WFS

Formation of sedimentary layers of white clay, Tamilnadu, India

Fossil site for wood fossils, Tamilnadu, India

Fossil site in Kerala, India

Fossil wood park maintained by geological survey of India at Tamilnadu

Cretaceous fossil sites india

Fossils in rack:-Cyad

Fossils in rack:-echiniderms

Fossils in rack:-Rastellum sp

Pre-historic seabed, Cretaceous period

Swift Drift Of Indian Plate Explained

May 16th, 2015

Riffin

In the history of continental drift, India has been a mysterious record-holder.

More than 140 million years ago, India was part of an immense supercontinent called Gondwana, which covered much of the Southern Hemisphere. Around 120 million years ago, what is now India broke off and started slowly migrating north, at about 5 centimeters per year. Then, about 80 million years ago, the continent suddenly sped up, racing north at about 15 centimeters per year — about twice as fast as the fastest modern tectonic drift. The continent collided with Eurasia about 50 million years ago, giving rise to the Himalayas.

For years, scientists have struggled to explain how India could have drifted northward so quickly. Now geologists at MIT have offered up an answer: India was pulled northward by the combination of two subduction zones — regions in the Earth’s mantle where the edge of one tectonic plate sinks under another plate. As one plate sinks, it pulls along any connected landmasses. The geologists reasoned that two such sinking plates would provide twice the pulling power, doubling India’s drift velocity.

Himalayan mountain. Scientists found relics of what may have been two subduction zones by sampling and dating rocks from the Himalayan region. (stock image)
Credit: © Maygutyak / Fotolia

The team found relics of what may have been two subduction zones by sampling and dating rocks from the Himalayan region. They then developed a model for a double subduction system, and determined that India’s ancient drift velocity could have depended on two factors within the system: the width of the subducting plates, and the distance between them. If the plates are relatively narrow and far apart, they would likely cause India to drift at a faster rate.

The group incorporated the measurements they obtained from the Himalayas into their new model, and found that a double subduction system may indeed have driven India to drift at high speed toward Eurasia some 80 million years ago.

“In earth science, it’s hard to be completely sure of anything,” says Leigh Royden, a professor of geology and geophysics in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “But there are so many pieces of evidence that all fit together here that we’re pretty convinced.”

Royden and colleagues including Oliver Jagoutz, an associate professor of earth, atmospheric, and planetary sciences at MIT, and others at the University of Southern California have published their results this week in the journal Nature Geoscience.

What drives drift?

Based on the geologic record, India’s migration appears to have started about 120 million years ago, when Gondwana began to break apart. India was sent adrift across what was then the Tethys Ocean — an immense body of water that separated Gondwana from Eurasia. India drifted along at an unremarkable 40 millimeters per year until about 80 million years ago, when it suddenly sped up to 150 millimeters per year. India kept up this velocity for another 30 million years before hitting the brakes — just when the continent collided with Eurasia.

“When you look at simulations of Gondwana breaking up, the plates kind of start to move, and then India comes slowly off of Antarctica, and suddenly it just zooms across — it’s very dramatic,” Royden says.

In 2011, scientists believed they had identified the driving force behind India’s fast drift: a plume of magma that welled up from the Earth’s mantle. According to their hypothesis, the plume created a volcanic jet of material underneath India, which the subcontinent could effectively “surf” at high speed.

However, when others modeled this scenario, they found that any volcanic activity would have lasted, at most, for 5 million years — not nearly enough time to account for India’s 30 million years of high-velocity drift.

Squeezing honey

Instead, Royden and Jagoutz believe that India’s fast drift may be explained by the subduction of two plates: the tectonic plate carrying India and a second plate in the middle of the Tethys Ocean.

In 2013, the team, along with 30 students, trekked through the Himalayas, where they collected rocks and took paleomagnetic measurements to determine where the rocks originally formed. From the data, the researchers determined that about 80 million years ago, an arc of volcanoes formed near the equator, which was then in the middle of the Tethys Ocean.

A volcanic arc is typically a sign of a subduction zone, and the group identified a second volcanic arc south of the first, near where India first began to break away from Gondwana. The data suggested that there may have been two subducting plates: a northern oceanic plate, and a southern tectonic plate that carried India.

