#ediacarans

I had come to Mistaken Point hoping to gain some understanding of why the first animals began to roam. I would have assumed the ur-trail-maker was propelled by either food, sex, or imminent danger. I hadn’t accounted for this counterintuitive but perhaps equally primal need: the desire for stability.

I thought back to my experience of being lost amid the Tuckamore, how intensely I had yearned for the comfort of a building, or even just a trail - something solid and familiar to which I could cling…

There is no sure way of knowing what the ancient Ediacarans felt, or if they even could feel. But here, written in stone, was a clue. In the end - or rather, the beginning - the first animals to summon the strength to venture forth may simply have wanted to go back home.”

Australia needs more state fossil emblems, but let the public decide

New South Wales has joined Western Australia to become the second state or territory in Australia to have formally adopted a fossil emblem.

The 365-million-year-old Devonian fish Mandageria fairfaxi was last month announced as the state fossil emblem of NSW.

Palaeocast Episode 50: Rangeomorph Reproduction

On today’s episode we’re revisiting Mistaken Point, Newfoundland, Canada. At this lagerstätte it is possible to find large bedding planes full of Precambrian organisms called rangeomorphs. These are an enigmatic group, which still can’t be placed on the ‘tree of life’.

We are joined by Dr Emily Mitchell of the University of Cambridge, who’s recent paper in Nature was able to show that you don’t need to be able to fully understand the anatomy of an organism to discern some of its most intricate details.

Evidence that Earth's first mass extinction was caused by critters not catastrophe

The Earth's first mass extinction event 540 million years ago was caused not by a meteorite impact or volcanic super-eruption but by the rise of early animals that dramatically changed the prehistoric environment.

Read more of the press release.

Biotic replacement and mass extinction of the Ediacara biota

Abstract

The latest Neoproterozoic extinction of the Ediacara biota has been variously attributed to catastrophic removal by perturbations to global geochemical cycles, ‘biotic replacement’ by Cambrian-type ecosystem engineers, and a taphonomic artefact. We perform the first critical test of the ‘biotic replacement’ hypothesis using combined palaeoecological and geochemical data collected from the youngest Ediacaran strata in southern Namibia. We find that, even after accounting for a variety of potential sampling and taphonomic biases, the Ediacaran assemblage preserved at Farm Swartpunt has significantly lower genus richness than older assemblages. Geochemical and sedimentological analyses confirm an oxygenated and non-restricted palaeoenvironment for fossil-bearing sediments, thus suggesting that oxygen stress and/or hypersalinity are unlikely to be responsible for the low diversity of communities preserved at Swartpunt. These combined analyses suggest depauperate communities characterized the latest Ediacaran and provide the first quantitative support for the biotic replacement model for the end of the Ediacara biota. Although more sites (especially those recording different palaeoenvironments) are undoubtedly needed, this study provides the first quantitative palaeoecological evidence to suggest that evolutionary innovation, ecosystem engineering and biological interactions may have ultimately caused the first mass extinction of complex life.

The original paper on Haootia quadriformis. 

Abstract:

The oldest members of the Ediacara biota include discoid and frondose forms. The fronds have been well described, but little has been done to quantify the relationship between the discoid fossils and the discoid holdfasts of fronds. Fossil surfaces from the middle Ediacaran of southeastern Newfoundland preserve fronds directly attached to their discoid holdfasts, along with numerous specimens of the isolated discoid fossils Aspidella and Hiemalora of less certain affinities. However, most specimens of Aspidella in Newfoundland are known from Fermeuse-style preservation of the base of discs, whereas most Mistaken Point fronds are known from Conception-style preservation of the tops of discs, hindering direct comparison of these fossils. The Discovery Surface on Bonavista Peninsula preserves both basal and top views of Aspidella-type discs on the same fossil surface, and thus serves as a morphological link between these preservational modes and permits reconstruction of these circular holdfasts in three-dimensions. We find a significant positive correlation between disc size and frond size within each frondose species, which is consistent with the purported function as holdfasts, tethering the frondose organisms to the seafloor. This supports the notion that discoid fossils relatable to Aspidella and its junior synonyms, and to Hiemalora, are the holdfasts of frondose forms whose petalodia escaped preservation, and not whole organisms or microbial colonies as has been suggested by some authors.

Insights into the Skeletonization, Lifestyle, and Affinity of the Unusual Ediacaran Fossil Corumbella

Abstract:

The Ediacaran fossil Corumbella is important because it is hypothesized to be a scyphozoan cnidarian, and thus might be one of the rare examples of bona fide Neoproterozoic animals. Unfortunately, its mode of life, style of skeletonization, and taxonomic affinity have been very controversial. Here, we use X-ray micro-CT, SEM, and taphonomic analysis to compare preservational modes of Corumbella, in order to better understand the symmetry, mode of construction, preservational style, and taxonomy of this group. Results suggest that articulated and disarticulated specimens of Corumbella from the Ediacaran of Brazil, Paraguay, and the United States, although sometimes preserved very differently, represent the same taxon—Corumbella werneri. Corumbellids had a thick but flexible theca and probably lived with their basalmost part anchored in the sediment, much like Conotubus. When considered together, these results suggest that Corumbella was one of the first animals to build a skeleton, employing a lamellar microfabric similar to conulariids.

Discovering missing body parts of ancient fossils: Waves and storms lifted fossils off the seafloor 550 million years ago

Certain specimens of the fossil Dickinsonia are incomplete because ancient currents lifted them from the sea floor, a team of paleontologists has found. Sand then got deposited beneath the lifted portion, the researchers report, strongly suggesting that Dickinsonia was mobile, easily separated from the sea floor and not attached to the substrate on which it lived.

Read more of the press release here

The paper:

Dickinsonia liftoff: Evidence of current derived morphologies

Abstract