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Mammals’ unique arms started evolving before the dinosaurs existed

Thrinaxodon
Thrinaxodon, a therapsid animal related to today’s mammals. The therapsids are the group where mammal relatives began developing diverse forelimbs. Credit: April I. Neander

Bats fly, whales swim, gibbons swing from tree to tree, horses gallop, and humans swipe on their phones — the different habitats and lifestyles of mammals rely on our unique forelimbs. No other group of vertebrate animals has evolved so many different kinds of arms: in contrast, all birds have wings, and pretty much all lizards walk on all fours. Our forelimbs are a big part of what makes mammals special, and in a new study in the Proceedings of the National Academy of Sciences, scientists have discovered that our early relatives started evolving diverse forelimbs 270 million years ago — a good 30 million years before the earliest dinosaurs existed.

“Aside from fur, diverse forelimb shape is one of the most iconic characteristics of mammals,” says the paper’s lead author Jacqueline Lungmus, a research assistant at Chicago’s Field Museum and a doctoral candidate at the University of Chicago. “We were trying to understand where that comes from, if it’s a recent trait or if this has been something special about the group of animals that we belong to from the beginning.”

To determine the origins of mammals’ arms today, Lungmus and her co-author, Field Museum curator Ken Angielczyk, examined the fossils of mammals’ ancient relatives. About 312 million years ago, land-dwelling vertebrates split into two groups — the sauropsids, which went on to include dinosaurs, birds, crocodiles, and lizards, and the synapsids, the group that mammals are part of. A key difference between sauropsids and synapsids is the pattern of openings in the skull where jaw muscles attach. While the earliest synapsids, called pelycosaurs, were more closely related to humans than to dinosaurs, they looked like hulking reptiles. Angielczyk notes, “If you saw a pelycosaur walking down the street, you wouldn’t think it looked like a mammal — you’d say, ‘That’s a weird-looking crocodile.'”

About 270 million years ago, though, a more diverse (and sometimes furry) line of our family tree emerged: the therapsids. “Modern mammals are the only surviving therapsids — this is the group that we’re part of today,” explains Lungmus. Therapsids were the first members of our family to really branch out — instead of just croc-like pelycosaurs, the therapsids included lithe carnivores, burly-armed burrowers, and tree-dwelling plant-eaters.

Lungmus and Angielczyk set out to see if this explosion of diversity came with a corresponding explosion in different forelimb shapes. “This is the first study to quantify forelimb shape across a big sample of these animals,” says Lungmus. The team examined the upper arm bones of hundreds of fossil specimens representing 73 kinds of pelycosaurs and therapsids, taking measurements near where the bones joined the shoulder and the elbow. They then analyzed the shapes of the bones using a technique called geometric morphometrics.

When they compared the shapes of arm bones, the researchers found a lot more variation in the bones of the therapsids than the pelycosaurs. They also noted that the upper part of the arm, near the shoulder, was especially varied in therapsids — a feature that might have let them move more freely than the pelycosaurs, whose bulky and tightly-fitting shoulder bones likely gave them a more limited range of motion.

Lungmus and Angielczyk found that a wide variety of different forelimb shapes evolved within the therapsids 270 million years ago. “The therapsids are the first synapsids to increase the variability of their forelimbs — this study dramatically pushes that trait back in time,” says Lungmus. Prior to this study, the earliest that paleontologists had been able to definitively trace back mammals’ diverse forelimbs was 160 million years ago. With Lungmus and Angielczyk’s work, that’s been pushed back by more than a hundred million years.

The researchers note that the study helps explain how mammals evolved traits that have made us what we are today. “So much of what we do every day is related to the way our forelimbs evolved — even simple things like holding a phone,” says Angielczyk.

“This is something that’s so cool about our evolutionary lineage,” says Lungmus. “These animals are in the same group as us — part of what makes this research compelling is that these are our relatives.”

Reference:
Jacqueline K. Lungmus, Kenneth D. Angielczyk. Antiquity of forelimb ecomorphological diversity in the mammalian stem lineage (Synapsida). Proceedings of the National Academy of Sciences, 2019; 201802543 DOI: 10.1073/pnas.1802543116

Note: The above post is reprinted from materials provided by Field Museum.

Fossil teeth from Kenya solve ancient monkey mystery

A 3D model of the mandible of Alophia rendered from high resolution CT scans.
A 3D model of the mandible of Alophia rendered from high resolution CT scans. It is dated to 22 million years in age, and measures 3.7 cm (1.45 inches) in length. Credit: The University of Texas at Austin

The teeth of a new fossil monkey, unearthed in the badlands of northwest Kenya, help fill a 6-million-year void in Old World monkey evolution, according to a study by U.S. and Kenyan scientists published in the Proceedings of the National Academy of Sciences.

The discovery of 22-million-year-old fossilized monkey teeth — described as belonging to a new species, Alophia metios — fills a void between a previously discovered 19-million-year-old fossil tooth in Uganda and a 25-million-year-old fossil tooth found in Tanzania. The finding also sheds light on how their diet may have changed the course of their evolution.

“For a group as highly successful as the monkeys of Africa and Asia, it would seem that scientists would have already figured out their evolutionary history,” said the study’s corresponding author John Kappelman, an anthropology and geology professor at The University of Texas at Austin. “Although the isolated tooth from Tanzania is important for documenting the earliest occurrence of monkeys, the next 6 million years of the group’s existence are one big blank. This new monkey importantly reveals what happened during the group’s later evolution.”

Since the time interval from 19 to 25 million years ago is represented by a small number of African fossil sites, the team targeted the famous fossil-rich region of West Turkana to try to fill in that blank.

“Today, this region is very arid,” said Benson Kyongo, a collections manager at the National Museums of Kenya. “But millions of years ago, it was a forest and woodland landscape crisscrossed by rivers and streams. These ancient monkeys were living the good life.”

While in the field, the team uncovered hundreds of mammal and reptile jaws, limbs and teeth ranging from 21 million to more than 24 million years old, including remains of early elephants. The newly discovered monkey teeth are more primitive than geologically younger monkey fossils, lacking what researchers referred to as “lophs,” or a pair of molar crests, thus earning the new species its name, Alophia, meaning “without lophs.”

“These teeth are so primitive that when we first showed them to other scientists, they told us, “Oh no, that isn’t a monkey. It’s a pig,” said Ellen Miller, an anthropology professor at Wake Forest University. “But because of other dental features, we are able to convince them that yes, it is in fact a monkey.”

The success of Old World monkeys appears to be closely tied to their unique dentition, researchers said. Today, the configuration of cusps and lophs on the molar teeth enable them to process the wide range of plant and animal foods encountered in the diverse environments of Africa and Asia.

“You can think of the modern-day monkey molar as the uber food processor, able to slice, dice, mince and crush all sorts of foods,” said Mercedes Gutierrez, an anatomy professor at the University of Minnesota.

“How and when this unique dentition evolved is one of the unanswered questions in primate evolution,” said James Rossie, an anthropology professor at Stony Brook University. The researchers speculated that Alophia’s primitive dentition was adapted to a diet that consisted of hard fruits, seeds and nuts, and not leaves, which are more efficiently processed by the more evolved dentition of fossil monkeys dating from after 19 million years ago.

“It is usually assumed that the trait responsible for a group’s success evolved when the group originated, but Alophia shows us this is not the case for Old World monkeys,” said Samuel Muteti, a researcher at the National Museums of Kenya. “Instead, the characteristic dentition of modern monkeys evolved long after the group first appeared.”

The researchers hypothesized that the inclusion of leaves in the diet is what later drove monkey dental evolution.

Monkeys originated at a time when Africa and Arabia were joined as an island continent, with its animals evolving in isolation until docking with Eurasia sometime between 20 million and 24 million years ago. It was only after docking that the mammals today typically considered “African” — antelope, pigs, lions, rhinos, etc. — made their entry onto the continent. So, researchers asked: Could this event and possible competition between the residents and the newly arrived Eurasian species have driven monkeys to exploit leaves, or did changing climates serve to make leaves a more attractive menu entrée?

“The way to test between these hypotheses is to collect more fossils,” Kappelman said. “Establishing when, exactly, the Eurasian fauna entered Afro-Arabia remains one of the most important questions in paleontology, and West Turkana is one of the only places we know of to find that answer.”

The team intends to be back in the field later this year.

Reference:
D. Tab Rasmussen, Anthony R. Friscia, Mercedes Gutierrez, John Kappelman, Ellen R. Miller, Samuel Muteti, Dawn Reynoso, James B. Rossie, Terry L. Spell, Neil J. Tabor, Elizabeth Gierlowski-Kordesch, Bonnie F. Jacobs, Benson Kyongo, Mathew Macharwas, and Francis Muchemi. Primitive Old World monkey from the earliest Miocene of Kenya and the evolution of cercopithecoid bilophodonty. Proceedings of the National Academy of Sciences, March 11, 2019; DOI: 10.1073/pnas.1815423116

Note: The above post is reprinted from materials provided by University of Texas at Austin.