Back at MIT, Royden and Jagoutz developed a model of double subduction involving a northern and a southern plate. They calculated how the plates would move as each subducted, or sank into the Earth’s mantle. As plates sink, they squeeze material out between their edges. The more material that can be squeezed out, the faster a plate can migrate. The team calculated that plates that are relatively narrow and far apart can squeeze more material out, resulting in faster drift.

“Imagine it’s easier to squeeze honey through a wide tube, versus a very narrow tube,” Royden says. “It’s exactly the same phenomenon.”

Royden and Jagoutz’s measurements from the Himalayas showed that the northern oceanic plate remained extremely wide, spanning nearly one-third of the Earth’s circumference. However, the southern plate carrying India underwent a radical change: About 80 million years ago, a collision with Africa cut that plate down to 3,000 kilometers — right around the time India started to speed up.

The team believes the diminished plate allowed more material to escape between the two plates. Based on the dimensions of the plates, the researchers calculated that India would have sped up from 50 to 150 millimeters per year. While others have calculated similar rates for India’s drift, this is the first evidence that double subduction acted as the continent’s driving force.

“It’s a lucky coincidence of events,” says Jagoutz, who sees the results as a starting point for a new set of questions. “There were a lot of changes going on in that time period, including climate, that may be explained by this phenomenon. So we have a few ideas we want to look at in the future.”

Reference:

Oliver Jagoutz, Leigh Royden, Adam F. Holt, Thorsten W. Becker. Anomalously fast convergence of India and Eurasia caused by double subduction. Nature Geoscience, 2015; DOI: 10.1038/ngeo2418

Citation :Massachusetts Institute of Technology. “Mystery of India’s rapid move toward Eurasia 80 million years ago explained.” ScienceDaily. ScienceDaily, 4 May 2015. <www.sciencedaily.com/releases/2015/05/150504120815.htm>.

Chicken Embryos With Dino Snouts ?

May 15th, 2015

Riffin

Chicks with dino-snouts? With a little molecular tinkering, for the first time scientists have created chicken embryos with broad, Velociraptor-like muzzles in the place of their beaks.

The bizarrely developing chickens shed new light on how the bird beak evolved, scientists added.

The Age of Dinosaurs came to an end with a bang about 65 million years ago, due to an impact from a giant rock from space, which was probably about 6 miles (10 kilometers) across. However, not all of the dinosaurs went extinct because of this catastrophe — birds, or avian dinosaurs, are now found on every continent on Earth..

Above is an artist rendition of the non-avian dinosaur Anchiornis (left) and a tinamou, a primitive modern bird (right), with snouts rendered transparent to show the premaxillary and palatine bones.

Above is an artist rendition of the non-avian dinosaur Anchiornis with snouts rendered transparent to show the premaxillary and palatine bones.

“There are between 10,000 and 20,000 species of birds alive today, at least twice as many as the total number of mammal species, and so in many ways it is still the Age of Dinosaurs,” study lead author Bhart-Anjan Bhullar, a paleontologist and developmental biologist at Yale University, told Live Science.

Fossil discoveries have recently yielded great insights into how birds evolved from their reptilian ancestors, such as how feathers and flight emerged. Another key structure that sets birds apart from their dinosaurs ancestors is their beaks. Researchers suspect that beaks evolved to act like tweezers to give birds a kind of precision grip. The beaks help make up for the dinosaurs’ grasping arms, which evolved into wings, giving them the ability to peck at food such as seeds and bugs.

“The beak is a crucial part of the avian feeding apparatus, and is the component of the avian skeleton that has perhaps diversified most extensively and most radically — consider flamingos, parrots, hawks, pelicans and hummingbirds, among others,” Bhullar said in a statement. “Yet little work has been done on what exactly a beak is, anatomically, and how it got that way either evolutionarily or developmentally.”

To learn more about how the beak evolved, a research team led by Bhullar and developmental biologist Arkhat Abzhanov at Harvard University have now successfully reverted the beaks of chicken embryos into snouts more similar to ones seen in Velociraptor and Archaeopteryx than in birds. These embryos did not live to hatch, researchers stressed. “They could have,” Bhullar said. “They actually probably wouldn’t have done that badly if they did hatch. Mostly, though, we were interested in the evolution of the beak, and not in hatching a ‘dino-chicken’ just for the sake of it.”

