Ancient trilobites, new study


This 2017 video is called The Trouble With Trilobites.

From the Fundação de Amparo à Pesquisa do Estado de São Paulo in Brazil:

Reconstruction of trilobite ancestral range in the southern hemisphere

January 9, 2019

Summary: Brazilian researchers used biogeographic analysis to study trilobites — arthropods that became extinct over 252 million years ago.

The first appearance of trilobites in the fossil record dates to 521 million years ago in the oceans of the Cambrian Period, when the continents were still inhospitable to most life forms. Few groups of animals adapted as successfully as trilobites, which were arthropods that lived on the seabed for 270 million years until the mass extinction at the end of the Permian approximately 252 million years ago.

The longer ago organisms lived, the more rare are their fossils and the harder it is to understand their way of life; paleontologists face a daunting task in endeavoring to establish evolutionary relationships in time and space.

Surmounting the difficulties inherent in the investigation of a group of animals that lived such a long time ago, Brazilian scientists affiliated with the Biology Department of São Paulo State University’s Bauru School of Sciences (FC-UNESP) and the Paleontology Laboratory of the University of São Paulo’s Ribeirão Preto School of Philosophy, Science and Letters (FFCLRP-USP) have succeeded for the first time in inferring paleobiogeographic patterns among trilobites.

Paleobiogeography is a branch of paleontology that focuses on the distribution of extinct plants and animals and their relations with ancient geographic features. The study was conducted by Fábio Augusto Carbonaro, a postdoctoral researcher at UNESP’s Bauru Macroinvertebrate Paleontology Laboratory (LAPALMA) headed by Professor Renato Pirani Ghilardi. Other participants included Max Cardoso Langer, a professor at FFCLRP-USP, and Silvio Shigueo Nihei, a professor at the same university’s Bioscience Institute (IB-USP).

The researchers analyzed the morphological differences and similarities of the 11 species of trilobites described so far in the genus Metacryphaeus; these trilobites lived during the Devonian between 416 million and 359 million years ago (mya) in the cold waters of the sea that covered what is now Bolivia, Peru, Brazil, the Malvinas (Falklands) and South Africa.

The Devonian Period is subdivided into seven stages. Metacryphaeus lived during the Lochkovian (419.2-410.8 mya) and Pragian (410.8- 407.6 mya) stages, which are the earliest Devonian stages.

The results of the research were published in Scientific Reports and are part of the project “Paleobiogeography and migratory routes of paleoinvertebrates of the Devonian in Brazil,” which is supported by São Paulo Research Foundation -FAPESP and Brazil’s National Council for Scientific and Technological Development (CNPq). Ghilardi is the project’s principal investigator.

“When they became extinct in the Permian, 252 million years ago, the trilobites left no descendants. Their closest living relatives are shrimps, and, more remotely, spiders, scorpions, sea spiders and mites”, Ghilardi said.

Trilobite fossils are found abundantly all over the world, he explained — so abundantly that they are sometimes referred to as the cockroaches of the sea. The comparison is not unwarranted because anatomically, the trilobites resemble cockroaches. The difference is that they were not insects and had three longitudinal body segments or lobes (hence the name).

In the northern hemisphere, the trilobite fossil record is very rich. Paleontologists have so far described ten orders comprising over 17,000 species. The smallest were 1.5 millimeters long, while the largest were approximately 70 cm long and 40 cm wide. Perfectly preserved trilobites can be found in some regions, such as Morocco. These can be beautiful when used to create cameos or intaglio jewelry. Trilobite fossils from Brazil, Peru and Bolivia, in contrast, are often poorly preserved, consisting merely of the impressions left in benthic mud by their exoskeletons.

“Although their state of preservation is far from ideal, there are thousands of trilobite fossils in the sediments that form the Paraná basin in the South region of Brazil, and the Parnaíba basin along the North-Northeast divide,” said Ghilardi, who also chairs the Brazilian Paleontology Society.

According to Ghilardi, their poor state of preservation could be due to the geological conditions and climate prevailing in these regions during the Paleozoic Era, when the portions of dry land that would one day form South America were at the South Pole and entirely covered by ice for prolonged periods.

