Earliest known dinosaur discovered in London museum

Earliest known dinosaur discovered in London museum - A fossil in the museum's collection has been identified as a dinosaur that lived 245 million years ago, 10 to 15 million years earlier than previously thought. - Researchers have found what could be the earliest known dinosaur to walk the Earth lurking in the corridors of London's Natural History Museum.

A mysterious fossil specimen that has been in the museum's collection for decades has now been identified as most likely coming from a dinosaur that lived about 245 million years ago - 10 to 15 million years earlier than any previously discovered examples.

The creature was about the size of a Labrador dog and has been named Nyasasaurus parringtoni after southern Africa's Lake Nyasa, today called Lake Malawi, and Cambridge University's Rex Parrington, who collected the specimen at a site near the lake in the 1930s.

"It was a case of looking at the material with a fresh pair of eyes," Paul Barrett from the Natural History Museum, who worked on the study, told Reuters. "This closes a gap in the fossil record and pushes back the existence of dinosaurs."

The London fossil was studied by researchers in the 1950s but no conclusion was reached and nothing was published, said Barrett. "It was a mystery what it was ... It just became this mythical animal."

Two features of the London fossil, together with a similar sample subsequently spotted at the Iziko South African Museum in Cape Town, are strong evidence that the animal belongs with the dinosaurs, the researchers said.

The bone tissues in the upper arm show marks of rapid growth, common in dinosaurs, and they also have a feature known as an elongated deltopectoral crest that anchored the upper arm muscles, a feature unique to dinosaurs.

"Although we only know Nyasasaurus from fossil fragments, the anatomy of its upper arm bone and hips have features that are unique to dinosaurs, making us confident that we're dealing with an animal very close to dinosaur origin," said Barrett.

The researchers believe Nyasasaurus probably stood upright, was a meter tall at the hip, 2-3 meters long from head to tail, and weighed 20-60 kg.

When it was alive, the world's continents were joined in a vast landmass called Pangaea, and the area of Tanzania where the fossils were found would have been part of the southern Pangaea that included Africa, South America, Antarctica and Australia.

Theorists have long argued there should have been dinosaurs walking the Earth in the Middle Triassic period, which ended about 237 million years ago, but until now the evidence has been ambiguous, said Sterling Nesbitt at the University of Washington in Seattle who led the study, published in the journal Biology Letters.

"If the newly named Nyasasaurus parringtoni is not the earliest dinosaur, then it is the closest relative found so far," said Nesbitt.

"What's really neat about this specimen is that it has a lot of history. Found in the '30s, first described in the 1950s ... Now 80 years later, we're putting it all together."

The researchers plan further field work in Tanzania to find more fossils and build a better picture of the animal's anatomy. ( msn.com )

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Canada’s newest horned dinosaur

Meet Xenoceratops: Canada’s newest horned dinosaur - Scientists have named a new species of horned dinosaur (ceratopsian) from Alberta, Canada, named Xenoceratops foremostensis. Dr. Michael Ryan, curator of vertebrate paleontology at The Cleveland Museum of Natural History, was lead author on research describing the new species.

Scientists have named a new species of horned dinosaur (ceratopsian) from Alberta, Canada. Xenoceratops foremostensis (Zee-NO-Sare-ah-tops) was identified from fossils originally collected in 1958. Approximately 20 feet long and weighing more than 2 tons, the newly identified plant-eating dinosaur lived 78 million years ago and represents the oldest known large-bodied horned dinosaur from Canada. Research describing the new species is published in the October 2012 issue of the Canadian Journal of Earth Sciences.

“Starting 80 million years ago, the large-bodied horned dinosaurs in North America underwent an evolutionary explosion,” said lead author Dr. Michael Ryan, curator of vertebrate paleontology at The Cleveland Museum of Natural History. “Xenoceratops shows us that even the geologically oldest ceratopsids had massive spikes on their head shields and that their cranial ornamentation would only become more elaborate as new species evolved.”

