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We report the first occurrence of microfossils in Ediacaran strata of the Camaquã Basin. The assemblage includes simple ( Leiosphaeridia sp. predominantly) and ornamented acritarchs associated with microbial mats. They are related to the Ediacaran Complex Acanthomorph Palynoflora (ECAP) and Late Ediacaran Leiosphere Palynoflora (LELP) due to the similar morphology and time interval assigned to those assemblages, though the observed specimens are a lot simpler and less diversified. However, different from the usual occurrences, this case study reports Neoproterozoic cosmopolitan communities living in marine (basal unit) and lacustrine (middle units) settings. Fossils within non-marine strata in the Precambrian record are rare. Therefore, this first finding of microfossils in the Camaquã Basin constitutes a new piece of the puzzle related to the history of the Panafrican-Brasiliano basins and shed some light on possible settings where the Ediacaran eukaryotes have evolved.

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Fotogra ia aeŕea do setor norte da Serra do Segredo, em Caçapava do Sul, RS, onde se destacam a Pedra do Segredo, em primeiro plano, e a Pedra da Abelha, logo à esquerda, geoformas esculpidas sobre conglomerados luviais da Bacia do Camaquã. Ao fundo, alguns cerros formados por rochas metamór icas e o imponente alto de Caçapava, sobre granitoides diversos, rochas que registram diferentes momentos do Ciclo Brasiliano no sul do Brasil. A paisagem faz parte do Geoparque Caçapava Aspirante Unesco e é parcialmente inserida no Parque Natural Municipal da Pedra do Segredo. Imagem obtida por Felipe Guadagnin. Legenda de André Weissheimer de Borba e Felipe Guadagnin.

Biomineralized and organic metazoan tubular skeletons are by far the most common in the fossil record. However, several groups of organisms are also able to agglutinate particles to construct more rigid structures. Here we present a novel type of agglutinated tube from the austral and endemic palaeobiota of the Malvinokaffric realm (Devonian, Brazil). This fossil is characterized by an agglutinated tube made of silt-sized particles forming an unusual flanged morphology that is not known from the fossil record. Besides being able to select specific particles, these organisms probably lived partially buried and were detritus/suspension feeders. Comparisons across different modern groups show that these fossils are strongly similar to tubes made by polychaetes, specifically from the family Maldanidae. If this interpretation is correct, then an early divergence of the Sedentaria clade may have occurred before the Devonian.