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New book by paleontologists Naish and Barrett is a treat for dinosaur fans

December 19, 2016 Leave a comment

naish-and-barrett-dinosaurs-how-they-lived-and-evolved-oct-2016

Those of us who love dinosaurs know that there is something poetic about these animals – the spectacular size of some,  their amazing variety, the mysteries of their long life on this planet . We still feel a thrill when we envision the fantastic beasts and we sometimes find ourselves drifting into a reverie in which we imagine the world under their 140 million-year domination. We can almost see, in our mind’s eye, the graceful long-necked sauropods nibbling the trees and shrubs, the stalking bipedal, sharp-toothed theropods tall and small, and the horned, crested, and armored herbivores wandering the landscape.

Our endless willingness to imagine the great beasts, and our persistent desire to learn more about them, is catered to by a growing variety of mass market books that aim to help us understand their biology and the ecosystems in which they lived. One of the best recent additions to this library, by the British paleontologists Darren Naish (author of the popular Tetrapod Zoology blog) and Paul Barrett (of London’s Natural History Museum), stands out for its depth and its wide-ranging look at dinosaurs’ anatomy, behavior, diversity, and evolution.

The book, Dinosaurs: How They Lived and Evolved, starts with a look at some basic biological principles and the history of dinosaur discoveries. Readers are provided a cogent overview of Earth’s geology and climate during the Mesozoic era, the value of cladistics as a tool to make sense of dinosaur variety, and the place of dinosaurs in the larger group of animals known as archosaurs.

Naish and Barrett then move on to a helpful explanation of the relationships among dinosaur species and a detailed look at dinosaur skeletal systems.

This discussion shines for its skillful and picturesque descriptions of the major dinosaur groups. The authors focus not just on the famous Saurischians and Ornithiscians; they take the reader into a just-deep-enough examination of the clades into which these groups are divided.

In the third section of the book Naish and Barrett shift to an examination of scientists’ current understanding of the deeper aspects of dinosaur biology: their diets, their mating habits, the intricacies of their movement, and their social behaviors. This part of the book is a smorgasbord of insights into how fossils, both trace and body, teach us about the structure of an animal’s life.

Next we are presented with a thorough discussion of modern dinosaurs. Here Naish and Barrett not only delve into the ways in which avian anatomy resembles that of their coelurosaur cousins, but also explain the current understanding of feather origins and the genesis of flight.

In the book’s final section Naish and Barrett, after a review of the impact by an asteroid or comet and its consequences for dinosaurs and their world, highlight another possible contributor to the Mesozoic terminus: active volcanoes around the planet.

The authors explain that, notwithstanding the ecological catastrophe that essentially ended their long reign over the planet’s biosphere (an incident known as the K-Pg event), dinosaurs may have been experiencing both climate change and a loss of diversity at the time it occurred. They take pains to emphasize that, contrary to popular myth, some dinosaurs did survive the end of the Cretaceous period. We know them, of course, as the birds.

Gracing the text are numerous photographs, graphs, and computer-generated reconstructions. Naish and Barrett did not, though, include citations to scientific papers or a bibliography.

Dinosaurs: How They Lived and Evolved is ideal for readers that have some basic familiarity with the biological sciences, though detailed knowledge is not required to enjoy the book.

Published by Smithsonian Books and carrying a cover price of $29.95, the book is a worthy and entertaining read for all of us who continue to be fascinated by the dinosaurs.

NOTE: This reviewer obtained a copy of Dinosaurs: How They Lived and Evolved on loan from the Arapahoe Library District. He was not asked by any publisher or author to prepare this review and has not been compensated for it.

Asian fossil discovery may help explain how tyrannosaurs became dominant predators

June 17, 2016 Leave a comment
Timurlengia euotica - March 2016 - courtesy

This artist’s conception shows the tyrannosaur Timurlengia euotica in its environment 90 million years ago, accompanied by two flying reptiles (Azhdarcho longicollis). The fossilized remains of a the horse-sized dinosaur help explain how Tyrannosaurus rex and its close relatives became top predators. The paper describing the discovery was published in March in the Proceedings of the National Academy of Sciences. Illustration by Todd Marshall.

