndor Estancia Fossati Estancia El Torito Estancia La Sin RumboLas Chacritas Member Puesto Almada MemberWings and larval casesIncertade Sedis
Vertebrates Fish Genus Species Location Stratigraphic position Material Notes ImagesArchaeomaenidae? indet. IndeterminateCerro Cóndor Cañadón Asfalto Cañadón Miyanao Estancia Fossati Localidad de Canela Cañadón Asfalto Quebrada SubsidiariaLas Chacritas MemberIsolated large median fin & Isolated ScalesMaybe related to the genus Oreochima, coming from layers coeval, coregional, and of identical deposition.
Amphibians Genus Species Location Stratigraphic position Material Notes ImagesAnura indet.IndeterminateCanelaLas Chacritas MemberNon clarifiedIncertade SedisNotobatrachusN. reigi Cf.N. spp.Cañadon Bagual Canela Cerro Cóndor Queso Rallado Sitio Frenguelli ZitarrosaLas Chacritas MemberMany articulated, mostly complete skeletonsAn early frog of the family Notobatrachidae.Salientia indet.IndeterminateCerro Cóndor Queso RalladoLas Chacritas MemberNon clarified"Notobatrachus-like"
Turtles Genus Species Location Stratigraphic position Material Notes ImagesCondorchelysC. antiqua C. cf.antiqua C. spp.Queso Rallado Cañadon Bagual Chucrut Canela facies Las Chacritas MemberHolotype: Most of a skull, carapace, and plastron. MPEF-PV 3163, left humerus MPEF-PV 3164, costal plateA stem turtle (Mesochelydian) outside both extant groups, closely related with Kayentachelys aprix of North America and Indochelys spatulata of India. Likely occupied aquatic or semiaquatic niches.Testudinata indet.IndeterminateCanela facies Las Chacritas MemberplastronsIncertade Sedis
Lepidosaurs Genus Species Location Stratigraphic position Material Notes ImagesSphenocondorS. gracilisQueso RalladoLas Chacritas MemberDentaryA Sphenodontian Rhynchocephalian, closely related with Godavarisaurus from the almost coeval Jurassic Kota Formation of India, maybe part of an endemic Gondwanan clade.
Crocodylomorpha Genus Species Location Stratigraphic position Material Notes ImagesCrocodylomorpha indet.Indeterminate Queso RalladoLas Chacritas MemberTeeth & several isolated remainsIndeterminate crocodylomorph remains that represent small carnivorous vertebrates linked with lacustrine facies.
Pterosaurs Genus Species Location Stratigraphic position Material Notes ImagesAllkaruenA. koiCanadón CarrizalLas Chacritas MemberA braincase, as well as a mandible and cervical vertebrae.A pterosaur either related with Breviquartossa or maybe even a sister group of monofenestratan (Wukongopteridae + Pterodactyloidea) pterosaursCtenochasmatidae? indet.IndeterminateQueso RalladoNot DeterminedIsolated toothResembles the teeth of Pterodaustro. The exact provenance of the specimen is unknownMelkamterM. pateko Queso RalladoLas Chacritas MemberPartial skull and associated postcranial elementsA monofenestratan pterosaur, representing the oldest known record of this cladeScaphognathinae? indet. IndeterminateLas ChacritasLas Chacritas MemberUncatalogued specimens, several mandibles, braincase, shoulder girdle, two humeri, several wing-finger phalangesPossibly a rhamphorhynchoid with a wingspan of about . The mandible morphology is similar to scaphognathines.
Dinosaurs 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 sauropods, and probably theropods, footprints on one of the canyon walls. In the same locality in 2021, articulated remains were 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. Genus Species Location Stratigraphic position Material Notes ImagesAsfaltovenatorA. vialidadiCerro CondorLas Chacritas MemberNearly compete skull and largely complete front half of the skeleton forward of the hips, distal pubis and fermur and proximal fibula and tibia, partial foot A probable early member of AllosauroideaAverostra indet.IndeterminateCerro Cóndor Puesto el Quemado