Oldest reptile live birth fossil discovery


This video is called The history of paleoillustrations: Ichthyosauria.

From LiveScience:

Oldest Fossil of Reptile Live Birth Found

By Becky Oskin, Staff Writer | February 12, 2014 05:04pm ET

A new fossil that captures both birth and death reveals the earliest ancestors of the giant prehistoric sea predators called ichthyosaurs birthed their babies headfirst, according to a new study.

The fossil of an ancient Chaohusaurus mother that likely died while in labor also suggests that reptilian live birth only evolved on land, researchers report today (Feb. 12) in the journal PLOS ONE.

Ichthyosaurs were top ocean predators during the age of the dinosaurs. Sleek, streamlined swimmers that grew as long as a bus, they had teeth-filled snouts and enormous eyes for snatching prey. These air-breathing carnivores arose from land reptiles that moved into the water from land during the early Triassic period, between 251 million and 247 million years ago. (The Triassic period follows one of the biggest mass extinctions on Earth, which killed 96 percent of marine species and 70 percent of land species.) [Image Gallery: Ancient Monsters of the Sea]

Previously found fossils of pregnant ichthyosaurs had already revealed the reptiles carried live embryos, not eggs. And one spectacular fossil of a Stenopterygius ichthyosaur in “childbirth,” from the Jurassic period, between 201 million and 145 million years ago, showed at least one species had newborns come out tail-first.

However, researchers didn’t know whether the earliest ichthyosaurs also gave birth headfirst or tail-first. Most air-breathing marine creatures that bear live young, such as whales and dolphins, birth their babies tail-first, so the newborns don’t suffocate during labor. But on land, babies tend to come out headfirst. And the earliest whales, which also evolved from land mammals, birthed their newborns headfirst.

The new fossil confirms that the first ichthyosaur babies came out headfirst, the study reports. The ichthyosaur mother died with three young: one outside the mother, one half-emerged headfirst from her pelvis and one still inside, waiting to be born. Because of the burial positions, it’s unlikely the babies were expelled from the mother after death, the researchers said.

“The reason for this animal dying is likely difficulty in labor,” said Ryosuke Motani, lead study author and a paleobiologist at the University of California, Davis. Motani believes the first baby was born dead, and the mother may have died of a labor complication from the second, which is stuck half-in, half-out of her body. “Obviously, the mother had some complications,” he said.

The skeleton was a lucky find. It was hidden in a rock slab with a Saurichthys fish fossil, and was only discovered when the fish fossil was prepared in the team’s lab in China. (The two fossils aren’t from the same time period, the researchers said.)

The Chaohusaurus fossil, from one of the oldest ichthyosaur species, is about 10 million years older than other fossil embryos from reptiles found so far.

The specimen is now at the Anhui Geological Museum in Hefei, China. The team recovered more than 80 new ichthyosaur skeletons during a recent field expedition to a fossil quarry in south Majiashan, China.

Earliest newborns

Live birth evolved independently in more than 140 different species, including about 100 reptiles. Other extinct aquatic reptiles that gave birth to live young include the plesiosaur and the mosasaur; in 2011, scientists discovered a pregnant plesiosaur, a marine reptile, which lived some 78 million years ago.

The new ichthyosaur fossil pushes back the known records of live birth to the earliest appearance of marine reptiles 248 million years ago, during the beginning of the Mesozoic era.

Until now, researchers thought live birth first appeared in marine reptiles after they took to the seas, Motani said. The ichthyosaur fossil counters this assumption, by providing an evolutionary link to the headfirst, terrestrial style of childbirth.

“This land-style of giving birth is only possible if they inherited it from their land ancestors,” Motani told Live Science. “They wouldn’t do it if live birth evolved in water.”

And because ichthyosaurs evolved from land reptiles, the discovery suggests that land reptiles also bore live young in the earliest Mesozoic, Motani said. The oldest fossil evidence for live birth in land reptiles is no more than 125 million years old, more than 100 million years younger than the new fossil discovery.

