News About The Ediacara Fossils

[uair01]

There is a lot happening around the mysterious pre-Cambrian Ediacara fossils. They did not survive and have no comparable modern species. They look and feel alien. No one knows what they were but research is continuing. A few nice recent lectures:

This lecturer stutters, but the content is very good:

 

[Mythopoeika]

Thanks - that's a really good introduction to Ediacaran lifeforms.

 

[hunck]

558m-year-old fossils identified as oldest known animal

A fossilised lifeform that existed 558m years ago has been identified as the oldest known animal, according to new research.

The findings confirm that animals existed at least 20m years before the so-called Cambrian explosion of animal life, which took place about 540m years ago and saw the emergence of modern-looking animals such as snails, bivalves and arthropods.

The new fossils, of the genus Dickinsonia, are the remains of an oval-shaped lifeform and part of an ancient and enigmatic group of organisms called Ediacarans. These creatures are some of the earliest complex organisms on Earth, but their place within the evolutionary tree has long puzzled scientists. Suggestions as to what they were have ranged from lichens to failed evolutionary experiments to bacterial colonies.

Now, by identifying the remains of organic matter on newly discovered Ediacaran fossils as ancient cholesterol, the scientists have been able to confirm Dickinsonia was an animal, which makes it the oldest known animal.

The fossils were discovered on two surfaces on a cliffside in the remote wilderness of north-west Russia by PhD student Ilya Bobrovskiy, who is lead author on the paper, published in the journal Science.
“I took a helicopter to reach this very remote part of the world – home to bears and mosquitoes – where I could find Dickinsonia fossils with organic matter still intact,” Bobrovskiy said.

“These fossils were located in the middle of cliffs of the White Sea that are 60-100m high. I had to hang over the edge of a cliff on ropes and dig out huge blocks of sandstone, throw them down, wash the sandstone and repeat this process until I found the fossils I was after.”

Charlotte Kenchington, a palaeobiologist based at the University of Cambridge, said: “It’s really, really unusual to have preservation of organic matter in the Ediacaran. The really neat thing about this study is that they’ve analysed both the sediment around the fossil and the fossil itself.

“The biomarker signal of the sediment is very different to the biomarker signal of the organic matter associated with the fossil. This gives you a huge deal of confidence in the results.”

 

[Yithian]

And for the lazy:

 

[EnolaGaia]

Move over, Dickinsonia ... It appears the newly described Ikaria is older, definitely bilateral, and definitely possessing a gut running between two apertures.

Meet the new oldest ancestor ...

​

... a burrowing worm-like creature about the size of a rice grain.

Ancestor of all animals identified in Australian fossils

A wormlike creature that lived more than 555 million years ago is the earliest bilaterian

Summary:
Geologists have discovered the first ancestor on the family tree that contains most animals today, including humans. The wormlike creature, Ikaria wariootia, is the earliest bilaterian, or organism with a front and back, two symmetrical sides, and openings at either end connected by a gut. It was found in Ediacaran Period deposits in Australia and was 2-7 millimeters long, with the largest the size of a grain of rice.

The tiny, wormlike creature, named Ikaria wariootia, is the earliest bilaterian, or organism with a front and back, two symmetrical sides, and openings at either end connected by a gut. The paper is published today in Proceedings of the National Academy of Sciences.

The earliest multicellular organisms, such as sponges and algal mats, had variable shapes. Collectively known as the Ediacaran Biota, this group contains the oldest fossils of complex, multicellular organisms. However, most of these are not directly related to animals around today, including lily pad-shaped creatures known as Dickinsonia that lack basic features of most animals, such as a mouth or gut.

The development of bilateral symmetry was a critical step in the evolution of animal life, giving organisms the ability to move purposefully and a common, yet successful way to organize their bodies. A multitude of animals, from worms to insects to dinosaurs to humans, are organized around this same basic bilaterian body plan.

Evolutionary biologists studying the genetics of modern animals predicted the oldest ancestor of all bilaterians would have been simple and small, with rudimentary sensory organs. Preserving and identifying the fossilized remains of such an animal was thought to be difficult, if not impossible.

For 15 years, scientists agreed that fossilized burrows found in 555 million-year-old Ediacaran Period deposits in Nilpena, South Australia, were made by bilaterians. But there was no sign of the creature that made the burrows, leaving scientists with nothing but speculation.

Scott Evans, a recent doctoral graduate from UC Riverside; and Mary Droser, a professor of geology, noticed miniscule, oval impressions near some of these burrows. With funding from a NASA exobiology grant, they used a three-dimensional laser scanner that revealed the regular, consistent shape of a cylindrical body with a distinct head and tail and faintly grooved musculature. The animal ranged between 2-7 millimeters long and about 1-2.5 millimeters wide, with the largest the size and shape of a grain of rice -- just the right size to have made the burrows. ...

