geozoic:

Andrea “Tracemaker” Baucon 

“Garden of Life”

Pteridinium

paleopedia:

The frond-shaped organism, Charnia (1958)

Phylum : Petalonamae
Genus : Charnia
Species : C. masoni

• Precambrian (579 - 555 Ma)
• 20 cm tall
• England

Charnia is a highly significant fossil for several reasons. Firstly it is the first fossil that was ever described that came from undoubted Precambrian rocks. Until this point the Precambrian was thought to be completely devoid of fossils and consequently possibly of life. Despite similar fossils being unearthed in the 1930s (in Namibia) and the 1940s (in Australia) these forms were assumed to be of Cambrian age and so were considered unremarkable at the time. Secondly, Charnia has become an enduring image of Precambrian animals. Originally interpreted as an alga (Ford), it was spectacularly recast as a sea pen (a sister group to the modern soft corals) from 1966 onwards (Glaessner). With this image of Precambrian sea pens in mind, the gates were open for the recognition of many other of the major animal groups in the Precambrian. However, this sea pen interpretation has recently been discredited, and the current “state of the art” is something of a “statement of ignorance”.

An increasingly popular theory has arisen since the mid-1980s, following the work of Prof Adolf Seilacher who suggested that Charnia belongs to an extinct group of unknown grade that was confined to the Ediacaran Period. This theory suggests that almost all the forms that have been postulated to be members of many and various modern animal groups are actually more closely related to each other than anything else. This new group was termed the Vendobionta, a clade whose position in the tree of life is unclear, perhaps united by its construction via unipolar iterations of one cell family.

paleopedia:

The Dickinsonia (1947)

Phylum : Proaticulata
Class : Dipleurozoa
Family : Dickinsoniidae
Genus : Dickinsonia
Species : D. costata, D. lissa, D. tenuis, D. menneri, D. rex

• Precambrian (560 - 555 Ma)
• 1 cm - 1,4 m long

Dickinsonia was first described by Reg Sprigg, the original discoverer of the Ediacaran biota in Australia, who named it after Ben Dickinson, then Director of Mines for South Australia, and head of the government department that employed Sprigg.

Dickinsonia is known from unskeletonised impressions in late Ediacaran quartz sandstones in Ediacara and elsewhere in the Flinders Ranges of South Australia, as well as, Podolia of Ukraine, and the White Sea area and Central Urals of Russia, and has an estimated time range of 560-555 Myr.

Dickinsonia is a “resistant” fossil – that is to say, it is preserved as a (usually concave) cast on the underside of overlying bedding planes—unlike most Ediacaran fronds. Where part and counterparts of the same impression are known, they are separated by as much as 3 mm, with the ribbing most prominent on the top surface; this suggests that the ornament was displayed on the top surface only, and that underlying sand supported the impression.

Arcing trackways of Dickinsonia fossils, termed Epibaion, have been found, but their interpretation too is insecure. They may be impressions the organism made while it rested on the sediment surface – perhaps by secreting slime in order to form a platform on the underlying microbial mat,or by sitting and dissolving the underlying microbes in order to devour them. They have also been interpreted as “tumble tracks” created by an organism rolling along the sea floor, perhaps as it was buffeted by currents, and as the bases of lichens or “mushrooms arranged in fairy rings”. However, in some cases these trackway imprints overlap. Ridges apparently produced by the channelling of sediment in digestive tubes seem to indicate that the trackways do indeed represent feeding traces; the sedimentary disturbance expected of tumbling-induced impressions is not observed.

Halo-like “reaction rims” surround specimens. Adjacent specimens deform as if to avoid entering their neighbour’s halo, suggesting they competed with one another. No body fossils have been found to overlap.

Some spectacular fossils which can be attributed to Dickinsonia appear to preserve internal anatomy, believed to represent a tract that both digested food and distributed it throughout the organism.

The organisms are preserved in positive or negative relief, usually in coarse sandstone, and are usually preserved by virtue of imprinting on microbial mats, though their preservation may also reflect the abundance of aerobic environments or microbial pyritisation in the Ediacaran era—or, if they are protists, possibly agglutination (although this hypothesis is not mainstream).

Where Dickinsonia is found to be folded or bent, it is not deformed in a brittle manner, as a “death mask” would be; indeed, it is not very flexible at all.