Xenoceratops (Xeno + ceratops) means “alien horned-face,” referring to the strange pattern of horns on its head and the scarcity of horned dinosaur fossils from this part of the fossil record. It also honors the Village of Foremost, located close to where the dinosaur was discovered. Xenoceratops had a parrot-like beak with two long brow horns above its eyes. A large frill protruded from the back of its skull featuring two huge spikes.

“Xenoceratops provides new information on the early evolution of ceratopsids, the group of large-bodied horned dinosaurs that includes Triceratops,” said co-author Dr. David Evans of the Royal Ontario Museum and University of Toronto. “The early fossil record of ceratopsids remains scant, and this discovery highlights just how much more there is to learn about the origin of this diverse group.”

The new dinosaur is described from skull fragments from at least three individuals from the Foremost Formation originally collected by Dr. Wann Langston Jr. in the 1950s, and is currently housed in the Canadian Museum of Nature in Ottawa, Canada. Ryan and Evans stumbled upon the undescribed material more than a decade ago and recognized the bones as a new type of horned dinosaur. Evans later discovered a 50-year-old plaster field jacket at the Canadian Museum of Nature containing more skull bones from the same fossil locality and had them prepared in his lab at the Royal Ontario Museum.

This dinosaur is just the latest in a series of new finds being made by Ryan and Evans as part of their Southern Alberta Dinosaur Project, which is designed to fill in gaps in our knowledge of Late Cretaceous dinosaurs and study their evolution. This project focuses on the paleontology of some of the oldest dinosaur-bearing rocks in Alberta, which is less intensely studied than that of the famous badlands of Dinosaur Provincial Park and Drumheller.

“This discovery of a previously unknown species also drives home the importance of having access to scientific collections,” says co-author Kieran Shepherd, curator of paleobiology for the Canadian Museum of Nature, which holds the specimen. “The collections are an untapped source of new material for study, and offer the potential for many new discoveries.”

Xenoceratops was identified by a team comprising palaeontologists Dr. Michael J. Ryan, curator of vertebrate paleontology at The Cleveland Museum of Natural History; and Dr. David Evans, curator, vertebrate palaeontology of the Department of Natural History at the Royal Ontario Museum; as well as Kieran Shepherd, curator of paleobiology for the Canadian Museum of Nature. Their findings are published today in the Canadian Journal of Earth Sciences (CJES). ( PRWeb )

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2-Ton 'Alien' Horned Dinosaur Discovered

2-Ton 'Alien' Horned Dinosaur Discovered - Paleontologists in Canada have discovered fossils of a new 2-ton, 20-foot-long horned dinosaur that roamed the Earth about 80 million years ago. And its headgear would've put on quite a show for the ladies.

The dinosaur, a distant cousin of Triceratops called Xenoceratops foremostensis, is one of the oldest specimens known to date of the ceratopsid group. The beast's name, Xenoceratops, translates to "alien horned-face," referring to its strange pattern of horns on its head and above its brow, and the rarity of such horned dinosaurs in this part of the fossil record.

"It seems to have the general types of ornamentation that we see taken to even greater extremes in later ceratopsids," said David Evans, a paleontologist at the Royal Ontario Museum. "That suggests the elaborate headgear evolved earlier."

A dinosaur in a drawer

In 1958, paleontologist Wann Langston Jr. discovered fragments of three skulls (now known to belong to Xenoceratops) in a rock formation in the badlands of Alberta, Canada. Though the area is now scrubby woodlands filled with hoodoos and sandstone hills, between 77 million and 90 million years ago, the dinosaur's stomping grounds were part of a river system filled with lush vegetation.

But Langston was busy with other discoveries, so he tossed the fossil fragments into a drawer at the Canadian Museum of Nature in Ottawa and promptly forgot about them.

In 2003, Evans and his colleagues learned of the fragments. The team was trying to fill in gaps in the fossil record for the late Cretaceous Period, when some of the most iconic dinosaurs, such as Tyrannosaurus rex and Triceratops, evolved.

