Dinosaurs laid blue-green eggs

Scientists have found evidence that dinosaurs laid blue-green eggs, telling us something about the prehistoric creatures’ behaviour and challenging what we know about how coloured eggs evolved.

(A) Pair of oviraptorid Heyuannia eggs (NMNS CYN-2004-DINO-05) from the Chinese province of Jiangxi before
 sampling. Porosity measurements and calculations of water vapour conductance are based on these eggs. Pieces 
of eggshell from each of the four zones depicted in (B) were used in porosity measurements. (B) Egg model 
separated into four zones used for zonal porosity measurements [Credit: PeerJ (2017)]

The team of researchers chemically analyzed eggshells recovered from the Late Cretaceous period, between about 100 million and 66 million years ago, and found two pigments in the makeup, suggesting that the eggshells were originally blue-green. A study in the journal PeerJ says the eggs, which were in a late stage of embryonic development, came from a species of oviraptor, a group of small theropods with feathers that lived in the area of Mongolia, and were collected from river deposits in eastern and southern China. The fact that the eggs were not white suggests that these particular dinosaur parents used open nests and were not constantly brooding over their unborn babies.

In modern birds, colouring on eggshells provides camouflage or diversion so that open-nesting birds can protect their children from potential predators. According to the study, “cryptic colouration evolved to match the predominant shades of colour found in the nesting environment.”

Meanwhile, birds that instead protect their eggs by hovering over them do not have much pigmentation in the shells. Crocodiles, which are close relatives, have unpigmented eggs too; they bury their eggs.

The researchers on this study compared the case of modern birds to those of non-avian dinosaurs that may have had coloured eggs. The blue-green eggs for this oviraptor, a creature that had a beak like a parrot and walked on its hind legs, “support an at least partially open nesting behaviour for oviraptorosaurs,” the authors wrote.

The two pigments found in the eggshells were protoporphyrin and biliverdin. Those two components can be found in the eggshells of many modern birds.

According to the study, scientists have assumed that egg colouration evolved in the last shared ancestor between birds and crocs.

That colouration would have been passed down in the genes even of birds that developed behaviour obviating the need for it. The study gives the example of ostriches, which sit on their eggs. Analysis shows that those eggshells still “contain minor amounts of eggshell pigment.” That lingering amount suggests that evolution gradually reduced the pigment in their eggs because their brooding over their eggs reduced evolutionary pressure on egg-colouring genes.

But this new finding shows a deeper history to the trait than just the last common ancestor of birds and crocodiles. The scientists say it may have evolved when some dinosaurs began building nests that were at least partially exposed, as opposed to burying all their eggs, which was a much more common practice.

“Selection for egg color would only have occurred after the eggs themselves became visible to parents, conspecifics, predators, or parasites,” the authors wrote.

The results of the egg analysis also represent an additional avenue for studying fossils, and the researchers said other fossilized dinosaur eggs could contain evidence of pigmentation.

Initially the scientists thought a bluish colouring on the oviraptor eggs was from mineralization.

“The result has important implications both for the origin of avian biology and the reproductive biology of theropods dinosaurs,” the study says.

Author: Elana Glowatz | Source: International Business Times [September 21, 2017]

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Big herbivorous dinosaurs ate crustaceans as a side dish

Some big plant-eating dinosaurs roaming present-day Utah some 75 million years ago were slurping up crustaceans on the side, a behavior that may have been tied to reproductive activities, says a new University of Colorado Boulder study.

CU Boulder Associate Professor Karen Chin excavating dinosaur coprolites at Grand Staircase-Escalante National 
Monument in Utah. The new study shows herbivorous dinosaurs also were eating crustaceans, likely seasonally 
[Credit: University of Colorado]

The evidence for the crustacean-chowing dinosaurs comes from fossilized feces samples known as coprolites, said Associate Professor Karen Chin, curator of paleontology at CU Boulder's Museum of Natural History. Dating to the late Cretaceous Period, the coprolites were discovered in Grand Staircase-Escalante National Monument in southern Utah by a team from the Denver Museum of Nature & Science who invited Chin out to their dig.

From what we know about dinosaurs, this was a totally unexpected behavior," said Chin. "It was such a surprising discovery we wondered what the motivation could have been."