Researchers have discovered 90 million-year old fossils of an early tyrannosaur that may help improve scientists’ understanding of how that group of dinosaurs evolved into the predatory giants that later roamed North America.

The horse-sized animal, which would have likely weighed about 250 kilograms, apparently had impressive hearing ability. Its capacity to hear low frequency sounds can be deduced from an elongated cochlear duct.

Named Timurlengia euotica, the newly-identified tyrannosaur helps fill a gap in knowledge about how the relatively small theropods, which had to compete with larger allosaurs, evolved into some of the largest land predators ever known.

The discovery indicates that the tyrannosaur clade probably gained the sensory tools needed to become apex predators before late Cretaceous enormity took hold.

“Tyrannosaurs had to get smart before they got big,” Dr. Stephen L. Brusatte, a paleontologist at the University of Edinburgh in the United Kingdom and lead author of the paper describing the discovery, said.

Enormity on the scale so obviously presented by later tyrannosaurs like Tyrannosaurus rex, which stood about five meters tall and about 12 meters long and weighed about 3,600 kilograms, evolved during the last 20 million years of the dinosaurs’ dominance of Earth.

Researchers found a brain case, which they then subjected to a computed microtomography (CT) scan. That scan revealed not only the animal’s inner ear structure, but also likely similarities between T. euotica‘s brain and the brain of Tyrannosaurus rex.

Brusatte wrote in The Conversation that these features likely helped T. euotica become a very skilled tracker of prey.

“Their intelligence and sharp senses made tyrannosaurs perfectly equipped to swoop into the top-predator role,” he wrote.

As the tyrannosaur head became larger, it became more useful for hunting.

“Their heads became giant killing machines and their arms, now unnecessary, shrunk down to nubbins,” Brusatte wrote in The Conversation feature.

The fossilized braincase, along with a variety of other bones, had been stored in a museum for about ten years. Brusatte and his colleagues examined them in 2014.

Reconstructed T. euotica skeleton

This is a reconstructed skeleton of Timurlengia euotica with discovered fossilized bones, highlighted in red, and other bones remaining to be discovered inferred from other related species of tyrannosaurs in white. Individual scale bars for the pictured fossilized bones each equal 2 centimeters. The fossilized remains of T. euotica may reveal how Tyrannosaurus rex and its close relatives became top predators. Graphic (c) National Academy of Sciences.

“Working on Timurlengia has been one of the highlights of my career,” Brusatte said. “It gives us a glimpse of what the ancestor of T. rex was – a tyrannosaur right on the cusp of becoming huge.”

The fossils were found in the remote Kyzylkum Desert of Uzbekistan. Their significance was described in a paper published in March in Proceedings of the National Academy of Sciences.

305 million year-old ancestor of spiders is identified

April 28, 2016 Leave a comment
Early arachnid

Idmonarachne brasieri lived about 305 million years ago. Image courtesy University of Manchester.

Paleontologists have identified an ancestor of modern spiders that lived before the dinosaurs began their long domination of the planet.

The arachnid’s fossil remains were found during the mid-1970s in Europe embedded in an iron-rich mineral, siderite, that is difficult for x-rays to penetrate. Researchers used a synchotron, which emits more powerful x-rays, to identify the organism.

Named Idmonarachne brasieri, the organism was likely a member of a group of arachnids called uraraneids. These animals lacked spinarets, which modern spiders use to spin webs, and instead would have discharged silk in sheets.

“Our new fossil occupies a key position in the evolution of spiders,” Dr. Russell Garwood of the University of Manchester, the lead author of a paper documenting the discovery, said. “It isn’t a true spider, but has given us new information regarding the order in which the bits of the anatomy we associate with spiders appeared as the group evolved.”

Scientists know little of the origin of spiders and the evolutionary path by which such anatomical features as spinarets formed is not well understood.

The paper appears in the March 30 edition of Proceedings of the Royal Society B.