During the Devonian, South America and Africa were connected as part of the supercontinent Gondwana. South Africa was joined with Uruguay and Argentina in the River Plate region, and Brazil’s southern states were continuous with Namibia and Angola.

Parsimonious analysis

The research began with an analysis of 48 characteristics (size, shape and structure of organs and anatomical parts) found in some 50 fossil specimens of the 11 species of Metacryphaeus.

“In principle, these characteristics serve to establish their phylogeny — the evolutionary history of all species in the universe, analyzed in terms of lines of descent and relationships among broader groups,” Ghilardi said.

Known as a parsimonious analysis, this method is widely used to establish relationships among organisms in a given ecosystem, and in recent years, it has also begun to be used in the study of fossils.

According to Ghilardi, parsimony, in general, is the principle that the simplest explanation of the data is the preferred explanation. In the analysis of phylogeny, it means that the hypothesis regarding relationships that requires the smallest number of characteristic changes between the species analyzed (in this case, trilobites of the genus Metacryphaeus) is the one that is most likely to be correct.

The biogeographic contribution to the study was made by Professor Nihei, who works at IB-USP as a taxonomist and insect systematist. The field of systematics is concerned with evolutionary changes between ancestries, while taxonomy focuses on classifying and naming organisms.

“Biogeographic analysis typically involves living groups the ages of which are estimated by molecular phylogeny, or the so-called molecular clock, which estimates when two species probably diverged on the basis of the number of molecular differences in their DNA. In this study of trilobites, we used age in a similar manner, but it was obtained from the fossil record,” Nihei said.

“The main point of the study was to use fossils in a method that normally involves molecular biogeography. Very few studies of this type have previously involved fossils. I believe our study paves the way for a new approach based on biogeographic methods requiring a chronogram [a molecularly dated cladogram] because this chronogram can also be obtained from fossil taxa such as those studied by paleontologists, rather than molecular cladograms for living animals.”

As a vertebrate paleontologist who specializes in dinosaurs, Langer acknowledged that he knows little about trilobites but a great deal about the modern computational techniques used in parsimonious analysis, on which his participation in the study was based. “I believe the key aspect of this study, and the reason it was accepted for publication in as important a journal as Scientific Reports, is that it’s the first ever use of parsimony to understand the phylogeny of a trilobite genus in the southern hemisphere,” he said.

Gondwanan dispersal

The results of the paleobiogeographical analyses reinforce the pre-existing theory that Bolivia and Peru formed the ancestral home of Metacryphaeus.

“The models estimate a 100% probability that Bolivia and Peru formed the ancestral area of the Metacryphaeus clade and most of its internal clades,” Ghilardi said. Confirmation of the theory shows that parsimonious models have the power to suggest the presence of clades at a specific moment in the past even when there are no known physical records of that presence.

In the case of Metacryphaeus, the oldest records in Bolivia and Peru date from the early Pragian stage (410.8-407.6 mya), but the genus is believed to have evolved in the region during the Lochkovian stage (419.2-410.8 mya).

Parsimony, therefore, suggests Metacryphaeus originated in Bolivia and Peru some time before 410.8 mya but not earlier than 419.2 mya. In any event, it is believed to be far older than any known fossils.

According to Ghilardi, the results can be interpreted as showing that the adaptive radiation of Metacryphaeus to other areas of western Gondwana occurred during episodes of marine transgression in the Lochkovian-Pragian, when the sea flooded parts of Gondwana.

“The dispersal of Metacryphaeus trilobites during the Lochkovian occurred from Bolivia and Peru to Brazil — to the Paraná basin, now in the South region, and the Parnaíba basin, on the North-Northeast divide — and on toward the Malvinas/Falklands, while the Pragian dispersal occurred toward South Africa,” he said.

Fossil trilobites have been found continuously in the Paraná basin in recent decades. Trilobites collected in the late nineteenth century in the Parnaíba basin were held by Brazil’s National Museum in Rio de Janeiro, which was destroyed by fire in September 2018.

“These fossils haven’t yet been found under the rubble and it’s likely that nothing is left of them. They were mere shell impressions left in the ancient seabed. Even in petrified form, they must have dissolved in the blaze,” Ghilardi said.