Chin said the Utah coprolites were similar to those she has examined from Montana -- which likely were from duck-billed dinosaurs known as hadrosaurs -- in that both were similar in size and held jumbled fragments of rotting wood. A closer look at some of the Utah coprolites also turned up thick bits and pieces of fossilized shell, an indication crustaceans were living in the decaying, coniferous wood, she said.

Because crustacean shells turned up in at least 10 coprolite samples in three different stratigraphic layers of the national monument over a distance of about 13 miles, Chin thinks their ingestion by the dinosaurs was purposeful and would have provided valuable protein and calcium sources.

Examples of modern crustaceans, which have hard exoskeletons, include lobsters, crab, shrimp and crayfish. Some of the coprolites examined were probably around two gallons in volume, Chin said.

The size of the crustacean shell bits in the coprolites indicate the crustaceans were at least two inches in length and perhaps larger, said Chin. Individual crustaceans comprised from 20 to 60 percent of the width of a common hadrosaur beak, suggesting it was unlikely the crustaceans were unwittingly swallowed, she said.

"While it is difficult to prove intent regarding feeding strategies, I suspect these dinosaurs targeted rotting wood because it was a great source of protein in the form of insects, crustaceans and other invertebrates," said Chin. "If we take into account the size of the crustaceans and that they were probably wriggling when they were scooped up, the dinosaurs would have likely been aware of them and made a choice to ingest them."

Even though the team is unable to determine what kind of crustaceans they were, fossil crab claws have been found in the same area in a slightly older geologic formation. Present-day Utah appears to have been next to or near a sea during the Cretaceous Period, said Chin.

Chin also suspects the consumption of crustaceans may have been a seasonal dietary shift, perhaps tied to breeding and egg-laying activities of dinosaurs. She notes contemporary bird species -- which are technically avian dinosaurs -- often consume more protein and calcium during the breeding season to support successful reproduction.

"If we found one coprolite with a crustacean fossil in it, that would be a really interesting scientific discovery," Chin said. "But it wouldn't necessarily indicate a recurring feeding behavior. We now have multiple coprolites with crustacean fossils, showing that at least some types of herbivorous dinosaurs occasionally engaged in this unanticipated feeding strategy."

The researchers sliced the coprolite material into thin sections that were then analyzed with an electron microprobe to determine their chemical composition -- in this case they found a preponderance of calcium, said Chin.

Hadrosaurs were one of the most common dinosaur type of the Cretaceous, growing up to 30 feet long and weighing up to three tons. Some species had characteristic crests on their heads. They also had specialized teeth for grinding plant material, and are thought by some paleontologists to have roamed in herds and nurtured their young.

A paper on the subject was published in the journal Scientific Reports.

Source: University of Colorado at Boulder [September 21, 2017]

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Dinosaur evolution: Lumbering giants had agile ancestors

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.

A couple of predator Mapusaurus try to isolate a herd of sauropods [Credit: Sergey Krasovskiy]

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.

Source: Ludwig-Maximilians-Universität München [September 20, 2017]

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New prehistoric crocodile species identified

Around 95 million years ago, a giant relative of modern crocodiles ruled the coastlines and waterways of what would one day become north central Texas.

Dr. Thomas Adams with the skull of Deltasuchus motherali 
[Credit: Arlington Archosaur Site]

A team including UT’s Stephanie Drumheller-Horton has identified this species, Deltasuchus motherali. They found that adults grew up to 20 feet long and, based on the bite marks discovered on the fossilized bones of prey animals, ate whatever they wanted in their environment, from turtles to dinosaurs.

The team found the bones in a place one normally doesn’t think to look for ancient fossils—in the heart of the Dallas-Fort Worth Metroplex.

The findings were recently published in the Journal of Vertebrate Paleontology.

Drumheller-Horton collaborated with Thomas Adams, curator of paleontology and geology at the Witte Museum in San Antonio, Texas, and Chris Noto of the University of Wisconsin–Parkside.

Deltasuchus motherali: A Large Neosuchian Crocodyliform from the Upper Cretaceous (Cenomanian) 
Woodbine Formation of North Texas [Credit: Arlington Archosaur Site]

The site that produced the new species was discovered in Arlington, Texas, in 2003 by amateur fossil hunters Art Sahlstein, Bill Walker, and Phil Kirchoff.

Dubbed the Arlington Archosaur Site, the area is undergoing rapid residential development, and paleontologists have been working with local volunteers and fossil enthusiasts to excavate the site over the past decade.

