Sauropod dinosaur evolution, new research


This video says about itself:

17 September 2015

“Saturnalia” is an extinct genus of basal sauropodomorph dinosaur known from the Triassic of Rio Grande do Sul, southern Brazil.

“Saturnalia” was originally named on the basis of three partial skeletons. The holotype, MCP 3844-PV, a well-preserved semi-articulated postcranial skeleton, was discovered in mid-summer at Sanga da Alemoa, Rio Grande do Sul, in Brazil, in the geopark of Paleorrota. The two paratypes are MCP 3845-PV, partial skeleton including natural cast of partial mandible with teeth and some postcranial remains, and MCP 3846-PV, partial skeleton including postcranial remains. All specimen were collected in the “Wald-Sanga” locality from the Alemoa Member of the Santa Maria Formation, dating to the Carnian faunal stage of the early Late Triassic, about 225 million years ago. A partial femur from the Carnian Pebbly Arkose Formation of Zimbabwe was also attributed to the genus. It is one of the oldest true dinosaurs yet found. It probably grew to about 1.5 meters long.

“Saturnalia” was first named by Max C. Langer, Fernando Abdala, Martha Richter, Michael J. Benton in 1999 and the type species is “Saturnalia tupiniquim“. The generic name is derived from “Saturnalia”, Latin for “Carnival“, in reference to the discovery of the paratypes during the feasting period. The specific name is derived from a Portuguese and Guarani word meaning “native”.

The primitive nature of “Saturnalia”, combined with its mixture of sauropodomorph and theropod characteristics, has made it difficult to classify. Paleontologist Max Cardoso Langer and colleagues, in their 1999 description of the genus, assigned it to the Sauropodomorpha. However, in a 2003 paper, Langer noted that features of its skull and hand were more similar to the sister group of sauropodomorphs, the theropods, and that “Saturnalia” could at best be considered a member of the sauropodomorph “stem-lineage”, rather than a true member of that group.

From the Ludwig-Maximilians-Universität München in Germany:

Dinosaur evolution: Lumbering giants had agile ancestors

September 20, 2017

The best known sauropod dinosaurs were huge herbivorous creatures, whose brain structures were markedly different from those of their evolutionary predecessors, for the earliest representatives of the group were small, lithe carnivores.

The sauropod group of dinosaurs included the largest animals that have ever walked the Earth — up to 40 meters long and weighing as much as 90 tons. Evolutionarily speaking, they were obviously very successful, giving rise to a diverse and widely distributed array of plant-eating species. These forms were characterized by a small head, a long and highly flexible neck that allowed them — like modern giraffes — to graze the tops of the tallest trees, and a massive body that made mature specimens invulnerable to predators. The sauropods survived for well over 100 million years before succumbing to the meteorite that snuffed out the dinosaurs at the end of the Cretaceous Era.

However, the early representatives of the lineage that led to these lumbering giants were strikingly different in form and habits. For a start, they were carnivores — like Saturnalia tupiniquim, an early sauropod dinosaur that was about the same size as a modern wolf. Recent work carried out by researchers for Ludwig-Maxilians-Universitaet (LMU) in Munich in collaboration with colleagues in Brazil now confirms this scenario and adds new details to the story. Most of the evidence for the early members of the Sauropodomorpha comes from their type of dentition. Now paleontologists Mario Bronzati and Oliver Rauhut, who are based at LMU and the Bavarian State Collection for Paleontology and Geology in Munich, have used computer tomography (CT) to analyze fossil skull bones assigned to S. tupiniquim. The high-resolution images of the cranial bones provided by this technique enabled them to deduce the overall surface morphology of the brain. The results suggest that despite being capable of consuming both meat and plants, S. tupiniquim could have followed a purely predatory lifestyle. The new findings appear in Scientific Reports.

The fossil material used in the study was discovered in Brazil over 20 years ago. It comes from a geological formation that dates back to the Triassic Era, and is about 230 million years old. According to the authors of the study, these are the oldest dinosaur bones that have been successfully reassembled with the aid of computer tomography at sufficiently high resolution to permit the reconstruction of the gross anatomy of the brain.