Researchers uncover new clues to surviving extinction

Scientists are peeking into ancient oceans to unravel the complexities of mass extinctions, past and future.
Scientists are peeking into ancient oceans to unravel the complexities of mass extinctions, past and future. A team of researchers examined fossils of ocean-dwelling invertebrate creatures like clams, snails, corals, and sponges from Utah, Nevada, and Texas. This region once comprised the shallow outskirts of the ancient and vast Panthalassa Ocean. Using numerical methods, the team grouped marine survivor species into functional groups with similar traits, like mobile bottom-dwelling omnivores such as sea urchins, to better understand the ecological transformation in the wake of the Great Dying. Credit: © 2019 Ashley Dineen

Scientists are peeking into ancient oceans to unravel the complexities of mass extinctions, past and future. A new examination of Earth’s largest extinction by scientists at the California Academy of Sciences and the University of Wisconsin-Milwaukee sheds light on how ecosystems are changed by such transformative events.

The study, published today in Biology Letters, suggests that the extinction survivors shared many of the same ecological roles as their predecessors, with one catch — there was a surge in the number of individuals with modern traits like greater mobility, higher metabolism, and more diverse feeding habits. These hardy stand-outs did a better job of driving recovery, making ecological interactions more intense in the process: fish were more agile, diverse predators and marine invertebrates like mussels became more defensive. Insights into this system and its occupants can help guide modern conservation in identifying Earth’s most resilient and best equipped species in the face of environmental stress.

“We’re interested in understanding why certain species and communities survived and recovered better than others,” says Dr. Ashley Dineen, a former Academy postdoctoral researcher and current Museum Scientist of Invertebrate Paleontology at the UC Museum of Paleontology at Berkeley. “For a long time biology has focused on the number of species that survive extinction events, but we need to also ask what those species did and how they reacted to stresses — these insights are important as we push our planet into an increasingly uncertain future.”

The massive extinction event, often referred to as the “Great Dying,” took place 252 million years ago and frequently serves as a proxy for the modern era. Similar to today, the climate regime was transitioning from a cooler period to a warmer period. This climatic fluctuation, driven by massive volcanic eruptions that spewed noxious gases, increased the temperature and acidity of the oceans, decreased oxygen concentrations, interrupted mighty ocean currents, and turned the ocean system on its head.

The researchers examined fossils of ocean-dwelling invertebrate creatures like clams, snails, corals, and sponges from Utah, Nevada, and Texas. This region once comprised the shallow outskirts of the ancient and vast Panthalassa Ocean. Using numerical methods, the team grouped marine survivor species into functional groups with similar traits, like mobile bottom-dwelling omnivores such as sea urchins, to better understand the ecological transformation in the wake of the Great Dying.

“We learned from our analysis that beyond documenting the number of species that arise during an ecological recovery, we need to know what they were actually doing — what scientists call their functional diversity,” says Dr. Peter Roopnarine, Academy Curator of Geology. “This helps us understand if the system has shifted toward favoring species with a variety of responses to stress.”

One surprising revelation: the study results showed significant ecological continuity among species — where species that were wiped out during the extinction event shared the same traits as those that originated in its aftermath. During recovery, however, there was a significant shift in numbers toward bigger and more active survivors that are strikingly similar to the inhabitants of our modern oceans. This shift in functional emphasis may be the the hallmark of an ecosystem set on the road to recovery.

“Our next step is to determine what kinds of species you want on the frontlines of recovery,” says Dineen. “For example, if you have a reef with twenty different species of corals but they all react the same to stressors, then they will all be similarly impacted when hit with a disturbance. But on a separate reef, if you have twenty coral species and each reacts differently to stress, the chance of losing the entire reef is lower. Having diverse coping mechanisms is critical for a future marked by increasing environmental stressors.”

The study team hopes their findings about species survivors will help scientists identify our modern — and urgently needed — conservation priorities.

“We’re often focused on estimating the number of species in an ecosystem, but we should also be learning about how — and how well — these species survive, and concentrate conservation efforts accordingly,” says Dineen. “When you consider the mass extinction we face today, it’s clear we have to take entire systems into account before it’s too late to correct course.”

Reference:
Ashley A. Dineen, Peter D. Roopnarine, Margaret L. Fraiser. Ecological continuity and transformation after the Permo-Triassic mass extinction in northeastern Panthalassa. Biology Letters, 2019; 15 (3): 20180902 DOI: 10.1098/rsbl.2018.0902

Note: The above post is reprinted from materials provided by California Academy of Sciences.

Alligator study reveals insight into dinosaur hearing

American Alligators make neural maps of sound the same way birds do
American Alligators make neural maps of sound the same way birds do. Credit: Ruth Elsey Louisiana Department of Wildlife and Fisheries

To determine where a sound is coming from, animal brains analyze the minute difference in time it takes a sound to reach each ear — a cue known as interaural time difference. What happens to the cue once the signals get to the brain depends on what kind of animal is doing the hearing.

Scientists have known that birds are exceptionally good at creating neural maps to chart the location of sounds, and that the strategy differs in mammals. Little was known, however, about how alligators process interaural time difference.

A new study of American alligators found that the reptiles form neural maps of sound in the same way birds do. The research by Catherine Carr, a Distinguished University Professor of Biology at the University of Maryland, and her colleague Lutz Kettler from the Technische Universität München, was published in the Journal of Neuroscience on March 18, 2019.

Most research into how animals analyze interaural time difference has focused on physical features such as skull size and shape, but Carr and Kettler believed it was important to look at evolutionary relationships.

Birds have very small head sizes compared with alligators, but the two groups share a common ancestor — the archosaur — which predates dinosaurs. Archosaurs began to emerge around 246 million years ago and split into two lineages; one that led to alligators and one that led to dinosaurs. Although most dinosaurs died out during the mass extinction event 66 million years ago, some survived to evolve into modern birds.

Carr and Kettler’s findings indicate that the hearing strategy birds and alligators share may have less to do with head size and more to do with common ancestry.

“Our research strongly suggests that this particular hearing strategy first evolved in their common ancestor,” Carr said. “The other option, that they independently evolved the same complex strategy, seems very unlikely.”

To study how alligators identify where sound comes from, the researchers anesthetized 40 American Alligators and fitted them with earphones. They played tones for the sleepy reptiles and measured the response of a structure in their brain stems called the nucleus laminaris. This structure is the seat of auditory signal processing. Their results showed that alligators create neural maps very similar to those previously measured in barn owls and chickens. The same maps have not been recorded in the equivalent structure in mammal brains.

“We know so little about dinosaurs,” Carr said. “Comparative studies such as this one, which identify common traits extending back through evolutionary time add to our understanding of their biology.”

Reference:
Lutz Kettler and Catherine Carr. Neural maps of interaural time difference in the American alligator: a stable feature in modern archosaurs. Journal of Neuroscience, March 18, 2019 DOI: 10.1523/JNEUROSCI.2989-18.2019

Note: The above post is reprinted from materials provided by University of Maryland.

Rukwa Rift Basin Project names new Cretaceous mammal from East African Rift System

Side view of the lower jaw of Galulatherium jenkinsi, the most complete mammal yet know from the Cretaceous Period of the African continent, and named this week by researchers from Ohio University.
Side view of the lower jaw of Galulatherium jenkinsi, the most complete mammal yet know from the Cretaceous Period of the African continent, and named this week by researchers from Ohio University. Credit: Patrick O’Connor, Ohio University

Ohio University researchers announced a new species of mammal from the Age of Dinosaurs, representing the most complete mammal from the Cretaceous Period of continental Africa, and providing tantalizing insights into the past diversity of mammals on the planet.

The National Science Foundation-funded OHIO team, in collaboration with international colleagues, identified and named the new mammal in an article published today in Acta Paleontologica Polonica. This nearly complete lower jaw represents the first named mammal species from the Late Cretaceous Period (100-66 million years ago) of the entire African continent. The squirrel-sized animal was probably related to a group of southern hemisphere mammals known as gondwanatherians, yet a bizarre combination of features (including evergrowing and enamel-less peg-like teeth) make it challenging to easily place within any group of mammals yet known, living or extinct.

The new mammal is named Galulatherium jenkinsi, a name based on the Galula rock unit (itself derived from one of the local villages in the field area) and therium, Latin for beast, with the species name “jenkinsi” honoring the late Farish Jenkins, distinguished professor of anatomy and organismic biology at Harvard University and a strong supporter of the Rukwa Rift Basin Project early in its development.

The type and only specimen of Galulatherium was discovered in 2002, when Rukwa Rift Basin Project researchers found a bone fragment eroding from Cretaceous-age red sandstones in the Rukwa Rift Basin in southwestern Tanzania. After painstakingly removing the rock from the delicate specimen, the team announced the discovery of a new mammal in 2003, yet they conservatively refrained from establishing a name for the enigmatic new species until additional details of its anatomy could be revealed. In the intervening years, improvements in high-resolution x-ray computed tomography enabled the team to document detailed anatomy of the specimen and to establish Galulatherium as a species new to science.

