Pliocene big marine life extinction discovered


This video from the USA says about itself:

Pliocene Epoch – Florida Fossils: Evolution of Life and Land

2 February 2010

This video from the Museum’s Florida Fossils exhibit describes the Pliocene Epoch, 5 million to 2 million years ago The formation of a land bridge across Panama in Central America about 3 million years ago was a major biotic event. Both North and South America had been previously isolated for millions of years. Each had evolved its own unique flora and fauna.

Contact between North and South America allowed for the overland dispersal of organisms between the two continents. Mammals living in North America invaded South America, and South American mammals moved north. The closure of the seaway between North and South America apparently resulted in extinctions of many marine organisms. However, newly formed habitats also promoted the evolution of many new species.

Produced, directed and filmed for the Florida Museum of Natural History by Wes C. Skiles/Karst Productions, Inc.

From the University of Zurich in Switzerland:

Previously unknown extinction of marine megafauna discovered

June 26, 2017

Summary: Over two million years ago, a third of the largest marine animals like sharks, whales, sea birds and sea turtles disappeared. This previously unknown extinction event not only had a considerable impact on the earth’s historical biodiversity but also on the functioning of ecosystems.

The disappearance of a large part of the terrestrial megafauna such as saber-toothed cat and the mammoth during the ice age is well known. Now, researchers at the University of Zurich and the Naturkunde Museum in Berlin have shown that a similar extinction event had taken place earlier, in the oceans.

New extinction event discovered

The international team investigated fossils of marine megafauna from the Pliocene and the Pleistocene epochs (5.3 million to around 9,700 years BC). “We were able to show that around a third of marine megafauna disappeared about three to two million years ago. Therefore, the marine megafaunal communities that humans inherited were already altered and functioning at a diminished diversity,” explains lead author Dr. Catalina Pimiento, who conducted the study at the Paleontological Institute and Museum of the University of Zurich.

Above all, the newly discovered extinction event affected marine mammals, which lost 55 per cent of their diversity. As many as 43 per cent of sea turtle species were lost, along with 35 per cent of sea birds and 9 per cent of sharks. On the other hand, the following new forms of life were to develop during the subsequent Pleistocene epoch: Around a quarter of animal species, including the polar bear Ursus [maritimus], the storm petrel Oceanodroma or the penguin Megadyptes had not existed during the Pliocene. Overall, however, earlier levels of diversity could not be reached again.

Effects on functional diversity

In order to determine the consequences of this extinction, the research team concentrated on shallow coastal shelf zones, investigating the effects that the loss of entire functional entities had on coastal ecosystems. Functional entities are groups of animals not necessarily related, but that share similar characteristics in terms of the function they play on ecosystems. The finding: Seven functional entities were lost in coastal waters during the Pliocene.

Even though the loss of seven functional entities, and one third of the species is relatively modest, this led to an important erosion of functional diversity: 17 per cent of the total diversity of ecological functions in the ecosystem disappeared and 21 per cent changed. Previously common predators vanished, while new competitors emerged and marine animals were forced to adjust. In addition, the researchers found that at the time of the extinction, coastal habitats were significantly reduced due to violent sea levels fluctuations.

Large warm-blooded marine animals are more vulnerable to global environmental changes

The researchers propose that the sudden loss of the productive coastal habitats, together with oceanographic factors such as altered sea currents, greatly contributed to these extinctions. “Our models have demonstrated that warm-blooded animals in particular were more likely to become extinct. For example, species of sea cows and baleen whales, as well as the giant shark Carcharocles megalodon disappeared,” explains Dr. Pimiento. “This study shows that marine megafauna were far more vulnerable to global environmental changes in the recent geological past than had previously been assumed.” The researcher also points to a present-day parallel: Nowadays, large marine species such as whales or seals are also highly vulnerable to human influences.

