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Total anky death
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Ernietta
Ernietta
Scientific classification

Ernettia is an extinct genus of Ediacaran organisms with an infaunal lifestyle. Fossil preservations and modeling indicate this organism was sessile and “sack”-shaped. It survived partly buried in substrate, with an upturned bell-shaped frill exposed above the sediment-water interface. Ernietta have been recovered from present-day Namibia, and are a part of the Ediacaran biota, a late Proterozoic radiation of multicellular organisms. They are among the earliest complex multicellular organisms and are known from the late Ediacaran (ca. 548 Ma to 541 Ma). Ernietta plateauensis remains the sole species of the genus

Biology and paleocology[]

Fossil specimens show individuals to have lived partly buried in the substrate, as well as filled to some degree by substrate material. An exposed frill extended out of the substrate and was thought to have conducted feeding in the water column. Modeling based on fossil specimens show that the frill possessed an “upturned bell” shape. Water and nutrients circulated within this bell cavity, and the organism is thought to have engaged in suspension feeding. It is possible that appendages which carried out feeding were not preserved in fossils. Previously, Ernietta were thought to have obtained nutrients by passive absorption, however, this is currently unsupported given the high volume to surface area ratio observed in Ernietta. Alternatively Ernietta may have lived from associated symbiotic algae.

Hydrodynamic modeling carried out by Gibson et al. in 2019 assumed that Ernietta inhabited shallow marine environments in aggregations. Nutrient delivery was found to be optimized when individuals were situated in “clumped” formations, with multiple individuals aggregated in groups located upstream or downstream from one another. This formation enhanced both vertical mixing and the direction of nutrient-rich currents to the bodies of downstream individuals. This may thus be one of the earliest examples of commensalism, in which organisms act to mutual benefit.

Ernietta plateauensis from the Kliphoek Member of the Dabis Formation. Farm Aar, Namibia.

Cross-sectional view of Ernietta plateauensis from the Ediacaran Kliphoek Member of the Dabis Formation. Farm Aar, near Aus, Namibia.

The body of Ernietta is composed of a layer of tubes (with some preservations indicating a double-layer of tubes). Perpendicular to these tubes is an equatorial seam. The body is asymmetrical along either side of this seam. The presence of this seam and offset symmetry unites the Ernettiomorpha, which includes taxa more similar to Ernietta (for example, PteridiniumSwartpuntia, and Mietta) than to the rangeomorphs.

Ernietta has been considered a benthic shallow marine fossil comparable with an anemone, however there is evidence for freshwater environments from its low boron content compared with other Ediacaran fossils. Specimens have also been found covered with thin layers of wind-drift sand of alluvial levees.

Biogeography[]

Taxonomy and history[]

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