“We simply don’t have that many North American fossils from the middle of the Cretaceous, the last period of the age of dinosaurs, and the eastern half of the continent is particularly poorly understood,” Drumheller-Horton said. “Fossils from the Arlington Archosaur Site are helping fill in this gap, and Deltasuchus is only the first of several new species to be reported from the locality.”

Deltasuchus motherali is named for one of the site volunteers, Austin Motheral, who first uncovered the fossils of this particular crocodile with a small tractor when he was just 15 years old.

Volunteers working to uncover fossils, including those of Deltasuchus, in 2009 
[Credit: Arlington Archosaur Site]

Work on the site is supported by a grant from the National Geographic Society, which is funding continued excavations and study of this unique fossil area. Fossils from the site, including the Deltasuchus motherali bones, are part of the collections of the Perot Museum of Nature and Science in Dallas.

Deltasuchus is the first of what may prove to be several new species described from this fossil site. The area preserves a complete ancient ecosystem ranging from 95 million to 100 million years old, and its fossils are important in advancing the understanding of ancient North American land and freshwater ecosystems.

While most of Texas was covered by a shallow sea at the time, the Dallas-Fort Worth area was part of a large peninsula that jutted out from the northeast. The peninsula was a lush environment of river deltas and swamps that teemed with wildlife, including dinosaurs, crocodiles, turtles, mammals, amphibians, fish, invertebrates, and plants.

Source: University of Tennessee at Knoxville [September 13, 2017]

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Scientists track the brain - skull transition from dinosaurs to birds

The dramatic, dinosaur-to-bird transition that occurred in reptiles millions of years ago was accompanied by profound changes in the skull roof of those animals -- and holds important clues about the way the skull forms in response to changes in the brain -- according to a new study.

These are CT scan images of the skull roof (front bone in pink, parietal in green) and 
brain (in blue) of, top to bottom, a chicken, the birdlike dinosaur Zanabazar, the primitive 
dinosaur Herrerasaurus, and Proterosuchus, an ancestral form that diverged before 
the bird/crocodile split [Credit: Yale University]

It is the first time scientists have tracked the link between the brain's development and the roofing bones of the skull. The findings appear in the journal Nature Ecology and Evolution.

"Across the dinosaur-bird transition, the skull transforms enormously and the brain enlarges. We were surprised that no one had directly addressed the idea that the underlying parts of the brain -- the forebrain and midbrain -- are correlated or somehow developmentally related to the overlying frontal and parietal bones," said co-senior author Bhart-Anjan Singh Bhullar, an assistant professor of geology and geophysics at Yale University and assistant curator of vertebrate paleontology and vertebrate zoology at the Yale Peabody Museum of Natural History. Matteo Fabbri, a graduate student in Bhullar's lab, is the first author of the study.

The developing skulls of an alligator (top) and a chicken (bottom) 
[Credit: Fabbri et al., 2017]

Although previous studies have shown a general relationship between the brain and skull, associations between specific regions of the brain and individual elements of the skull roof have remained unclear. This has led to conflicting theories on some aspects of skull development.

Bhullar and his colleagues set out to trace the evolution of brain and skull shape not simply in the dinosaurs closest to birds, but in the entire lineage leading from reptiles to birds. They discovered that most reptile brains and skulls were markedly similar to each other. It was the dinosaurs most closely related to birds, as well as birds themselves, that were divergent, with enlarged brains and skulls ballooning out around them.

The skull bones and brain shape of an American alligator and a chicken 
[Credit: Fabbri et al., 2017]

"We found a clear relationship between the frontal bones and forebrain and the parietal bones and midbrain," Bhullar said. The researchers confirmed this finding by looking at embryos of lizards, alligators, and birds using a new contrast-stained CT scanning technique.

"We suggest that this relationship is found across all vertebrates with bony skulls and indicates a deep developmental relationship between the brain and the skull roof," Bhullar said. "What this implies is that the brain produces molecular signals that instruct the skeleton to form around it, although we understand relatively little about the precise nature of that patterning."

Bhullar added: "Ultimately, one of the important messages here is that evolution is simpler and more elegant than it seems. Multiple seemingly disparate changes -- for instance to the brain and skull -- could actually have one underlying cause and represent only a single, manifold transformation."

Author: Jim Shelton | Source: Yale University [September 11, 2017]

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