Mammal-like reptile’s brain, new research


Kawingasaurus fossilis at Museum of Paleontology, Tuebingen, Germany

From the Universität Duisburg-Essen in Germany:

A skull with history: A fossil sheds light on the origin of the neocortex

June 26, 2017

According to a recent study an early relative of mammals already possessed an extraordinarily expanded brain with a neocortex-like structure. This has been discovered by Michael Laaß from the Institute of General Zoology at the University of Duisburg-Essen (UDE).

Today, mammals possess large and efficient brains. But, what was the bauplan of the brain of their far relatives, the therapsids? When and why evolved the neocortex?

For his doctoral thesis the palaeontologist Michael Laaß invesitgated a ca. 255 million years old fossil skull of the therapsid Kawingasaurus fossilis in collaboration with Dr. Anders Kaestner from the Paul Scherrer Institute in Switzerland by means of neutron tomography and reconstructed the internal cranial anatomy in 3D.

The results were amazing: The relative brain volume of Kawingasaurus was about two or three-times larger than in other non-mammalian therapsids. Laaß: “Interestingly, Kawingasaurus already possessed a large forebrain with two distinct cerebral hemispheres.” Obviously, a neocortex-like structure at the forebrain similar to the mammalian neocortex was present in this animal.

Why is this brain structure evolved in Kawingasaurus? “Kawingasaurus was a burrower and special sensory adaptations were crucial for life under ground,” explained the UDE scientist. For example, this therapsid possessed frontally placed eyes, which were probably useful for binocular vision in dimlight environments as it is known from modern cats and owls. Furthermore, extremely ramified trigeminal nerve endings penetrated the snout, which might be an indication for a well developed sense of touch. The inner ear vestibules were also very large, which suggests that Kawingasaurus was well adapted to detect seismic vibrations from the ground.

Laaß: “These special sensory adaptaions also required a more efficient neural processing of the brain than in other therapsids.” It seems reasonable that these special adaptations of the sense organs and the brain to underground life triggered the expansion of the brain. Interestingly, a similar scenario for the origin of the neocortex has been also proposed for early mammals. Consequently, the recent study at the UDE supports this hypothesis.

Moreover, the new discovery also shows that a neocortex-like structure already developed in the therapsid Kawingasaurus about 25 million years earlier before the emergence of the first mammals. However, Kawingasaurus was not a direct ancestor of mammals. Consequently, neocortex-like structures evolved several times independently in pre-mammalian and mammalian evolution.

Fish to amphibian evolution, new research


This video says about itself:

The Evolution of Amphibians

23 January 2016

The first major groups of amphibians developed in the Devonian period, around 370 million years ago, from lobe-finned fish which were similar to the modern coelacanth and lungfish.

These ancient lobe-finned fish had evolved multi-jointed leg-like fins with digits that enabled them to crawl along the sea bottom. Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required.

Eventually, their bony fins would evolve into limbs and they would become the ancestors to all tetrapods, including modern amphibians, reptiles, birds, and mammals. Despite being able to crawl on land, many of these prehistoric tetrapodomorph fish still spent most of their time in the water. They had started to develop lungs, but still breathed predominantly with gills.

From the University of Calgary in Canada:

Fossil holds new insights into how fish evolved onto land

‘It’s like a snake on the outside, but a fish on the inside’

June 21, 2017

The fossil of an early snake-like animal — called Lethiscus stocki — has kept its evolutionary secrets for the last 340 million years.

Now, an international team of researchers, led by the University of Calgary, has revealed new insights into the ancient Scottish fossil that dramatically challenge our understanding of the early evolution of tetrapods, or four-limbed animals with backbones.

Their findings have just been published in the research journal Nature. “It forces a radical rethink of what evolution was capable of among the first tetrapods,” said project lead Jason Anderson, a paleontologist and Professor at the University of Calgary Faculty of Veterinary Medicine (UCVM).

Before this study, ancient tetrapods — the ancestors of humans and other modern-day vertebrates — were thought to have evolved very slowly from fish to animals with limbs.

