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Posts tagged with "Palaeontology"

Oldest Feathered Dinosaur

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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.



In Danish:


In Norwegian:




Academics

Is Paleodictyon a Living Fossil?

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A team of a dozen scientists now report new in situ observations and laboratory studies of specimens of a small (diameter 2.4–7.5 cm) strikingly hexagonal form originally described from sedimented steps in a wall of the axial valley of the Mid-Atlantic Ridge (water depth 3430–3575 m) near 26°N, 45°W that appears to be identical to the iconic form Paleodictyon nodosum described as a trace fossil from Eocene flysch deposits at sites in Europe and Wales.


(This photo of Paleodictyon is from the Benkovac Stone Unit. The Late Eocene Benkovac Stone Member of the Promina Formation of northern Dalmatia, Croatia, is a thinly bedded succession of alternating carbonate sandstones and calcareous mudstones, ca. 40 m thick, exposed as a narrow, SE-trending outcrop belt near the town of Benkovac. The Eocene was an epoch from ca. 56 - 34 million years ago.)

The team has gathered enough evidence to prove that the organism represents one of the world’s oldest living fossils, perhaps the oldest. The ancestors of the creature, Paleodictyon nodosum, go back to the dawn of complex life. And the creature itself, known from fossils, was once thought to have gone extinct some 50 million years ago.

So far it has not been possible to capture one of the creatures alive. It thrives in restricted areas of Atlantic seabed. Its only visible feature consists of tiny holes arranged in six-sided pattern. Until the real creature has been caught the scientists still vigorously debate what it is. The main question is whether the hexagonal patterns are burrows or body parts, vacant residences or animal remains.

The new paper seeks no consensus on the question of whether the holes and subsurface networks represent burrows or body parts. Dr. Seilacher, who backs the burrow idea, sees the tunnels as a kind of farm where an unknown type of worm or other organism raises micro-organisms to eat, while Dr. Rona sees the holes as body parts, perhaps from a type of compressed sponge. The lack of biological clues, he said in an interview, may arise because microbial predators eat the remains after the creatures die.

Reference:
Rona et al.
Paleodictyon nodosum: A living fossil on the deep-sea floor
doi:10.1016/j.dsr2.2009.05.015
(Article in Press)





AcademicsTop Blogs

Did Earliest Animals Live In Lakes?

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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



AcademicsTop Blogs

Mammals Eating Dinosaurs

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The Mesozoic Era from about 251 - 65 million years ago was the age of the dinosaurs. After their extinction the mammals took over. But the story is, as usual, not as simple as that. Although the dinosaurs dominated in the Mesozoic, the first mammals actually turned up only about 10 million years later than the first dinosaurs.

Repenomamus was an opossum-sized mammal about 1 m long and weighing around 14-15 kg living around 130 million years ago.


In China a fossil of Repenomamus robustus was discovered a few years ago with the remains of a juvenile psittacosaur in its stomach area. This fossil is a direct evidence that some primitive mammals fed on small vertebrates, including young dinosaurs.


Repenomamus giganticus was of similar size as Repenomamus robustus but a little bit larger, and thereby the largest mammal known from the Cretaceous (circa 145.5 ± 4 to 65.5 ± 0.3 million years ago).

The dinosaur-eating mammal fossil was found in the Liaoning Fossil Beds in China, sometimes called a Mesozoic Pompeii. Consisting of layers of volcanic and sedimentary rock, the Yixian Formation in China's Liaoning Province has yielded an enormous variety of fossil fish, birds, insects, reptiles, shrimp, flowers, mammals, and dinosaurs dating back to the late Jurassic (the Jurassic period extends from about 199.6± 0.6 to 145.5± 4 million years ago) and early Cretaceous periods-more than 128 million years ago. At that time, the region was dotted with freshwater lakes, streams, rivers, and volcanoes. Volcanic explosions rained fine ash into the lakes, and animals that died or fell into the water were quickly buried in the fine-grained sediment at the bottom where they were preserved with remarkable detail.

