Dinosaur extinction and bird evolution


This American Museum of Natural History video from the USA says about itself:

18 March 2016

This spellbinding animation from the Museum’s new exhibition “Dinosaurs Among Us” traces the evolutionary transition from dinosaurs to birds.

Based on recent scientific research that examines fossils using new technologies, the transformation story unfolds as low-polygonal silhouettes of dinosaurs morph from ground-dwelling animals into flight-capable birds. The mass extinction that erased most dinosaurs 65 million years ago left a few bird lineages unscathed. Within only 15 million years all of our familiar bird groups were flourishing. These extraordinary living dinosaurs provide a vivid link to the ancient past. The Museum’s new exhibition, “Dinosaurs Among Us,” explores the continuities between living dinosaurs—birds—and their extinct ancestors, showcasing remarkable new evidence for what scientists now call one of the best-documented evolutionary transitions in the history of life.

From Cornell University in the USA:

Dino-killing asteroid’s impact on bird evolution

September 21, 2017

Human activities could change the pace of evolution, similar to what occurred 66 million years ago when a giant asteroid wiped out the dinosaurs, leaving modern birds as their only descendants. That’s one conclusion drawn by the authors of a new study published in Systematic Biology.

Cornell University Ph.D. candidate Jacob Berv and University of Bath Prize Fellow Daniel Field suggest that the meteor-induced mass extinction (a.k.a. the K-Pg event) led to an acceleration in the rate of genetic evolution among its avian survivors. These survivors may have been much smaller than their pre-extinction relatives.

“There is good evidence that size reductions after mass extinctions may have occurred in many groups of organisms,” says Berv. “All of the new evidence we have reviewed is also consistent with a Lilliput Effect affecting birds across the K-Pg mass extinction.” Paleontologists have dubbed this phenomenon the “Lilliput Effect” — a nod to the classic tale Gulliver’s Travels.

“Smaller birds tend to have faster metabolic rates and shorter generation times,” Field explains. “Our hypothesis is that these important biological characters, which affect the rate of DNA evolution, may have been influenced by the K-Pg event.”

The researchers jumped into this line of inquiry because of the long-running “rocks and clocks” debate. Different studies often report substantial discrepancies between age estimates for groups of organisms implied by the fossil record and estimates generated by molecular clocks. Molecular clocks use the rate at which DNA sequences change to estimate how long ago new species arose, assuming a relatively steady rate of genetic evolution. But if the K-Pg extinction caused avian molecular clocks to temporarily speed up, Berv and Field say this could explain at least some of the mismatch. “Size reductions across the K-Pg extinction would be predicted to do exactly that,” says Berv.

“The bottom line is that, by speeding up avian genetic evolution, the K-Pg mass extinction may have temporarily altered the rate of the avian molecular clock,” says Field. “Similar processes may have influenced the evolution of many groups across this extinction event, like plants, mammals, and other forms of life.”

The authors suggest that human activity may even be driving a similar Lilliput-like pattern in the modern world, as more and more large animals go extinct because of hunting, habitat destruction, and climate change.

“Right now, the planet’s large animals are being decimated — the big cats, elephants, rhinos, and whales,” notes Berv. “We need to start thinking about conservation not just in terms of functional biodiversity loss, but about how our actions will affect the future of evolution itself.”

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Some herbivorous dinosaurs really omnivorous?


This 2012 video from the USA says about itself:

Maiasaura: Learn About Dinosaurs with World Book’s Professor Nick

Maiasaura was a large plant-eating dinosaur noted for its nesting behavior. Its name means good mother lizard, though dinosaurs were not lizards. Evidence suggests that its hatchlings were completely dependent on their parents for food and protection. Maiasaura lived about 75 to 80 million years ago in the area of what is now Montana. It belonged to a group known as duckbilled dinosaurs or hadrosaurids. These dinosaurs ate plants using a beak that somewhat resembled a duck’s bill.

By Carolyn Gramling, 9:00am, September 21, 2017:

Shhhh! Some plant-eating dinos snacked on crunchy critters

Crustacean shells discovered in fossilized poop reveal diet secrets of ancient herbivores

Some dinosaurs liked to cheat on their vegetarian diet.

