Dinosaur experts bust up prehistoric party theory

SALT LAKE CITY – So maybe there was no dinosaur dancing after all.

Paleontologists say there are no signs of dinosaur tracks at a remote spot along the Utah-Arizona border that was previously described by University of Utah geologists as a "dinosaur dance floor" for its density of tracks.

"We didn't observe a single footprint," said Andrew Milner, paleontologist at the St. George Dinosaur Discovery Site at Johnson Farm in southwestern Utah.

He was one of four paleontologists who hiked into the area last week after a heavily publicized study claiming there were more than 1,000 previously unknown dinosaur tracks crammed onto less than an acre in the Arizona portion of Vermillion Cliffs National Monument.

"We went up there optimistic, really hoping we were going to find footprints," Milner said Friday.

They quickly determined there were none. Instead, it was a dense collection of potholes caused by erosion in the sandstone, they said.

And the supposed tail-drag marks in the rock? Probably another result of erosion, the paleontologists said.

Marjorie Chan, a University of Utah researcher who co-authored the "dinosaur dance floor" study, said she's open to the paleontologists' views and says she'll team up with other researchers for another examination of the site.

"I'm interested in the truth, no matter what the outcome is," Chan said.

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Fearsome T-Rex was one nosy dinosaur

PARIS (AFP) – Tyrannosaurus Rex could sniff out distant prey even at night, yet another reason the flesh-ripping predator reigned supreme as king of the dinosaurs, according to a study published on Wednesday.
Earlier research had shown that the towering T-rex could see better than an eagle and would have been able to run down the fastest of humans.
The new study now unveils a previously unheralded weapon in the fearsome theropod's arsenal: a dangerously keen sense of smell.
Any trace of the brains of dinosaurs, which roamed Earth for tens of millions of years up to the end of the Cretaceous Period 65 million years ago, has long since disappeared.
But a trio of scientists led by Darla Zelenitsky at the University of Calgary in Alberta, Canada found a novel way to gage the sniffing prowess of T-rex and a couple dozen other meat-eating dinosaurs and primitive birds.
By examining fossil skull bones, the researchers were able to measure the size of indentations made by olfactory bulbs, the part of the brain associated with the sense of smell.
"Living birds and mammals that rely heavily on smell to find meat have large olfactory bulbs," Zelenitisky said in a statement.
The same animals also tend to prowl for prey at night, and cover vast areas, he added.
Of all the dinosaurs examined, the T-rex had the largest olfactory bulb relative to its overall size.
The study, published in the British journal Proceedings of the Royal Society B, also found that primitive birds had high-performance odor detectors, challenging a long-held assumption about the evolution of winged vertebrates.
"It has been previously suggested that smell had become less important than eye sight in the ancestors of birds, but we have shown that this wasn't so," said Zelenitsky.
Archaeopteryx, for example, which took to the skies during the Jurassic Period some 150 million years ago, had a sense of smell comparable to meat-eating dinosaurs along with excellent eye sight, the study said.
Somewhere along the way birds began to lose their sense of smell, but the decline probably happened far later than previously thought, the study concludes.

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Dodo

Dodo
The Dodo (Raphus cucullatus) was a flightless bird that lived on the islands of Mauritius. Related to pigeons and doves, it stood about a metre tall (three feet), lived on fruit and nested on the ground.
The dodo has been extinct since the mid-to-late 17th century. It is commonly used as the archetype of an extinct species because its extinction occurred during recorded human history, and was directly attributable to human activity. The phrase "as dead as a dodo" means undoubtedly and unquestionably dead.