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Big Triassic reptiles discovery in Texas


This video says about itself:

Texas Tech University Scientists Discover Prehistoric Crocodile Species

28 Jan 2014

Texas Tech scientists recently discovered a new species of phytosaur, which is like a modern-day crocodile. The skull was found near Post, Texas, and is believed to be 210 million years old.

Though phytosaurs look like crocodiles, there is doubt how closely related to them they were.

Today, not only news from China about the discovery of a gigantic dinosaur from the Cretaceous age.

Also news from Texas in the USA about the discovery of another reptile species; much older; smaller, but still big.

From Texas Tech University today:

Paleontologists discover new Triassic swamp monster (w/ Video)

18 hours ago by John Davis

In the dangerous waters of an ancient oxbow lake created by a flooded and unnamed meandering river, the female phytosaur died and sank to the bottom 205 million years ago. About 40 yards away the remains of a larger male also came to rest, and both disappeared in a tomb of soil and sediment.

Evidence for the cause of their deaths and the rest of their bodies have vanished with time, but their skulls remained. After careful research, a Texas Tech paleontologist says he and others have discovered a new species of the Triassic-age monster in the wilds of West Texas.

Their findings were published in the peer-reviewed journal, Earth and Environmental Science Transactions of the Royal Society of Edinburgh.

Bill Mueller, assistant curator of Paleontology at the Museum of Texas Tech University, said the team named their find Machaeroprosopus lottorum after the Lott family who own the ranch on which the animal was discovered.

“We found them in an area we’d been excavating in,” Mueller said. “I think we’ve gotten four skulls out of that area already. Doug Cunningham found this specimen, and then we dug it up. When he found it, just the very back end of the skull was sticking out of the ground. The rest was buried. We excavated it and brought it into the museum to finish preparation.”

Cunningham, currently a field research assistant at the museum and a retired firefighter, remembered finding the unusual female skull on June 27, 2001. After removing it from the mudstone, he recalls looking it over carefully with others and wondering if his discovery would add a new animal to science.

“It was really well preserved with the teeth and everything,” Cunningham said. “Finding one with teeth is pretty rare. It was so odd, but when they come out of the ground, you have a long way to go to actually see what you have because they’re still covered in matrix. We were all kind of in awe of it. It had this long, skinny snout. It was quite a bit different. It took me years to get it prepped and ready. At the time, I was working full-time and I did that on my days off.”

By looking an opening on the skull called the supratemporal fenestra, the snout and the shape of the bones at the back of the head, the team compared it to other phytosaurs and determined they’d discovered a separate species.

While West Texas is dry and dusty today, Mueller said the landscape looked more like a swampy, tropical rainforest during the Triassic period. Our planet’s landmasses had converged to form the supercontinent of Pangaea. In the forest undergrowth covered by tall conifers and choked with ferns, phytosaurs lurked beneath the water and waited for prey.

“A phytosaur resembles a crocodile,” Mueller said. “They had basically the same lifestyle as the modern crocodile by living in and around the water, eating fish, and whatever animals came to the margins of the rivers and lakes. But one of the big differences is the external nares, the nose, is back up next to its eyes instead of at the end of its snout.”

Mueller said scientists can tell the sexes of the animals by a distinctive feature on males. A bony crest stretched from the nostrils by the eyes to the tip of the animal’s beak – a feature lady phytosaurs probably found sexy.

Judging by the female’s skull size, which is more than three feet in length, Mueller guessed she would have measured 16 to 17 feet in length from nose to tail tip. The male would have measured about 17 to 18 feet. Their thin jaws suggested they hunted mainly fish as opposed to big prey.

Mueller said phytosaurs lived throughout the Triassic period from 230 to 203 million years ago, but died out during a mysterious mass extinction. Highly successful animals, they are commonly found because these animals liked to live in swampy areas and were more likely to become covered in sediment and fossilized.

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How dinosaurs originated


This video is called Brief Lecture on the Origin of Dinosaurs.

From Current Biology, Volume 24, Issue 2, R87-R95, 20 January 2014:

Summary

Dinosaurs arose in the early Triassic in the aftermath of the greatest mass extinction ever and became hugely successful in the Mesozoic. Their initial diversification is a classic example of a large-scale macroevolutionary change.