Both illustrations are from Wikipedia.

http://www.nature.com/nature/journal/v433/n7022/full/nature03102.html
http://www.amnh.org/science/papers/mesozoic_mammal.php
http://news.bbc.co.uk/2/hi/science/nature/4165973.stm




Academics

Microbial Mats - a Slimy Story?

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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.




Molecular Palaeontology - Dinosaurs & Birds

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Julia (The Ethical Palaeontologist) has already commented on the Science article Molecular Phylogenetics of Mastodon and Tyrannosaurus rex here and here.

There is not much meat on the article itself, it is just one single page, so it may be no surprise, that the media add lots of feathers. Never the less I found the article quite interesting because of the method used to confirm the relationship between dinosaurs and birds.

Evidence of close evolutionary relationships among birds and non-avian dinosaurs have been accumulating for a long time. See a.o. my post on the Archaeopteryx - probably the most famous fossil, and considered an important link between dinosaurs and birds.

In 2005 it became known that a group of dinosaur researchers had discovered soft tissues in fossil Tyrannosaurus rex bone unearthed in 2003 by Jack Horner in the Hell Creek Formation in Montana, USA. As the bone was 68 million years old it is surprising to have found still elastic soft tissues looking like blood vessels and cells. We are not talking Jurassic park and no DNA could be analysed. By using mass spectrometry protein sequenced from collagen were however detected. Collagen is a protein that is the basic building block of connective tissues.

Phylogenetics is the classification of organisms based on how closely they are related in terms of evolutionary differences - or in other words the construction of a (phylogenetic) tree structure, a diagram that represent the evolutionary tree of life. A tree of life for the 22 organisms compared in the study is shown in figure 1 of the article. For those of you who do not have access to Science I can refer to this account - NB in Norwegian - of the article, where the figure is shown. Please do note that this tree does not indicate that chicken “descended from the fearsome Tyrannosaurus rex” as mentioned in the heading of Sun here, but merely that Tyrannosaurus, Ostrich (Struthio) and Chicken (Gallus gallus) are related (within the taxon Archosauria). I have redrawn the Archosauria bit from the figure.

A serious problem with using molecular methods, be it on DNA or collagen, is that the samples are extremely easily contaminated (from other organisms, including living species). Furthermore fossil material is destroyed by the analysis, and the analysis is expensive. Of course nondestructive examination of unique fossils are preferred if possible.

Molecular palaeontology in the modern sense probably began with a report by Abelson in 1956 of the recovery of proteinaceous components of fossils. As technology expanded and increased in accuracy, sensitivity, and reliability, new analytical methods began to be applied to fossil material. A piece on the future of molecular paleontology by Mary Highby Schweitzer is found here.

http://www.livescience.com//animals/080424-dino-birds.html
http://www.msnbc.msn.com/id/24297066/
http://www.eurekalert.org/pub_releases/2008-04/hu-mac041808.php
http://www.thesun.co.uk/sol/homepage/news/article1087903.ece
http://palaeo-electronica.org/2002_2/editor/r_and_p.htm



Most Famous Fossil?

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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




Largest Known Mammal

The heaviest, longest, highest mammal ever known to have existed is the Indricotherium.

Indricotherium is a genus of extinct mammals that lived in Asia during the late Oligocene and early Miocene epoch of the Tertiary Period (37-32 million years ago). Indricotherium is the largest land mammal known, rivalling in size with the gigantic Mammuthus sungari. The mean size of adults is estimated to have been 5.2 m tall, 8.2 m in length and a weight of about 15 tons. It was a herbivore that stripped leaves from trees with its down-pointing, tusk-like upper teeth that occluded forward-pointing lower teeth. It could probably reach vegetation in 8 m height.

Indricotherium is named after a mythical Russian beast called the "indrik", considered the most powerful creature and the father of the animals.

Indricotherium appears in episode 3 of the BBC series Walking with Beasts as the main character.

http://en.wikipedia.org/wiki/Indricotherium
http://www.prehistory.com/indricth.htm
http://www.abdn.ac.uk/mammal/land.shtml
http://www.ocellated.com/2006/01/09/indricotherium/





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