“The analysis of Galulatherium has been a collaborative process, engaging with a group of experts to tackle the unique morphology of this specimen,” noted Dr. Patrick O’Connor, professor of anatomy at Ohio University and lead author of the paper. “Additional information gleaned from density-based microCT analyses, particularly the presence of ever-growing, enamel-less teeth, has allowed us to compare Galulatherium with other Mesozoic and early Cenozoic mammals, as well as with modern groups like sloths, in order to establish the best anatomical and functional analogs for this unique type of dentition.”

Gonwanatherian mammals are best known from Cretaceous and early Cenozoic rock units in Madagascar and Argentina, with other specimens known from India and Antarctica. Members of the research team have worked across the globe in search of early mammals.

“The fact that this is the first discovery of an identifiable mammal fossil in the Late Cretaceous of all of mainland Africa is incredibly exhilarating on so many levels,” added co-author David Krause, curator of paleontology at the Denver Museum of Nature and Science. “The needle is very small and the haystack is very big. And we know that there are so many more needles to find there.”

The perplexing story of Galulatherium and identifying its closest relatives is just the starting point. Getting ANY insight into what mammals lived on the continent during this time is groundbreaking, but it seems that Galulatherium is not a predecessor of any of the mammals that live on Africa today. So what happened to it and its kin? Were they wiped out at the end of the Cretaceous? When did the ancestors of Africa’s extant mammalian lineages arrive on the continent? Or were they living alongside Galulatherium and just have not yet been found?

“All great questions that will only be answered with the discovery of additional fossils, underscoring the need for exploratory research in places like the Rukwa Rift Basin and elsewhere on the continent,” added O’Connor.

The study included experts from several institutions to pore over the tiny jaw. Yet the specimen preserved a truly unique combination of anatomical features, making it difficult to place in the existing framework of mammalian evolution, and ultimately raising more questions than it answers.

“What began with the description of a compact specimen became a broader quest to understand how this jaw fits into the complex puzzle of mammalian evolution,” said Dr. Nancy Stevens, Ohio University professor and co-author on the paper.

Galulatherium is not the only animal discovered by the research team in the Rukwa Rift Basin. Other Cretaceous-age finds include bizarre relatives of early crocodiles and three distinct species of long-necked herbivorous sauropod dinosaurs. Finds from younger rocks in the region contain the oldest evidence of the split between monkeys and apes. Taken together, these findings from the East African Rift reveal a crucial glimpse into ancient ecosystems of Africa and encourage additional field exploration on the continent.

Other Cretaceous findings by the Rukwa Rift Basin Project research team in the Rukwa Rift Basin include:

  • Mnyamawantuka moyowamkia — titanosaurian sauropod dinosaur, Rukwa Rift Basin
  • Shingopana songwensis — titanosaurian sauropod dinosaur, Rukwa Rift Basin
  • Rukwatitan bisepultus — titanosaurian sauropod dinosaur, Rukwa Rift Basin
  • Pakasuchus kapilimai — mammal-like crocodile, Rukwa Rift Basin

The team has also made discoveries in the younger Paleogene deposits of the Rukwa Rift Basin:

  • Early evidence for monkey-ape split, Rukwa Rift Basin
  • Oldest fossil evidence of venomous snakes, Rukwa Rift Basin
  • Early evidence of insect farming — Fossil Termite Nests, Rukwa Rift Basin
  • Bobcat-sized carnivore, Rukwa Rift Basin

The study was funded by the US National Science Foundation Division of Earth Sciences, the National Geographic Society, the Ohio University Heritage College of Osteopathic Medicine, and the OHIO Office of the Vice President for Research and Creative Activity.

Reference:
Patrick OConnor, David Krause, Nancy Stevens, Ross MacPhee, Joseph Groenke, Daniela Kalthoff. A new mammal from the Upper Cretaceous (Turonian–Campanian) Galula Formation, southwestern Tanzania. Acta Palaeontologica Polonica, 2019; 64 DOI: 10.4202/app.00568.2018

Note: The above post is reprinted from materials provided by Ohio University.

What is Monomineralic Rock?

Quartzite. Credit: Museum of Geology at University of Tartu collection

Monomineralic rocks are rocks that are composed of only one mineral.

Examples of Monomineralic Rock

Monomineralic igneous rocks are dunite (more than 90% olivine) and anorthosite (more than 90% plagioclase feldspar).

Common monomineralic metamorphic rocks are marble and quartzite although they do not need necessarily to be monomineralic. Similar is the situation with their sedimentary protoliths – limestone and sandstone which may be very pure.

What is Polymineralic Rock?

Granite.
Granite. Credit: Museums Victoria

Polymineralic rocks are rocks formed by more than one type of rock forming minerals.

The rheology of polymineralic rocks is complex as the various minerals within the rock have different deformational behaviors (e.g. deformation mechanisms, activation energies). This results in unequal distribution of stress and strain throughout the rock (Jordan, 1988; Passchier & Trouw, 2005).

The stress network of a polymineralic rock depends on the type of minerals found within the rock (hard and soft minerals), and the ratio in which they exist. Experimental deformations of two solid-phase rocks indicated that the soft minerals have a disproportionally large effect on the strength of the rock (Le Hazif, 1978). External conditions also have a big impact on the interaction of these hard and soft minerals (Passchier & Trouw, 2005).

Polymineralic rocks display three end‐member types of mechanical and microstructural behavior:

  1. Strong minerals form a load‐bearing framework that contains spaces filled with weaker minerals;
  2. Two or more minerals with low relative strengths control bulk rheology and form elongate boudins;
  3. One very weak mineral governs bulk rheology, while the stronger minerals form clasts.

An example of a polymineralic rock

Granite, which is mainly composed of quartz along with plagioclase feldspar.

Reference:

  • Gower, R. J., & Simpson, C. (1992). Phase boundary mobility in naturally deformed, high-grade quartzofeldspathic rocks: evidence for diffusional creep. Journal of Structural Geology, 14(3), 301-313.
  • Handy, M. R. (1990). The solid‐state flow of polymineralic rocks. Journal of Geophysical Research: Solid Earth (1978–2012), 95(B6), 8647-8661.
  • Hippertt, J., Rocha, A., Lana, C., Egydio-Silva, M., & Takeshita, T. (2001). Quartz plastic segregation and ribbon development in high-grade striped gneisses. Journal of Structural Geology, 23(1), 67-80.
  • The solid‐state flow of polymineralic rocks

What is Black Quartz?

Black Quartz Cluster
Natural Rare Black Quartz Cluster Crystal, Size: 145 x 87 x 69 mm. Credit: catawiki

Smoky quartz is a grey, translucent variety of quartz that ranges in clarity from almost complete transparency to an almost-opaque brownish-gray or black crystal. Like other quartz gems, it is a silicon dioxide crystal. The smoky colour results from free silicon formed from the silicon dioxide by natural irradiation.

Varieties

Morion

A very dark brown to black opaque variety is known as morion. Morion is the German, Danish, Spanish and Polish synonym for smoky quartz. The name is from a misreading of mormorion in Pliny the Elder. It has a density of 5.4.

Cairngorm

Cairngorm is a variety of smoky quartz crystal found in the Cairngorm Mountains of Scotland. It usually has a smoky yellow-brown colour, though some specimens are greyish-brown.

It is used in Scottish jewellery and as a decoration on kilt pins and the handles of sgianan-dubha (anglicised: sgian-dubhs or skean dhu). The largest known cairngorm crystal is a 23.6 kg (52 lb) specimen kept at Braemar Castle.

What makes Quartz Black?

Irradiation of pure quartz will cause electrons to be ejected from some of the oxygen atoms. The electrons will return immediately, and the crystal is colorless.

The addition of Al to the SiO2 structure (about 1 Al atom for every 10000 Si atoms) results in a change in color in the crystal. If Al3+ replaces the Si4+ ion in the SiO2 framework to maintain electrical neutrality of the crystal, a proton (H+) could be present. If irradiation ejects an electron from an oxygen atom near the aluminum ion, the electron can be trapped by the proton. The whole (AlO4)5- entity creates a “hole” color centre, being converted to (AlO4)4-.The hydrogen atom does not absorb light. (AlO4)4-) absorbs light to produce the gray-to-brown-to-black color of smoky quartz.

Reference:

Smoky quartz
Smoky quartz: “hole” color center

What the world’s oldest eggs reveal about dinosaur evolution

Illustration of Massospondylus eggs and young dinosaurs
Illustration of Massospondylus eggs and young dinosaurs. Credit: Julius Csotonyi

A study of the world’s earliest known dinosaur eggs reveals new information about the evolution of dinosaur reproduction.