“We used to think that the fin-to-limb transition was a slow evolution to becoming gradually less fish like,” he said. “But Lethiscus shows immediate, and dramatic, evolutionary experimentation. The lineage shrunk in size, and lost limbs almost immediately after they first evolved. It’s like a snake on the outside but a fish on the inside.”

Lethicus’ secrets revealed with 3D medical imaging

Using micro-computer tomography (CT) scanners and advanced computing software, Anderson and study lead author Jason Pardo, a doctoral student supervised by Anderson, got a close look at the internal anatomy of the fossilized Lethiscus. After reconstructing CT scans its entire skull was revealed, with extraordinary results.

“The anatomy didn’t fit with our expectations,” explains Pardo. “Many body structures didn’t make sense in the context of amphibian or reptile anatomy.” But the anatomy did make sense when it was compared to early fish.

“We could see the entirety of the skull. We could see where the brain was, the inner ear cavities. It was all extremely fish-like,” explains Pardo, outlining anatomy that’s common in fish but unknown in tetrapods except in the very first. The anatomy of the paddlefish, a modern fish with many primitive features, became a model for certain aspects of Lethiscus’ anatomy.

Changing position on the tetrapod ‘family tree’

When they included this new anatomical information into an analysis of its relationship to other animals, Lethiscus moved its position on the ‘family tree’, dropping into the earliest stages of the fin-to-limb transition. “It’s a very satisfying result, having them among other animals that lived at the same time,” says Anderson.

The results match better with the sequence of evolution implied by the geologic record. “Lethiscus also has broad impacts on evolutionary biology and people doing molecular clock reproductions of modern animals,” says Anderson. “They use fossils to calibrate the molecular clock. By removing Lethiscus from the immediate ancestry of modern tetrapods, it changes the calibration date used in those analyses.”

From dinosaur age mammal to human, new research


Placental mammal family tree

Numbers on red branches from the first eutherian ancestor to Homo sapiens are the numbers of breakpoints in reconstructed ancestral chromosome fragments. Breakpoints are locations where a chromosome broke open, allowing for rearrangements. The number of breakpoints per million years is in parentheses. A total of 162 chromosomal breakpoints were identified between the eutherian ancestor and the formation of humans as a species.
Credit: Harris Lewin, UC Davis

From the University of California – Davis in the USA:

Reconstruction of ancient chromosomes offers insight into mammalian evolution

June 21, 2017

Summary: Researchers have gone back in time, at least virtually, computationally recreating the chromosomes of the first eutherian mammal, the long-extinct, shrewlike ancestor of all placental mammals.

What if researchers could go back in time 105 million years and accurately sequence the chromosomes of the first placental mammal? What would it reveal about evolution and modern mammals, including humans?

In a study published this week in Proceedings of the National Academy of Sciences, researchers have gone back in time, at least virtually, computationally recreating the chromosomes of the first eutherian mammal, the long-extinct, shrewlike ancestor of all placental mammals.

“The revolution in DNA sequencing has provided us with enough chromosome-scale genome assemblies to permit the computational reconstruction of the eutherian ancestor, as well as other key ancestors along the lineage leading to modern humans,” said Harris Lewin, a lead author of the study and a professor of evolution and ecology and Robert and Rosabel Osborne Endowed Chair at the University of California, Davis.

“We now understand the major steps of chromosomal evolution that led to the genome organization of more than half the existing orders of mammals. These studies will allow us to determine the role of chromosome rearrangements in the formation of new mammal species and how such rearrangements result in adaptive changes that are specific to the different mammalian lineages,” said Lewin.

The findings also have broad implications for understanding how chromosomal rearrangements over millions of years may contribute to human diseases, such as cancer.

“By gaining a better understanding of the relationship between evolutionary breakpoints and cancer breakpoints, the essential molecular features of chromosomes that lead to their instability can be revealed,” said Lewin. “Our studies can be extended to the early detection of cancer by identifying diagnostic chromosome rearrangements in humans and other animals, and possibly novel targets for personalized therapy.”