As they pieced together the skull fragments and analyzed the distinctive ornamentation on the skull, they realized that Xenoceratops was a completely new species.

"The frills and hooks are the calling card of the ceratopsian species," Evans told LiveScience. "We knew instantly that it was a brand new type of horned dinosaur."

Oddities evolve

Xenoceratops was about the size of a rhinoceros — about 20 feet (6 meters) long including the tail — and weighed about 2 tons, Evans said. The dinosaur used its birdlike beak to graze on the cattails, ferns and flowers in primeval river deltas.

The species most distinct feature, however, is its spiky head: Two hooks jutting from its forehead, two massive spikes rest at the top of its head and a frilly shield adorns its neck.

The new species helps fill in a gap in the evolutionary record, said Andrew Farke, a paleontologist at the Raymond M. Alf Museum of Paleontology in Claremont, Calif.

"The bits of anatomy that are preserved on this species give us a lot of great information about how horned dinosaurs as a group evolved," said Farke, who was not involved in the study.

The stags of the dinosaur world, male Xenoceratops probably used their outlandish headgear to show dominance or impress the females, increasing their odds of reproducing, Evans said.

"Evolution sometimes produces some pretty amazing -- and sometimes really bizarre -- structures that maybe to us don't seem particularly attractive and menacing," Evans said. "But at the same time they were really important for that species to reproduce." ( LiveScience.com )

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Ancient 'Predator X' Sea Monster Gets Official Name

Ancient 'Predator X' Sea Monster Gets Official Name - A giant, marine reptile that roamed the seas roughly 150 million years ago is a new species, researchers say. The animal, now named Pliosaurus funkei, spanned about 40 feet (12 meters) and had a massive 6.5-foot-long (2 m) skull with a bite four times as powerful as Tyrannosaurus rex.

"They were the top predators of the sea," said study co-author Patrick Druckenmiller, a paleontologist at the University of Alaska Museum. "They had teeth that would have made a T. rex whimper."

 

P. funkei likely preyed on plesiosaurs, related long-necked, small-headed reptiles.

Combined with other fossil finds, the newly discovered behemoth skeletons of P. funkei paint a picture of an ancient Jurassic-era ocean filled with giant predators.

In 2006, scientists unearthed two massive pliosaur skeletons in Svalbard, Norway, a string of islands halfway between Europe and the North Pole. The giant creatures, one of which was dubbed Predator X at the time, looked slightly different from other pliosaurs discovered in England and France over the last century and a half.

Now, after years of painstaking analysis of the jaw, vertebrae and forelimbs, the researchers have determined that Predator X is in fact a new species, and they have officially named it for Bjorn and May-Liss Funke, volunteers who first discovered the fossils.

The pliosaurs, marine reptiles that prowled the seas 160 million to 145 million years ago during the Jurassic period, had short necks, tear-shaped bodies and four large, paddle-shaped limbs that let them "fly through the water," Druckenmiller told LiveScience.

The new species likely lived closer to 145 million years ago and ate plesiosaurs, related long-necked, small-headed reptiles.

The new analysis shows P. funkei had proportionally longer front paddles than other pliosaurs, as well as slightly different vertebrae shape and different spacing of teeth within the jaw, Druckenmiller said.

In 2008, scientists initially estimated that Predator X could have been up to 50 feet (15 m) long. The current study suggests the creature is smaller than that, but still bigger than the largest living apex predator, the killer whale, which tops out at about 30 feet (9 m) long, Druckenmiller said.

The Pliosaurus funkei fossils were just two of nearly 40 specimens discovered at the Svalbard site. In the Oct. 12 issue of the Norwegian Journal of Geology, the authors also describe two new ichthyosaurs, or dolphinlike reptiles, the longest-necked Jurassic-era plesiosaur on record, and several invertebrates.

Together, the fossils suggest an ancient Arctic sea teeming with fearsome predators and invertebrate fauna, said study co-author Jorn Hurum of the University of Oslo in an email.