The height of the specimens preserved bears little relation to their length or width, suggesting that the mode of decay resembled that of a lichen, leaf or mushroom. Assuming their pneus were originally cylindrical, they were more rigid than worms, jellyfish or logs.

Organisms of all sizes are found on bedding plane assemblages; this shows that they were commonly preserved in life position, as currents would preferentially remove smaller specimens.Further, their preservation on the top of certain sedimentary structures shows that they must have been firmly attached to the substrate at their time of burial.

Dickinsonia is found in sedimentary beds 8 mm thick; allowing for compaction, this allows these specimens a maximum height of 1 cm.

mucholderthen:

Translucent swimmers, comb jellies come in a variety of forms. New genetic data suggest that these relatively complex animals may have evolved before, not after, sponges.

[Credit: Clockwise from top left: L.L. Moroz & M. Citarella/Univ. of Florida; Dimijian Greg/Getty Images;  Ingo Arndt/Minden Pictures/Corbis; Boris Pamikov/Shutterstock; Dimijian Greg/Getty Images; Casey Dunn/Brown Univ.]
________________________________________

COMPLEXITY MAY EVOLVE MORE OFTEN THAN WE THINK
[Selections from:  ”Evolutionary enigmas Comb jelly genetics suggest a radical redrawing of the tree of life” by Amy Maxmen in Science News May 2, 2013 - Print edition: May 18, 2013; Vol.183 #10 (p. 20)]
Go to article …

Comb jellies [phylum Ctenophora] are gelatinous like jellyfish, but the similarity ends there. In body plan, jellyfish resemble the largely sessile, almost plantlike sea anemones, corals and other cnidarians: a group that dates back at least 550 million years. While jellyfish and other cnidarians have nerve cells that form a loose network in their bodies, comb jellies have a more sophisticated nervous system with a rudimentary brain and cellular connections called synapses that are also found in flies, humans and most other animals.

Yet, detailed looks at the genomes of two species of comb jellies suggest, surprisingly, that they are the more primitive animals, and not the jellyfish, sea anemones or corals, as has long been thought. It’s even possible that the sophisticated comb jelly lineage may have evolved before the brainless, gutless, muscle-less sea sponges. …

The notion that comb jellies may elbow out sponges from the base of the animal tree of life is a radical one. If true, it means that comb jellies evolved nerves, muscles and other complex features, which in some ways resemble our own, independent of the ancestor that led to most animals.

Alternatively, and even more difficult for biologists to accept, is the possibility that the last common ancestor of all animals might have possessed complex features that remained in the comb jellies but were lost without a trace in the sponges, jellyfish and their kin. Both options muddle traditional assumptions that multifaceted features do not pop up and vanish willy-nilly over evolutionary time. …

• Leonid Moroz, a neurobiologist at the University of Florida’s Whitney Laboratory for Marine Bioscience in St. Augustine, recently sequenced the genome of the sea gooseberry comb jelly, Pleurobrachia bachei. The new genetic findings imply that “there may be many ways to make a complex animal,” he says.
• Others disagree. “It would be remarkably fascinating if comb jellies evolved neurons and muscles independently, and astonishing if they were at the base of the tree,” says Graham Budd, a paleontologist at Uppsala University in Sweden. “It is effectively saying animals evolved twice. Frankly, I’m not ready to believe it.”

(Evolutionary enigmas | Science News)

mucholderthen:

Time Scale
by *Banvivirie  [Rachel Caauwe]

(via scientificillustration)

This year’s International Chronostratigraphic Chart. 

mucholderthen:

Origin & Development of Life Visual - Encyclopaedia Universalis

Times Atlas of the world (concise edition) 6th Ed. Hammond World Atlas Corporation.

First published in 1982, this book has become a classic of reference publishing around the globe.

The acknowledgements section gives picture credit to “Encyclopaedia Universalis”.

Seems like this is pretty dated, but the layout, coloring, etc. - gorgeous!

Look closely and you’ll see some Ediacarans on there. 

atanapotnia:

…. as well as an excess of Sculpey and an obsession with the Ediacaran biota…

If it is, ah well, I’ve done it anyway. The group is called All Things Pertaining to the Ediacaran Era and could become an interesting place for discussion and updates. 

geologicaltravels:

2011: Flinders Ranges

(via geologyrocks)