The evolution of the so-called Sauropodomorpha, of which Saturnalia tupiniquim is an early representative, and the Sauropoda sensu stricto, is marked by a clear tendency towards extension of the neck region, which is accompanied by reduction of the size of the skull — with a corresponding decrease in the volume of the brain — relative to the skeleton as a whole. Saturnalia tupiniquim stands at the beginning of this process. But the new study reveals that, unlike the case in the true sauropods, a specific area in the cerebellum, which encompasses the two lobes known as the flocculus and paraflocculus, is particularly prominent in the brain of S. tupiniquim. These structures are known to play an important role in controlling voluntary movements of the head and neck, and are involved in regulating the oculomotor system, which stabilizes the animal’s field of view.

Bronzati, Rauhut and their co-authors therefore argue that these features enabled S. tupiniquim to adopt a predatory lifestyle. Their findings strongly suggest that, in contrast to the true sauropods, it had a bipedal gait. Moreover, it was nimble enough to hunt, seize and kill its prey — thanks to its inferred ability to track moving objects with its eyes and to execute rapid movements of its head and neck in a coordinated and precise fashion. With the aid of CT-based reconstruction of the surface anatomy of the brain, the researchers now hope to retrace other stages in the evolution of the sauropodomorphs.

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Fish evolution, new discovery


Fukangichthys

By Viviane Callier, 2:17pm, September 18, 2017:

3-D scans of fossils suggest new fish family tree

Analysis of specimens from China implies ray-finned fishes are younger than previously thought

When it comes to some oddball fish, looks can be deceiving.

Polypterus, today found only in Africa, and its close kin have generally been considered some of the most primitive ray-finned fishes alive, thanks in part to skeletal features that resemble those on some ancient fish. Now a new analysis of fish fossils of an early polypterid relative called Fukangichthys [from the Triassic] unearthed in China suggests that those features aren’t so old. The finding shakes up the evolutionary tree of ray-finned fishes, making the group as a whole about 20 million to 40 million years younger than thought, researchers propose online August 30 in Nature.

Ray-finned fishes named for the spines, or rays, that support their fins — are the largest group of vertebrates, making up about half of all backboned animals. They include 30,000 living species, such as gars, bowfins and salmon. The group was thought to originate about 385 million years ago, in the Devonian Period. But the new research, using 3-D CT scans of the previously discovered fossils, shifts the fishes’ apparent origin to the start of the Carboniferous Period some 360 million years ago, says study coauthor Matt Friedman, a paleontologist at the University of Michigan in Ann Arbor.

One of the largest extinction events in Earth’s history marks the boundary between the Devonian and Carboniferous. “We know that many groups of backboned animals were hard hit by the event,” Friedman says. But after the massive die-off, ray-finned fishes popped up and, according to previous fossil evidence, their diversity exploded. The new finding “brings the origin of the modern ray-finned fish group in line with this conspicuous pattern that we see in the fossil record,” Friedman says. It suggests these vertebrates didn’t survive the event. They came after, then flourished.

Horned Triassic reptile discovery in India


This video says about itself:

23 August 2017

Line art and coloration, for Shringasaurus by the time this uploads it will be 3 days since its discovery! I mean, look at it! It’s awesome!

Also having revised the dates- I accidentally mixed up the years as it is 252 ma, not 240 ma. I do apologize for that mistake.

By Pete Buchholz, 28 August 2017:

India’s bull-headed reptile adds to Triassic menagerie

A large plant-eating reptile fossil from the Middle Triassic of India shows that some adults had brow horns and some didn’t. Researchers have suggested that the horned individuals were males who used their horns in combat trying to woo females.

When exploring the Middle Triassic Denwa Formation of Central India, paleontologists unearthed seven skeletons of one of the most remarkable fossil reptiles ever discovered.

Shringasaurus indicus was a barrel-chested reptile like a long-necked pig, with two curved horns over its eyes.

The horns emerge from the top of the skull and are forward-curving cones; remarkably similar to the brow horns of Triceratops. They are the most conspicuous features of Shringasaurus, which led paleontologists Saradee Sengupta and colleagues to use the Sanskrit word for horn, “śṛṅga,” in its name. Its teeth show that it was an herbivore, and at nearly four meters (13 feet) long, it was one of the largest herbivores alive at the time.

The neck was long and muscular, nearly as long as the torso. The round torso, muscular limbs, and relatively short tail give Shringasaurus the distinct look of a bruiser.