Can skull shape and function determine what kind of food was on prehistoric plates?

May 12th, 2015

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When paleontologists put together a life history for a long-extinct animal, it’s common to infer the foods it ate by looking at modern animals with similar skull shapes and tooth patterns. But this practice is far from foolproof. New modeling and tests based on living species done at the American Museum of Natural History show that the link between animal diets and skull biomechanics is complex, with a stronger influence from ancestry than previously thought.

“Traditionally, when we looked at a fossilized skull with pointy piercing teeth and sharp slicing blades, we assumed that it was primarily a meat eater, but that simplistic line of thinking doesn’t always hold true,” said John J. Flynn, the Museum’s Frick Curator of Fossil Mammals and a co-author on the new work published today in the journal PLOS ONE. “We’ve found that diet can be linked to a number of factors–skull size, biomechanical attributes, and often, most importantly, the species’ position in the tree of life.”

Flynn and Z. Jack Tseng, a National Science Foundation and Frick Postdoctoral Fellow in the Museum’s Division of Paleontology, looked at the relationship between skull shape and function of five different modern carnivore species, including meat-eating “hypercarnivore” specialists such as wolves and leopards, and more omnivorous “generalists” such as mongooses, skunks, and raccoons. The initial modeling, which mapped bite force against the stiffness of the animal’s skull, yielded a surprise.

This image shows the skulls of the different species the researchers studied along with biomechanical profiles, which were made by mapping each animal’s bite force against skull stiffness. They found that ancestry has a strong influence on the models, with closely related animals like leopards and mongooses grouping together, but also that predications about diet can be made based on the shape of the individual biomechanical profiles.
Credit: Copyright AMNH/Z.-J. Tseng

“Animals with the same diets and biomechanical demands, like wolves and leopards–both hypercarnivores–were not linking together,” Tseng said. “Instead, we saw a strong signal driven mostly by ancestry, where, for example, the leopard and the mongoose bind together because they’re more closely related in an evolutionary context, although they have very different dietary preferences and feeding strategies.”

But once Tseng and Flynn accounted for the strong effects of ancestry and skull size on the models, hypercarnivores and generalists still could be distinguished based on biomechanics, in particular by looking at where along the tooth row the skull is strongest. Meat specialist skulls are stiffest when hunting with front teeth and/or slicing or crushing with back teeth, whereas skulls of generalists show incrementally increasing stiffness when biting sequentially from the front to the back of the tooth row.

The researchers then applied this improved shape-function computer model to two extinct species: Thinocyon velox, a predatory mammal that was part of the now-extinct Creodont group, and Oodectes herpestoides, an early fossil predecessor of modern carnivores,. They found that T. velox likely had a unique hypercarnivorous feeding style that allowed for skull strength at two places: prey capture with its front teeth and powerful slicing and crushing with its back teeth. The biomechanical profile of O. herpestoides, meanwhile, suggests that it was a generalist, but compared to living relatives of similar body size, it might have fed on smaller prey because of its weaker skull.

“Beyond feeding adaptations of extinct species, we also want to decipher how adaptations evolved using reconstructed ancestors of living and fossil forms,” Tseng said. “We are applying similar types of skull shape and biomechanical analyses to reconstructed hypothetical ancestor skulls of Carnivora and their relatives to map out and better understand the long history of feeding adaptation of living top predators.”

Credits: American Museum of Natural History. (2015, April 29). Can skull shape and function determine what kind of food was on prehistoric plates?.ScienceDaily. Retrieved May 11, 2015 from www.sciencedaily.com/releases/2015/04/150429145448.htm

Explosive volcanoes fueled by water

May 9th, 2015

Riffin

University of Oregon geologists have tapped water in surface rocks to show how magma forms deep underground and produces explosive volcanoes in the Cascade Range.