Descrambling chromosomes

To recreate the chromosomes of these ancient relatives, the team began with the sequenced genomes of 19 existing placental mammals — all eutherian descendants — including human, goat, dog, orangutan, cattle, mouse and chimpanzee, among others.

The researchers then utilized a new algorithm they developed called DESCHRAMBLER. The algorithm computed (“descrambled”) the most likely order and orientation of 2,404 chromosome fragments that were common among the 19 placental mammals’ genomes.

“It is the largest and most comprehensive such analysis performed to date, and DESCHRAMBLER was shown to produce highly accurate reconstructions using data simulation and by benchmarking it against other reconstruction tools,” said Jian Ma, the study’s co-senior author and an associate professor of computational biology at Carnegie Mellon University in Pittsburgh.

In addition to the eutherian ancestor, reconstructions were made for the six other ancestral genomes on the human evolutionary tree: boreoeutherian, euarchontoglires, simian (primates), catarrhini (Old World monkeys), great apes and human-chimpanzee. The reconstructions give a detailed picture of the various chromosomal changes — translocations, inversions, fissions and other complex rearrangements — that have occurred over the 105 million years between the first mammal and Homo sapiens.

Rates of evolution vary

One discovery is that the first eutherian ancestor likely had 42 chromosomes, four less than humans. Researchers identified 162 chromosomal breakpoints — locations where a chromosome broke open, allowing for rearrangements — between the eutherian ancestor and the formation of humans as a species.

The rates of evolution of ancestral chromosomes differed greatly among the different mammal lineages. But some chromosomes remained extremely stable over time. For example, six of the reconstructed eutherian ancestral chromosomes showed no rearrangements for almost 100 million years until the appearance of the common ancestor of human and chimpanzee.

Orangutan chromosomes were found to be the slowest evolving of all primates and still retain eight chromosomes that have not changed much with respect to gene order orientation as compared with the eutherian ancestor. In contrast, the lineage leading to chimpanzees had the highest rate of chromosome rearrangements among primates.

“When chromosomes rearrange, new genes and regulatory elements may form that alter the regulation of expression of hundreds of genes, or more. At least some of these events may be responsible for the major phenotypic differences we observe between the mammal orders,” said Denis Larkin, co-senior author of the study and a reader in comparative genomics at the Royal Veterinary College at the University of London.

The chromosomes of the oldest three ancestors (eutherian, boreoeutherian, and euarchontoglires) were each found to include more than 80 percent of the entire length of the human genome, the most detailed reconstructions reported to date. The reconstructed chromosomes of the most recent common ancestor of simians, catarrhini, great apes, and humans and chimpanzees included more than 90 percent of human genome sequence, providing a structural framework for understanding primate evolution.

Dinosaur age caecilian amphibian ancestor discovered?


This video says about itself:

19 June 2017

A new analysis of a pair of tiny fossils found in the 1990s has helped scientists to uncover the backstory of the most mysterious amphibian alive. Researchers used 3D X-rays to map out the remains of a now-extinct species that walked the Earth [220] million years ago. They found that the species is a long-missing amphibious link that expands the known history of frogs, toads and salamanders by at least 15 million years. Chinlestegophis jenkinsi (artist’s impression) was a tiny subterranean carnivore.

From Science News:

New fossils shake up history of amphibians with no legs

Tiny skulls and other bits hint at unexpected backstory for today’s snake-shaped caecilians

by Susan Milius

3:30pm, June 19, 2017

Newly named fossils suggest that a weird and varied chapter in amphibian deep history isn’t totally over.

Small fossils about 220 million years old found along steep red slopes in Colorado represent a near-relative of modern animals called caecilians, says vertebrate paleontologist Adam Huttenlocker of the University of Southern California in Los Angeles.

