olelog

A near-complete fossil of the (so far) oldest feathered bird-like dinosaur has been found in the Chinese province Liaoning. It has been dated to earliest late Jurassic - 151-161 million years ago - and this Anchiornis huxleyi is (it seems) older than Archaeopteryx lithographica that lived in the late Jurassic Period around 150–145 million years ago.

Long feathers cover the arms and tail, but also the feet, suggesting that a four-winged stage may have existed in the transition to birds. It is by the way not the first four-winged dinosaur found. Microraptor gui e.g. was another (with six specimens also found in the rich fossil beds of Liaoning Province in northeastern China).

Find by find provides yet more evidence that birds evolved from dinosaurs, and more links unravelling how a group of ground-dwelling flightless dinosaurs evolve to a feathered animal capable of flying. The transition from dinosaurs to birds is still poorly understood because of the lack of well-preserved fossils and, although supported by most palaeontologists, still many scientists argue that bird-like dinosaurs appear too late in the fossil record to be the true ancestors of birds. Earlier finds of Anchiornis huxleyi were much less complete, and it was previously thought to be a primitive bird, but closer inspection reveals that it should be assigned to the Troodontidae — a group of dinosaurs closely related to birds.

• http://www.nature.com/news/2009/090925/full/news.2009.949.html
  
• http://www.nature.com/nature/journal/v461/n7264/full/nature08322.html
  
• http://www.sciencedaily.com/releases/2009/09/090928205415.htm
  

In Danish:

• http://www.videnskab.dk/composite-3085.htm
  

In Norwegian:

• http://www.forskning.no/artikler/2009/september/230631
  

For some 3 billion years, single-celled life forms such as bacteria dominated the planet. Then, roughly 600 million years ago, the first multi-cellular animals appeared on the scene, diversifying rapidly. So far it was commonly assumed that animal evolution began in the ocean, with animal life adapting much later in Earth history to terrestrial environments.

Now a team of researchers studying ancient rock samples in South China has found that the first animal fossils in the paleontological record are preserved in ancient lake deposits, in the Doushantuo Formation. It may sound surprising that the first evidence of animals found is associated with lakes, a far more variable environment than the ocean. The scientists detailed their findings online July 27 in the Proceedings of the National Academy of Sciences(PNAS). The study raises questions such as what aspects of the Earth’s environment changed to enable animal evolution.

In their research, the authors focused on South China’s Doushantuo Formation, one of the oldest fossil beds that houses highly preserved fossils dated to about 600 million years ago. Taken as a whole, the Doushantuo Formation ranges from about 590 Ma at its base to about 565 Ma at its top. The studied beds have no adult fossils. Instead, many of the fossils appear as bundles of cells interpreted to be animal embryos.

Smectite is abundant in the region. Smectite is a clay mineral that normally is transformed into other types of clay in rocks of this age. The smectite in these South China rocks, however, underwent no such transformation and have a special chemistry that, for the smectite to form, requires specific conditions in the water – conditions commonly found in salty, alkaline lakes.

The rocks’ minerals and geochemistry are not compatible with deposition in seawater. Smectite is only found in some locations in South China, and not uniformly as one would expect for marine deposits. This was an important indicator that the rocks hosting the fossils were not marine in origin. Taken together, several lines of evidence indicated that these early animals lived in a lake environment.

The study raises questions such as what aspects of the Earth’s environment changed to enable animal evolution. If animals did first develop in lakes, one aspect of lake environments that could have spurred on their evolution is how much easier it is for air to percolate through them, given how much shallower they typically are than the ocean.

Reference:
Bristow et al.
Mineralogical constraints on the paleoenvironments of the Ediacaran Doushantuo Formation
Published online before print
PNAS July 29, 2009
doi: 10.1073/pnas.0901080106

• http://newsroom.ucr.edu/news_item.html?action=page&id=2144
• http://www.sciencedaily.com/releases/2009/07/090727191732.htm
• http://www.livescience.com/animals/090727-first-life.html
• http://news.softpedia.com/news/Early-Animals-Lived-in-Lakes-not-Oceans-117691.shtml
• http://www.terradaily.com/reports/Earliest_Animals_Lived_In_A_Lake_Environment_999.html
• http://news.yahoo.com/s/livescience/oldestanimalfossilsfoundinlakesnotoceans

This post is about slime - microbial slime (mucilage), better known as biofilm. Biofilms are formed by single-celled microorganisms living together in large communities and connected to each other through slime that also functions as an community-internal transport mechanism. Biofilms can contain many different types of microorganism, where each group perform specialised biochemical functions. However, some organisms will form monospecies films under certain conditions. The slime or matrix protects the cells within it and facilitates communication among them through biochemical signals. Some biofilms have been found to contain water channels that help distribute nutrients and signalling molecules. This matrix is strong enough that under certain conditions, biofilms can become fossilized.


Biofilm in Yellowstone National Park. Longest raised mat area is about half a meter long. Image: Wikipedia.

In the geological record biofilms are (so far) mainly known from stromatolites.


Modern stromatolites in Australia. Image: Wikipedia

Fossil stromatolites are connected with carbonates (like limestone). Stromatolites are threadlike cyanobacteria that grow upward through sediment as carbonate mud and sand are trapped.

