Robert W. Gess: The oldest animal fossils
South African Journal of Science, 2012; 108(1/2), Art. #1064, 2 pages. http://dx.doi.org/10.4102/sajs.v108i1/2.1064
The description by Brain et al. in this issue, of sponge-like organisms from Namibian rocks ranging in age between 760 Ma and 550 Ma, is extremely significant as these organisms represent the earliest record of metazoan life. This discovery places the origin of animals 100 million years to 150 million years earlier than has previously been accepted. That these organisms arose prior to the ‘snowball earth’2 and survived its extremes, presents a challenge to contemporary scientific thought.
[ … ]
By contrast, the fossils newly reported by Brain et al. demonstrate a complex rigid structure consistent with requirements for the feeding mechanism of sponges, suggesting the presence of animals of a high level of organisation. The rocks of southern Africa have yet again yielded up key evidence regarding the history of life.
The first animals: ca. 760-million-year-old sponge-like fossils from Namibia.
C. K. ‘Bob’ Brain, Anthony R. Prave, Karl-Heinz Hoffmann, Anthony E. Fallick, Andre Botha, Donald A. Herd, Craig Sturrock, Iain Young, Daniel J. Condon, Stuart G. Allison
South African Journal of Science, 2012; 108(1/2), Art. #658, 8 pages. http://dx.doi.org/10.4102/sajs.v108i1/2.658
One of the most profound events in biospheric evolution was the emergence of animals, which is thought to have occurred some 600-650 Ma. Here we report on the discovery of phosphatised body fossils that we interpret as ancient sponge-like fossils and term them Otavia antiqua gen. et sp. nov. The fossils are found in Namibia in rocks that range in age between about 760 Ma and 550 Ma. This age places the advent of animals some 100 to 150 million years earlier than proposed, and prior to the extreme climatic changes and postulated stepwise increases in oxygen levels of Ediacaran time. These findings support the predictions based on genetic sequencing and inferences drawn from biomarkers that the first animals were sponges. Further, the deposition and burial of Otavia as sedimentary particles may have driven the large positive C-isotopic excursions and increases in oxygen levels that have been inferred for Neoproterozoic time.