Etymology

The etymology of the word dodo is not clear. It may be related to dodaars ("plump-arse"), the Dutch name of the Little Grebe. The connection may have been made because of similar feathers of the hind end or because both animals were ungainly. However, the Dutch are also known to have called the Mauritius bird the walghvogel ("loathsome bird" or "nauseating fowl") in reference to its taste. This last name was used for the first time in the journal of vice-admiral Wybrand van Warwijck who visited and named the island Mauritius in 1598. Dodo or Dodaerse is recorded in captain Willem van West-Zanen's journal four years later, but it is unclear whether he was the first one to use this name, because before the Dutch, the Portuguese had already visited the island in 1507, but did not settle permanently.
According to Encarta Dictionary and Chambers Dictionary of Etymology, "dodo" comes from Portuguese doudo (currently doido) meaning "fool" or "crazy". However, the present Portuguese name for the bird, dodô, is of English origin. The Portuguese word doudo or doido may itself be a loanword from Old English (cf. English "dolt").
Yet another possibility is that dodo was an onomatopoeic approximation of the bird's own call, a two-note pigeony sound like 'doo-doo'.

Biology
Systematics and evolution

The dodo is a close relative of modern pigeons and doves. mtDNA cytochrome b and 12S rRNA sequences analysis suggests that the dodo's ancestors diverged from those of its closest known relative, the Rodrigues Solitaire (which is also extinct), around the Paleogene-Neogene boundary. As the Mascarenes are of volcanic origin and less than 10 million years old, both birds' ancestors remained most likely capable of flight for considerable time after their lineages' separation. The same study has been interpreted[6] to show that the Southeast Asian Nicobar Pigeon is the closest living relative of the dodo and the Reunion Solitaire.
However, the proposed phylogeny is rather questionable as regards the relationships of other taxa and must therefore be considered hypothetical pending further research; considering biogeographical data, it is very likely to be erroneous. All that can be presently said with any certainty is that the ancestors of the didine birds were pigeons from Southeast Asia or the Wallacea, which agrees with the origin of most of the Mascarenes' birds. Whether the dodo and Rodrigues Solitaire were actually closest to the Nicobar Pigeon among the living birds, or whether they are closer to other groups of the same radiation such as Ducula, Treron or Goura pigeons is not clear at the moment.
For a long time, the dodo and the Rodrigues Solitaire (collectively termed "didines") were placed in a family of their own, the Raphidae. This was because their relationships to other groups of birds (such as rails) had yet to be resolved. As of recently, it appears more warranted to include the didines as a subfamily Raphinae in the Columbidae.
The supposed "White Dodo" is now thought to be based on misinterpreted reports of the Réunion Sacred Ibis and paintings of apparently albinistic dodos; a higher frequency of albinos is known to occur occasionally in island species (see also Lord Howe Swamphen).

Morphology and flightlessness

In October 2005, part of the Mare aux Songes, the most important site of dodo remains, was excavated by an international team of researchers. Many remains were found, including bones from birds of various stages of maturity, and several bones obviously belonging to the skeleton of one individual bird and preserved in natural position. These findings were made public in December 2005 in the Naturalis in Leiden. Before this, few associated dodo specimens were known, most of the material consisting of isolated and scattered bones. Dublin's Natural History Museum and the Oxford University Museum of Natural History, among others, have a specimen assembled from these disassociated remains. A Dodo egg is on display at the East London museum in South Africa. Until recently, the most intact remains, currently on display at the Oxford University Museum of Natural History, were one individual's partly skeletal foot and head which contain the only known soft tissue remains of the species.
In June 2007, adventurers exploring a cave in the Indian Ocean discovered the most complete and well-preserved dodo skeleton ever
The remains of the last known stuffed dodo had been kept in Oxford's Ashmolean Museum, but in the mid-18th century, the specimen - save the pieces remaining now - had entirely decayed and was ordered to be discarded by the museum's curator or director in or around 1755. According to the current curator, Malgosia Nowak-Kemp, the commonly-cited story that the remains were merely damaged - implying that more material could or should have been salvaged, and/or that the present remains were serendipitiously saved against the curator's orders - is an urban legend arising from a mistranslation of the Latin museum records.[citation needed] Nevertheless, from artists' renditions we know that the Dodo had greyish plumage, a 23-centimetre (9-inch) bill with a hooked point, very small wings, stout yellow legs, and a tuft of curly feathers high on its rear end. Dodos were very large birds, weighing about 23 kg (50 pounds). The sternum was insufficient to support flight; these ground-bound birds evolved to take advantage of an island ecosystem with no predators.
The traditional image of the dodo is of a fat, clumsy bird, but this view has been challenged in recent times. The general opinion of scientists today is that the old drawings showed overfed captive specimens. As Mauritius has marked dry and wet seasons, the dodo probably fattened itself on ripe fruits at the end of the wet season to live through the dry season where food was scarce; contemporary reports speak of the birds' "greedy" appetite. Thus, in captivity, with food readily available, the birds would become overfed very easily.