FULL STORY: https://www.sciencedaily.com/releases/2020/03/200323152108.htm

See Also (UC Riverside webpage about the discovery):

https://news.ucr.edu/articles/2020/03/23/ancestor-all-animals-identified-australian-fossils

 

[EnolaGaia]

Here are the bibliographic particulars and publicly-accessible summary of the published research article:

Discovery of the oldest bilaterian from the Ediacaran of South Australia

Scott D. Evans, Ian V. Hughes, James G. Gehling, and Mary L. Droser

PNAS first published March 23, 2020
https://doi.org/10.1073/pnas.2001045117

Significance

The transition from simple, microscopic forms to the abundance of complex animal life that exists today is recorded within soft-bodied fossils of the Ediacara Biota (571 to 539 Ma). Perhaps most critically is the first appearance of bilaterians—animals with two openings and a through-gut—during this interval. Current understanding of the fossil record limits definitive evidence for Ediacaran bilaterians to trace fossils and enigmatic body fossils. Here, we describe the fossil Ikaria wariootia, one of the oldest bilaterians identified from South Australia. This organism is consistent with predictions based on modern animal phylogenetics that the last ancestor of all bilaterians was simple and small and represents a rare link between the Ediacaran and the subsequent record of animal life.

Abstract

Analysis of modern animals and Ediacaran trace fossils predicts that the oldest bilaterians were simple and small. Such organisms would be difficult to recognize in the fossil record, but should have been part of the Ediacara Biota, the earliest preserved macroscopic, complex animal communities. Here, we describe Ikaria wariootia gen. et sp. nov. from the Ediacara Member, South Australia, a small, simple organism with anterior/posterior differentiation. We find that the size and morphology of Ikaria match predictions for the progenitor of the trace fossil Helminthoidichnites—indicative of mobility and sediment displacement. In the Ediacara Member, Helminthoidichnites occurs stratigraphically below classic Ediacara body fossils. Together, these suggest that Ikaria represents one of the oldest total group bilaterians identified from South Australia, with little deviation from the characters predicted for their last common ancestor. Further, these trace fossils persist into the Phanerozoic, providing a critical link between Ediacaran and Cambrian animals.

SOURCE: https://www.pnas.org/content/early/2020/03/17/2001045117

 

[skinny]

From this

to this

in less than 557 million years?

Seems improbable.

 

[uair01]

Fossils of the Ediacara and Miaohe biotas (575–542 Ma) represent the earliest known macroscopic and complex life forms. Unlike the Miaohe biota, which is dominated by macroscopic algae preserved as carbonaceous compressions in black shale (Xiao et al., 2002), most of the Ediacara fossils are preserved as casts and molds in relatively coarse silici clastic sedimentary rocks (Narbonne, 2005). Their unusual morphology presents significant challenges for phylogenetic interpretation. Thus, they have been variously interpreted as lichens (Retallack, 1994), fungus-like organisms (Peter son et al., 2003), prokaryotes (Steiner and Reitner, 2001), stem- or crown-group animals (Glaessner, 1984; Conway Morris, 1993a; Fedonkin and Waggoner, 1997), or vendobionts that are phylogenetically distant from animals (Seilacher, 1992). Their interpretation is further complicated by their unique preservation, exemplified by the iconic Ediacara fossil Dickinsonia (Gehling et al., 2005).

Eight-armed Ediacara fossil preserved in contrasting taphonomic windows from China and Australia (2015)

We report the preservation of the eight-armed Ediacara fossil Eoandromeda octobrachiata as carbonaceous compressions in the Doushantuo black shale of south China and as casts and molds in the Rawnsley Quartzite in South Australia. ... It is the fi rst and only unambiguously identifi ed Ediacaran macrofossil that occurs in two drastically different taphonomic windows, thus bridging the conventional biological and taxonomic gaps between the Ediacara and Miaohe biotas, which collectively record the earliest known macroscopic and complex life.

How E. octobrachiata functioned remains uncertain. There is no functional morphological evidence indicating that E. octobrachiata was a fi lter feeder or a predator. Its morphology (and presumably function) is also distinct from known fossil and extant algae. The tubular arms that consist of the modular elements of E. octobrachiata suggest that surface area to volume ratio may be a critical constraint on its functional morphology. As such, E. octobrachiata was likely an absorber that acquired dissolved nutrients from the ambient environment.

 

[uair01]

A very good documentary but still no solution.