Some scenarios of the Mesozoic continental and coastal biota in Argentina.

APESTEGUIA; S; ARMELLA, CLAUDIA; BONAPARTE, JOSÉ; CABALERI, NORA; CAGNONI, MARIANA; GARRIDO; A.; GASPARINI, ZULMA; GONZALEZ RIGA, B.; LEANZA, HÉCTOR; LOPEZ ARBARELLO, A.; MANCUSO, A; MARQUILLAS, R; MARSISCANO, C; QUATTROCCHIO, M.,; RAMOS, ADRIANA; RAUHUT, O.; SALFITY, J.; SILVA NIETO, DIEGO GONZALO; VOLKHEIMER,WOLFGANG

Mendoza

Congreso; Gondwana 12 "Geological and Biological Heritage of Gondwana"; 2005

Academia Nacional de Ciencias

The principal sedimentary basins of the Argentinian Mesozoic are plotted on four paleogeographic maps of southern South America: a. Mid Triassic; b. Mid Jurassic, c. Mid Cretaceous and d. latest Cretaceous. On these basic maps is indicated the location of 20 scenarios of the continental and coastal biota, which represent, along the Mesozoic Era, 20 time slices within the mentioned area. Each of the scenarios is shown as a blockdiagram. An example is the Mid Triassic Chañares Formation of the Ischigualasto-Villa Union Basin, important through its tetrapod assemblage, which includes dinosauromorphs ("dinosaur precursors") not recorded, until now, elsewhere. The Mid-Triassic Los Rastros Formation of the same basin represents a cyclic lacustrine-deltaic environment. The lake margins are dominated by Ginkgoales, small Corystospermales and Sphenophyta; the river margins by Sphenophyta and the woodlands upstream in the floodplain with Corystospermales, at the fluvial floodplain and insects (Blattoptera, Homeoptera and Coleoptera) associated with shore-lake vegetation and woodlands of the fluvial system. Fish and temnospondyl amphibians inhabitate the affluent fluvial system. Therapsids, crurotarsal archosaurs and putative dinosaurs are represented by ichnites.- The Ischigualasto succession (Middle and Late Triassic) is particularly important worldwide, as it includes themost complete and, among the oldest, remains of dinosaurs recorded.- In a similar way is treated the Mid- to Late Jurassic Cañadón Asfalto Basin (Extraandean Patagonia, middle valley of the Chubut River), which yielded the only diverse Jurassic dinosaur faunas known from South America, and some of the most important Jurassic dinosaur faunas from the Southern Hemisphere. Middle Jurassic dinosaurs from the mainly lacustrine Cañadón Asfalto Formation (Callovian) are represented by two basal tetanuran theropods and three basal, nonneosauropodan sauropods. Late Jurassic dinosaurs from the fluvio-lacustrine Cañadón Calcáreo Formation (Kimmeridgian-Tithonian) are represented by a teranuran theropod, and three sauropods, a basal camarasauromorph, a brachiosaurid and a dicraeosaurid.- Middle Jurassic dinosaurs do not present evidence of differential evolution on the Southern and Northern Hemispheres. Late Jurassic dinosaurs indicate the beginning of different evolutionary pathways on the two hemispheres.- The nearly 800 km long and 300 km wide Neuquén Basin exhibits a huge amount of fossiliferous Jurassic and Cretaceous strata. Marine reptiles (non-articulated Plesiosauroidea: cf. Muraenosaurus sp. and cf. Clyptoclidus sp.) in coastal high energy environments are present in Early Callovian strata at Chacaico Sur.– On Early Callovian tidal flats in southern Mendoza (Calabozo Fm.) developed bivalves (Pholadomya), gastropods (nerineids), echinoderms, brachiopods, bryozoans, forams, dasycladacean algae and halimedaceans covered by filaments of cyanobacteria.- The Late Cretaceous continental filling of the basin produced by far one of the most fossiliferous terrestrial areas of South America. The Neuquén Group (Cenomanian–Early Campanian) comprises a thick continental succession which represents alluvial fans, fluvial systems, aeolian dunes and playa-lake environments. In the northern part of the Neuquén Basin (Mendoza Province), the presence of huge herbivores, like the titanosaur Mendozasaurus neguyelap González Riga, associated with theropods, crocodyliforms, Chelidae turtles, coniferous wood and Scoyenia ichnofacies indicate an important biologic activity in fluvial systems. In contrast, the Malargue Group (Late Campanian–Paleocene) includes fluvial, lacustrine, littoral and marine facies related to a first Atlantic ingression that covered central-northern Patagonia. In the Loncoche Formation, base of the Malargue Group, diverse vertebrate concentrations (fish, turtles, snakes, dinosaurs and plesiosaurs) indicate transporting and mixture of continental, freshwater and littoral taxa.- From the southern part of the Neuquén Basin (Neuquén and Río Negro provinces), diverse scenarios of the biota corresponding to the Candeleros, Portezuelo and Bajo de la Carpa formations are presented. Particularly the Limayan tetrapod assemblage (Cenomanian to Early Turonian) of the Candeleros Formation is characterized by the co-occurrence of early Gondwanan linages. It includes basal titanosaurs, rebbachisaurids and carcharodontosaurid theropods, among other vertebrates, characterized by their similarity with the African vertebrate faunas.- The assemblage of Late Cretaceous mammals found at Los Alamitos (northern Patagonia) is the only assemblage of mammals known in the Gondwanan Region for this time, being the evolution of gondwanic mammals very different from that of Laurasia.Muraenosaurus sp. and cf. Clyptoclidus sp.) in coastal high energy environments are present in Early Callovian strata at Chacaico Sur.– On Early Callovian tidal flats in southern Mendoza (Calabozo Fm.) developed bivalves (Pholadomya), gastropods (nerineids), echinoderms, brachiopods, bryozoans, forams, dasycladacean algae and halimedaceans covered by filaments of cyanobacteria.- The Late Cretaceous continental filling of the basin produced by far one of the most fossiliferous terrestrial areas of South America. The Neuquén Group (Cenomanian–Early Campanian) comprises a thick continental succession which represents alluvial fans, fluvial systems, aeolian dunes and playa-lake environments. In the northern part of the Neuquén Basin (Mendoza Province), the presence of huge herbivores, like the titanosaur Mendozasaurus neguyelap González Riga, associated with theropods, crocodyliforms, Chelidae turtles, coniferous wood and Scoyenia ichnofacies indicate an important biologic activity in fluvial systems. In contrast, the Malargue Group (Late Campanian–Paleocene) includes fluvial, lacustrine, littoral and marine facies related to a first Atlantic ingression that covered central-northern Patagonia. In the Loncoche Formation, base of the Malargue Group, diverse vertebrate concentrations (fish, turtles, snakes, dinosaurs and plesiosaurs) indicate transporting and mixture of continental, freshwater and littoral taxa.- From the southern part of the Neuquén Basin (Neuquén and Río Negro provinces), diverse scenarios of the biota corresponding to the Candeleros, Portezuelo and Bajo de la Carpa formations are presented. Particularly the Limayan tetrapod assemblage (Cenomanian to Early Turonian) of the Candeleros Formation is characterized by the co-occurrence of early Gondwanan linages. It includes basal titanosaurs, rebbachisaurids and carcharodontosaurid theropods, among other vertebrates, characterized by their similarity with the African vertebrate faunas.- The assemblage of Late Cretaceous mammals found at Los Alamitos (northern Patagonia) is the only assemblage of mammals known in the Gondwanan Region for this time, being the evolution of gondwanic mammals very different from that of Laurasia.