“Water is a key player,” says Paul J. Wallace, a professor in the UO’s Department of Geological Sciences and coauthor of a paper in the May issue of Nature Geoscience. “It’s important not just for understanding how you make magma and volcanoes, but also because the big volcanoes that we have in the Cascades — like Mount Lassen and Mount St. Helens — tend to erupt explosively, in part because they have lots of water.”

A five-member team, led by UO doctoral student Kristina J. Walowski, methodically examined water and other elements contained in olivine-rich basalt samples that were gathered from cinder cone volcanoes that surround Lassen Peak in Northern California, at the southern edge of the Cascade chain.

Mount Hood, Oregon.
Credit: © dschreiber29 / Fotolia

The discovery helps solve a puzzle about plate tectonics and Earth’s deep water cycle beneath the Pacific Ring of Fire, which scientists began studying in the 1960s to understand the region’s propensity for big earthquakes and explosive volcanoes. The ring stretches from New Zealand, along the eastern edge of Asia, north across the Aleutian Islands of Alaska and south along the coast of North and South America. It contains more than 75 percent of the planet’s volcanoes.

To understand how water affects subduction of the oceanic plate, in which layers of different rock types sink into the mantle, the UO team studied hydrogen isotopes in water contained in tiny blobs of glass trapped in olivine crystals in basalt.

To do so, the team used equipment in Wallace’s lab, CAMCOR, the Carnegie Institution in Washington, D.C., and a lab at Oregon State University. CAMCOR is UO’s Advanced Materials Characterization in Oregon, a high-tech extension service located in the underground Lorry I. Lokey Laboratories.

Next, the team fed data gained from the rocks into a complex computer model developed by co-author Ikudo Wada, then of Japan’s Tohoku University. She has since joined the University of Minnesota.

That combination opened a window on how rising temperatures during subduction drive water out of different parts of the subducted oceanic crust, Walowski said. Water migrates upwards and causes the top of the subducted oceanic crust to melt, producing magma beneath the Cascade volcanoes.

The key part of the study, Wallace said, involved hydrogen isotopes. “Most of the hydrogen in water contains a single proton,” he said. “But there’s also a heavy isotope, deuterium, which has a neutron in addition to the proton. It is important to measure the ratio of the two isotopes. We use this ratio as a thermometer, or probe, to study what’s happening deep inside the earth.”

“Melting of the subducting oceanic crust and the mantle rock above it would not be possible without the addition of water,” Walowski said. “Once the melts reach the surface, the water can directly affect the explosiveness of magma. However, evidence for this information is lost to the atmosphere during violent eruptions.”

University of Oregon. “Explosive volcanoes fueled by water.” ScienceDaily. ScienceDaily, 6 May 2015. <www.sciencedaily.com/releases/2015/05/150506125115.htm>

Archaeornithura meemannae : a new bird fossil

May 6th, 2015

Riffin

Scientists in China have described a new species of early bird, from two fossils with intact plumage dating to 130 million years ago.

Based on the age of the surrounding rocks, this is the earliest known member of the clade that produced today’s birds: Ornithuromorpha.It pushes back the branching-out of this evolutionary group by at least five million years.The little bird appears to have been a wader, capable of nimble flight.The discovery is reported in the journal Nature Communications.

Archaeornithura meemannae

Birds began to evolve from the dinosaurs some 150 million years ago at the tail end of the Jurassic period. This is the age of the famous but hotly contested “first bird” Archaeopteryx – now considered by many to be a feathered dinosaur.

Some 20 million years later, when the newfound species was wading and flitting through what would become north-eastern China, palaeontologists believe there was quite a variety of bird life.

Bare legs

About half of those species were Enantiornithes, a group of early birds with teeth and clawed wings that eventually all died out.

The other half, including the new find, were Ornithuromorpha – a group that eventually gave rise to modern birds and looked much more like them.The branching event behind that forked diversity is what the new discovery pushes back in time; previously the earliest known Ornithuromorph was 125 million years old.The well-preserved fossils included signs of the animal’s plumage

The pair of skeletons that define the new species, christened Archaeornithura meemannae, were dug up from the Sichakou basin in Hebei province.

“The new fossil represents the oldest record of Ornithuropmorpha,” said first author Wang Min, from the Chinese Academy of Sciences in Beijing. “It pushes back the origination date… by at least five million years.”