"It's not just that we found a new species, we've been discovering a whole ecosystem," Druckenmiller said. ( LiveScience.com )

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'Dracula' Dinosaur Had Bristles and Fangs

'Dracula' Dinosaur Had Bristles and Fangs - A bizarre dinosaur had vampire-like fangs, a parrot beak and porcupine bristles, researchers say.

The ancient creature, which was found 50 years ago in southern Africa but drew relatively little attention until now, may shed light on the evolution of the major group of dinosaurs that included famous giants such as Stegosaurus and Triceratops.

The 200-million-year-old dinosaur "was two-legged, probably fleet-footed, and had grasping hands," said researcher Paul Sereno, a paleontologist at the University of Chicago.

 

This is a Heterodontosaurus flesh model and skull. Skin, scales and quills are added to a cast of the skull of Heterodontosaurus, the best known heterodontosaurid from South Africa.

Named Pegomastax africanus, or "thick jaw from Africa," it was less than 2 feet (0.6 meters) long and weighed less than a house cat at 15 pounds (6.8 kilograms) at most, "and was mostly tail and neck," Sereno added.

Strangely, bristles somewhat like porcupine quills may have spread across most of the body of Pegomastax. Such bristles first appeared in a relative named Tianyulong recently discovered in China. Buried in lake sediments and covered by volcanic ash, Tianyulong was preserved with hundreds of bristles covering its body from its neck to the tip of its tail.

"It would have looked a bit like a two-legged porcupine, covered in these weird, funky, quill-like things," Sereno said of Pegomastax. "The bristles were not quite as strong as a porcupine's, and they don't look as if they were especially effective for insulation. Perhaps they had colors and helped differentiate species, or made Pegomastaxlook bigger than it actually was to potential predators."

Extending from its parrot-beaked skull, which was less than 2 inches (5 centimeters) long, were serrated canines a half-inch (0.8 cm) long from both its upper and lower jaws.

"It would have looked like Dracula," Sereno told LiveScience. "Probably appropriate, since we're now moving toward Halloween."

The dinosaur was originally chipped out of red rock near the border of Lesotho and South Africa by Harvard researchers in the 1960s. Sereno recently came across it while going through Harvard archives.

"I was just amazed," Sereno recalled.

Although the long stabbing fangs might hint that Pegomastax was a predator, its parrotlike beak instead suggests it ate seeds and nuts, or maybe plucked fruit. When the jaws closed, the fangs slid into sockets in the opposing jaws instead of sliding past one another for the optimized cutting or gripping expected of a carnivore.

"The canines probably had nothing to do with meat-eating," Sereno said. "They may have been used to spite rivals, nip at others, defend themselves, maybe root around for food."

Tall teeth in the back of the jaw probably helped slice plants, with surfaces that slid past one another when the jaws closed, operating like self-sharpening scissors. "Pegomastax and kin were the most advanced plant-eaters of their day," Sereno said.

Pegomastax belonged to one of two major divisions of dinosaurs, the "bird-hipped" ornithischians, which included armored ankylosaurs, bony-plated stegosaurs, duck-billed hadrosaurs and horned, frilled ceratopsians such as Triceratops. Ironically, birds themselves belong to the other major group of dinosaurs, the "lizard-hipped" saurischians, which included the carnivorous theropods such as Tyrannosaurusand the long-necked herbivorous sauropods such as Diplodocus.

When Pegomastax was alive, the supercontinent Pangaea had just begun to split into northern and southern land masses. Pegomastax appears to lie near the base of the family tree of the ornithischians, and as such could shed light on the evolution of this major group, Sereno said. ( LiveScience.com )

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230million-year-old insects found perfectly preserved in amber

The 'Jurassic Park' bugs: 230million-year-old insects found perfectly preserved in amber - Insects are 100 million years older than any other amber arthropod ever collected - Arthropods first to be found in amber from the Triassic Period - Find echoes the amber-preserved insect used to recreate dinosaurs in the hit film

Scientists have found the oldest bugs ever to be preserved in amber.