An international team of researchers led by Robert Reisz of the Department of Biology at the University of Toronto Mississauga studied the fossilized remains of eggs and eggshells discovered at sites in Argentina, China and South Africa—widely separated regions of the supercontinent Pangea. At 195 million years old, they are the earliest known eggs in the fossil record, and they were all laid by a group of stem sauropods—long-necked herbivores that ranged in size from four to eight metres in length and were the most common and widely spread dinosaurs of their time.

Reisz is puzzled by the fact that “reptile and mammal precursors appear as skeletons in the fossil record starting 316 million years ago, yet we know nothing of their eggs and eggshells until 120 million years later. It’s a great mystery that eggs suddenly show up at this point, but not earlier.”

According to Koen Stein, a post-doctoral researcher at Universiteit Gent and lead author of the project, the eggs represent a significant step in the evolution of dinosaur reproduction. Spherical, and about the size of a goose egg, these dinosaur eggshells were paper-thin and brittle, much thinner than similar-sized eggs of living birds.”We know that these early eggs had hard shells because during fossilization they cracked and broke, but the shell pieces retained their original curvature.”

Members of the team, including Edina Prondvai and Jean-Marc Baele, analyzed shell thickness, membrane, mineral content and distribution of pores, looking for clues about why these early eggs might have developed hard shells. The results of the study show that hard-shelled eggs evolved early in dinosaur evolution with thickening occurring independently in several groups, but a few million years later other reptiles also developed hard-shelled eggs. One possibility is that hard and eventually thicker shells may have evolved to shield fetal dinosaurs and other reptiles from predators. “The hard shells would protect the embryos from invertebrates that could burrow into the buried egg nests and destroy them,” says Reisz.

Reisz adds that the study raises interesting questions for future investigation. “For example, we would like to understand why dinosaurs and their avian descendants never developed viviparity (live birth) and continued to rely on egg laying, while non dinosaurian reptiles and mammals, including ancient aquatic reptiles succeeded in evolving this more advanced reproductive strategy.”

The study is co-authored by Koen Stein and Edina Prondvai (Universiteit Gent), Timothy Huang (Jilin University), Jean-Marc Baele (Université de Mons) and P. Martin Sander (Universität Bonn) and is published in the journal Scientific Reports. It follows up on earlier research by Reisz, published in 2012, that examined nests of Massospondylus embryos in eggs discovered at nesting sites in South Africa, and a 2013 publication on dinosaur embryology in Lufengosaurus from China.

Reference:
Koen Stein et al. Structure and evolutionary implications of the earliest (Sinemurian, Early Jurassic) dinosaur eggs and eggshells, Scientific Reports (2019). DOI: 10.1038/s41598-019-40604-8

Note: The above post is reprinted from materials provided by University of Toronto Mississauga.

Tectonics in the tropics trigger Earth’s ice ages

Over the last 540 million years, as the Earth's tectonic plates have shifted, MIT researchers have found that periods of major tectonic activity (orange lines) in the tropics (green belt) were likely triggers for ice ages during those same periods.
Over the last 540 million years, as the Earth’s tectonic plates have shifted, MIT researchers have found that periods of major tectonic activity (orange lines) in the tropics (green belt) were likely triggers for ice ages during those same periods. Credit: Courtesy of the researchers

Over the last 540 million years, the Earth has weathered three major ice ages — periods during which global temperatures plummeted, producing extensive ice sheets and glaciers that have stretched beyond the polar caps.

Now scientists at MIT, the University of California at Santa Barbara, and the University of California at Berkeley have identified the likely trigger for these ice ages.

In a study published in Science, the team reports that each of the last three major ice ages were preceded by tropical “arc-continent collisions” — tectonic pileups that occurred near the Earth’s equator, in which oceanic plates rode up over continental plates, exposing tens of thousands of kilometers of oceanic rock to a tropical environment.

The scientists say that the heat and humidity of the tropics likely triggered a chemical reaction between the rocks and the atmosphere. Specifically, the rocks’ calcium and magnesium reacted with atmospheric carbon dioxide, pulling the gas out of the atmosphere and permanently sequestering it in the form of carbonates such as limestone.

Over time, the researchers say, this weathering process, occurring over millions of square kilometers, could pull enough carbon dioxide out of the atmosphere to cool temperatures globally and ultimately set off an ice age.

“We think that arc-continent collisions at low latitudes are the trigger for global cooling,” says Oliver Jagoutz, an associate professor in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “This could occur over 1-5 million square kilometers, which sounds like a lot. But in reality, it’s a very thin strip of Earth, sitting in the right location, that can change the global climate.”

Jagoutz’ co-authors are Francis Macdonald and Lorraine Lisiecki of UC Santa Barbara, and Nicholas Swanson-Hysell and Yuem Park of UC Berkeley.

A tropical trigger

When an oceanic plate pushes up against a continental plate, the collision typically creates a mountain range of newly exposed rock. The fault zone along which the oceanic and continental plates collide is called a “suture.” Today, certain mountain ranges such as the Himalayas contain sutures that have migrated from their original collision points, as continents have shifted over millenia.

In 2016, Jagoutz and his colleagues retraced the movements of two sutures that today make up the Himalayas. They found that both sutures stemmed from the same tectonic migration. Eighty million years ago, as the supercontinent known as Gondwana moved north, part of the landmass was crushed against Eurasia, exposing a long line of oceanic rock and creating the first suture; 50 million years ago, another collision between the supercontinents created a second suture.

The team found that both collisions occurred in tropical zones near the equator, and both preceded global atmospheric cooling events by several million years — which is nearly instantaneous on a geologic timescale. After looking into the rates at which exposed oceanic rock, also known as ophiolites, could react with carbon dioxide in the tropics, the researchers concluded that, given their location and magnitude, both sutures could have indeed sequestered enough carbon dioxide to cool the atmosphere and trigger both ice ages.

Interestingly, they found that this process was likely responsible for ending both ice ages as well. Over millions of years, the oceanic rock that was available to react with the atmosphere eventually eroded away, replaced with new rock that took up far less carbon dioxide.

“We showed that this process can start and end glaciation,” Jagoutz says. “Then we wondered, how often does that work? If our hypothesis is correct, we should find that for every time there’s a cooling event, there are a lot of sutures in the tropics.”

Exposing Earth’s sutures

The researchers looked to see whether ice ages even further back in Earth’s history were associated with similar arc-continent collisions in the tropics. They performed an extensive literature search to compile the locations of all the major suture zones on Earth today, and then used a computer simulation of plate tectonics to reconstruct the movement of these suture zones, and the Earth’s continental and oceanic plates, back through time. In this way, they were able to pinpoint approximately where and when each suture originally formed, and how long each suture stretched.

They identified three periods over the last 540 million years in which major sutures, of about 10,000 kilometers in length, were formed in the tropics. Each of these periods coincided with each of three major, well-known ice ages, in the Late Ordovician (455 to 440 million years ago), the Permo-Carboniferous (335 to 280 million years ago), and the Cenozoic (35 million years ago to present day). Importantly, they found there were no ice ages or glaciation events during periods when major suture zones formed outside of the tropics.

“We found that every time there was a peak in the suture zone in the tropics, there was a glaciation event,” Jagoutz says. “So every time you get, say, 10,000 kilometers of sutures in the tropics, you get an ice age.”

He notes that a major suture zone, spanning about 10,000 kilometers, is still active today in Indonesia, and is possibly responsible for the Earth’s current glacial period and the appearance of extensive ice sheets at the poles.

This tropical zone includes some of the largest ophiolite bodies in the world and is currently one of the most efficient regions on Earth for absorbing and sequestering carbon dioxide. As global temperatures are climbing as a result of human-derived carbon dioxide, some scientists have proposed grinding up vast quantities of ophiolites and spreading the minerals throughout the equatorial belt, in an effort to speed up this natural cooling process.

But Jagoutz says the act of grinding up and transporting these materials could produce additional, unintended carbon emissions. And it’s unclear whether such measures could make any significant impact within our lifetimes.

“It’s a challenge to make this process work on human timescales,” Jagoutz says. “The Earth does this in a slow, geological process that has nothing to do with what we do to the Earth today. And it will neither harm us, nor save us.”

Reference:
Francis A. Macdonald, Nicholas L. Swanson-Hysell, Yuem Park, Lorraine Lisiecki, Oliver Jagoutz. Arc-continent collisions in the tropics set Earth’s climate state. Science, 2019; eaav5300 DOI: 10.1126/science.aav5300

Note: The above post is reprinted from materials provided by Massachusetts Institute of Technology. Original written by Jennifer Chu.

On the front lines in Kilauea

Lava flow, Kilauea eruption, 2018. Drone image from Einat Lev
Lava flow, Kilauea eruption, 2018. Drone image from Einat Lev. Credit: Julie Oppenheimer

In the early spring, volcanologists monitoring the ground around Kilauea, the most active volcano on the island of Hawai’i, noticed a significant increase in seismicity, a sign of an impending eruption. Meanwhile, in Palisades, New York, Lamont volcanologist Einat Lev was also watching developments at Kilauea closely, scanning United States Geological Survey (USGS) reports and keeping in regular touch with friends and colleagues directly tasked with monitoring volcanic activity.