The specimens were well preserved, revealing a number of details about A. meemannae. The bird stood about 15cm tall and its legs, even on the upper regions, had no feathers, which suggests a wading lifestyle.The size and shape of its bones also suggest good manoeuvrability in the air.

Rupture along the Himalayan Front

May 4th, 2015

Riffin

In their article for Lithosphere on 12 March, authors Kristin Morell and colleagues write, “The ∼700-km-long ‘central seismic gap’ is the most prominent segment of the Himalayan front not to have ruptured in a major earthquake during the last 200-500 years. This prolonged seismic quiescence has led to the proposition that this region, with a population of more 10 million, is overdue for a great earthquake. Despite the region’s recognized seismic risk, the geometry of faults likely to host large earthquakes remains poorly understood.”

A little more than a month on, the area experience a magnitude 7.8 earthquake, centered in Nepal (25 Apr. 2015).

Date and rupture patches for large historical Himalayan earthquakes (Rajendran and Rajendran, 2005; Kumar et al., 2006) with reference to the Uttarakhand region of the central seismic gap, and the physiographic transition 2 of Uttarakhand (UPT2 ) and Nepal (NPT2 ) (Wobus et al., 2006a). (B) Simplified geologic map for area shown in A (Célérier et al., 2009a; Webb et al., 2011). Focal mechanisms of all earthquakes within the recording period (Mw 5-7) are shown with location as white circle. Earthquake locations are based on Ni and Baranzangi (1984) and the National Earthquake Information Center (NEIC) catalog (earthquake.usgs.gov). Focal mechanisms are based on Ni and Baranzangi (1984) or the Global Centroid-Moment-Tensor (CMT) catalog (globalcmt.org). STD–South Tibetan Detachment; THS–Tethyan Himalayan Sequence; MCT–Main Central Thrust; GHS–Greater Himalayan Sequence; LHS–Lesser Himalayan Sequence; MBT–Main Boundary Thrust; MFT–Main Frontal Thrust.
Credit: Morell et al. and Lithosphere

In their study, Morell and colleagues use a series of complementary geomorphic and erosion rate data to define the ramp-flat geometry of the active detachment fault that is likely to host a large earthquake within the hinterland of the northwest Himalaya. Their analysis indicates that this detachment is sufficiently large to host another great earthquake in the western half of the central Himalayan seismic gap.

Specifically, their data sets point to a distinctive physiographic transition at the base of the high Himalaya in the state of Uttarakhand, India, characterized by abrupt strike-normal increases in channel steepness and a tenfold increase in erosion rates.

When combined with previously published geophysical imaging and seismicity data sets, Morell and colleagues interpret the observed spatial distribution of erosion rates and channel steepness to reflect the landscape response to spatially variable rock uplift due to a structurally coherent ramp-flat system of the Main Himalayan Thrust. They write, “Although it remains unresolved whether the kinematics of the Main Himalayan Thrust ramp involve an emergent fault or duplex, the landscape and erosion rate patterns suggest that the décollement beneath the state of Uttarakhand provides a sufficiently large and coherent fault segment capable of hosting a great earthquake.”

In conclusion, they note, “While this hypothesis remains speculative, it is supported by independent records of historical seismicity.”

Citation:Geological Society of America. “Rupture along the Himalayan Front.” ScienceDaily. ScienceDaily, 30 April 2015. <www.sciencedaily.com/releases/2015/04/150430134933.htm>.

Journal Ref: K. D. Morell, M. Sandiford, C. P. Rajendran, K. Rajendran, A. Alimanovic, D. Fink, J. Sanwal. Geomorphology reveals active decollement geometry in the central Himalayan seismic gap. Lithosphere, 2015; DOI: 10.1130/L407.1

WFS: Ariyalur Fossils ( Arctostrea )

May 2nd, 2015

Riffin

WFS: Ariyalur Fossils ( Arctostrea ): This upper Cretaceous oyster is characterized by long and curved valves. Stout ribs cross the upper valve. The sample is obtained from Ariyalur/Dalmiapuram area. samples collected by Riffin T Sajeev and Russel T Sajeev from World Fossil society.