The horns also gave Sengupta and colleagues unique insights into the life of Shringasaurus and may explain why it grew so large. They found at least seven individuals of different ages in a small bone bed. Six of them have horns, but one nearly fully grown specimen lacked horns completely but was otherwise identical to the others. What’s more, those individuals with horns show a great deal of individual variation.

Sengupta and colleagues proposed that Shringasaurus was sexually dimorphic, with the horned individuals being males and the unhorned individual being a female. They imagined that the horns were used in combat between males, making a comparison to modern mammals like deer and sheep, whose males engage in combat using horns or antlers, and whose females have smaller or no horns. The large adult size, strong build, and horns are all thought to be the result of sexual selection where larger stronger males with more prominent horns were selected as mates by females.

Shringasaurus was an allokotosaur, a lineage of weird plant-eating reptiles from the Triassic including some iguana-like forms as well as long-necked barrel-chested animals like Shringasaurus. Allokotosaurs are part of a larger lineage called the archosauromorphs, which includes living birds and crocodilians, as well as a huge number of distinctive extinct groups of animals.

Archosauromorphs like Shringasaurus diversified rapidly in the Early Triassic in the aftermath of the Permian-Triassic extinction, the largest mass extinction in Earth’s history. Shringasaurus lived a mere five to ten million years after the extinction and is one of the several strange Triassic archosauromorphs like the long-necked fishing Tanystropheus, leg-winged gliding Sharovipteryx, and the thick-skulled Triopticus.

The Triassic was a unique time in Earth’s history, documenting a rapid biological recovery after the extinction event. New fossil discoveries like Shringasaurus show that the Triassic still has much to offer. The period ended with another mass extinction wiping out many archosauromorphs, including the allokotosaurs, leaving just crocodilians, pterosaurs, and dinosaurs, which gave rise to birds.

Read the original research in Scientific Reports.

Ancient Triassic reptile was not aquatic


LAND LIVING Eusaurosphargis dalsassoi, an ancient lizardlike critter (illustrated), wouldn’t swim well, scientists now say, arguing the creature’s style of motion and protective coverings were more suited to land. T. Scheyer/Palaeontological Institute and Museum/University of Zurich, Switzerland

By Ashley Yeager, 7:00am, August 9, 2017:

Fossil find suggests this ancient reptile lurked on land, not in the water

Exquisitely preserved specimen may overturn ideas about spiny creature’s home

A round belly, stubby feet and a tapering tail made one armored reptile a lousy swimmer. Despite earlier reports, Eusaurosphargis dalsassoi might not have swum at all, scientists now say.

E. dalsassoi was first identified in 2003. Fossils were found near Monte San Giorgio at the Swiss-Italian border alongside the remains of marine reptiles and fish that lived roughly 240 million years ago. That association led scientists to conclude the creature was aquatic. But a complete skeleton of E. dalsassoi unearthed in 2002 in the Swiss Alps and recently assembled contradicts that idea.

At just under 20 centimeters long, the fossil, probably of a youngster, shows that E. dalsassoi widened at the stomach and slithered forward with stiff elbow and knee joints and spadelike claws. That’s not a swimmer’s build, paleontologist Torsten Scheyer of the University of Zurich and colleagues report June 30 in Scientific Reports.

Armed with rows of small spikes along its back and spear-shaped plates framing its head, sides and tail, the animal resembled today’s girdled lizards. The researchers speculate that this particular E. dalsassoi died on a beach and then got washed into the ocean.

Big Triassic fossil fish discovered in Nevada, USA


Possible look of the newly discovered predatory fish species Birgeria americana with the fossil of the skull shown at bottom right. Artwork: Nadine Bösch

From the University of Zurich in Switzerland:

Large-mouthed fish was top predator after mass extinction

July 26, 2017

Summary: The food chains recovered more rapidly than previously assumed after Earth’s most devastating mass extinction event about 252 million years ago as demonstrated by the fossilized skull of a large predatory fish called Birgeria americana discovered by paleontologists from the University of Zurich in the desert of Nevada.

The most catastrophic mass extinction on Earth took place about 252 million years ago — at the boundary between the Permian and Triassic geological periods. Up to 90 percent of the marine species of that time were annihilated. Worldwide biodiversity then recovered in several phases throughout a period of about five million years. Until now, paleontologists have assumed that the first predators at the top of the food chain did not appear until the Middle Triassic epoch about 247 to 235 million years ago.