Lev had a particular interest because of her prior experience at Kilauea, having studied the lava lake that has occupied the summit crater since 2008. Her fascination with this volcano came to a crescendo on May 3, 2018, when the anticipated eruption began. Lev started searching for a way to help response efforts and to place her team sufficiently close to the newly opened fissures to observe the developing phenomenon. It took her several days to lock down a plan, obtain a permit, and book plane tickets for herself and her two postdoctoral researchers. All of this she carefully orchestrated so as to serve as well the response team on the ground.

“I didn’t want to go there without coordination,” Lev said. “Obviously, they closed the region. I tried to work directly with the USGS, but they’re not allowed to work with anyone external, so I had to find other ways. I contacted colleagues at the University of Hawai’i-Hilo and learned they had a permit to go in. They are people I’ve worked with before, and since we all had the proper certifications and drone operational and field experience, they invited us to join them. When we heard that, we bought our tickets. I felt I really needed to be there.”

This expedition would lead Lev and her team to the front lines of an active, dangerous volcanic eruption, thrusting her into the center of the action and the news media spotlight. Lev’s first-person accounts and analysis made for lead stories across major outlets, including CNN, BBC, and NPR. Her descriptions brought home the immediacy of the situation.

“Our volcanology team at Lamont-Doherty Earth Observatory is on-site to witness this historic natural event, and to be of service to the local authorities in their constant, exhausting chase to monitor the eruption and protect the public,” Lev wrote, while chronicling her activities on the scene.

Lev’s team was prepared to support the effort and offered both sophisticated drones and reinforcements to relieve the already exhausted UH-Hilo team, the USGS scientists, and emergency-response workers.

“We had brand new equipment. It was an opportunity for us to try it within the context of a dynamic event for the first time. Our drone has both a standard video camera and an infrared video camera. It was very helpful because the team in Hilo had similar equipment but not a single drone that could conduct both video and the thermal imaging at the same time. To get that coverage they needed two flights. Using our equipment was faster and more efficient,” added Lev.

The three-person Lamont team also joined shifts as the necessary 24/7 monitoring continued.

“While we were not allowed to fly our drones ourselves, we could serve as the required flight observers, help with the setup and provide equipment, so the official responders could have a break. Our team helped reduce the load on them,” said Lev.

Ultimately, the eruption forced the evacuation of thousands of people. The lava flow consumed 700 homes. A series of as many as 18,000 earthquakes forced the closure of Hawai’i Volcanoes National Park, and lava haze (“laze”), spatter, and lava bombs became serious health threats. For volcanologists, however, the Kilauea eruption – more than 100 days long – was also an opportunity to study an enigmatic planetary process as it unfolded.

“For those of us grounded in the academic theory of what lava does and the physics behind lava flows, it was fascinating to see the response on the ground. We were part of it all, what the road crews have to deal with, what the fire crews have to deal with, how the community responds, and how people evacuate or don’t evacuate. Seeing all of this unfold and not just reading about it was really fascinating. People think lava moves slowly, that it’s not a rapid-response emergency. But actually, at Kilauea, things kept changing. Overall, 22 fissures erupted, and the active sites kept jumping around. The response had to be very dynamic. Many times I thought a fissure was done, but then it would start again. It was really about responding to what was happening,” Lev said.

Lev has been studying the science of volcanoes since her arrival at Lamont in 2009, but her work at Kilauea was revelatory for her.

“It’s different experiencing something with your body and your eardrum from thinking about it mathematically,” noted Lev. “It was definitely the most emotional connection to my subject that I’ve had…ever. For us that was the greatest benefit from going there, a chance to develop an intuitive connection to a subject we’ve long been studying from afar.”

Lev believes these observations and the ongoing sampling led by the USGS will inform volcanology, advancing science’s understanding, improving predictive modeling, and strengthening the case for a uniform methodology for responses to eruptions elsewhere. In the spring, during the weeks prior to the Kilauea eruption, she had been part of a cadre of volcanologists working on a proposal to the National Science Foundation to fund a data sharing and response coordination system. After her work on the front lines at Kilauea, she believes even more strongly that such a system is essential.

“The response was so complex at Kilauea, in the United States, a modern country with modern systems, and still there was room for improvement. This eruption and the response to it should serve as the model and a lesson for the future.”

Note: The above post is reprinted from materials provided by Columbia University.

Dyke cutting Canary Islands, Spain

Dyke cutting Canary Islands, Spain
Dyke cutting Canary Islands, Spain

Canary Islands

The Canary Islands is a Spanish archipelago and the southernmost autonomous community of Spain located in the Atlantic Ocean, 100 kilometres (62 miles) west of Morocco at the closest point. The Canary Islands, which are also known informally as the Canaries, are among the outermost regions (OMR) of the European Union proper. It is also one of the eight regions with special consideration of historical nationality recognized as such by the Spanish Government. The Canary Islands belong to the African Plate like the Spanish cities of Ceuta and Melilla, the two on the African mainland.

Geology of Canary Islands

The seven major islands, one minor island, and several small islets were originally volcanic islands, formed by the Canary hotspot. The Canary Islands is the only place in Spain where volcanic eruptions have been recorded during the Modern Era, with some volcanoes still active (El Hierro, 2011). Volcanic islands such as those in the Canary chain often have steep ocean cliffs caused by catastrophic debris avalanches and landslides.

The Teide volcano on Tenerife is the highest mountain in Spain, and the third tallest volcano on Earth on a volcanic ocean island. All the islands except La Gomera have been active in the last million years; four of them (Lanzarote, Tenerife, La Palma and El Hierro) have historical records of eruptions since European discovery. The islands rise from Jurassic oceanic crust associated with the opening of the Atlantic. Underwater magmatism commenced during the Cretaceous, and reached the ocean’s surface during the Miocene. The islands are considered as a distinct physiographic section of the Atlas Mountains province, which in turn is part of the larger African Alpine System division.

In the summer of 2011 a series of low-magnitude earthquakes occurred beneath El Hierro. These had a linear trend of northeast-southwest. In October a submarine eruption occurred about 2 km (1 1⁄4 mi) south of Restinga. This eruption produced gases and pumice, but no explosive activity was reported.

Volcanism in Canary Islands

Volcanism in this ∼800-km-long and ∼400-km-wide volcanic belt (located at 33–27°N and 18–12°W) decreases in age from the northeast (Lars Seamount, 68 million years) to the southwest (Hierro Island, 1 million years) and is interpreted to represent the Canary hotspot track. The Canary volcanic province is located on Jurassic ocean crust (∼150 million years old beneath the western part of the province to ∼180 million years old beneath the eastern part of the province), and contains some of the oldest ocean crust preserved in ocean basins.

Dyke descriptions

Dyke diversity and morphology

Dyke cutting Canary Islands, Spain
Fig. 2 Examples of dyke morphologies and textures. a Example of representative massive and crushed dyke, b example of dyke with gently deviating strike. Note the dyke injection formed a tension gash within the country rock, c example of dyke containing vesicles; in this case, the vesicles are concentrated in bands parallel to the margins and they start to form fracture-like parallel joints

The dyke morphology is diverse, ranging from massive to intensely fractured or crushed, from highly vesicular to low vesicularity and from straight to bendy (Fig. 2). Orientations of individual dykes are usually constant at the outcrop scale, but local changes in strike, in dip or both have sometimes been observed (Fig. 2a, b). Changes in orientation (strike, dip or both) can occur at the boundary between layers of different competence, such as between a lava flow and its basal breccia, but occurs also within the same layer (e.g. Hoek 1995; Gudmundsson 2002).

Vesicle shapes and sizes are also variable. An interesting feature to note is that sometimes vesicles concentrate along straight bands parallel to dyke margins and, when their number and size becomes significant, they form fracture-like parallel structures within the dykes (Fig. 2c). In such cases, vesicles are elongate, stretched and often ruptured.

A few dykes contain centimetre-sized xenoliths of local country rock. Short finger-like intrusions into the adjacent rocks are sometimes observed (Fig. 2b), similar to those described by e.g. Mathieu and van Wyk de Vries (2009). These intrusive fingers may be tension gash-like features or dyke tip branching relics.

Dyke thickness and density

The average of all dyke thicknesses for the entire study area is 128 cm (Fig. 1,N0531 dykes). Dyke thicknesses for each sector (Fig. 1b) are displayed and were calculated as follows: when only an estimate of a dyke’s thicknesse was available, i.e. dykes observed from a distance, the values were not taken into account for the calculation. Within a dyke, thickness variations can occur, especially when the dyke passes from a low competence zone (e.g. scoria) into a more resistant stratum (e.g. a lava flow) where the dyke becomes thinner (see the Electronic Supplementary Material). If a dyke was accessible and measurable with a tape measure, then the thickest part of the dyke was considered.