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How plant roots originated


This 2014 video from India says about itself:

Rhynia by (B.Sc, M.Sc) Dr. Ruby Singh Parmar

In this video, Dr. Ruby Singh, HOD Science, Biyani Group of Colleges explains the morphological and anatomical structure of “Rhynia“. It is a fossil plant. In this video characters and structure of sporangia are discussed.

From the University of Oxford in England:

Getting to the root of plant evolution

August 22, 2018

Despite plants and vegetation being key to the Earth’s ecosystem, little is known about the origin of their roots. However in new research, published in Nature, Oxford University scientists describe a transitional root fossils from the earliest land ecosystem that sheds light on how roots have evolved.

The findings suggest that plant roots have evolved more than once, and that the characteristics of roots developed in a step-wise manner — with the central root organ evolving first. And the root cap subsequently coming later.

Dr Sandy Hetherington and Professor Liam Dolan — both of Oxford’s Department of Plant Sciences and Magdalen College Oxford, conducted a microscopic study of the oldest known plant ecosystem — the 407 million-year-old Rhynie chert.

Dr Hetherington said: ‘The level of preservation in the Rhynie chert is truly remarkable — it never ceases to amaze me that I am able to examine the cellular organisation of plants that were growing 407 million years ago. It provides an exceptional window into life on the terrestrial surface at that time.’

The defining feature of modern-day plant roots is the meristem — a self-renewing structure that is covered by a cap at its apex. Root meristems are hard to spot in the fragmentary fossil record, which can make it challenging to unearth the evolutionary origin of roots.

The authors found evidence of root meristems belonging to the lycopsid plant Asteroxylon mackiei. Lycopsids — commonly known as club mosses, are vascular plants (those with tissues that internally move resources) whose lineage branched off early, before the other higher plants (the euphyllophytes).

The team were able to build a 3D reconstruction of the fossil meristem.

The fossil analysis reveals that the meristems of A. mackiei lack both root hairs and caps — they are covered instead by a continuous layer of surface tissue. This structure makes these roots unique among the vascular plants.

The paper’s conclusion suggests that these roots are a transitional step towards modern-style, rooted vascular plants. The findings support the idea that, as this cap-less transitional structure appears in a plant that is already a lycopsid, roots with caps evolved separately in lycopsids and euphyllophytes from their common, root-less ancestors.

Discussing plans to expand on this work, Professor Dolan said: ‘Our discovery suggests that plant organs were built up step-by-step during the course of plant evolution.

‘The evolution of roots was a critical time in Earth’s history and resulted in a dramatic reduction of atmospheric carbon. Now that we know that roots evolved in a step by step manner, we can go back to ancient rocks looking for structures that are missing “parts” that are present in extant roots.

‘I really want to find out where root caps came from. They seemed to have appeared out of thin air. They are very important in extant roots; the root cap is important to protect the root as it pushes through the soil and it is the site where roots detect gravity. How did these ancient roots manage without a cap to provide these functions?’

Fossil fish and human skeletons


This 24 July 2018 video says about itself:

420 million years ago, some fish were more medieval. They wore armor, sometimes made of big plates, and sometimes made of interlocking scales. But that armor may actually have served a totally different purpose, one that many animals still use today.

From the University of Manchester in England:

160-year-old mystery about the origin of skeletons solved

July 31, 2018

Scientists at The University of Manchester and the University of Bristol have used powerful X-rays to peer inside the skeletons of some of our oldest vertebrate relatives, solving a 160-year-old mystery about the origin of our skeletons.

Living vertebrates have skeletons built from four different tissue types: bone and cartilage (the main tissues that human skeletons are made from), and dentine and enamel (the tissues from which our teeth are constructed). These tissues are unique because they become mineralised as they develop, giving the skeleton strength and rigidity.

Evidence for the early evolution of our skeletons can be found in a group of fossil fishes called heterostracans, which lived over 400 million years ago. These fishes include some of the oldest vertebrates with a mineralised skeleton that have ever been discovered. Exactly what tissue heterostracan skeletons were made from has long puzzled scientists.