Diversifications at such deep-time scales can now be dissected, modelled and tested. New fossils suggest that dinosaurs originated early in the Middle Triassic, during the recovery of life from the devastating Permo-Triassic mass extinction. Improvements in stratigraphic dating and a new suite of morphometric and comparative evolutionary numerical methods now allow a forensic dissection of one of the greatest turnovers in the history of life. Such studies mark a move from the narrative to the analytical in macroevolutionary research, and they allow us to begin to answer the proposal of George Gaylord Simpson, to explore adaptive radiations using numerical methods.

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Triassic fossil fish discovery in Switzerland


This video says about itself:

Body elongation in early fish evolution

7 Oct 2013

In Saurichthys, an early ray-finned fish, the vertebral arches of the axial skeleton are doubled, resulting in the elongation of the body and giving it a needlefish-like appearance. This video illustrates the hypothetical evolutionary transformation from a generalized fish in the late Permian to the specialized vertebral column and body shape of Saurichthys in the early Triassic.

From Sci-News.com:

Saurichthys: Unusual 240-Million-Year-Old Fossil Fish

Oct 8, 2013 by Enrico de Lazaro

A newly discovered fossil of an early ray-finned fish, named Saurichthys curionii, from the Middle Triassic of Switzerland reveals a previously unknown mechanism of axial skeleton elongation.

The extreme elongation of body axis occurred in one of two ways: through the elongation of the individual vertebrae of the vertebral column; or through the development of additional vertebrae and associated muscle segments.

Unlike other known fish with elongate bodies, the vertebral column of Saurichthys does not have one vertebral arch per myomeric segment, but two, which is unique. This resulted in an elongation of the body and gave it an overall elongate appearance.

“This evolutionary pattern for body elongation is new,” said Dr Erin Maxwell from the University of Zurich, lead author of the paper published in Nature Communications.

“Previously, we only knew about an increase in the number of vertebrae and muscle segments or the elongation of the individual vertebrae.”

According to Dr Maxwell and his colleagues, Saurichthys was certainly not as flexible as today’s eels and, unlike modern oceanic fishes such as tuna, was probably unable to swim for long distances at high speed.

Based upon its appearance and lifestyle, the roughly half-meter-long fish is most comparable to the garfish or needlefish that exist today.

Polish Triassic amphibian burrowing discovery


Skeleton of Metoposaurus diagnosticus krasiejowensi in the Krasiejów museum in Poland

Not only news today about living amphibians … but also about their very distant relatives, extinct since over 200 million years.

From the Society of Vertebrate Paleontology:

Giant Triassic amphibian was a burrowing youngster

Krasiejów, Poland was a vastly different place 230 million years ago during the Triassic Period. It was part of a giant continent called Pangea, had a warm climate throughout the year, and was populated by giant amphibians that weighed half a ton and were 10 feet long. Metoposaurus diagnosticus was one of these giant amphibians, and its environment had only two seasons: wet and dry. Like modern amphibians, Metoposaurus needed water for its lifestyle, but the extremely long dry season in Triassic Krasiejów drove this species to burrow underground and go dormant when water was scarce.

The burrowing behavior of Metoposaurus was recently discovered by Dorota Konietzko-Meier of the University of Opole, Poland and the University of Bonn, Germany, and P. Martin Sander also of the University of Bonn and was recently published in a study in the Journal of Vertebrate Paleontology. This study examined both the overall structure of the skeleton of Metoposaurus as well as the microscopic structure of its bones.

The broad, flat head, broad flat arm bones, wide hands, and large tail of Metaposaurus diagnosticus led the investigators to conclude that this species swam in ephemeral lakes during the wet season and used its broad, flat head and forearms to burrow under the ground when the dry season began. The authors also examined cross-sections of the bones of Metoposaurus looking for growth rings, called annuli. These annuli are similar to tree rings, where a band of light and a band of dark indicate one year of growth. In other early amphibians one annulus usually consists of a broad zone of rapid growth (wet season) followed by a thin band of slow growth (dry season), but in Metoposaurus, a period of prolonged slow growth was followed by a cessation of growth during the dry season. According to lead author Dorota Konietzo-Meier, “The histology of Metoposaurus long bones seems to be unique. In our interpretation it corresponds to the two-seasonal climate with a short, more favorable wet season and a long dry part of the year when life conditions were worse.”