Reference:

  1. Canary Islands
  2. https://core.ac.uk/download/pdf/11896861.pdf
  3. Dykes and structures of the NE rift of Tenerife, Canary Islands: A record of stabilisation and destabilisation of ocean island rift zones

Teenage T. rex was already chomping on prey

Joseph Peterson, a vertebrate paleontologist at the University of Wisconsin Oshkosh, demonstrates how a T. rex takes a bite.
Joseph Peterson, a vertebrate paleontologist at the University of Wisconsin Oshkosh, demonstrates how a T. rex takes a bite. Credit: Patrick Flood, UW Oshkosh

New research from the University of Wisconsin Oshkosh indicates that even as a teenager the Tyrannosaurus rex showed signs that it would grow up to be a ferocious predator.

In a study published last week in the peer-reviewed journal Peerj — the Journal of Life and Environmental Sciences, UWO scientists reported evidence that a juvenile T. rex fed on a large plant-eating dinosaur, even though it lacked the bone-crushing abilities it would develop as an adult.

While studying fossils from an Edmontosaurus — a plant-eating Hadrosaurid or duck-billed dinosaur, UWO vertebrate paleontologist Joseph Peterson noticed three large, v-shaped, bite marks on a tail bone and wondered, “Who made these?”

Peterson knew that T. rex — a member of the meat-eating dinosaur suborder known as Theropoda — was “a likely culprit.”

“We suspected that T. rex was responsible for the bit marks, because in the upper Cretaceous rock formation, where the hadrosaur was discovered, there are only a few carnivorous dinosaurs and other reptiles in the fossil record. Crocodile fossils are found there, but such a crocodile would have left tooth marks that are round rather than the elliptical punctures we found on the vertebra,” Peterson explained.

“There also were small Velociraptor-like dinosaurs, but their teeth are too small to have made the marks. Finally, an adult T. rex would have made punctures that would have been too large! That’s when we started considering a juvenile tyrannosaur.”

To test the hypothesis, Peterson and geology student Karsen Daus, of Suamico, coated the fossil with a silicon rubber to make a silicone peel of the puncture marks.

They found that the dimensions of the “teeth” better matched a late-stage juvenile T. rex (11 to 12 years) than an adult (approximately 30 years).

“Although this T. rex was young, it really packed a punch,” Peterson said.

“This is significant to paleontology because it demonstrates how T. rex — the most popular dinosaur of all time — may have developed changes in diet and feeding abilities while growing,” he said. “This is part of a larger, ongoing research initiative by many paleontologists to better understand how T. rex grew and functioned as a living creature over 65 million years ago.”

Most theropod feeding traces and bite marks are attributed to adults; juvenile tooth marks rarely have been reported in the literature, he added.

“We really are in the ‘Golden Age’ of paleontology,” Peterson said. “We are learning more now than we ever thought we would know about dinosaurs. And, we’re learn more about how they grew up.”

Reference:
Joseph E. Peterson, Karsen N. Daus. Feeding traces attributable to juvenile Tyrannosaurus rex offer insight into ontogenetic dietary trends. PeerJ, 2019; 7: e6573 DOI: 10.7717/peerj.6573

Note: The above post is reprinted from materials provided by University of Wisconsin Oshkosh.

Scientists go to extremes to reveal make-up of Earth’s core

Representative Image : The Earth’s layers, showing the Inner and Outer Core, the Mantle, and Crust

Experiments conducted at extreme conditions are giving scientists new insights into the chemical make-up of the Earth’s core.

Advanced laboratory techniques reveal that our planet’s metal centre — more than 1,800 miles below the surface — also contains silicon, an element commonly found in stony meteorites.

The findings support an existing theory that suggests Earth’s formation around 4.5 billion years ago was driven by extensive interactions between stony and iron-rich meteorites inside a cloud of dust and gas. This huge cloud of material also formed the Sun.

The chemical composition of the Earth’s core is still poorly understood, despite more than 60 years of research, scientists say.

Previous studies had suggested the core is composed of an alloy of iron and nickel, though other elements are thought to be present.

A team led by experts from the University of Edinburgh made the discovery by inserting tiny mixtures of iron, nickel and silicon into a device known as a diamond anvil cell. It can recreate the extreme pressures and temperatures present deep inside planets.

By squeezing the mixture together, they were able to achieve the same density as that found at the Earth’s core. The scientists predict that the temperature at the planet’s centre exceeds 5500 degrees Celsius.

The experiments were conducted at the Deutsches Elektronen-Synchrotron, Germany, and the European Synchrotron Radiation Facility in France.

The study, published in the journal Earth and Planetary Science Letters, received funding from the European Research Council. The work also involved researchers from the University of Bayreuth, Germany, and Hiroshima and Osaka Universities in Japan.

Dr Tetsuya Komabayashi, of the University of Edinburgh’s School of GeoSciences, who led the study, said: “The nature of the Earth’s core is the key to understanding a number of processes operating inside the planet. Our findings are an important step towards understanding how the planet was formed and how it may evolve in the future.”

Reference:
Tetsuya Komabayashi, Giacomo Pesce, Ryosuke Sinmyo, Takaaki Kawazoe, Helene Breton, Yuta Shimoyama, Konstantin Glazyrin, Zuzana Konôpková, Mohamed Mezouar. Phase relations in the system Fe–Ni–Si to 200 GPa and 3900 K and implications for Earth’s core. Earth and Planetary Science Letters, 2019; 512: 83 DOI: 10.1016/j.epsl.2019.01.056

Note: The above post is reprinted from materials provided by University of Edinburgh.

Ancient records prompt rethink of animal evolution timeline

Researchers conducting fieldwork in Namibia as part of a previous study.
Researchers conducting fieldwork in Namibia as part of a previous study. Credit: Rachel Wood

Scientists are rethinking a major milestone in animal evolution, after gaining fresh insights into how life on Earth diversified millions of years ago.

Bursts of evolutionary activity that increased the number and variety of animals began earlier, occurred over a longer timeframe, and were more frequent than previously thought, researchers say.

Their findings challenge a long-held theory that suggests the huge expansion in the types of animals on the planet more than 500 million years ago was triggered by a single, rapid surge of evolution — known as the Cambrian Explosion.

Geoscientists from the University of Edinburgh re-assessed the timeline of early animal evolution by analysing records of fossil discoveries and environmental change.

Until now, the Cambrian Explosion — which took place between 540 and 520 million years ago — was thought to have given rise to almost all the early ancestors of present-day animals.

Scientists say, however, that it was probably just one in a series of similar events, the first of which took place at least 571 million years ago during the late Ediacaran Period.

These bursts of evolutionary activity may have coincided with dramatic fluctuations in the levels of oxygen and essential nutrients in the oceans, the team says.

The review is published in the journal Nature Ecology & Evolution. It was supported by the Natural Environment Research Council. The research also involved the Universities of Bristol, Cambridge and Helsinki, Tokyo Institute of Technology, Japan, and Memorial University of Newfoundland in Canada.

Professor Rachel Wood, of the University of Edinburgh’s School of GeoSciences, who led the study, said: “Integrating data from the fossil record with that of environmental changes that affected the whole planet is revealing the patterns and drivers of the rise of complex life on Earth. We used to think early animals emerged rapidly following a single evolutionary event, but our findings suggest it actually happened in stages.”

Reference:
Rachel Wood, Alexander G. Liu, Frederick Bowyer, Philip R. Wilby, Frances S. Dunn, Charlotte G. Kenchington, Jennifer F. Hoyal Cuthill, Emily G. Mitchell, Amelia Penny. Integrated records of environmental change and evolution challenge the Cambrian Explosion. Nature Ecology & Evolution, 2019; DOI: 10.1038/s41559-019-0821-6

Note: The above post is reprinted from materials provided by University of Edinburgh.

What are the minerals and Gems that found in the Sedimentary rocks?

Opal found in Coober Pedy
Representative Image, Opal found in Coober Pedy. Credit: PXHere

What is Sedimentary rock?

Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of mineral or organic particles on the floor of oceans or other bodies of water at the Earth’s surface. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of geological detritus (minerals) or biological detritus (organic matter). Before being deposited, the geological detritus was formed by weathering and erosion from the source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers, which are called agents of denudation. Biological detritus was formed by bodies and parts (mainly shells) of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies (marine snow). Sedimentation may also occur as dissolved minerals precipitate from water solution.

The sedimentary rock cover of the continents of the Earth’s crust is extensive (73% of the Earth’s current land surface), but the total contribution of sedimentary rocks is estimated to be only 8% of the total volume of the crust. Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding. The study of sedimentary rocks and rock strata provides information about the subsurface that is useful for civil engineering, for example in the construction of roads, houses, tunnels, canals or other structures. Sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores.

The study of the sequence of sedimentary rock strata is the main source for an understanding of the Earth’s history, including palaeogeography, paleoclimatology and the history of life. The scientific discipline that studies the properties and origin of sedimentary rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geomorphology, geochemistry and structural geology. Sedimentary rocks have also been found on Mars.