Now a team of researchers from the University of Manchester, the University of Bristol and the Paul Scherrer Institute in Switzerland have taken a detailed look inside heterostracan skeletons using Synchrotron Tomography: a special type of CT scanning using very high energy X-rays produced by a particle accelerator. Using this technique, the team have identified this mystery tissue.

Lead researcher Dr Joseph Keating, from Manchester’s School of Earth of Environmental Scientists, explained: “Heterostracan skeletons are made of a really strange tissue called ‘aspidin’. It is crisscrossed by tiny tubes and does not closely resemble any of the tissues found in vertebrates today. For a 160 years, scientists have wondered if aspidin is a transitional stage in the evolution of mineralised tissues.”

The results of this study, published in Nature Ecology and Evolution, show that the tiny tubes are voids that originally housed fibre-bundles of collagen, a type of protein found in your skin and bones.

These findings enabled Dr Keating to rule out all but one hypothesis for the tissue’s identity: aspidin is the earliest evidence of bone in the fossil record.

Co-author, Professor Phil Donoghue from the University of Bristol concludes: “These findings change our view on the evolution of the skeleton. Aspidin was once thought to be the precursor of vertebrate mineralised tissues. We show that it is, in fact, a type of bone, and that all these tissues must have evolved millions of years earlier.”

Fish-amphibian transition fossils discovered in South Africa


This video from South Africa says about itself:

The Centre of Excellence in Palaeosciences based at the University of the Witwatersrand today announced the discovery of two new Devonian tetrapod species and the first Devonian tetrapods discovered in Africa (8 June 2018). The species have been named Tutusius umlambo (named in honour of Archbishop Emeritus Desmond Tutu) and Umzantsia amazana and were discovered by Dr Rob Gess of the Albany Museum and supported by the Millenium Trust.

Thank you to Rhodes University journalism department for the video clip.

From the Times in South Africa:

Not so fishy: Africa’s first ever fish-with-legs discovered

07 June 2018 – 20:07

By Tanya Farber

An extraordinary find has been made near the university town of Grahamstown in the Eastern Cape.

Up until today‚ when a paper was published in Science‚ it was believed that Devonian tetrapods (fish that had developed four legs as the evolution from aquatic to land animals began) had only existed in the tropics.

But‚ in a groundbreaking study that shakes up our entire notion of the moment we adapted to move beyond the water‚ it has now been discovered that that is simply not true.

The newly discovered tetrapods – which would have resembled a cross between a crocodile and a fish‚ with a crocodile-like head‚ stubby legs‚ and a tail with a fish-like fin – were found in the Devonian Waterloo Farm near Grahamstown‚ and were living within the Antarctic circle some 360 million years ago.

The two new species are named Tutusius and Umzantsia. The metre-long Tutusius umlambo‚ named in honour of Archbishop Emeritus Desmond Tutu‚ and the somewhat smaller Umzantsia amazana‚ are both incomplete.

Tutusius is represented by a single bone from the shoulder girdle‚ whereas Umzantsia is known from a greater number of bones‚ but they both appear similar to previously known Devonian tetrapods.

This find represents two dramatic shifts. Firstly, it means the first appearance of tetrapods on African soil shifts to 70-million years earlier than thought‚ but it also means that one of the most fundamental understandings of our shift from the water to the land has to be reassessed.

The evolution of tetrapods from fish during the Devonian period was a major turning point in our ancestry‚ and all research on that turning point has up until now‚ hinged on the fact that this happened (or so we thought) between 30 degrees north and south of the equator. Almost all come from Laurussia‚ a supercontinent that later fragmented into North America‚ Greenland and Europe.

“Whereas all previously found Devonian tetrapods came from localities which were in tropical regions during the Devonian‚ these specimens lived within the Antarctic circle”, explains lead author‚ Dr Robert Gess of the Albany Museum in Grahamstown‚ and co-author Professor Per Ahlberg of Uppsala University in Sweden.

Minister of Science and Technology‚ Mmamoloko Kubayi-Ngubane‚ congratulated Dr Gess‚ saying this groundbreaking discovery places South Africa at the forefront of the study of the evolution of land-living vertebrate animals‚ including the ancestry of all the wildlife we see in the country’s game parks.