Caecilians today have long wormy bodies with either shrunken legs or none at all. Yet the nearly 200 modern species of these toothy, burrow-dwelling tropical oddballs are genuine amphibians. The fossil creatures, newly named Chinlestegophis jenkinsi, still had legs but could be the oldest known near-relatives of caecilians, Huttenlocker and colleagues suggest.

A popular view of the amphibian family tree has put caecilians on their own long, peculiar branch beside the ancient frogs and salamanders. But a close look at the new fossils suggests a much earlier split from ancestral frogs and salamanders, the researchers propose June 19 in Proceedings of the National Academy of Sciences. The move puts the caecilians into “a strange but incredibly diverse” group, the stereospondyls, Huttenlocker says. These species included elongated, short-legged beasts with heads shaped like toilet lids.

Among the many stereospondyls, Huttenlocker speculates that caecilians came from “an aberrant branch of miniaturized forms that went subterranean.” And today’s legless burrowers could be this once-flourishing group’s sole survivors.

Ocean predatory animals are growing


This video says about itself:

17 November 2016

Researchers discovered snail species that use their shells to hit predators. Snails were thought to withdraw into their shells when attacked, but land snail species Karaftohelix gainesi and Karaftohelix selskii manifest an active defence behaviour, counterattacking predators by swinging their shells.

Credit:

Parallel evolution of passive and active defence in land snails.

Yuta Morii, Larisa Prozorova & Satoshi Chiba.

Scientific Reports.

From Science News:

Ancient attack marks show ocean predators got scarier

Holes in shells reveal predators that kill by drilling just kept getting bigger

By Susan Milius

4:12pm, June 15, 2017

In pumped-up sequels for scary beach movies, each predator is bigger than the last. Turns out that predators in real-world oceans may have upsized over time, too.

Attack holes in nearly 7,000 fossil shells suggest that drilling predators have outpaced their prey in evolving ever larger bodies and weapons, says paleontologist Adiël Klompmaker of the University of California, Berkeley. The ability to drill through a seashell lets predatory snails, octopuses, one-celled amoeba-like forams and other hungry beasts reach the soft meat despite prey armor. Millions of years later, CSI Paleontology can use these drill holes to test big evolutionary ideas about the power of predators.

“Predators got bigger — three words!” is Klompmaker’s bullet point for the work. Over the last 450 million years or so, drill holes have grown in average size from 0.35 millimeters to 3.25 millimeters, Klompmaker and an international team report June 16 in Science. Larger holes generally mean larger attackers, the researchers say, after looking at 556 modern drillers and the size of their attack holes.

Prey changed over millennia, too, but there’s no evidence for a shift in body size. The ratio of drill-hole size to prey size became 67 times greater over time, the researchers conclude.

It’s “the rise of the bullies,” says coauthor Michal Kowalewski of the University of Florida in Gainesville.

All these data on shell holes allow researchers to test a key part of what’s called the escalation hypothesis. In 1987, Geerat Vermeij proposed a top-down view of evolutionary change, where predators, competitors and other enemies growing ever more powerful drive the biggest changes in their victims. This wasn’t so much an arms race between predators trading tit for tat with their prey as a long domination of underdogs repeatedly stomped by disproportionate menace. (Unless the prey somehow flips the relationship and can do deadly harm in return.) Vermeij, now at the University of California, Davis, and others have drawn on escalating threats to explain prey evolutionary innovations in thick shells, spines and spikes, mobility, burrowing lifestyles and toxins.

One aspect of escalation scenarios has been especially hard to test: the idea that predators can become more dangerous and a stronger evolutionary force over time. Drill holes suggesting bigger, more powerful attackers allowed a rare way of exploring the idea, Klompmaker says. He now reads the deep history as showing predators escalated in size, but prey didn’t.