Diet

The tambalacoque, also known as the "dodo tree", was hypothesized by Stanley Temple to have been eaten from by Dodos, and only by passing through the digestive tract of the dodo could the seeds germinate; he claimed that the tambalacocque was now nearly extinct due to the dodo's disappearance. He force-fed seventeen tambalacoque fruits to wild turkeys and three germinated. Temple did not try to germinate any seeds from control fruits not fed to turkeys so the effect of feeding fruits to turkeys was unclear. Temple also overlooked reports on tambalacoque seed germination by A. W. Hill in 1941 and H. C. King in 1946, who found the seeds germinated, albeit rarely, without abrading.

Extinction
As with many animals evolving in isolation from significant predators, the dodo was entirely fearless of people, and this, in combination with its flightlessness, made it easy prey. But journals are full of reports regarding the bad taste and tough meat of the dodo, while other local species such as the Red Rail were praised for their taste. It is commonly believed that the Malay sailors held the bird in high regard and killed them only to make head dressings used in religious ceremonies. However, when humans first arrived on Mauritius, they also brought with them other animals that had not existed on the island before, including dogs, pigs, cats, rats, and Crab-eating Macaques, which plundered the dodo nests, while humans destroyed the forests where the birds made their homes; currently, the impact these animals — especially the pigs and macaques — had on the dodo population is considered to have been more severe than that of hunting. The 2005 expedition's finds are apparently of animals killed by a flash flood; such mass mortalities would have further jeopardized an already extinction-prone species.
Although there are scattered reports of mass killings of dodos for provisioning of ships, archaeological investigations have hitherto found scant evidence of human predation on these birds. Some bones of at least two dodos were found in caves at Baie du Cap which were used as shelters by fugitive slaves and convicts in the 17th century, but due to their isolation in high, broken terrain were not easily accessible to dodos naturally. By 1755, Cossigny reports that the number of refugees and settlers which cut down the inland forest was so high that the well-flighted Mauritius Blue Pigeon was rapidly declining all over the island.[citation needed]
There is some controversy surrounding the extinction date of the dodo. Roberts & Solow state that "the extinction of the Dodo is commonly dated to the last confirmed sighting in 1662, reported by shipwrecked mariner Volkert Evertsz" (Evertszoon), but many other sources suggest the more conjectural date 1681. Roberts & Solow point out that because the sighting prior to 1662 was in 1638, the dodo was likely already very rare by the 1660s, and that thus a disputed report from 1674 cannot be dismissed off-hand. Statistical analysis of the hunting records of Issac Johannes Lamotius, carried out by Julian Hume and coworkers,[citation needed] give a new estimated extinction date of 1693, with a 95% confidence interval of 1688 to 1715. Considering more circumstantial evidence such as travellers' reports and the lack of good reports after 1689, it is likely that the dodo became extinct before 1700; thus, the last Dodo died barely more than a century after the species' discovery in 1581.Few took particular notice of the extinct bird. By the early 19th century it seemed altogether too strange a creature, and was believed by many to be a myth. With the discovery of the first batch of dodo bones in the Mare aux Songes and the reports written about them by George Clarke, government schoolmaster at Mahébourg, from 1865 on,[22] interest in the bird was rekindled. In the same year in which Clarke started to publish his reports, the newly-vindicated bird was featured as a character in Lewis Carroll's Alice's Adventures in Wonderland. With the popularity of the book, the dodo became a well-known and easily recognizable icon of extinction.