The specimens - one fly and two mites - were found in millimeter-scale droplets of amber from northeastern Italy.

They are about 100million years older than any other amber arthropod - invertebrate animals that include insects, arachnids, and crustaceans - ever collected.

The finding has echoes of Jurassic Park, in which dinosaurs are cloned from DNA found in blood from a mosquito preserved in amber.

The specimens, one fly and two mites, were found in millimeter-scale droplets of amber from northeastern Italy.

The group's findings, which are published today in the Proceedings of the National Academy of Sciences, pave the way for a better evolutionary understanding of the most diverse group of organisms in the world.

'Amber is an extremely valuable tool for paleontologists because it preserves specimens with microscopic fidelity, allowing uniquely accurate estimates of the amount of evolutionary change over millions of years,' said author David Grimaldi, a curator in the American Museum of Natural History's Division of Invertebrate Zoology and a world authority on amber and fossil arthropods.

In the hit 1993 film, Richard Attenborough hires scientists use dinosaur DNA taken from a mosquito preserved in amber to clone the animals and create a theme park.

Even though arthropods are more than 400 million years old, until now, the oldest record of the animals in amber dates to about 130 million years.

The newly discovered arthropods break that mold with an age of 230 million years.

They are the first arthropods to be found in amber from the Triassic Period.

These photomicrographs are of the two new species of ancient gall mites in 230-million-year-old amber droplets from northeastern Italy, taken at 1000x magnification. The gall mites were named (left) Triasacarus fedelei and (right) Ampezzoa triassica.

WHAT IS AMBER?

Globules of fossilized resin are typically called amber.

Amber ranges in age from the Carboniferous (about 340 million years ago) to about 40,000 years ago.

It is produced by myriad plants, from tree ferns to flowering trees, but predominantly by conifers.

The amber droplets, most between 2-6 millimeters long, were buried in outcrops high in the Dolomite Alps of northeastern Italy and excavated by Eugenio Ragazzi and Guido Roghi of the University of Padova.

About 70,000 of the miniscule droplets were screened for by a team of German scientists.

Two of the specimens are new species of mites, named Triasacarus fedelei and Ampezzoa triassica.

They are the oldest fossils in an extremely specialized group called Eriophyoidea that has about 3,500 living species, all of which feed on plants and sometimes form abnormal growth called 'galls.' The ancient gall mites are surprisingly similar to ones seen today.

'You would think that by going back to the Triassic you'd find a transitional form of gall mite, but no,' Grimaldi said.

'Even 230 million years ago, all of the distinguishing features of this family were there—a long, segmented body; only two pairs of legs instead of the usual four found in mites; unique feather claws, and mouthparts.'

The ancient mites likely fed on the leaves of the tree that ultimately preserved them, a conifer in the extinct family Cheirolepidiaceae.

Although about 97 percent of today's gall mites feed on flowering plants, Triasacarus fedelei and Ampezzoa triassica existed prior to the appearance and rapid radiation of flowering plants.

This finding reveals the evolutionary endurance of the mites.

'We now know that gall mites are very adaptable,' Grimaldi said.

Life imitating art? Richard Attenborough in Jurassic Park, with (left to right) Laura Dern, Arianna Richards, Martin Ferrero, Jeff Goldblum and Sam Neill

Jeff Goldblum, Richard Attenborough, Laura Dern and Sam Neill on the set of Jurassic Park in 1993. Now, it could become reality thanks to an Australian billionaire.

'When flowering plants entered the scene, these mites shifted their feeding habits, and today, only 3 percent of the species live on conifers.

'This shows how gall mites tracked plants in time and evolved with their hosts.'

The third amber specimen, a fly, cannot be identified because, outside of the insect's antennae, its body parts were not well preserved.

But now that the researchers have shown that amber preserved Triassic arthropods, they are eager to find more specimens.

