CABALERI nora Graciela
SPINICAUDATANS FROM THE UPPER JURASSIC OF ARGENTINA AND THEIR PALEOENVIRONMENTS
MONFERRÁN, M. D.; CABALERI, NORA; GALLEGO, OSCAR F.; ARMELLA, CLAUDIA; CAGNONI, MARIANA
SEPM-SOC SEDIMENTARY GEOLOGY
Lugar: Lawrence; Año: 2016 vol. 31 p. 405 - 420
Spinicaudatans are a diverse and geographically widespread group of small branchiopod crustaceanswith an excellent fossil record. They inhabit ephemeral freshwater habitats with warm conditions and pH levelsfrom neutral to alkaline. Many studies have been performed on the systematics of this group, also known as?conchostracans?, although the paleoecology of these clam shrimp has not been widely analyzed. This paperexamines some aspects of the relationship between spinicaudatans and their environments from the UpperJurassic (Ca?nad´on Asfalto Formation) of Argentina. We used sedimentological analysis to infer paleoenvironmentalfactors. Spinicaudatan features were also measured, including carapace size, growth band width, andgrowth lines. The results of this study reveal that the observed spinicaudatan species (Congestheriella rauhuti,Wolfestheria smekali, and Wolfestheria sp.) would have lived in carbonate lacustrine systems characterized bybenthic microbial communities dominated by cyanobacteria. However, environmental factors such as oxygenation,pyroclastic deposits, and associated fauna (fish, ostracods, bivalves, and charophytes) were different at eachlocality. The spinicaudatan carapaces also show varying morphological features such as small or large carapacesize, narrow or wide growth bands and low or high density of growth lines. These differences are related to abiotic(volcanic-oxygen) and biotic (fish and microbial) factors regarded as important agents for the development of thespinicaudatan populations.