The research was supported by the South African DST-NRF Centre of Excellence in Palaeosciences‚ based at the University of the Witwatersrand and the Millennium Trust.

See also here.

Oldest amphibians not in freshwater


This 2015 video is called Ancestral Evolution – Ichthyostega to Varanops.

By Carolyn Gramling, 5:29pm, May 30, 2018:

The first land-walking vertebrates may have emerged from salty estuaries

An analysis casts doubt on views that the ancient creatures arose in freshwater

Earth’s earliest land-walking vertebrates didn’t paddle about in freshwater lakes or rivers. Instead, these four-footed creatures, which appeared about 375 million years ago, lived in the brackish waters of an estuary or delta, researchers report online May 30 in Nature.

Early tetrapods, such as Ichthyostega and Acanthostega, lived an amphibious existence between land and sea: They had feet, but also gills and tails made for swimming. A new study by paleontologist Jean Goedert of Université Lyon in France and colleagues suggests that the animals also could have tolerated rapid changes in salinity, such as is found in an estuary.

The researchers analyzed sulfur and oxygen isotopes — forms of these elements with the same number of protons, but different masses — in 51 fossilized tetrapod bones from locations in what’s now Greenland and China. Compared with freshwater, seawater has a higher ratio of the sulfur-34 isotope relative to sulfur-32. The tetrapod bones tended to show elevated sulfur-34, the researchers report, suggesting that the creatures spent at least some time in seawater. But oxygen isotope analyses of the bones show that freshwater was also present, arguing against a purely salty environment such as an ocean.

The results challenge a long-held view that the earliest tetrapods emerged from freshwaters, such as rivers or lakes. In 1929, the first Ichthyostega fossils were found in a series of red sandstone layers in eastern Greenland that geologists once thought had been deposited in a freshwater environment. But later discoveries of tetrapod fossils found associated with known marine species suggested that the early walkers may have lived in saltier waters than once thought.

An ability to tolerate different salinity environments could have helped tetrapods — a group that includes today’s amphibians, reptiles and mammals — survive a mass extinction of ocean-dwellers that occurred by the end of the Devonian Period about 359 million years ago, the researchers say.

World’s oldest trees, new research


This video from the USA says about itself:

Devonian forest

4 November 2013

This scene is excerpted from the Colorado Geology: Devonian-Mississippian video (in progress). These trees are the Progymnosperm Archaeopteris, and the forest floor includes Racophyton. Major soils did not develop until the first trees evolved on land.

Animation by Joseph Rogers and Leo Ascarrunz. Special thanks to Ian Miller and James Hagedorn (DMNS) for their input.

Interactive Geology Project, University of Colorado-Boulder.

From Cardiff University in Wales:

Fossils from the world’s oldest trees reveal complex anatomy never seen before

Intricate web of woody strands inside 374-million-year-old tree trunks point to most complicated trees to have ever grown on Earth

The first trees to have ever grown on Earth were also the most complex, new research has revealed.

Fossils from a 374-million-year-old tree found in north-west China have revealed an interconnected web of woody strands within the trunk of the tree that is much more intricate than that of the trees we see around us today.

The strands, known as xylem, are responsible for conducting water from a tree’s roots to its branches and leaves. In the most familiar trees the xylem forms a single cylinder to which new growth is added in rings year by year just under the bark. In other trees, notably palms, xylem is formed in strands embedded in softer tissues throughout the trunk.

Writing in the journal Proceedings of the National Academy of Sciences, the scientists have shown that the earliest trees, belonging to a group known as the cladoxlopsids, had their xylem dispersed in strands in the outer 5 cm of the tree trunk only, whilst the middle of the trunk was completely hollow.

The narrow strands were arranged in an organised fashion and were interconnected to each other like a finely tuned network of water pipes.

The team, which includes researchers from Cardiff University, Nanjing Institute of Geology and Palaeontology, and State University of New York, also show that the development of these strands allowed the tree’s overall growth.

Rather than the tree laying down one growth ring under the bark every year, each of the hundreds of individual strands were growing their own rings, like a large collection of mini trees.

As the strands got bigger, and the volume of soft tissues between the strands increased, the diameter of the tree trunk expanded. The new discovery shows conclusively that the connections between each of the strands would split apart in a curiously controlled and self-repairing way to accommodate the growth.