Based on the shape of their teeth and jaws, large plant-eating dinosaurs are generally thought to have been exclusively herbivorous. But for one group of dinosaurs, roughly 75-million-year-old poop tells another story. Their fossilized droppings, or coprolites, contained tiny fragments of mollusk and other crustacean

Mollusks and crustaceans are two different groups.

shells along with an abundance of rotten wood, researchers report September 21 in Scientific Reports. Eating the crustaceans as well as the wood might have given the dinosaurs an extra dose of nutrients during breeding season to help form eggs and nourish the embryos.

“Living herd animals do occasionally turn carnivore to fulfill a particular nutritional need,” says vertebrate paleontologist Paul Barrett of the Natural History Museum in London. “Sheep and cows are known to eat carcasses or bone when they have a deficiency in a mineral such as phosphorus or calcium, or if they’re pregnant or ill.” But the discovery that some plant-eating dinos also ate crustaceans is the first example of this behavior in an extinct herbivore, says Barrett, who was not involved in the new study.

Ten years ago, paleoecologist Karen Chin of the University of Colorado Boulder described finding large pieces of rotted wood in dino dung. The coprolites were within a layer of rock in Montana, known as the Two Medicine Formation, dating to between 80 million and 74 million years ago. That layer also contained numerous fossils of Maiasaura, a type of large, herbivorous duck-billed dinosaur, or hadrosaur (SN: 8/9/14, p. 20).

Chin wondered whether the wood itself was the dino’s real dietary target. “The coprolites in Montana were associated with the nesting grounds of the Maiasaura,” she says. “I suspected that the dinosaurs were after insects in the wood. But I never found any insects in the coprolites there.”

Her hunch wasn’t too far off. Now she’s found evidence of some kind of crustaceans in dino poop. The new evidence comes from an 860-meter-thick layer of rock in Utah known as the Kaiparowits Formation, which dates to between 76.1 million and 74 million years ago. Ten of the 15 coprolites that Chin and her team examined contained tiny fragments of shell that were scattered throughout the dung. They were too small to identify by species, and may have been crabs, insects or some other type of shelled animal, Chin says. Based on the scattering of shell fragments, the animals were certainly eaten along with the wood rather than being later visitors to the dung heap.

Since bones from hadrosaurs are especially abundant in the Kaiparowits Formation, Chin suspects those kinds of dinos deposited the dung. Other large herbivores, such as three-horned ceratopsians and armored ankylosaurs, also roamed the area (SN: 6/24/17, p. 4).

The crustacean diet cheat may have been a seasonal event, related perhaps to breeding to obtain extra nutrients, Chin and colleagues say.

But how often — or why — the dinosaurs ate the shelled critters is hard to prove from the fossil dung alone, Barrett says. Herbivore coprolites are rare in the fossil record because a diet of leaves and other green plant material doesn’t leave a lot of hard material to preserve (unlike bones in carnivore dung). Coprolites with crustaceans, on the other hand, are more likely to get fossilized — and that preferential preservation might make it appear that this behavior was more frequent than it actually was. “These kinds of things give neat snapshots of specific behaviors that those animals are doing at any one time,” he adds. “But it’s difficult to build that into a bigger picture.”

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.

New sauropod dinosaur discovery in Tanzania


This video says about itself:

24 August 2017

A titanosaur the size of a killer whale once stomped across Africa

A humongous “wide-necked” dinosaur — one that weighed as much as two cars — stomped across the landscape of prehistoric Africa during the Cretaceous period, a new study finds.

The 5-ton beast, a titanosaur (an herbivorous long-necked and long-tailed dinosaur) was tall; its head reached 13 feet (4 meters) in the air when its neck was extended. The dinosaur’s remains were found in rock in southwestern Tanzania dating between 100 million and 70 million years ago, the researchers said.

It’s not uncommon to unearth titanosaurs in South America, but it’s rare to find the giant dinosaurs in Africa, making the newly identified creature a remarkable find, the researchers said.

Researchers named the titanosaur Shingopana songwensis, which they said was 26 feet (8 meters) long, or about the size of an orca whale. Its genus name means “wide neck” in Swahili, whereas “shingo” and “pana” are the Swahili words for “neck” and “wide,” respectively, in reference to the giant’s “bulbous” neck vertebra, the researchers wrote in the study. The species name honors the Songwe region of the Great Rift Valley in Tanzania, where the dinosaur was first discovered in 2002, and excavated in the following years.