Sedimentary Cycle

The sedimentary cycle is the second largest cycle in mineral and rock formation. Sedimentary rocks are formed by erosion, transport in rivers, ice etc. and involve the decay and disintegration of a preexisting rock mass. Usually there are no new minerals formed, only found.

When these particles eventually settle, they form alluvial gravels, sands or clays. When they are either cemented or compressed, then they form sedimentary rocks such a conglomerations, sandstones and limestones.

Chemical action in the environment leads to some material dissolving in water. Eventually the water may evaporate and deposits of borax and other salt “evaporates” may form this way.

Plant and animal remains are commonly incorporated among the rock fragments and these may be preserved as fossils.

Many gemstones are found in “alluvial deposits”. These deposits have their origin in the destruction of the original rocks and the resulting materials by rivers, floods and glacial movement. During this movement the heavier minerals tend to remain relatively close to the source, whilst lighter minerals are carried further away.

The heavier and harder materials do not wear as much as the lighter ones and tend to retain more of their crystal shape. Stones such as sapphire and topaz do not show as much abrasion as softer minerals like quartz.

However, due to the continuous grinding and tumbling over a period of time, a large number of gem minerals are found as rounded “water-worn” pebbles. The gem gravels in Sri Lanka contain a wide variety of such minerals.

Because of their supreme hardness and density many diamonds survive the sedimentary processes and are frequently found in alluvial deposits.

Minerals found in sedimentary rocks:

Reference:

Sedimentary rock
Sedimentary rocks

What are the minerals and Gems that found in the Metamorphic rocks?

Opal found in Coober Pedy
Representative Image, Opal found in Coober Pedy. Credit: PXHere

What is Metamorphic rock?

Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means “change in form”. The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (100 megapascals (1,000 bar) or more), causing profound physical or chemical change. The protolith may be a sedimentary, igneous, or existing metamorphic rock.

Metamorphic rocks make up a large part of the Earth’s crust and form 12% of the Earth’s land surface. They are classified by texture and by chemical and mineral assemblage (metamorphic facies). They may be formed simply by being deep beneath the Earth’s surface, subjected to high temperatures and the great pressure of the rock layers above it. They can form from tectonic processes such as continental collisions, which cause horizontal pressure, friction and distortion. They are also formed when rock is heated by the intrusion of hot molten rock called magma from the Earth’s interior. The study of metamorphic rocks (now exposed at the Earth’s surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth’s crust. Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite.

Metamorphic Cycle

The metamorphic cycle is the third largest cycle in mineral and rock formation. Metamorphism is the alteration of mineral paragenesis (the order of formation) after their deposition, by external action such as contact with magmetic rocks, regional changes in the pressure and temperature (e.g. contact metamorphosed limestones, crystalline schists, etc.). The consolidated rocks are altered in composition, texture or internal structure through pressure, heat and new chemical substances.

There are two kinds of metamorphism: Regional and Contact

  1. Regional metamorphism is caused due to a rise in temperature and directed pressure, effecting the earth’s crust.
  2. Contact metamorphism is caused when magma is intruded into a preexisting rock mass. The heat and pressure of this magma, causes a metamorphic change in the rock it intrudes.

Both igneous and sedimentary rocks can change in texture or chemical composition as the result of either contact or regional metamorphism. Thus existing rocks change into new types of rocks. They are usually harder and denser than the original material.

For example, shale may alter into slate and further metamorphose into schist. Limestone is converted into marble. Sometimes schists contain gem minerals like garnet, emerald and corundum.

Some minerals that grow in metamorphic rocks are:

  • Beryl
  • Corundum
  • Danburite
  • Garnets
  • Iolite
  • Lapis lazuli
  • Jadeite
  • Nephrite
  • Spinel
  • Alexandrite
  • Andalusite

Reference:

Metamorphic rock
Metamorphic rocks

What are the minerals and Gems that found in the Igneous rocks?

Opal found in Coober Pedy
Representative Image, Opal found in Coober Pedy. Credit: PXHere

Igneous Rocks

Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet’s mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form natural glasses. Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended crust and oceanic crust.

Minerals that in igneous rocks

Mafic rocks (basalt, gabbro): olivine, pyroxene, plagioclase (ca-feldspar)
Intermediate rocks (andesite, diorite): pyroxene, plagioclase (sodium feldspar), hornblende, biotite, quartz
Felsic rocks (granite, rhyolite): quartz, feldspar (potassium or sodium), hornblende, biotite, muscovite

Basic

By the cooling down of magma, atoms are linked into crystalline patterns and subsequently different minerals are formed. When the formation takes place in the depths of the earth’s crust (approx. 33km deep) quite large rocks may be formed (for instance, granites).

Igneous rocks are formed and created by magmatic processes in the earth. To form very large crystals of rare minerals, exceptional conditions are needed. For instance, a rock called pegmatite is formed by the crystallization of magma enriched with water in the veins of other rocks, and may contain beryl, tourmaline and topaz.

Igneous rocks are divided into two types — volcanic rock (extrusive) and plutonic rock (intrusive) — depending on where the magma cools.
Volcanic or extrusive rock

This is rock that is formed on the surface of the earth. In contact with air or seawater, molten rock cools rapidly and either quenches to a glass (like obsidian) or forms small crystals (basalt). Volcanic rocks are usually finely grained or glassy in structure.

Basalt is an extrusive rock, finely grained due to its rapid cooling. It largely consists of tiny feldspar and pyroxene crystals (like diopside and enstatite). Some basalts contain gemstones like corundum, zircon and garnets.

Another volcanic rock is called kimberlite. Kimberlite pipes are the most major source of diamond.

Occasionally, varieties of volcanic glass, obsidian, are cut and fashioned as gemstones. Obsidian is an amorphous mineraloid with the hardness of approximately 5.5. Varieties of obsidian include:

  • Snowflake obsidian ( with inclusions of the mineral cristobalite)
  • Rainbow obsidian
  • Red mahogany obsidian
  • Silver sheen obsidian
  • Midnight lace obsidian
  • Pumpkin obsidian
  • “Apache tears” obsidian

Plutonic or intrusive rock

When molten rock solidifies within preexisting rock, it cools slowly, forming plutonic rocks with larger crystals. They tend to be coarse grained.

Granite is a coarse grained intrusive rock which contains the minerals quartz and feldspar, and usually carries mica or hornblende. In some circumstances, granite undergoes “fractional crystallization”, a process where slow cooling creates crystals of different minerals as they form at different temperatures.

Minerals of the pegmatite group are among the last to be formed, often occuring as veins penetrating their surroundings.

Associated minerals that find their origin in igneous rocks:

  • Beryl
  • Chrysoberyl
  • Corundum
  • Diamond
  • Garnet
  • Feldspar
  • Peridot
  • Quartz
  • Spinel
  • Topaz
  • Tourmaline
  • Zircon

Advanced

Stages of the igneous or magmatic cycle

The stages of the igneous or magmatic cycle are as follows:

1. Early magmatic phase (early crystallization) from the fiery hot magma:

  • Chromite
  • Magnetite
  • Titanium magnetite

2. Liquid magmatic phase (main crystallization) 1500-600 degrees C:

  • Spinel
  • Zircon
  • Apatite
  • Peridot
  • Diamond

3. Pegmatite phase (rest crystallization) 700-400 degrees C:
The residual part of the magma, which is rich in fluxes, is known as the pegmatite stage. The melt becomes a watery solution as solidification proceeds. Because of this fluidity, the liquids can penetrate fissures and cracks in the surrounding rocks. Under the concentrated pressure and temperatures, individual crystals form that can measure several centimeters, and occasionally several meters! The prismatic crystals grow perpendicular to the walls of the vein. Pegmatite veins are some of the best examples of gemstone formation.

4. Pneumatolytic phase 500-300 degrees C:
Minerals formed in this phase form at lower temperatures and rising pressure. Superheated volatile components are involved. The most prominent of these components is water vapor, boron and fluorine gases. Under the influence of these vapors, other minerals are often formed in the contact zone of limestone.

  • Topaz
  • Euclase
  • Vesuvianite
  • Fluorite
  • Cassiterite
  • Sheelite
  • Wolframite

5. Hydrothermal phase 400-50 degrees C:
This is a process associated with igneous activity that involves heated or super-heated water. Water at very high temperature and pressure is an exceedingly active substance, capable of breaking down silicates and dissolving many substances normally thought to be insoluble. This is the last stage of minerals that can be considered to be formed directly from magma.

Expert

Zircon to calculate the age of the earth

Zircon forms in granites deep in the earth’s crust (plutonic rock). Through movement of tectonic plates, this granite is brought to the surface and starts mountain building. Through erosion, the granite (and the contained zircon) builds sediments which will eventually be buried deep enough to transform into metamorphic rocks.