Unexpected find of a large predatory fish

Swiss and U.S. American researchers led by the Paleontological Institute and Museum of the University of Zurich have discovered the fossil remains of one of the earliest large-sized predatory fishes of the Triassic period: an approximately 1.8-meter-long primitive bony fish with long jaws and sharp teeth. This fish belongs to a previously unknown species called Birgeria americana. This predator occupied the sea that once covered present-day Nevada and the surrounding states already one million years after the mass extinction.

Triassic “Jaws

In the United States, almost no vertebrate fossils from the Early Triassic epoch (252 to 247 million years ago) have been scientifically described until now. “The surprising find from Elko County in northeastern Nevada is one of the most completely preserved vertebrate remains from this time period ever discovered in the United States,” emphasizes Carlo Romano, lead author of the study. The fossil in question is a 26-centimeter-long partial skull of a fierce predator, as evidenced by three parallel rows of sharp teeth up to 2 centimeters long along the jaw margins, as well as several smaller teeth inside the mouth.

Birgeria hunted similarly to the extant great white shark: the prey fish were pursued and bitten, then swallowed whole. Species of Birgeria existed worldwide. The most recent discovery is the earliest example of a large-sized Birgeria species, about one and a half times longer than geologically older relatives.

Predators appeared earlier than assumed

According to earlier studies, marine food chains were shortened after the mass extinction event and recovered only slowly and stepwise. In addition, researchers assumed that the ancient equatorial regions were too hot for vertebrates to live during the Early Triassic. Finds such as the newly discovered Birgeria species and the fossils of other vertebrates now show that so-called apex predators (animals at the very top of the food chain) already lived early after the mass extinction. The existence of bony fish close to the equator — where Nevada was located during the Early Triassic — indicates that the temperature of the sea was a maximum of 36°C. The eggs of today’s bony fish can no longer develop normally at constant temperatures above 36°C.

“The vertebrates from Nevada show that previous interpretations of past biotic crises and associated global changes were too simplistic,” Carlo Romano says. Despite the severity of the extinctions of that time and intense climatic changes, the food webs were able to redevelop faster than previously assumed.

Swiss Triassic reptile, new study


Eusaurosphargis dalsassoi, new specimen PIMUZ A/III 4380. Credit: Beat Scheffold; Palaeontological Institute and Museum, University of Zurich, Switzerland

From the University of Zurich in Switzerland:

Ancient Swiss reptile shows its bizarre scale armor for the first time

June 30, 2017

Grisons, 241 million years ago — Instead of amidst high mountains, a small reptile suns itself on an island beach in a warm shallow sea, where many fish and marine reptiles frolic. This is the story told by an excellently preserved new discovery of the reptile Eusaurosphargis dalsassoi studied by paleontologists from the University of Zurich.

About 20 centimeters in length, the Swiss reptile was small and juvenile, but its skin was already strongly armored with variously formed smooth, jagged or even thorny osteoderms. Its skeleton indicates a life on land, even though the animal was found together with fish and marine reptiles in the 241 million year old calcareous deposits of the Prosanto Formation near Ducanfurgga at an altitude of 2,740 meters south of Davos in the canton Grisons, Switzerland. The Swiss-British team of researchers led by Torsten Scheyer, paleontologist at the University of Zurich, and James Neenan from the Oxford University Museum of Natural History therefore assumes that it was washed off a nearby island into the sea basin and became embedded in the finely layered marine sediments after death.

Skeleton and appearance reconstructed

14 years ago, the species Eusaurosphargis dalsassoi was described using a partially preserved, completely disarticulated sample from the vicinity of the Swiss-Italian UNESCO World Heritage Site Monte San Giorgio. The new find from the Grisons Mountains, on the other hand, is very well-preserved, allowing researchers to reconstruct the skeleton and outward appearance of the animal for the first time.

In the process, they discovered something astonishing: Externally, Eusaurosphargis dalsassoi looks very similar to girdled lizards (Cordylidae), a group of small, scaled reptiles (Lepidosauria) that usually live in the dry regions of southern Africa. Some of the more strongly armored girdled lizard species could have served as the basis of mythical dragon legends due to their appearance. “This is a case of convergent development as the extinct species is not closely related to today’s African lizards”, Scheyer explains.