From the National Science Foundation in the USA:

New species of sauropod dinosaur discovered in Tanzania

Fossil remains recovered from 70 to 100 million-year-old rocks in southwestern Tanzania

August 25, 2017

Paleontologists have identified a new species of titanosaurian dinosaur. The research is reported in a paper published this week in the Journal of Vertebrate Paleontology and is funded by the National Science Foundation (NSF).

The new species is a member of the gigantic, long-necked sauropods. Its fossil remains were recovered from Cretaceous Period (70-100 million years ago) rocks in southwestern Tanzania.

Titanosaur skeletons have been found worldwide, but are best known from South America. Fossils in this group are rare in Africa.

The new dinosaur is called Shingopana songwensis, derived from the Swahili term “shingopana” for “wide neck”; the fossils were discovered in the Songwe region of the Great Rift Valley in southwestern Tanzania.

Part of the Shingopana skeleton was excavated in 2002 by scientists affiliated with the Rukwa Rift Basin Project, an international effort led by Ohio University Heritage College of Osteopathic Medicine researchers Patrick O’Connor and Nancy Stevens.

Additional portions of the skeleton — including neck vertebrae, ribs, a humerus and part of the lower jaw — were later recovered.

“There are anatomical features present only in Shingopana and in several South American titanosaurs, but not in other African titanosaurs,” said lead paper author Eric Gorscak, a paleontologist at the Field Museum of Natural History in Chicago. “Shingopana had siblings in South America, whereas other African titanosaurs were only distant cousins.”

The team conducted phylogenetic analyses to understand the evolutionary relationships of these and other titanosaurs.

They found that Shingopana was more closely related to titanosaurs of South America than to any of the other species currently known from Africa or elsewhere.

“This discovery suggests that the fauna of northern and southern Africa were very different in the Cretaceous Period,” said Judy Skog, a program director in NSF’s Division of Earth Sciences, which supported the research. “At that time, southern Africa dinosaurs were more closely related to those in South America, and were more widespread than we knew.”

Shingopana roamed the Cretaceous landscape alongside Rukwatitan bisepultus, another titanosaur the team described and named in 2014.

“We’re still only scratching the surface of understanding the diversity of organisms, and the environments in which they lived, on the African continent during the Late Cretaceous,” said O’Connor.

During the tectonically active Cretaceous Period, southern Africa lost Madagascar and Antarctica as they split off to the east and south, followed by the gradual northward “unzipping” of South America.

Northern Africa maintained a land connection with South America, but southern Africa slowly became more isolated until the continents completely separated 95-105 million years ago. Other factors such as terrain and climate may have further isolated southern Africa.

Paper co-author Eric Roberts of James Cook University in Australia studied the paleo-environmental context of the new discovery.

The bones of Shingopana, he found, were damaged by the borings of ancient insects shortly after death.

Roberts said that “the presence of bone-borings provides a CSI-like opportunity to study the skeleton and reconstruct the timing of death and burial, and offers rare evidence of ancient insects and complex food webs during the age of the dinosaurs.”

The study was also funded by the National Geographic Society, Jurassic Foundation, Paleontological Society, Ohio University Student Enhancement Award, Ohio University Original Work Grant, Ohio University Heritage College of Osteopathic Medicine, Ohio University Office of the Vice President for Research and Creative Activity, and James Cook University.

See also here.

Did oviraptor dinosaurs behave like birds?


This 24 August 2017 video is called New discovery of dinosaurs suggests: new species [roosting] together like modern birds.

From the Society of Vertebrate Paleontology:

New dinosaur discovery suggests new species roosted together like modern birds

August 24, 2017

The Mongolian Desert has been known for decades for its amazing array of dinosaurs, immaculately preserved in incredible detail and in associations that give exceedingly rare glimpses at behavior in the fossil record. New remains from this region suggest an entirely unknown behavior for bird-like dinosaurs about 70 million years ago. At least some dinosaurs likely roosted together to sleep, quite possibly as a family, much like many modern birds do today. Gregory Funston, Ph.D. Candidate at the University of Alberta, will present the team’s research findings at the annual meeting of the Society of Vertebrate Paleontology, held this year in Calgary, Alberta (Canada) on Friday, Aug. 25th.