The Rastellum genus of oysters lived between 161 to 65 million years ago during the Jurassic and Cretaceous periods. Occurring in many locations across the globe, the Rastellum oyster species inhabited shallow marine environments such as lagoons, bioherms and biostromes, and peritidal areas exposed to air and more harsh extreme variations of temperature, salinity, and storm activity, and also lived in shallow subtidal areas, above, on, and below reefs, coastal areas, and offshore shelves along continents. Rastellum oysters would remain stationary, attached to the surfaces of rocks, pilings, and to the sea floor itself, where they would filter feed on small foods suspended in the water column. This specimen is Rastellum carinatum, a species which seems to have occurred from 144 to 65 million years ago, evidently becoming extinct during the same event that ended the reign of the dinosaurs.

Arctostrea (Rastellum Species). Specimen Collected by Riffin T Sajeev & Russel T Sajeev Of World Fossil Society .Photo Copyright@ World Fossil Society.

Phylum :	Mollusca
Class :	Bivalvia
Family :	Ostreidae
Genus :	Rastellum (Arctostrea)
Species :	carinatum (Lamarck)
Stage :	Cenomanian

Brachiopod shell shows sign of evolution

May 1st, 2015

Riffin

Researchers of Ludwig-Maximilians-Universitaet (LMU) in Munich have carried out the first detailed study of the molecular mechanisms responsible for formation of the brachiopod shell. Comparison with shell synthesis in other groups reveals the deep evolutionary roots of the process.

Brachiopods (lamp shells) are marine invertebrates, which were a highly successful and widespread group in the Palaeozoic era. Indeed, the group is best known for its rich fossil record. Some 30,000 fossil species have been described so far, and the oldest specimens date from Cambrian times, and are thus around 500 million years old. Brachiopods are now represented by comparatively few species, which are found in various regions of the world’s oceans. One of their most characteristic features is their bipartite shell. “The molecular basis of how this shell is actually built has been virtually unknown up to now,” says Professor Gert Wörheide of the Department of Earth and Environmental Sciences and the Geobio-Center at LMU. “To find out more, we have carried out the first comprehensive survey of the genes and proteins involved in shell formation in brachiopods.” The results of the study appear in the journal Genome Biology and Evolution.

Although brachiopods look very much like mollusks at first sight, they are not related to the latter. In contrast to the typical mollusk shell, their bipartite shell is not left/right symmetrical. Instead it comprises an upper (dorsal) part and a lower (ventral) ‘valve’, with the ventral valve usually being the larger. The valves are made of either calcium carbonate (calcite) or calcium phosphate in association with a diverse array of proteins and polysaccharides, which are secreted by the cells of the underlying mantle during shell formation and are incorporated into the biomineral formed. “This is why the proteins occluded within the shell can provide insights into its mode of formation,” Wörheide explains.

brachiopod shell

To gain such insights, the researchers identified the complete set of proteins (the proteome) found in the shell of the South American brachiopod Magellania venosa. This enabled them to then characterize the genes that encode the blueprints for synthesis of the proteins from the mantle tissue secreting the shell (the mantle transcriptome). “This is the first time that such a screening approach has been applied to any species of brachiopod, and it was the combination of the two methods that allowed us to identify the molecular components involved in formation of the shell,” Wörheide points out.

The results of these two types of molecular screen are of particular interest when compared with data from other groups of shell-forming organisms, such as corals, sea urchins and mollusks. The seven most abundant proteins found in the Magellania shell turn out to be unique to brachiopods, but they exhibit biochemical features similar to those of proteins that are known to serve similar functions in other animal phyla. Other proteins show significant structural resemblances to shell proteins that are known from other animals. Based on these analyses, the researchers conclude that the genetic program and the molecular mechanisms utilized in biomineralization — the biochemical processes by which living organisms synthesize mineral-based structures in a controlled manner — have, in part, been evolutionarily conserved among invertebrates. “Our results provide entirely new insights into the evolution of shell formation in the brachiopods,” Wörheide says, “and these data will also be very useful in future studies.”