 

Fossils of largest-ever marine crocodile found in Africa

April 28, 2016 Leave a comment

Scientists have found evidence that a ocean-dwelling crocodile about 10 meters long once roamed the area we now know as north Africa.

The beast, which also likely weighed at least three tons, lived about 120-130 million years ago.

Dubbed Machimosaurus rex, the crocodile is the largest known of its kind. A marine reptile, it thrived at a time in Earth’s geologic history when the land now known as north Africa was submerged under an ocean.

machimosaurus-rex-reconstruction

Machimosaurus rex was a marine reptile, about 12 meters long, that swam in Cretaceous oceans. Illustration courtesy University of Alberta, illustration (c) Davide Bonadonna. All rights reserved.

Researchers discovered the species in 2014 when a skull measuring almost two meters in length was unearthed in Tunisia. The specimen has teeth that are are shaped like bullets, which the creature may have used to crush the carapaces of marine turtles.

The length of the animal is an estimate, based on the dimensions of similar organisms within the animal’s genus that lived during the Jurassic and Cretaceous periods.

“We have been digging in that area since 2011 because the rocks there are nothing like other places,” Federico Fanti, a paleontologist at the University of Bologna in Italy and lead author of the paper documenting the find, said in a statement. “Globally, good fossils are rare from this age—130 million years ago.”

Fanti and his team later found more of the specimen, including vertebrae, but were not able to remove those parts of the fossil because of ongoing unrest in the country.

The species is part of a larger genus that was first discovered in the nineteenth century. Among M. rex‘s close relatives are crocodilians that roamed Jurassic and Cretaceous period seas that then covered the part of Earth now known as Europe.

M. rex was the largest of the teleosaurids (marine crocodiles) in its genus.

While large, the croc is not the largest known from the planet’s long history of life. At least several species of freshwater crocodile that lived during the time of the dinosaurs, Sarcosuchus imperator and those in the genus Deinosuchus, were more imposing than M. rex.

S. imperator was about two meters longer than M. rex, while some Deinosuchus species may have been only slightly longer than M. rex.

The paper documenting the discovery of M. rex was published online in the Jan. 10, 2016 edition of Cretaceous Research.

 

 

 

 

Remains of oldest horned dinosaur in North America found

December 11, 2014 Leave a comment
This artist's conception shows Aquilops americanus in its early Cretaceous period ecosystem. Image courtesy Raymond M. Alf Museum of Paleontology, copyright Brian Engh.

This artist’s conception shows Aquilops americanus in its early Cretaceous period ecosystem. Image courtesy Raymond M. Alf Museum of Paleontology, copyright Brian Engh.

Paleontologists have identified a species of horned dinosaur that lived in Montana more than 100 million years ago, the oldest known ceratopsian in North America.

The two foot-long animal – about as long as a crow or a raven – was an ancestor much larger horned and frilled creatures that roamed Cretaceous period landscapes on the continent.

Known as Aquilops americanus, the animal is a clue to a pattern of dinosaur migration from Asia to North America.

“Aquilops lived nearly 20 million years before the next oldest horned dinosaur named from North America,” Andrew A. Farke, a paleontologist at the Raymond A. Alf Museum of Paleontology in Claremont, Calif. and lead author of a paper documenting the discovery. “Even so, we were surprised that it was more closely related to Asian animals than those from North America.”

Those relatives included Liaoceratops yanzigouensis, another tiny predecessor of Triceratops, Styracosaurus, and other ceratopsian dinosaurs whose fossils were discovered in China and described in 2002.

Researchers found only the remnants of one, probably adolescent, Aquilops’ skull, about 84 millimeters long. But those bones are distinctive enough to set the fossils apart as a holotype. Among the most distinctive features of the skull is a downward-curving, bumped beak.

The Aquilops americanus fossils were found in 1997. The name means “American eagle face.”

The paper documenting the discovery was published in the Dec. 10 edition of PLOS One.

Scientists discover first known aquatic dinosaur in Morocco

September 11, 2014 Leave a comment

Paleontologists have discovered the first dinosaur known to have lived much of its life in the water.