The energetics worked out, in large part, because early hard-shelled prey called brachiopods — a bit like clams but with one shell-half larger than the other — became scarcer over time, while clams and their fellow mollusks grew abundant. Mollusks typically have more flesh inside their shells than brachiopods, and prey overall grew denser on the ocean bottom. Killer drillers, able to dine at this buffet, could thus support bigger bodies even when prey size wasn’t rising, too.

Prey don’t make drilling easy, Klompmaker says. An hour’s work gets a typical modern predatory snail only about 0.01 to 0.02 millimeters deeper into a mollusk shell. So finally striking lunch could take days of effort with the thickest shells. And that’s with specialty equipment: A snail alternates grinding away using a hard, rasplike driller and then switching to its accessory boring organ that releases acids and enzymes, weakening the drilling spot for the next bout.

The role of such animal clashes in evolution has been notoriously difficult to study, says marine ecologist Nick Dulvy of Simon Fraser University in Burnaby, Canada. Nutrients, climate and other factors that don’t swim away into the blue are much easier to measure. Even after a robust century of ecological study, “the discoveries that otters propped up kelp forests, triggerfishes garden coral reefs, and wolves and cougars create lush diverse watersheds are comparatively recent,” Dulvy says. Until the new drill-hole study, he could think of only one earlier batch of evidence (crabs preying on mollusks) for the long rise of predators as an evolutionary force.

The story from drill holes, says Vermeij, is “very convincing.”

Fossil giant brush turkey discovery in Australia


A reconstruction of Progura gallinacea (right), alongside a kangaroo and modern bush turkey (Alectura lathami). Image credit: Elen Shute / Kim Benson / Tony Rodd / Aaron Camens

From Sci-News.com:

Giant Flying Turkeys Lived in Australia 1-3 Million Years Ago

June 15, 2017

Progura gallinacea, a species of extinct giant brush turkey that lived in Australia during the Late Pliocene and Early Pleistocene (1-3 million years ago), is among five megapode birds described (or redescribed) by Flinders University paleontologists.

After carefully comparing megapode fossils from Queensland, New South Wales, South Australia and Western Australia, the paleontologists have concluded that the remains belong to five different extinct species: Garrdimalga mcnamarai (new species), Progura gallinacea and P. campestris (new species), Latagallina naracoortensis and L. olsoni (new species).

All five birds were chunky relatives of extant malleefowl (Leipoa ocellata) and brush turkeys (Alectura lathami), but Progura gallinacea soars above the others.

The earliest-described extinct megapode, Progura gallinacea had an estimated mass of 7.7 kg.

Progura campestris, Latagallina naracoortensis, Garrdimalga mcnamarai and Latagallina olsoni had average masses of 6.2 kg, 5.2 kg, 5.2 kg and 2.9 kg, respectively.

Progura gallinacea had long, slender legs. Latagallina naracoortensis and L. olsoni had shorter legs and broad bodies.

These giant megapodes lived during the Pleistocene, between 5 million and 11,000 years ago, alongside Australia’s giant extinct marsupials such as diprotodons, marsupial lions and short-faced kangaroos.

It seems that none of these birds built mounds like their living Australian cousins because they lacked the large feet and specialized claws seen in mound-builders.

It’s more likely that they buried their eggs in warm sand or soil, like some living megapodes in Indonesia and the Pacific.

Unlike many large extinct birds, such as dodos, these megapodes were not flightless.

While big and bulky, their long, strong wing bones show they could all fly, and probably roosted in trees.

“These discoveries are quite remarkable because they tell us that more than half of Australia’s megapodes went extinct during the Pleistocene, and we didn’t even realize it until now,” said Elen Shute, a PhD candidate at Flinders University and lead author of a paper in the journal Royal Society Open Science.

“Given several of the largest birds to have lived in Australia in recent times have escaped detection in the fossil record until now, our research shows how little we know of Australia’s immediate pre-human avifauna,” said co-author Dr. Trevor Worthy, an associate professor at Flinders University.

“Probably many smaller extinct species also await discovery by paleontologists.”