WFS: Dinosaur Diary: AVIMIMUS

April 29th, 2015

Riffin

Name Means:	“Bird mimic”	Length:	5 feet (1.5 m)
Pronounced:	AYV-ee-MIME-us	Weight:	45 pounds (20 kilos)
When it lived:	Late Cretaceous – 95 MYA
Where found:	Mongolia, China

Avimimus was discovered by Russian paleontologist Sergei Mikhailovich Kurzanov during the exploration of the Joint Soviet-Mongolian paleontological expedition in the summer of 1973, at the Udan-Sayr (southern Gobi) location in Mongolia. It was a fairly complete skeleton of a bird-like theropod. With the exception of a crushed skull fragment, the bones were very well preserved. Udan-Sayr is in the foothills of the Gurvan-Sayhan mountain range. The red colored sand he deposits are 15 meters thick and can be very accurately dated. This is proven by the presence of teeth from Tarbosaurus, a carnosaur, known from the deposits of that age from various locations in the Southern Gobi. Three other partial skeletons were later recovered. It was named by Kurzanov in 1981.

Avimimus looked so much like a bird that its name literally means that it imitates a bird. It looks like a large reptilian roadrunner. Avimimus had a long, lean neck topped by a short skull that was equipped with a toothless beak and a relatively large braincase. It had long, slender back legs built for fast running. But its front limbs had not yet evolved into wings. They were lightly built and equipped with sharp, curved claws. The bones in it’s wrists were actually fused together, much like that of the modern day cockatoo. In fact, Avimimus had the ability to fold its whole arm against its body, much like the wings of a bird. Unlike a bird however, Avimimus had a long bony tail. What’s more, its pelvis resembled that of other theropods.
It was the first dinosaur to so clearly express bird features, in such large numbers. It is also the first theropods with such unusual structure of the pelvis. Such a combination of unique features places Avimimus in a category all its own.

Roadrunner – Geococcyx californianus

It is possible that Avimimus had feathers, however, deposits around its body are too coarse for such features to be preserved. However it was unearthed near other dinosaurs similar to itself, particularly Sinosauropteryx and Caudipteryx and their feathers were preserved. Even though none have so far been found, there is evidence that Avimimus could have had feathers. There are small ridges on its forearm that could be anchor points for feather shafts. Modern birds have bone “dimples” at the point of feather attachment, however the ridges present in Avimimus could be a pre-adaptation to feather attachment. Even if Avimimus did have feathers, it would seem very unlikely that it would be able to achieve flight, particularly due to its large body.

One of the great enigmas to have surfaced in the last quarter century of dinosaur paleo, Avimimus has features that could be ascribed to sauropods, hadrosaurids, basal theropods, oviraptorids, birds, and ornithomimids. Sometimes considered a chimera, recent remains indicate it was an Oviraptor.

Avimimus belonged to the:

Kingdom Animalia (animals)
Phylum Chordata (having a hollow nerve chord ending in a brain)
Class Archosauria (diapsids with socket-set teeth, etc.)
Order Saurischia – lizard-hipped dinosaurs
Suborder Theropoda – bipedal carnivores
Infraorder Coelurosauria – lightly-built fast-running predators with hollow bones and large brains
Superfamily Maniraptoriformes – advanced coelurosaurs with a fused wrist bone
Family Avimimidae
Genus Avimimus
Species portentosus (the type species, Kurzanov, 1981)
Avimimus illustration

‘platypus’ dinosaur: Vegetarian relative of T. rex

April 28th, 2015

Riffin

Although closely related to the notorious carnivore Tyrannosaurus rex, a new lineage of dinosaur discovered in Chile is proving to be an evolutionary jigsaw puzzle, as it preferred to graze upon plants.

Palaeontologists are referring to Chilesaurus diegosuarezi as a ‘platypus’ dinosaur because of its bizarre combination of characters that resemble different dinosaur groups. For example, Chilesaurus boasted a proportionally small skull, hands with two fingers like Tyrannosaurus rex and feet more akin to primitive long-neck dinosaurs.

Chilesaurus diegosuarezi is nested within the theropod group of dinosaurs, the dinosaurian group that gathers the famous meat eaters Velociraptor, Carnotaurus and Tyrannosaurus, and from which birds today evolved. The presence of herbivorous theropods was up until now only known in close relatives of birds, but Chilesaurus shows that a meat-free diet was acquired much earlier than thought.

