The origin, affinity and paleoecology of macrofossils of soft-bodied organisms of the terminal Ediacaran Period have been highly debated. Previous discoveries in South America are restricted to small shelly metazoans of the Nama Assemblage. Here we report for the first time the occurrence of discoidal structures from the Upper Ediacaran Cerro Negro Formation, La Providencia Group, Argentina. Specimens are preserved in tabular sandstones with microbially-induced sedimentary structures. Flute marks and linear scours at the base of the sandstone layers indicate deposition under high energy, episodic flows. Stratigraphic, sedimentologic, petrographic and taphonomic analyses indicate that the origin of these structures is not related to abiotic process. Preservational and morphological features, as invagination and the presence of radial grooves, indicate that they resemble typical morphs of the Aspidella plexus. The large number of small-sized individuals and the wide range of size classes with skewed distribution suggest that they lived in high-density communities. The presence of Aspidella in the Cerro Negro Formation would represent the first reliable record of Ediacaran soft-bodied organisms in South America. It also supports the paleogeographic scenario of the Clymene Ocean, in which a shallow sea covered part of the southwest Gondwana at the end of the Ediacaran.

The Cingulata Glyptodontidae (Xenarthra) are one of the most conspicuous Cenozoic herbivore clades in South America reaching North America during the Great American Biotic Interchange. The evidence of predation on these large armoured mammals is very scarce and limited to a Pliocene skull (Glyptotherium) in North America and some latest Pleistocene-early Holocene specimens in South America, with signals of human consumption. In this contribution, we present the first case of scavenging on a glyptodont belonging to cf. Eosclerocalyptus lineatus (Hoplophorini) from the Pliocene of the Pampean region (Argentina). In addition, we analyze the potential scavengers and the paleoenvironmental context in which this occurred. The evidence suggests that: a) the carcass was covered by a shallow water body, probably an abandoned channel; b) the carcass was completely covered during a brief lapse of time, probably less than a year; c) the morphology of the bite marks clearly coincide with the dentition of the procyonid Chapalmalania (Mammalia, Procyonidae), thus corroborating some presumptions about the paleoautoecological trends of this taxon.Martín de los Reyes. Facultad de Ciencias Naturales y Museo de La Plata. Paseo del Bosque s/n (1900),

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