The find of a variety of bones from an animal called Spinosaurus aegyptiacus vastly improves scientists’ understanding of the role played by the huge predatory dinosaur in the Cretaceous period ecosystem of modern-day North Africa.

“Today we are resurrecting a giant from deep time,” Dr. Nizar Ibrahim, a paleontologist at the University of Chicago and the lead author of a paper published in the Sept. 11, 2014 edition of Science Express, said. “The animal we are resurrecting is so bizarre, it is going to force dinosaur experts to re-think many things they thought they knew about dinosaurs.”

Spinosaurus aegyptiacus was first identified in 1915 by the German anatomist, geologist, and paleontologist Ernst Stromer von Reichenbach. He identified an animal unlike any other theropod dinosaur then known.

Spinosaur fossils mounted on the wall of a German museum before a Royal Air Force bombing in 1944. Courtesy Washington University.

Spinosaur fossils mounted on the wall of a German museum before a Royal Air Force bombing in 1944. Courtesy Washington University.

“The size of the bones suggested to Stromer that the animal rivaled Tyrannosaurus rex in size, but it clearly differed from the North American predator in many ways,” Ibrahim said. “The skull was more elongate and the tall spines formed a large sail on the back of Spinosaurus.”

Stromer stored the holotype in the Paläontologische Staassammlung in Munich, Germany. Unfortunately, an April 1944 bombing raid by Britain’s Royal Air Force destroyed Stromer’s fossils.

The German scientist’s drawings survived.

Stromer's drawings of Spinosaurus aegyptiacus were detailed and survived the World War Ii bombing. Courtesy Wikimedia.

Stromer’s drawings of Spinosaurus aegyptiacus were detailed and survived the World War Ii bombing. Courtesy Wikimedia.

During the ensuing decades paleontologists used those drawings, along with a few fragmentary finds of additional Spinosaurus remains, to develop a rudimentary idea of the animal’s appearance. They conceived Spinosaurus as a land animal, the largest predatory dinosaur known.

The findings published Thursday cast no doubt on Spinosaurus’ size, but revealed a number of body features that are unique among dinosaurs and that indicate the animal likely searched for food in the rivers that were ubiquitous in the region now known as North Africa during the Mesozoic era. Those features include a nasal opening high on the skull, long teeth shaped like cones, and wide and flat feet that may have been webbed.

“Other more subtle, but equally startling, finds were made,” Dr. Paul C. Sereno, a vertebrate paleontologist at the University of Chicago and a principal author of the paper published online in Science Express, said. “The thigh bone was robust and shorter than the shin bone, a very unusual proportion for a large dinosaur. And all of the long bones were solid without a marrow cavity, something never before observed in a predatory dinosaur.”

The highly dense bones are similar to those found in modern-day penguins.

“This adaptation is useful to facilitate buoyancy control,” Dr. Simone Maganuco, a vertebrate paleontologist at Italy’s Museo di Storia Naturale di Milano and another co-author on the paper, said.

Spinosaurus’ skull also exhibited small pits at the end of its snout called foramina. The authors of the study used computer tomography to examine them and found that they served to regulate pressure.

The foramina closely resemble those found in modern-day crocodiles and that have been confirmed in at least one species of extinct marine reptile.

“The pressure receptors of crocs play a key role in capturing prey based on water movements, and permit to hunt even in darkness or in muddy water, without relying on sight,” Dr. Cristiano Dal Sasso, curator of vertebrate paleontology at the Museo di Storia Naturale di Milano and a co-author of the paper, said.

She explained that their presence in Spinosaurus’ skull is an indication that the dinosaur may have used its long snout to find prey, with no need to see it.

Sereno noted that the new Spinosaurus specimen also exhibited a tail with characteristics similar to those found in some modern fish.

“These facts strongly supported a semi-aquatic existence for Spinosaurus, the first water-adapted non-avian dinosaur on record,” Sereno said.

The spines on the animal’s back and the sail-like structure they formed were a means of communication.