Dr. Michel Laurin from the Muséum National d’Histoire Naturelle who was not involved with this study, commented, “This interpretation is interesting, but problematic in some respects. This animal was much larger than any extant burrowing species I know of, and if it dug, I suspect that the snout and tail played a far greater role than the limbs, as we observe in most extant aquatic vertebrates.”

These annuli also give an estimate of age. Co-author P. Martin Sander said, “A common problem with these large amphibians is that you can’t tell from the shape of their bones if they are grown or not; sometimes the youngsters get described as a different species from the grown-ups”. This technique solves that problem. It turns out that all of the specimens preserved at Krasiejów were juveniles. The smallest specimen was only one year old, while the largest specimen was four. Adulthood in these large amphibians was usually reached around year seven. The authors do not know if this mode of life was unique to juveniles or if adults also burrowed.

Sander concludes, “It amazes me time and again how much we can learn from these extinct animals. The techniques we used have been around since the 1840s, but only in the last 20 years have researchers asked the right questions and drawn comparisons with living animals.”

###

ABOUT THE SOCIETY OF VERTEBRATE PALEONTOLOGY

Founded in 1940 by thirty-four paleontologists, the Society now has over 2,000 members representing professionals, students, artists, preparators, and others interested in VP. It is organized exclusively for educational and scientific purposes, with the object of advancing the science of vertebrate paleontology.

The Journal of Vertebrate Paleontology

The Journal of Vertebrate Paleontology (JVP) is the leading journal of professional vertebrate paleontology and the flagship publication of the Society. It was founded in 1980 by Dr. Jiri Zidek and publishes contributions on all aspects of vertebrate paleontology.

For complimentary access to the full article, visit: http://www.tandfonline.com/toc/ujvp20/current (on or after September 3, 2013)

The article appears in the Journal of Vertebrate Paleontology 35(5), published by Taylor and Francis.

Citation: Koneitzko-Meier, Dorota and P. Martin Sander. 2013. Long Bone Histology of Metaposaurus diagnosticus (Temnospondyli) from the Late Triassic of Krasiejów (Poland) and its Paleobiological Implications. Journal of Vertebrate Paleontology 35(5):1-16.

South African Triassic fossil discovery


This video says about itself:

3D reconstruction of an Early Triassic amphibian and therapsid sharing a burrow.

From Prensa Latina news agency:

250 Million Year Old Fossil Couple Found in South Africa

Washington, 24 June

Scientists from South Africa, Australia and France have discovered a world first association while scanning a 250 million year old fossilised burrow from the Karoo Basin of South Africa.

The study revealed two unrelated vertebrate animals nestled together and fossilised after being trapped by a flash flood event.

Facing harsh climatic conditions subsequent to the Permo-Triassic (P-T) mass extinction, the amphibian Broomistega and the mammal forerunner Thrinaxodon cohabited in a burrow.

Scanning shows that the amphibian, which was suffering from broken ribs, crawled into a sleeping mammal’s shelter for protection.

Some would call Thrinaxodon a mammal-like reptile, not a real mammal yet.

This research suggests that short periods of dormancy, called aestivation, in addition to burrowing behaviour, may have been a crucial adaptation that allowed mammal ancestors to survive the extinction.

The results of this research resulted in a paper entitled Synchrotron reveals Early Triassic odd couple: injured amphibian and aestivating therapsid share burrow and that is published in a scientific journal. Kristian Carlson, from the South Africa Universities of Witts, denied that the evidence shows that they were feeding on each other, even when one of them had broken ribs.

See also here. And here.

The use of communal latrines has only been known for some recent mammals, such as horses, tapirs, and elephants, and for some birds such as the ancient, ostrich-like Moa. The new findings show that the complex behavior was also present in distant relatives of mammals, the rhino-like reptiles called dicynodonts, dating to a time much older than previously suspected: here.