At the very bottom of the tree there was also a peculiar mechanism at play — as the tree’s diameter expanded the woody strands rolled out from the side of the trunk at the base of the tree, forming the characteristic flat base and bulbous shape synonymous with the cladoxylopsids.

Co-author of the study Dr Chris Berry, from Cardiff University’s School of Earth and Ocean Sciences, said: “There is no other tree that I know of in the history of Earth that has ever done anything as complicated as this. The tree simultaneously ripped its skeleton apart and collapsed under its own weight while staying alive and growing upwards and outwards to become the dominant plant of its day.

“By studying these extremely rare fossils, we’ve gained an unprecedented insight into the anatomy of our earliest trees and the complex growth mechanisms that they employed.

“This raises a provoking question: why are the very oldest trees the most complicated?”

Dr Berry has been studying cladoxylopsids for nearly 30 years, uncovering fragmentary fossils from all over the world. He’s previously helped uncovered a previously mythical fossil forest in Gilboa, New York, where cladoxylopsid trees grew over 385 million years ago.

Yet Dr Berry was amazed when a colleague uncovered a massive, well-preserved fossil of a cladoxylopsid tree trunk in Xinjiang, north-west China.

“Previous examples of these trees have filled with sand when fossilised, offering only tantalising clues about their anatomy. The fossilised trunk obtained from Xinjiang was huge and perfectly preserved in glassy silica as a result of volcanic sediments, allowing us to observe every single cell of the plant,” Dr Berry continued.

The overall aim of Dr Berry’s research is to understand how much carbon these trees were capable of capturing from the atmosphere and how this effected Earth’s climate.

Fossil prehistoric amphibians died young


This 2011 video is called 360 Million Year Old Tetrapod Acanthostega.

From Science News:

Preteen tetrapods identified by bone scans

Improved technique suggests large four-limbed Acanthostega were still juveniles

By Susan Milius

1:00pm, September 7, 2016

Better bone scanning of fossils offers a glimpse of preteen life some 360 million years ago.

Improved radiation scanning techniques reveal accumulating growth zones in chunks of four fossil upper forelimb bones from salamander-shaped beasts called Acanthostega, scientists report online September 7 in Nature. Vertebrate bones typically show annual growth zones diminishing in size around the time of sexual maturity. But there’s no sign of that slowdown in these four individuals from East Greenland’s mass burial of Acanthostega, says study coauthor Sophie Sanchez of Uppsala University in Sweden. They were still juveniles.

The bones came from tropical Greenland of the Devonian Period. Aquatic vertebrates were developing four limbs, which would serve tetrapods well when vertebrates eventually conquered land. This mass die-off doomed at least 20 individuals, presumably when a dry spell after a flood trapped them all in a big, vanishing puddle.

This find makes the strongest case yet for identifying genuine youngsters among ancient tetrapods, Sanchez says. She suspects other individuals trapped could have been juveniles too.

Not many other species were found in the mass burial. So young tetrapods may have stuck together much as today’s young fish schools, Sanchez speculates. The limb shape clearly indicates that the youngsters took a long time to start adding hard bone to the initial soft cartilage, she says. So these early tetrapods were at least 6-year-olds and probably 10 years old or more.

For identifying stages of life, the improved technique “allows greater resolution and rigor, so in that regard it is a plus,” says Neil Shubin of the University of Chicago, who studies a fossil fish with some tetrapod-like features called Tiktaalik. There are Tiktaalik preteens, too, he notes.

What interests Nadia Fröbisch of Museum für Naturkunde in Berlin is that some of Acanthostega individuals were different sizes but had reached the same stage of bone development. She muses that they might even have been developing along different trajectories of growth, a flexibility that would be useful in a changeable environment.

Animals emerged from the water and clamored onto land more than 300 million years ago, but paleontologists are looking for even more details about the transition. A healed broken bone that later fossilized is offering some new and unexpected clues. A new fossil from Australia pushes back the origin of tetrapods, or four-limbed animals, more than two million years. The creature, Ossinodus, lived during the Devonian Period 333 million years ago in what would have been temperate forests: here.