“Even the big sail on the back of Spinosaurus may, in part, be an adaptation to a life often spent in water,” Ibrahim said. “It would have been a great display structure, and would remain visible even when the animal is partially submerged.”

Spinosaurus would not have been an agile creature, at least on land, and would have had most of its weight at its front.

“It’s quite short, but surprisingly, solid,” Dr. Thomas Holtz, a vertebrate paleontologist at the University of Maryland who was not a part of the research team, said. “These adaptations don’t make sense for a terrestrial strider but they are very reasonable for an animal that’s spending its time in the water and shuffling on land occasionally.”

“How it walked on land and swam are of much interest, its center of gravity far forward compared to other land-based predators,” Sereno said. “Foot-propelled paddling with webbed feet seems likely, to explain the anatomical findings at the rear of the beast. At the other end, its neck and trunk are particularly long, which give the skeletal model and mount its record-shattering 50-foot length. The bones at the base of the neck are also adapted for bending downward, perhaps for fishing while swimming.”

Nevertheless, Sereno explained, the animal would have been a formidable opponent of any land predator of its time, including the nearly T-rex-sized Carcharodontasaurus.

“Spinosaurus had a large head,” Sereno said. “It was nothing to sneer at. You would not want to encounter this animal.”

Despite its odd adaptations, Spinosaurus probably reproduced in a conventional way for its order: Like all other dinosaurs, it was almost certainly oviparous.

“As far as we know, no member of the dinosaur group was ever able to make that switch away from laying eggs,” Holtz explained. “It seems, until we have evidence to the contrary, that Spinosaurus probably did shuffle up onto land to lay its eggs there.”

Spinosaurus illustration

Spinosaurus aegyptiacus, the largest known predator ever to walk the Earth, lived in Cretaceous period Africa. The dinosaur’s unique aquatic adaptations would have allowed it to hunt fish and other prey in the region’s then-ubiquitous rivers. Illustration by Davide Bonadonna, courtesy University of Chicago.

Most of the fossils that serve as the basis for the new paper are of one individual, which also help scientists to understand the proportions of Spinosaurus aegyptiacus. The recently discovered remains were found in the Kem-Kem fossil beds of southeastern Morocco.

On Friday the National Geographic Society will premiere an exhibition in Washington, D.C. focused on Spinosaurus aegyptiacus.

Fossil showing birth of early Triassic ichthyosaur shows viviparity may have evolved on land

February 16, 2014 Leave a comment

Image

This photograph shows the locations of two embryos and one neonate, along with the female ichthyosaur, documented in a new study that indicates marine reptile viviparity may have evolved on land. Image courtesy Ryosuke Motani.

Scientists have discovered a fossil that preserves an infant prehistoric marine reptile in the process of being born, a find that indicates live birth may have first evolved among land-dwelling organisms.

The specimen dates to about 248 million years ago, during the early Triassic period, and is of a female ichthyosaur, along with two embryos and one neonatal individual.

One of the embryos was still inside its mother when death came, another was partially outside the adult individual’s pelvis, and a third was entirely outside its mother.

The position of the embryo that is half-way out of its mother’s body indicates that head-first birth occurred among ichthyosaurs. If so, then the birth may have occurred on land and not in the water, as has generally been presumed by scientists to be likely in the case of early Mesozoic animals.

Viviparity, as live birth of infants is known, has independently evolved across a wide variety of organisms. It is known in fishes, amphibians, reptiles, and mammals and, even among ichthyosaurs, the phenomenon has been observed in fossils dating from the middle Triassic period to the Cretaceous period.

Mosasaurs and plesiosaurs are other Mesozoic era marine organisms that were viviparous. Those reptiles lived during the Cretaceous period.

The fossil preserved individuals of the genus Chaohusaurus would have plied seas near present-day Chaohu and Yuanan, China. The adult specimen was about 100 centimeters long, while the embryos and neonate were about 18 centimeters long.

A paper documenting the fossil discovery appears in the Feb. 14, 2014 edition of PLOS One.

The fossils documented in it are at the Anhui Geological Museum in Hefei City, China.

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