Artist’s interpretation of Chilesaurus diegosuareziis.
Credit: Gabriel Lío

Chilesaurus diegosuarezi is named after the country where it was collected, as well as honouring Diego Suárez, the seven year old boy who discovered the bones. He discovered the fossil remains of this creature at the Toqui Formation in Aysén, south of Chilean Patagonia, in rocks deposited at the end of the Jurassic Period, approximately 145 million years ago.

Diego was in the region with his parents, Chilean geologists Manuel Suarez and Rita de la Cruz, who were studying rocks in the Chilean Patagonia, with the aim to better understand the formation of the Andes mountain range. Diego stumbled across the fossils while him and his sister, Macarena, were looking for decorative stones.

Due to Chilesaurus‘ unusual combination of characters, it was initially thought that Diego had uncovered several species. However, since Diego’s find, more than a dozen Chilesaurus specimens have been excavated, including four complete skeletons — a first for the Jurassic Period in Chile — and they demonstrate that this dinosaur certainly combined a variety of unique anatomical traits.

Most of the specimens are the size of a turkey, but some isolated bones reveal that the maximum size of Chilesaurus was around three metres long. Chilean and Argentinian palaeontologists from institutions including the University of Birmingham, along with Diego’s parents, have been studying these skeletons, with the findings published in full in Nature on April 27th.

Other features present in very different groups of dinosaurs Chilesaurus adopted were robust forelimbs similar to Jurassic theropods such as Allosaurus, although its hands were provided with two blunt fingers, unlike the sharp claws of fellow theropod Velociraptor. Chilesaurus‘ pelvic girdle resembles that of the ornithischian dinosaurs, whereas it is actually classified in the other basic dinosaur division — Saurischia.

The different parts of the body of Chilesaurus were adapted to a particular diet and way of life, which was similar to other groups of dinosaurs. As a result of these similar habits, different regions of the body of Chilesaurus evolved resembling those present in other, unrelated groups of dinosaurs, which is a phenomenon called evolutionary convergence.

Chilesaurus represents one of the most extreme cases of mosaic convergent evolution recorded in the history of life. For example, the teeth of Chilesaurus are very similar to those of primitive long-neck dinosaurs because they were selected over millions of years as a result of a similar diet between these two lineages of dinosaurs.

Martín Ezcurra, Researcher, School of Geography, Earth and Environmental Sciences, University of Birmingham said: ‘Chilesaurus can be considered a ‘platypus’ dinosaur because different parts of its body resemble those of other dinosaur groups due to mosaic convergent evolution. In this process, a region or regions of an organism resemble others of unrelated species because of a similar mode of life and evolutionary pressures. Chilesaurus provides a good example of how evolution works in deep time and it is one of the most interesting cases of convergent evolution documented in the history of life.

‘Chilesaurus shows how much data is still completely unknown about the early diversification of major dinosaur groups. This study will force palaeontologists to take more care in the future in the identification of fragmentary or isolated dinosaur bones. It comes as false relationship evidence may arise because of cases of convergent evolution, such as that present in Chilesaurus.’

Dr. Fernando Novas, Bernardino Rivadavia Natural Sciences Museum, Buenos Aires, Argentina, led the research on Chilesaurus and said: ‘Chilesaurus is the first complete dinosaur from the Jurassic Period found in Chile and represents one of the most complete and anatomically correct documented theropod dinosaurs from the southern hemisphere. Although plant-eating theropods have been recorded in North America and Asia, this is the first time a theropod with this characteristic has been found in a southern landmass.

Chilesaurus was an odd plant-eating dinosaur only to be found in Chile. However, the recurrent discovery in beds of the Toqui Formation of its bones and skeletons clearly demonstrates that Chilesaurus was, by far, the most abundant dinosaur in southwest Patagonia 145 million years ago.’

courtesy & Citation: University of Birmingham. “Bizarre ‘platypus’ dinosaur: Vegetarian relative of T. rex.” ScienceDaily. ScienceDaily, 27 April 2015. <www.sciencedaily.com/releases/2015/04/150427124631.htm>