How turtles got their shells


Eunotosaurus africanus

By Roxanne Palmer:

Turtle Shell Origin Story Gets New Chapter Thanks To Fossil Reptile

May 30 2013 12:55 PM

Rudyard Kipling’s fanciful “Just So Stories” have offered explanations for how the leopard got his spots and how the camel got his hump. Kipling didn’t offer an origin story for the turtle’s shell, but scientists have now come to the rescue.

In a new paper published in the journal Current Biology, researchers led by Yale University and Smithsonian Institution researcher Tyler Lyson present the earliest evidence yet for how some ancient reptiles turned into swimming tanks.

The turtle’s shell is a unique specimen of evolution. Other animals with shells usually have ones made from bony scales on the outsides of their bodies – like the crocodile, whose skin is dotted with thick bony plates called osteoderms. But a turtle’s shell is made from the fusion of more than 50 bones, including parts of the pelvis, ribs and vertebrae.

To get a better picture of how the turtle shell was made, Lyson and his colleagues studied an ancient South African reptile called Eunotosaurus africanus, which hails from about 260 million years ago. Scientists have found fossils of other turtle ancestors, but these ones had either fully developed shells. In 2008, Chinese scientists uncovered the remains of the 220 million-year-old Odontochelys semitestacea, which had a complete shell on its belly side, but only a partially developed shell on the back. The new specimen goes back even earlier.

“Eunotosaurus neatly fills an approximately 30-55-million year gap in the turtle fossil record,” Lyson said in a statement. “There are several anatomical and developmental features that indicate Eunotosaurus is an early representative of the turtle lineage; however, its morphology is intermediate between the specialized shell found in modern turtles and primitive features found in other vertebrates.”

The fossil shares several characteristics with modern turtles, including broad ribs and a lack of intercostal muscles, which run between the ribs and which provide support and movement for the chest wall.

“The reason, I think, that more animals don’t form a shell via the broadening and eventually suturing together of the ribs is that the ribs of mammals and lizards are used to help ventilate the lungs,” Lyson says. “If you incorporate your ribs into a protective shell, then you have to find a new way to breathe!”

Since their shells don’t let modern turtles breathe by expanding and contracting their ribs, they have other methods. One part of the process is called “buccal pumping,” and it involves gulping air and pushing it into the lungs using movements of the throat. Turtles can also sometimes achieve a limited amount of respiration via the cloaca – hence the popular myth that turtles breathe through their rear ends. Some species of turtle have sacs called bursae on either side of the cloaca, with thin membranes that allow for gas exchange.

Most turtles don’t rely on their rear ends to breathe, but an Australian species called the Fitzroy River turtle has exploited this feature. This turtle can pump water in and out of the sacs near its cloaca and meet up to two-thirds of its oxygen needs this way.

Solving the mystery of how turtle breathing developed over time is the next research frontier for Lyson and his colleagues.

“It is clear that this novel lung ventilation mechanism evolved in tandem with the origin of the turtle shell,” he says.

SOURCE: Lyson et al. “Evolutionary Origin of the Turtle Shell.” Current Biology published online 30 May 2013.

Triassic wildlife after mass extinction


This video is called Excavating Triassic Fossils in Antarctica.

From ANI news agency:

Ups and downs of biodiversity after mass extinction unveiled

Saturday 22nd December, 2012

Marine animal groups like ammonoids and conodonts already peaked three or four million years earlier, namely still during the Early Triassic, researchers say.

The climate after the largest mass extinction so far 252 million years ago was cool, later very warm and cool again. Thanks to the cooler temperatures, the diversity of marine fauna ballooned, as paleontologists from the University of Zurich have reconstructed.

The warmer climate, coupled with a high CO2 level in the atmosphere, initially gave rise to new, short-lived species. In the longer term, however, this climate change had an adverse effect on biodiversity and caused species to become extinct.

Until now, it was always assumed that it took flora and fauna a long time to recover from the vast mass extinction at the end of the Permian geological period 252 million years ago.