Modern sandy tidal flats are widely overgrown by a great variety of biofilms (especially of cyanobacteria). The microbes form thin, organic coatings around individual (siliclastic, that is noncarbonate) sand grains at the sedimentary surface. The biofilms contain adhesive mucilages that enable the microorganisms to attach themselves to solid substrates (such as the surface of a quartz grain), to transport nutrients toward the cell, and to buffer
the microbes against the changing salinities in their microhabitat. During times of little water movement, the biofilms continue to grow.

Quite similar microbial mats also existed about 3000 million years ago. Already in the 1980s–1990s, it was suggested that crinkled upper bedding planes (“elephant skin textures”) might record ancient microbial mats. The term “microbially induced sedimentary structures” (MISS) was coined in 1996, based on quantitative analyses of mat-related structures in sandy tidal flats. Systematic studies, leading from modern to increasingly older deposits, have revealed that fossil MISS occur in tidal flat and shelf sandstones of Phanerozoic, Proterozoic, and Archean ages and appear not to have changed identifiably for at least 3200 million years.

MISS arise exclusively from the interaction of biofilms and microbial mats with the physical sediment dynamics, which contrasts with the formation of stromatolites, in which chemical precipitation plays a major role. Because of their unique biotic-physical genesis, MISS differ significantly in morphology from stromatolites.

A paper in the October 2008 issue of GSA Today (open access) deals with such microbial mats under the title “ Turbulent lifestyle: Microbial mats on Earth's sandy beaches—Today and 3 billion years ago”.

The 2900 million year old Pongola Supergroup in South Africa includes MISS that possibly point to the oldest known cyanobacterial community preserved in Earth’s history. MISS are found in equivalent settings throughout Earth’s history, and the recently detected Nhlazatse Section of the Pongola Supergroup shows that neither morphologies nor distributions of MISS have changed for at least 2900 million years.

“Microbially induced sedimentary structures” (MISS) are adding to our knowledge of both past life and palaeo-environments. Research on MISS is still in its infancy, and reports on modern and fossil occurrences are likely to increase as the research matures.

• http://www.gsajournals.org/perlserv/?request=get-abstract&doi=10.1130%2FGSATG7A.1
• http://www.uta.edu/paleomap/homepage/Schieberweb/microbial_mat_page.htm
• http://en.wikipedia.org/wiki/Microbial_mat

A couple of years ago I studied a large variety of fabulous billion year old stromatolites somewhere in South Africa, probably at the outskirts of the Kalahari Desert. A couple of weeks later (still in South Africa) I saw new (and thus certainly not yet fossilised) dried-out microbial mats in a dry river bed.

I was in Berlin all last week. The timing was not optimal. The weather was bad and public transports were striking. Fortunately the natural history museum - Museum für Naturkunde - is in walking distance from the main station, indoors, and well worth a visit. The exhibitions include the famous Berlin specimen of the Archaeopteryx, which may well be the most famous fossil in the world. It is well worth mentioning that they exhibit the original, and not just a mould (or cast or replica or whatever they are called).

My photo here is of such a mould exhibited in a museum at Solnhofen, and thus not far from where the fossil was discovered in 1876 or 1877. Archaeopteryx lived in the late Jurassic Period around 155–150 million years ago. It is considered an important link between dinosaurs and birds, and has been called things like “a flying dinosaur” or “the first bird”. Similar in size and shape to a European Magpie, Archaeopteryx could grow to about 50 centimetres in length. Despite its small size, broad wings, and ability to fly, Archaeopteryx has more in common with small theropod dinosaurs than it does with modern birds.

This next image shows a model of Archaeopteryx lithographica on display at the Oxford University Museum.

I find it interesting to follow the evolution from feet to wings, and of course from hair to feather - two important steps towards flying. In fact the name Archaeopteryx is derived from the Ancient Greek archaios meaning 'ancient' and pteryx meaning 'feather' or 'wing'. Three fingers still had claws.

In the year 2000 palaeontologists found tiny feathers encased in a lump of amber in a quarry in the Poitou-Charentes region of France. The seven feathers are ca. a hundred million years old (Early Cretaceous, Late Albian) and have features of both feather-like fibers found with some two-legged dinosaurs known as theropods and of modern bird feathers. This is yet another link in or proof of the gradual evolution of feathers from the primitive filaments of some theropod dinosaurs to the modern feathers of Archaeopteryx and Cretaceous birds.

The work is reported in the Proceedings of the Royal Society, Biological Sciences, of 7 March 2008 under the title
“The early evolution of feathers: fossil evidence from Cretaceous amber of France”.

And finally below an image of a reconstruction of the Archaeopteryx skeleton from the Berlin museum.


My earlier post on the Berlin Museum für Naturkunde is here and on the Archaeopteryx here.

• http://journals.royalsociety.org/content/102024/?k=Perrichot+feathers
• http://www.ncbi.nlm.nih.gov/pubmed/18285280
• http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=&xml=/earth/2008/02/20/scidino120.xml
• http://news.nationalgeographic.com/news/2008/03/080311-amber-feathers.html