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Tyrannosaurus Rex (T-REX)

Tyrannosaurus is a genus of theropod dinosaur. The species Tyrannosaurus rex, commonly abbreviated to T. rex, is one of the dinosaurs most often featured in popular culture around the world. It hails from what is now western North America. Some scientists consider Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus, while others maintain Tarbosaurus as a separate genus.
Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small and retained only two digits. Although other theropods rivaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring over 13 metres (43 feet) in length and up to 6.8 metric tons (7.5 short tons) in weight.
Fossils of T. rex have been found in North American rock formations dating to the last three million years of the Cretaceous Period at the end of the Maastrichtian stage, approximately 68.5 to 65.5 million years ago; it was among the last dinosaurs to exist prior to the Cretaceous-Tertiary extinction event. More than 30 specimens of T. rex have been identified, some of which are nearly complete skeletons. Some researchers claim to have discovered soft tissue as well. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics. The feeding habits, physiology and potential speed of T. rex are a few of the topics which remain controversial.

Description

Tyrannosaurus rex was one of the largest land carnivores of all time, measuring 12 to 13 meters (40 to 43.3 feet) long, and 4.5-5 m (14-16.6 ft) tall, when fully-grown. Mass estimates have varied widely over the years, from more than 7,200 kilograms (8 tons), to less than 4,500 kg (5 tons), with most modern estimates ranging between 5,400 and 6,800 kg (between 6 and 7.5 tons).The largest known T. rex skulls measure up to 1.5 m (5 ft) in length. Compared to other theropods, the skull was heavily modified. The skull was extremely wide posteriorly, with a narrow snout, allowing some degree of binocular vision. Some of the bones, such as the nasals, were fused, preventing movement between them. Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment. The bones themselves were massive, as were the serrated teeth which, rather than being bladelike, were oval in cross-section. Like other tyrannosaurids, T. rex displayed marked heterodonty, with the premaxillary teeth at the front of the upper jaw closely-packed and D-shaped in cross-section. Large bite marks found on bones of other dinosaurs indicate that these teeth could penetrate solid bone. T. rex had the greatest bite force of any dinosaur and one of the strongest bite forces of any animal. Worn or broken teeth are often found, but unlike those of mammals, tyrannosaurid teeth were continually replaced throughout the life of the animal.The neck of T. rex formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The two-fingered forelimbs were very small relative to the size of the body, but heavily built. In contrast, the hindlimbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow. This reduced the weight of the skeleton while maintaining much of the strength of the bones.

Classification

Tyrannosaurus is the type genus of the superfamily Tyrannosauroidea, the family Tyrannosauridae, and the subfamily Tyrannosaurinae. Other members of the tyrannosaurine subfamily include the North American Daspletosaurus and the Asian Tarbosaurus, both of which have occasionally been synonymized with Tyrannosaurus. Tyrannosaurids were once commonly thought to be descendants of earlier large theropods such as megalosaurs and carnosaurs, although more recently they were reclassified with the generally smaller coelurosaurs.
In 1955, Soviet paleontologist Evgeny Maleev named a new species, Tyrannosaurus bataar, from Mongolia. By 1965, this species had been renamed Tarbosaurus bataar. Despite the renaming, many phylogenetic analyses have found Tarbosaurus bataar to be the sister taxon of Tyrannosaurus rex, and it has often been considered an Asian species of Tyrannosaurus. A recent redescription of the skull of Tarbosaurus bataar has shown that it was much narrower than that of Tyrannosaurus rex and that during a bite, the distribution of stress in the skull would have been very different, closer to that of Alioramus, another Asian tyrannosaur. A related cladistic analysis found that Alioramus, not Tyrannosaurus, was the sister taxon of Tarbosaurus, which, if true, would suggest that Tarbosaurus and Tyrannosaurus should remain separate.
Other tyrannosaurid fossils found in the same formations as T. rex were originally classified as separate taxa, including Aublysodon and Albertosaurus megagracilis, the latter being named Dinotyrannus megagracilis in 1995. However, these fossils are now universally considered to belong to juvenile T. rex. A small but nearly complete skull from Montana, 60 cm (2 ft) long, may be an exception. This skull was originally classified as a species of Gorgosaurus (G. lancensis) by Charles W. Gilmore in 1946, but was later referred to a new genus, Nanotyrannus. Opinions remain divided on the validity of N. lancensis. Many paleontologists consider the skull to belong to a juvenile T. rex. There are minor differences between the two species, including the higher number of teeth in N. lancensis, which lead some scientists to recommend keeping the two genera separate until further research or discoveries clarify the situation.