'There was a huge change in the flora and fauna in the Triassic because it was right after one of the most profound mass extinctions in history, at the end of the Permian,' Grimaldi said. 'It's an important time to study if you want to know how life evolved.' ( dailymail.co.uk )

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Dinosaur Boom Linked to Rise of Rocky Mountains

Dinosaur Boom Linked to Rise of Rocky Mountains - The evolution of new dinosaur species may have surged due to the rise of the Rocky Mountains and the emergence of a prehistoric inner sea in North America, researchers say.

Duck-billed and horned dinosaurs flourished in North America, reaching a peak about 75 million years ago, a time known as the Campanian. For instance, one Campanian region known as the Dinosaur Park formation in what is now Canada saw seven different duck-billed dinosaur species and five horned dinosaur species emerge. A comparable region known as the Hell Creek formation in the United States from the Maastrichtian, the time that led up to the end of the Age of Dinosaurs 65 million years ago, saw only a single duck-billed dinosaur species and maybe three horned dinosaur species at most.

"The reason for this discrepancy in dinosaur diversity has never been adequately explained," said researcher Terry Gates, a vertebrate paleontologist at Ohio University.

Dinosaurs and geology

To help solve the mystery behind this pattern of evolution, Gates and colleagues analyzed the ancient geology of western North America, since environmental alterations often influence evolution. After focusing on trends in mountain and ocean formation 70 million to 80 million years ago, they found the landscape experienced profound changes back then that may have influenced dinosaur evolution.

During the early to middle Cretaceous, geological forces lifted the western United States, creating a huge mountain range known as the Sevier Mountains. This extended in a line from the American southwest through Alberta, Canada. Later, one of the tectonic plates under North America's crust shifted, building another mountain range farther east — the Laramide Orogeny, the infant stage of the modern-day Rocky Mountains.

The area just to the east of the new Sevier Mountains dipped downward, creating a shallow inner sea known as the Western Interior Seaway that flooded the continent from the Canadian Arctic to the Gulf of Mexico. This seaway divided the continent into three large islands to the north, east and west that were densely populated with dinosaurs.

The wild west

The dinosaurs of the west dwelled on an island called Laramidia. "Western North America has been a hotbed for dinosaur discoveries for more than a century, but the recent explosion of new dinosaur species coming out of Utah is sending waves through the paleontological community and revolutionized our understanding of dinosaur evolution on the continent," researcher Lindsay Zanno said in a statement. Zanno is the director of the Paleontology and Geology Research Laboratory at the Nature Research Center of the North Carolina Museum of Natural Sciences.

Specifically, the new finds helped illustrate how dinosaurs evolved on an island with changing geography. The growth of the Sevier Mountains and the Western Interior Seaway caused dinosaur habitat to shrink on Laramidia.

"It appears that geographic as well as probably also ecological barriers created by the rise of mountain ranges and the seaway caused isolation of the northern and southern populations of the crested duck-billed and horned plant-eating dinosaurs," researcher Albert Prieto-Márquez at the Bavarian State Collection for Paleontology and Geology in Munich, Germany, said in a statement. "We hypothesize that such isolation facilitated rapid speciation and increased diversity in these animals."

New species of duck-billed and horned dinosaurs were being born at an explosive rate of every few hundred thousand years during the brief time when the two mountain ranges and the seaway coexisted. Isolated populations often evolve new features more rapidly, Gates said.

Eventually, the continued rise of the Rocky Mountains kept the sea away from the continent's interior. This change opened up a vast territory for these dinosaurs to roam. This, in turn, reduced how fast new species evolved in the region to every few million years, the researchers suggest.

"Our data suggests that changing geography contributed to the pattern we see in western North America," Gates said.

During the times of isolation, a number of species of giant duck-billed dinosaurs "roamed a much smaller area than you might think given that many were larger than elephants," Gates said. It may be possible these dinosaurs evolved to eat specialized plants found only in certain regions, explaining why they lived in relatively tight confines.

Dinosaur diversity dip

Researchers had suggested that dinosaurs were declining before their mass extinction, due to a dip in diversity in the years leading up to the calamity.

