INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Insect fauna in the south-eastern extreme of Gondwana (Argentina): Co-association insect/plant and climate provincialism during Triassic times
LARA, M.B. & ZAVATTIERI, A.M.
Congreso; 4th International Palaeontological Congress; 2014
International Palaeontological Association
The richness of insects found in the Triassic continental sediments positions Argentina as the main paleoentomological region of South America and one of the most important from southern Gondwana. At the moment, the insect faunas of the Molteno Formation, Karoo Basin, South Africa (335 species), and the Ipswich Series, Queensland, Australia (115 species) are more abundant and diverse. The bioestratigraphic distribution of the insect fauna occurs mostly in association with the typical and diverse Dicroidium Flora during the Middle and Late Triassic. The paleogeographic position of Argentina, South Africa and Australia Triassic basins explains the presence of a marked floristic provincialism through southern Gondwana, and a similar eco-environment and climate patterns. The Dicroidium Flora occupied middle to high paleolatitudes (>30º) in the extratropical belt of Gondwana. It progressed under temperate/warm and humid conditions in a megamonzonic climate. The insects would be thus adapted to strongly seasonal conditions. The significant paleoentomological potential of the Argentine Triassic is based on more than 510 specimens of insects classified into 12 orders, 25 families and 83 species. The insect bearing levels come from fluvial environments of the: Ischichuca (~Anisian-Ladinian) and Los Rastros (~Carnian) formations, Bermejo Basin, San Juan and La Rioja Provinces; Cerro de Las Cabras (~Anisian-Ladinian) and Potrerillos (~Carnian) formations, Cuyo Basin, Mendoza Province; Llantenes Formation (~Norian), Malargüe Basin, Mendoza. The Los Rastros (44 species) and Potrerillos (23 species) formations contribute with 61% of collected specimens, being essentially similar in taxonomic composition. The insect records comprise fragmentary and occasionally articulated specimens with different preservation modes as impressions/molds of wings, part of bodies and complete bodies attributable to blattids, hemipterans, beetles, orthopterans, mecopterans, miomopterans, grylloblattids, plecopterans, miomopterans, dipterans, hymenopterans, odonatans and glosselytrodeans. Most of the groups exhibit terrestrial habit (adult stages); however, records of aquatic forms (immature stages) are also present. The dominant forms of the assemblages are insects with sclerotized wings: Coleoptera (32 species), Blattodea (17 species) and Hemiptera (16 species), a similar characteristic to the largest entomological deposits of South Africa and Australia. Among the most important findings of insects in Argentina are the first records of several orders/families for South America and Gondwana that provide new evidence about close faunal connections between Laurasia and Gondwana during the Mesozoic. The study of fossil insects provides valuable information about the taxonomical composition of the Triassic communities, the evolution of Mesozoic insects, the relationship plantinsects- habitat, and the reconstruction of ecosystems in response to paleoenvironment and climatic conditions.