According to the scientific consensus, complex ecological communities only began to reappear in the Middle Triassic, so 247 million years ago.

However, a Swiss team headed by paleontologist Hugo Bucher from the University of Zurich chart the temperature curves, demonstrating that the climate and the carbon dioxide level in the atmosphere fluctuated greatly during the Early Triassic and what impact this had on marine biodiversity and terrestrial plants.

For their climate reconstruction, Bucher and his colleagues analyzed the composition of the oxygen isotopes in conodonts, the remains of chordates that once lived in the sea. According to the study, the climate at the beginning of the Triassic 249 million years ago was cool.

This cooler phase was followed by a brief very warm climate phase. At the end of the Early Triassic, namely between 247.9 and 245.9 million years ago, cooler conditions had resumed.

The scientists then examined the impact of the climate on the development of flora and fauna.

“Biodiversity increased most in the cooler phases,” Bucher said.

“The subsequent extremely warm phase, however, led to great changes in the marine fauna and a major ecological shift in the flora,” he said.

Bucher and his team can reveal that this decline in biodiversity in the warm phases correlates with strong fluctuations in the carbon isotope composition of the atmosphere.

These, in turn, were directly related to carbon dioxide gases, which stemmed from volcanic eruptions in the Siberian Large Igneous Province.

Through the climatic changes, conodont and ammonoid faunae were initially able to recover very quickly during the Early Triassic as unusually short-lived species emerged. However, the removal of excess CO2 by primary producers such as algae and terrestrial plants had adverse effects in the long run: The removal of these vast amounts of organic matter used up the majority of the oxygen in the water. Due to the lack of oxygen in the oceans, many marine species died out.

“Our studies reveal that greater climatic changes can lead to both the emergence and extinction of species. Thus, it is important to consider both extinction rates and the rate at which new species emerged,” Bucher added.

The study has been published in Nature Geoscience.

More than 200 million years ago, a massive extinction decimated 76 percent of marine and terrestrial species, marking the end of the Triassic period and the onset of the Jurassic. The event cleared the way for dinosaurs to dominate Earth for the next 135 million years, taking over ecological niches formerly occupied by other marine and terrestrial species: here.

World’s oldest dinosaur discovery in Tanzania?


This video is called Dinosaur Evolution, 1 of 5.

From Discover magazine:

Scientists Discover the Oldest Dinosaur Yet…Maybe

By Breanna Draxler

December 6, 2012 11:13 am

Paleontologists in Tanzania have unearthed fossils from a new species of prehistoric reptile. The bones may have belonged to the world’s oldest dinosaur—or they may be from a reptile that kind of looks like a dinosaur.

Currently, the oldest confirmed dinosaur fossil dates back 230 million years. By this point in time, dinosaurs had grown in size and population to dominate the Earth. But when exactly did dinosaurs first enter the prehistoric picture, and how long did it take them to rise to such prominence? Paleontologists have narrowed the timeline down to the early or middle Triassic—the period of 20 million years before the oldest known dinosaur came to be.  The newfound species, dubbed Nyasasaurus parringtoni, predates this fossil by another 10 to 15 million years, and falls right in the middle of paleontologists’ projected timeframe for the first appearance of dinosaurs.

With only one upper arm bone and six vertebrae to work with, the researchers were able to glean a surprising amount of information about the newly discovered two-legged creature. It measured between 6 and 10 feet from head to tail, and only weighed between 45 and 130 pounds. Certain indicators in the fossils are unique to dinosaurs, namely an “elongated deltopectoral crest”—the attachment necessary to support strong chest muscles. Without more material the researchers cannot definitively declare the creature a dinosaur, rather than a silesaurid, the dinosaurs’ closest relative. Still, scientists say the fossils are the best available evidence of the presence of dinosaurs in the middle Triassic period, and regardless of how it ends up being classified, the new species offers a valuable view of the lives of early reptiles.

Image courtesy of Sterling J. Nesbitt, et. al.

A cross-section through the outer portion of the cortex shows the deltopectoral crest, among other indicators