Manospondylus controversy

The first fossil specimen which can be attributed to Tyrannosaurus rex consists of two partial vertebrae (one of which has been lost) found by Edward Drinker Cope in 1892 and described as Manospondylus gigas. Osborn recognized the similarity between M. gigas and T. rex as early as 1917 but, due to the fragmentary nature of the Manospondylus vertebrae, he could not synonymize them conclusively.
Controversy erupted in June 2000 after the Black Hills Institute located the type locality of M. gigas in South Dakota and unearthed more tyrannosaur bones there. These were judged to represent further remains of the same individual, and to be identical to those of T. rex. According to the rules of the International Code of Zoological Nomenclature (ICZN), the system that governs the scientific naming of animals, Manospondylus gigas should therefore have priority over Tyrannosaurus rex, because it was named first. However, the Fourth Edition of the ICZN, which took effect on January 1, 2000, states that "the prevailing usage must be maintained" when "the senior synonym or homonym has not been used as a valid name after 1899" and "the junior synonym or homonym has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years..." Tyrannosaurus rex easily qualifies as the valid name under these conditions and would most likely be considered a nomen protectum ("protected name") under the ICZN if it was ever challenged, which it has not yet been. Manospondylus gigas would then be deemed a nomen oblitum ("forgotten name").

Life history

The identification of several specimens as juvenile Tyrannosaurus rex has allowed scientists to document ontogenetic changes in the species, estimate the lifespan, and determine how quickly the animals would have grown. The smallest known individual (LACM 28471, the "Jordan theropod") is estimated to have weighed only 29.9 kg (66 lb), while the largest, such as FMNH PR2081 ("Sue") most likely weighed over 5400 kg (6 short tons). Histologic analysis of T. rex bones showed LACM 28471 had aged only 2 years when it died, while "Sue" was 28 years old, an age which may have been close to the maximum for the species.
Histology has also allowed the age of other specimens to be determined. Growth curves can be developed when the ages of different specimens are plotted on a graph along with their mass. A T. rex growth curve is S-shaped, with juveniles remaining under 1800 kg (2 short tons) until approximately 14 years of age, when body size began to increase dramatically. During this rapid growth phase, a young T. rex would gain an average of 600 kg (1600 lb) a year for the next four years. At 18 years of age, the curve plateaus again, indicating that growth slowed dramatically. For example, only 600 kg (1,300 lb) separated the 28-year-old "Sue" from a 22-year-old Canadian specimen (RTMP 81.12.1). Another recent histological study performed by different workers corroborates these results, finding that rapid growth began to slow at around 16 years of age. This sudden change growth rate may indicate physical maturity, a hypothesis which is supported by the discovery of medullary tissue in the femur of a 16 to 20-year-old T. rex from Montana (MOR 1125, also known as "B-rex"). Medullary tissue is found only in female birds during ovulation, indicating that "B-rex" was of reproductive age. Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes.
Over half of the known T. rex specimens appear to have died within six years of reaching sexual maturity, a pattern which is also seen in other tyrannosaurs and in some large, long-lived birds and mammals today. These species are characterized by high infant mortality rates, followed by relatively low mortality among juveniles. Mortality increases again following sexual maturity, partly due to the stresses of reproduction. One study suggests that the rarity of juvenile T. rex fossils is due in part to low juvenile mortality rates; the animals were not dying in large numbers at these ages, and so were not often fossilized. However, this rarity may also be due to the incompleteness of the fossil record or to the bias of fossil collectors towards larger, more spectacular specimens.