Zircon has two important properties:

  1. Relative high hardness
  2. Resistance to chemical attacks

Due to its hardness of 7.5 on the scale of Mohs, the zircons usually survive the sedimentary process intact. Because of its resistance to chemical attacks, zircon will survive the contact metamorphism process which is trying to attack it with heat and pressure. The latter is important as the liquid mass surrounding the zircon will cause a new rim to be formed around the old zircon, just like the formation of tree rings. This first cycle usually will take hundreds of million years.

The old crystal with its newly formed rim is then pushed up again through tectonic plate interactions, then this geologic cycle repeats itself.

A third and well known property of zircon is that it can accommodate radioactive elements like uranium. Uranium has the ability to decay into lead at a fixed time rate. Calculation of the uranium-lead ratio may give a clue of the age of the zircon (and thus Earth’s age). However, lead may leak from the zircon, disturbing the uranium-lead ratio.

Fortunately, scientists found a new way of calculation by using isotopes. The uranium-238 isotope (with a half-life of 4.468 billion years) decays to lead-206, while uranium-235 (with a half-life of 703.8 million years) decays to lead-207. The “secondary ion mass spectrometry” (or SIMS) technique is used for this kind of measurement. By measuring both ‘parent-daughter’ decays of both these processes, an accurate age of the zircon can be calculated — that is, if both measurements are consistent (which is not always the case).

The Isua rocks on Greenland are a source for this way of dating the earth’s age. Current calculations indicate Earth is 4.6 billion years old.

Reference:

Origins of minerals
Natural Gemstones

New wallaby-sized dinosaur from the ancient Australian-Antarctic rift valley

Galleonosaurus dorisae
Artist’s impression of a Galleonosaurus dorisae herd on a riverbank in the Australian-Antarctic rift valley during the Early Cretaceous, 125 million years ago. The newly-named, dinosaur wallaby-sized herbivorous dinosaur, was identified from five fossilized upper jaws in 125-million-year-old rocks from the Cretaceous period of Victoria, southeastern Australia. Credit: Image copyright James Kuether

A new, wallaby-sized herbivorous dinosaur has been identified from five fossilized upper jaws in 125 million year old rocks from the Cretaceous period of Victoria, southeastern Australia.

Reported in the Journal of Paleontology, the new dinosaur is named “Galleonosaurus dorisae,” and is the first dinosaur named from the Gippsland region of Australia in 16 years. According to Dr. Matthew Herne, a Postdoctoral Fellow at the University of New England, NSW, and lead author of the new study, “the jaws of Galleonosaurus dorisae include young to mature individuals—the first time an age range has been identified from the jaws of an Australian dinosaur.”

Galleonosaurus was a small-bodied herbivorous dinosaur within the large family called ornithopods. “These small dinosaurs would have been agile runners on their powerful hind legs,” explained Dr. Herne.

The name Galleonosaurus dorisae refers to the shape of the upper jaw, resembling the upturned hull of a sailing ship called a galleon, and also honours the work of Dr. Doris Seegets-Villiers, who produced her Ph.D. thesis on the palaeontology of the locality where the fossils were discovered.

Galleonosaurus is the fifth small ornithopod genus named from Victoria, which according to Dr. Herne, “confirms that on a global scale, the diversity of these small-bodied dinosaurs had been unusually high in the ancient rift valley that once extended between the spreading continents of Australia and Antarctica.” Small ornithopods appear to have thrived on the vast forested floodplain within the ancient rift valley.

At the time of Galleonosaurus, sediments were shed from a four thousand km long massif of large, actively erupting volcanoes that once existed along the eastern margin of the Australian continent. Some of these sediments were carried westward by large rivers into the Australian-Antarctic rift valley where they formed deep sedimentary basins. However, as these sediments washed down the rivers of the rift valley the bones of dinosaurs, such as Galleonosaurus and other vertebrates, along with the logs of fallen trees, became mixed in. According to Dr. Herne, “this land has now vanished, but as ‘time-travellers’ we get snapshots of this remarkable world via the rocks and fossils exposed along the coast of Victoria.”

The new article shows that Galleonosaurus dorisae is a close relative of Diluvicursor pickeringi; another small ornithopod named by Dr. Herne and his team in 2018, from excavations along the Otway coast to the west of the Gippsland region. Interestingly, “the jaws of Galleonosaurus and the partial skeleton of Diluvicursor were similarly buried in volcanic sediments on the floor of deep powerful rivers,” explained Dr. Herne. “However, Galleonosaurus is about 12 million years older than Diluvicursor, showing that the evolutionary history of dinosaurs in the Australian-Antarctic rift had been lengthy.”

The jaws of Galleonosaurus were discovered by volunteers of the Dinosaur Dreaming project during excavations near the town of Inverloch. The most complete jaw and the key specimen carrying the name Galleonosaurus dorisae was discovered in 2008 by the seasoned fossil hunter Gerrit (‘Gerry’) Kool, from the nearby town of Wonthaggi. Gerry and his wife Lesley have been instrumental in organizing the Dinosaur Dreaming excavations along the Victorian coast for 25 years.

Prior to discovery of Galleonosaurus dorisae, the only other ornithopod known from the Gippsland region was Qantassaurus intrepidus, named in 1999. However, Qantassaurus had a shorter more robust snout than that of Galleonosaurus, explained Dr. Herne, who added, “we consider that these two, similarly-sized dinosaurs fed on different plant types, which would have allowed them to coexist.”

The new study reveals that the ornithopods from Victoria are closely related to those from Patagonia in Argentina. “We are steadily building a picture of terrestrial dinosaur interchange between the shifting Gondwanan continents of Australia, South America and Antarctica during the Cretaceous period,” added Dr. Herne

These are exciting times for dinosaur research, explained Dr. Herne: “Using advanced techniques, such as 3-D micro-CT scanning and printing, new anatomical information is being revealed on dinosaurs such as Galleonosaurus dorisae. These techniques are helping us to delve deeper into the mysterious world of dinosaur ecology—what they ate, how they moved and how they coexisted—and their evolutionary relationships with dinosaurs from other continents.”

Reference:
New small-bodied ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic rift system, with revision of Qantassaurus intrepidus Rich and Vickers-Rich, 1999. Matthew C. Herne, Jay P. Nair, Alistair R. Evans, and Alan M. Tait. Journal of Paleontology (2019). DOI: 10.1017/jpa.2018.95

Note: The above post is reprinted from materials provided by Cambridge University Press.

Small animals with big impact

Copepods
Copepods, the world’s most common animal, release unique substances into the oceans. Concentrations of these substances are high enough to affect the marine food web, according to new research from the University of Gothenburg. The studies also show that phytoplankton in the oceans detect the special scent of copepods and do their utmost to avoid being eaten. Credit: University of Gothenburg

Copepods, the world’s most common animal, release unique substances into the oceans. Concentrations of these substances are high enough to affect the marine food web, according to new research from the University of Gothenburg. The studies also show that phytoplankton in the oceans detect the special scent of copepods and do their utmost to avoid being eaten.

The substances that copepods release into seawater are called copepodamides.

When phytoplankton in the water sense copepodamides, they activate their defence mechanisms to avoid being eaten. Some phytoplankton then produce light, bioluminescence; other plankton use chemical warfare and produce toxins or shrink in size.

“Since the phytoplankton in the ocean are the basis of all marine life, the effects become large-scale,” says Erik Selander at the Department of Marine Sciences at the University of Gothenburg, who heads the research team.

Increased understanding of algal blooms

Selander compares the effect of copepodamides with the effect of hormones in the body.

“The substances are remarkably potent. Very small quantities produce large systemic effects. The amount of copepodamide that would fit in a grain of salt are enough to cause phytoplankton in a whole swimming pool to mobilise their defences. Some of the defences involve very strong toxins, and as a result copepodamides can have far-reaching effects such as toxic algal blooms.”

The article, which has now been published in Science Advances, also shows that copepodamides affect more of the ocean’s inhabitants than researchers previously recognised.

“Including a diatom that produces the domoic acid neurotoxin. It is toxic for many organisms and causes memory loss, among other things, in humans. Other diatoms respond by changing their appearance, going from long, contiguous chains of cells to shorter or single-celled variations.”

Size matters

Size is an important property in the ocean. When it changes, there are repercussions in a series of other processes.

“For example, the amount of carbon exported from the surface to deeper water or who eats whom in the plankton community.”

The new discoveries increase our understanding of the marine food web, and especially the mechanisms that lead to toxic algal blooms.

“We previously have not been able to understand why and when toxic algal blooms occur. Copepodamides seem to be an important and overlooked mechanism that contributes to the occurrence of toxic algal blooms by causing producers of toxins to produce as much as 10 times more toxins than normal.”

Reference:
E. Selander et al. Copepods drive large-scale trait-mediated effects in marine plankton, Science Advances (2019). DOI: 10.1126/sciadv.aat5096

Note: The above post is reprinted from materials provided by University of Gothenburg.

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