Related to Helveticosaurus

An exact examination of the phylogenetic relationships rather confirms that its closest relatives are marine reptiles such as ichthyosaurs (Ichthyosauria or “fish lizards”), sauropterygians (Sauropterygia “lizard flippers”) or even Helveticosaurus, a marine reptile that is unique to Switzerland, all of which have been found at Monte San Giorgio. The skeleton of Eusaurosphargis, however, shows neither a streamlined body structure, nor arms and legs that have transformed into flippers, as well as no tail fin, which would indicate a life at sea.

Discovery initially identified as fish remains

The astonishing fossil was originally discovered 15 years ago by amateur paleontologist and fossil preparator Christian Obrist during systematic fossil excavations of the University of Zurich under the leadership of Heinz Furrer, which were sponsored by the Natural History Museum of the Grisons in Chur and by the Grisons canton. It took more than a decade for the scientific value of the exceptional discovery to gradually be recognized as a result of elaborate preparation. The fossil was namely initially identified as simple fish remains. “The excavations at Ducanfurgga are still in progress today and will hopefully reveal other spectacular discoveries in the future,” Furrer says.

See also here.

Big fish, little fish in Permian-Triassic mass extinction


This video says about itself:

The Permian-Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252 million years ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras.

It is the Earth’s most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. It is the only known mass extinction of insects. Some 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event, possibly up to 10 million years.

Catastrophe by Tony Robinson (2008).

From the University of Bristol in England:

Size not important for fish in the largest mass extinction of all time

June 30, 2017

Understanding modern biodiversity and extinction threats is important. It is commonly assumed that being large contributes to vulnerability during extinction crises.

However, researchers from the University of Bristol and the Chengdu Center of the China Geological Survey, have found that size played no role in the extinction of fish during the largest mass extinction of all time.

The study focused on the evolution of bony fishes during the Permian-Triassic mass extinction 252 million years ago. During this crisis, as many as 90 percent of all species on Earth were killed by massive climate change triggered by huge volcanic eruptions in Russia.

The erupted gases led to worldwide acid rain and atmospheric warming of as much as 20 degrees centigrade. This killed plants, and soil was stripped by rainfall and washed into the sea. Oceans were also heated and life fled from the tropics.

It was expected that a key feature in extinction would have been body size: the large animals would suffer heat and starvation stress first. However, in the new paper, published in Palaeontology, it is shown that larger fish were no more likely to go extinct than small fish.

The study used a detailed summary of all information on fossil fish through a span of over 100 million years, from well before to well after the disaster. Body size information was identified for over 750 of these fishes, and multiple calculations were carried out to allow for variations in the shape of the evolutionary tree and the exact dating of all the species. The result was clear — body size did not provide any advantages or disadvantages to fish during the crisis.

Lead researcher Dr Mark Puttick from the Natural History Museum and University of Bristol’s School of Earth Sciences, explained: “These results continue the trend of recent studies that suggest body size played no role in determining which species survive or go extinct. This is the opposite result we would expect, but provides increasing support for previous studies that show body size plays no role in extinction selectivity.”

The team explored the largest dataset used in an analysis of this type and applied a range of computational evolutionary models to understand these patterns in deep time. The models take account of uncertainties in the quality of the fossil data and the reconstructed evolutionary tree, and the result was clear.

Professor Michael Benton, also from the University of Bristol, added: “These are exciting results. What is important also is that we were able to deploy new methods in the study that take greater account of uncertainties.

“The methods are based around a detailed evolutionary tree so, unlike most previous work in the field, we paid attention to the relationships of all the species under consideration.”

Professor Shixue Hu, leader of the China Geological Survey: “It’s great to see this new analytical work. We were able to include many new fossils from our exceptional biotas in China, and we can see the full impact of the extinction and the subsequent recovery of life during the Triassic.”

Lead author Dr Dunhill, from the School of Earth and Environment at Leeds, said: “While the Late Triassic mass extinction had a big impact on the overall number of marine species, there was still enough diversity among the remaining species that the marine ecosystem was able to function in the same way it had before”: here.

Variation in the recovery of tetrapods after the Permian extinction opened the door for dinosaurs and mammals: here.