This new evidence for dinosaur roosting stems from a confiscated fossil block that was illegally exported from Mongolia, which preserved the amazing remains of three juvenile dinosaurs known as oviraptorids (part of the bird line of dinosaur evolution). These three dinosaurs represent the same species that were roughly the same age, preserved in a sleeping posture, so close to each other that they would have been touching in life. Known as “communal roosting,” this behavior is seen in many birds today including chickens and pigeons. The specimen luckily made its way into the hands of researchers currently led by Gregory Funston of the University of Alberta, along with his advisor Dr. Philip Currie (also of the University of Alberta) and the Institute of Paleontology and Geology of Mongolia (based in Ulaanbaatar). Regarding the finding, Funston said, “It’s a fantastic specimen. It’s rare to find a skeleton preserved in life position, so having two complete individuals and parts of a third is really incredible.”

The three juvenile oviraptors had several features that indicated they belonged to a whole new species. Other fossils found in Mongolia also seem to belong to this new species, and further flesh out the life history of these animals. The notable head crest is present even at a young age, but the dinosaurs would have had gradually shorter tails as they aged, and some of their bones fused across their lifetime. Their head crests and tails have been argued to represent sexual display features used in mating, somewhat similar to modern peacocks or turkeys. Funston added “The origins of communal roosting in birds are still debated, so this specimen will provide valuable information on roosting habits in bird-line theropods.”

Dinosaur discovery in Chile, missing link?


This video says about itself:

4 September 2015

“Chilesaurus” is an extinct genus of herbivorous theropod dinosaur. The genus is monotypic, represented by the type species “Chilesaurus diegosuarezi“. “Chilesaurus” lived approximately 145 million years ago in the Late Jurassic period of Chile.

Fossils of “Chilesaurus”, a vertebra and a rib, were first discovered on 4 February 2004 by the seven-year-old Diego Suárez who, together with his parents, geologists Manuel Suárez and Rita de la Cruz, was searching for decorative stones in the Aysén Region. More specimens were present that in 2008 were reported as representing several dinosaurian species. Only later was it realised that these belonged to a single species with a bizarre combination of traits.

In 2015, the type species “Chilesaurus diegosuarezi” was named and described by Fernando Emilio Novas, Leonardo Salgado, Manuel Suárez, Federico Lisandro Agnolín, Martín Dário Ezcurra, Nicolás Chimento, Rita de la Cruz, Marcelo Pablo Isasi, Alexander Omar Vargas and David Rubilar-Rogers. The generic name refers to Chile. The specific name honours Diego Suárez.

The holotype, “SNGM-1935”, was found in a layer of the Toqui Formation dating from the late Tithonian. It consists of an articulated rather complete skeleton with skull of a juvenile individual, lacking the feet and most of the tail. Four other partial skeletons and several single bones are the paratypes. They represent juvenile and adult individuals.

“Chilesaurus” measures 3.2 m from nose to tail. The holotype is a smaller individual of half that length.

That was in 2015. But now …

From Biology Letters:

A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaurs

Matthew G. Baron, Paul M. Barrett

16 August 2017

Abstract

The enigmatic dinosaur taxon Chilesaurus diegosuarezi was originally described as a tetanuran theropod, but this species possesses a highly unusual combination of features that could provide evidence of alternative phylogenetic positions within the clade.

In order to test the relationships of Chilesaurus, we added it to a new dataset of early dinosaurs and other dinosauromorphs. Our analyses recover Chilesaurus in a novel position, as the earliest diverging member of Ornithischia, rather than a tetanuran theropod. The basal position of Chilesaurus within the clade and its suite of anatomical characters suggest that it might represent a ‘transitional’ taxon, bridging the morphological gap between Theropoda and Ornithischia, thereby offering potential insights into the earliest stages of ornithischian evolution, which were previously obscure. For example, our results suggest that pubic retroversion occurred prior to some of the craniodental and postcranial modifications that previously diagnosed the clade (e.g. the presence of a predentary bone and ossified tendons).

1. Introduction

Chilesaurus diegosuarezi is from the Late Jurassic (Tithonian; ca 150 Ma) Toqui Formation of Chile and possesses a bizarre suite of anatomical features that, if considered individually, are usually thought to characterize distantly related dinosaur clades.