"The major question I've been thinking about for 10 years was, 'Were dinosaurs really declining before they went extinct?'" Gates told LiveScience. "It turns out the time period of dinosaur diversity we were looking at, the Campanian, was a bit of an anomaly. It saw three converging geologic structures all coming together to form perfect conditions for a dinosaur species boom. Everyone was using this time as a baseline for dinosaur diversity, when it should have been seen as an anomaly, and the decrease in diversity later on was really a return to the status quo."

The mountain and seaway changes not only influenced dinosaur diversity in North America, but they also may have had effects elsewhere in the world. For instance, the rise of the predecessor to the Rocky Mountains created a barrier, meaning that only species living in the southern part of Laramidia could get to South America, and only species living north of the mountains could reach Asia across modern-day Alaska.

"These giant herbivores were truly invasive species that seemingly came to dominate these other continents," Gates said. ( LiveScience )

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Dinosaur cold-blood theory in doubt

Dinosaur cold-blood theory in doubt - One of the strongest lines of evidence that dinosaurs were cold-blooded, like modern reptiles, has been knocked down.

Prior studies of dinosaur bones uncovered what are known as "lines of arrested growth".

The creatures were presumed to be cold-blooded because modern cold-blooded animals show these same lines.

But scientists reporting in Nature have studied the bones of 41 modern mammal species from around the world, finding every one had these lines as well.

The idea that dinosaurs are cold-blooded, or ectothermic, goes back to the 19th Century. But a number of discoveries 1960s have been challenging that notion.

Because soft tissues such as organs and skin are not preserved (with a few notable exceptions), much of what is known about dinosaurs must be inferred from their bones, and comparisons made with modern animals that can be studied in greater detail.
Lagging behind

Lines of arrested growth, or Lags, occur because organisms tend to suspend their growth and rally their resources during seasonal periods of environmental stress such as cold or dry conditions.

This forms a boundary from one season to the next as growth resumes when conditions are more favourable.

They are familiar in creatures such as molluscs, whose slow annual accumulations can be seen as ridges in their shells.

Lags have also been found in the bones of reptiles and amphibians and have until now been assumed to be limited to ectotherms - cold-blooded animals - that are more subject to the whims of harsh environments.

Meike Koehler of the Catalan Institute of Palaeontology in Barcelona and her colleagues were therefore surprised by what they found.

"Originally this was not a paper that we aimed to do," Dr Koehler told BBC News.

"We were very curious to know how environmental conditions and changes affect bone growth in fossil and extant mammals, to get a good idea about... how they may have coped with these changes in the past."

As the team studied the thigh bones of animals from all over the world - ranging from the Svalbard reindeer in the Arctic to muntjac deer species from South Asia - Lags showed up in every one.

"These lines of arrested growth have been used a lot in dinosaurs, but nobody has ever had a really deep look at mammals," Dr Koehler explained.

David Weishampel, a palaeontologist at the Center for Functional Anatomy and Evolution at Johns Hopkins University School of Medicine in Maryland called the new work "a wonderful paper" and said it was a welcome addition to the debate.

"I think most (palaeontologists) regard dinosaurs as being [warm-blooded] but there's a lot of waffling in the data that appeared before that wasn't conclusive," he told BBC News.

"It's about time we have a connection between the modern bone histology and fossil bone histology, through a very nice ecological and metabolic comparison."

While Prof Weishampel considers it a closed case, Dr Koehler herself is more reserved about the result.

"I don't think that this debate is really settled," she said. "But this is the first time that you can say that Lags do not say anything about warm- or cold-bloodedness."

She and her team will go on and put the Lags to use in studies of modern animals instead.

"It's like dendrochronology - the rings in trees. You can do skeletal chronology in bones and infer things like longevity, age at maturity, juvenile states - traits which are very, very important to get an idea about the health of a population and whether it is vulnerable.

"It is very good to know now that mammals do show these Lags and we can use them in the same way that we do in amphibians and reptiles to understand the situation of a population." ( bbc.co.uk )

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