CONICET | Buscador de Institutos y Recursos Humanos

In Argentina, invertebrates represent an important component of the continental Mesozoi faunas, and are represented mainly by arthropods (spinicaudatans='conchostracans', insects and ostracods) and mollusks (bivalves and gastropods). Despite their importance, there are few studies on the diversity and ecology of the invertebrate groups from the non-marine geological units. In the last few years, new field collections and studies by our research team have provided a more complete picture of the invertebrate diversity in South America during the Mesozoic Era (mainly Triassic Jurassic). Our initial studies were primarily descriptions of several new taxa; however, more recently, we have focused on other objectives such as biostratigraphy, palaeocology, taphonomy and geochemistry. The significant palaeo-invertebrate potential of the Argentinean Mesozoic sequences derives mainly from two extensive geological areas: Central-Western and Patagonia. The Central-Western Argentina region has two main Triassic basins: 1) Ischigualasto-Villa Unión Basin (=Bermejo Basin), La Rioja-San Juan provinces; and 2) Cuyana Basin (also named 'Cuyo Basin'), Mendoza-SanJuan provinces. The Patagonia region includes: 1) Extra-Andean Chubut in the homonymous province, Cañadón Asfalto Basin (Jurassic Cretaceous) and 2) Deseado Massif, Santa Cruz Provinc (Jurassic Cretaceous). The studied fossil specimens (insects, spinicaudatans, and ostracods) are housed in the collection at the Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA-CCT-CONICET), Mendoza City, under IANIGLA-PI acronym; Museo Egidio Feruglio, Chubut, under MEF-PI, Paleoinvertebrate collection, Museo Regional Provincial "Padre Manuel Jesús Molina", under MPM-PI, Río Gallegos, Santa Cruz Province and temporarily in the Paleontological Collection "Dr. Rafael Herbst", Paleozoology Section (CTES-PZ) at the Universidad Nacional del Nordeste (UNNE), Corrientes City, Argentina.In the Triassic sequences, the most common and best studied fossil invertebrates are spinicaudatans and insects; however several undescribed notostracan crustaceans and ostracods (darwinuloids) as well as bivalved mollusks have also been recorded. The Triassic spinicaudatans include thousand specimens and around 30 described species that belong to the families Lioestheriidae (2 spp.), Palaeolimnadiopseidae (1), Pemphilimnadiopseidae (1), Ulugkemiidae (3), Euestheriidae (12), Loxomegaglyptidae (6), Eosestheriidae (1), Polygraptiidae (2), Fushunograptidae (1) and Estheriteoidea (1). The Triassic insect fauna includes more than 510 specimens of insects classified into 12 orders, 25 families and 87 described species. The insect records comprise both fragmentary and (occasionally) articulated specimens with various preservation modes including impressions/molds of wings, part of bodies and complete bodies attributable mainly to hemipterans, blattids, beetles and, less commonly, orthopterans, mecopterans, grylloblattids, plecopterans, miomopterans, dipterans, hymenopterans, odonatans and glosselytrodeans (e.g., Lara, 2016). Until now, the studied fossil insects have provided valuable information about the ecological organization of the Triassic communities, the evolution of Mesozoic insects, and have been valuable tools for local stratigraphic correlations and preliminary phylogenetic analyses. Additionally, they have provided taphonomical and palaeobiological information about the relationships of plant-insects-habitat and the reconstruction of ecosystems in response to palaeoenvironmental and climatic conditions The Jurassic units contain fossil invertebrate remains of bivalved mollusks (Unionids, 3 spp.) and gastropods (2 spp.), as well as spinicaudatans, ostracods and insects. Fourteen spinicaudatan speciesfrom the families Euestheridae (2 spp.), Anthronestheriidae (2), Eosestheriidae (3), ?Triglyptidae (1), Fushunograptidae (4), Afrograptidae (1), and Palaeolimnadiopseidae (1) have been recorded, many of them representing the first fossil records of these species. These species are separated into distinct, stratigraphically-disjunct assemblages that allow us to tentatively define informal biozones and that may be useful for stratigraphic correlation and relative dating of the various stratigraphicunits. Additionally, twelve species of ostracod, including darwinuloids (7 spp.) and cytheroids (5), four described species of fossil insects (hemipterans, mecopterans, beetles, trichopterans, and dipterans), and four ichnospecies of trichopteran larval cases, have been recorded in the Jurassic strata from Argentina (Monferran et al., 2016). The Cretaceous invertebrates are poorly represented, primarily due to limited field collecting. At present, four spinicaudatan species have been described (Polygraptidae (1), Anthronestheriidae (2) and Euestheriidae (1)) and there are two undescribed species, one belonging to Anthronestheriidae. Different authors have also recorded seventy ostracod species (cytheroids Limnocytheridae (18 spp.), cypridoids Ilyocyprididae (32), Cyprididae (6), Candonidae (9), Pontocyprididae (2), andParacyprididae (1) and darwinuloids (2)). The Cretaceous insect fauna is known from only five species described from eight specimens (blattids, odonatans, hemipterans, beetles, orthopterans, trichopterans). These results allow us to observe the structure of arthropods communities, particularly their palaeodiversity and palaeogeographical distribution, over different periods. For example, the Triassic spinicaudatan fauna includes the oldest record of some families (e.g., Eosestheriidae), the first appearances of other groups (e.g., Lioestheriidae, Pemphilimnadiopseidae) and provides information about the local stratigraphic distribution of some taxa and the predominance of Euestheriidae andLoxomegaglyptidae in the Triassic sequences. Furthermore, the spinicaudatan studies provide information about different associations that inhabited perennial lakes (large Euestheriidae and Eosestheriidae) and shallow ephemeral lakes (small Afrograptidae, Fushunograptidae and Anthronestheriidae) during Jurassic times. Finally, these results are also relevant on a broader geographic scale, providing the first records for a number of taxa in any Triassic deposits worldwide (e.g., Xyelinae-Hymenoptera), in Triassic deposits in South America (e.g., Diptera, Hymenoptera, Sternorrhyncha-Hemiptera, Eoscarterellidae-Hemiptera, Geinitziidae-Grylloblattida) and in Triassicdeposits in Gondwana (e.g., Hennigmattidae-Diptera). These also provide new evidence of the close faunal connections between Laurasia and Gondwana during the Mesozoic. Further studies on the palaeoecology and palaeogeography of invertebrates from Argentina will offer an excellent opportunity to expand the regional palaeocommunity reconstructions of the Mesozoic Era in South America.