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Mammoth

A mammoth is any of a number of an extinct genus of proboscidean (of which the elephant remains), often with long curved tusks and, in northern species, a covering of long hair. They lived from the Pliocene epoch from 4.8 million years ago to around 4,000 years ago. The word mammoth comes from the Russian мамонт mamont, probably in turn from the Khanty

Evolutionary history

Mammoth remains have been found in Europe, Africa, Asia, and North America. They are believed to have originally evolved in North Africa about 4.8 million years ago, during the Pliocene, where bones of Mammuthus africanavus have been found in Chad, Libya, Morocco and Tunisia. Mammuthus subplanifrons, found in South Africa and Kenya, is also believed to be one of the oldest species (about 4 million years ago).
Despite their African ancestry, they are in fact more closely related to the modern Asian Elephant than either of the two African elephants (as both Mammuthus and Elephas also originated in Africa). The common ancestor of both mammoths and Asian elephants split from the line of African elephants about 6 - 7.3 million years ago. The Asian elephants and mammoths diverged about half a million years later (5.5 - 6.3 million years ago).
In due course the African mammoth migrated north to Europe and gave rise to a new species, the southern mammoth (Mammuthus meridionalis). This eventually spread across Europe and Asia and crossed the now-submerged Bering Land Bridge into North America.
Around 700,000 years ago, the warm climate of the time deteriorated markedly and the savannah plains of Europe, Asia and North America gave way to colder and less fertile steppes. The southern mammoth consequently declined, being replaced across most of its territory by the cold-adapted steppe mammoth (Mammuthus trogontherii). This in turn gave rise to the woolly mammoth, Mammuthus primigenius) around 300,000 years ago. Woolly mammoths were better able to cope with the extreme cold of the Ice Ages.
The woollies were a spectacularly successful species; they ranged from Spain to North America and are thought to have existed in huge numbers. The Russian researcher Sergei Zimov estimates that during the last Ice Age, parts of Siberia may have had an average population density of sixty animals per hundred square kilometres - equivalent to African elephants today.

Extinction

Most mammoths died out at the end of the last Ice Age. A definitive explanation for their mass extinction is yet to be agreed upon. A small population survived on St. Paul Island, Alaska, up until 6000 BC , and the small mammoths of Wrangel Island became extinct only around 1700 to 1500 BC.
Whether the general mammoth population died out for climatic reasons or due to overhunting by humans is controversial. Another theory suggests that mammoths may have fallen victim to an infectious disease. A combination of climate change and hunting by humans is probably the most likely explanation for their extinction.
New data derived from studies done on living elephants and reported by the American Institute of Biological Sciences (BioScience, April 2006, Vol. 56 No. 4, pp. 292-298) suggests that though human hunting may not have been the primary cause toward the mammoth's final extinction, human hunting was likely a strong contributing factor. Homo erectus is known to have consumed mammoth meat as early as 1.8 million years ago (BioScience, April 2006, Vol. 56 No. 4, p. 295).
However, the American Institute of Biological Sciences also notes that bones of dead elephants, left on the ground and subsequently trampled by other elephants, tend to bear marks resembling butchery marks, which have previously been misinterpreted as such by archaeologists.
The survival of the dwarf mammoths on Russia's Wrangel Island was due to the fact that the island was very remote, and uninhabited in the early Holocene period. The actual island was not discovered by modern civilization until the 1820s by American whalers. A similar dwarfing occurred with Mammoths on the outer Channel Islands of California, but at an earlier period. Those animals were very likely killed by early Paleo-Native Americans, and habitat loss caused by a rising sea level that split the Santa Rosae into the outer Channel Islands.

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