‘Dinosaur decline already before mass extinction’


This video from Britain says about itself:

Dinosaurs in decline BEFORE asteroid apocalypse

18 April 2016

Dinosaurs were already in an evolutionary decline tens of millions of years before the asteroid impact that finally wiped them out, scientists from the University of Reading and University of Bristol have found. Read more here.

Dr Manabu Sakamoto and Dr Chris Venditti, University of Reading, explain more.

This research was published on 18 April 2016 in the journal PNAS.

Filming took place in the Cole Museum of Zoology, University of Reading.

Asteroid animation courtesy of NASA.

See also here.

North American mammoths, new study


This video says about itself:

1 December 2014

Woolly Mammoth: The Autopsy

Science Documentary hosted by Steven Mackintosh, published by Channel 4 in 2014 – English narration

The 2013 discovery in Siberia of the best-preserved mammoth yet has quickened the pace of one of the most ambitious and controversial projects in science: the cloning of the woolly mammoth. This one is unlike any mammoth found before; when it was dug out of the permafrost, a dark red liquid oozed from the frozen body. Speculation is rife: could the liquid be mammoth blood? And does the freshness of the mammoth’s flesh mean that a clone is now achievable?

This documentary follows an international team of mammoth specialists and cloning scientists as they carry out a historic autopsy in Siberia, and follows those who strive to bring these iconic giants of the Ice Age back from extinction. As the animal is carefully dissected and its tusks are examined, the programme reveals the life story of this mammoth in forensic detail.

From Frontiers in Ecology and Evolution:

Mammuthus Population Dynamics in Late Pleistocene North America: Divergence, Phylogeography and Introgression

06 April 2016

After evolving in Africa at the close of the Miocene, mammoths (Mammuthus sp.) spread through much of the northern hemisphere, diversifying morphologically as they entered various habitats. Paleontologically, these morphs are conventionally recognized as species.

In Pleistocene North America alone, several mammoth species have been recognized, inhabiting environments as different as cold tundra-steppe in the north and the arid grasslands or temperate savanna-parklands of the south. Yet mammoth phylogeographic studies have overwhelmingly focused on permafrost-preserved remains of only one of these species, Mammuthus primigenius (woolly mammoth).

Here we challenge this bias by performing a geographically and taxonomically wide survey of mammoth genetic diversity across North America. Using a targeted enrichment technique, we sequenced 67 complete mitochondrial genomes from non-primigenius specimens representing M. columbi (Columbian mammoth), M. jeffersonii (Jeffersonian mammoth), and M. exilis (pygmy mammoth), including specimens from contexts not generally associated with good DNA preservation.

While we uncovered clear phylogeographic structure in mammoth matrilines, their phylogeny as recovered from mitochondrial DNA is not compatible with existing systematic interpretations of their paleontological record. Instead, our results strongly suggest that various nominal mammoth species interbred, perhaps extensively.

We hypothesize that at least two distinct stages of interbreeding between conventional paleontological species are likely responsible for this pattern – one between Siberian woolly mammoths and resident American populations that introduced woolly mammoth phenotypes to the continent, and another between ecomorphologically distinct populations of woolly and Columbian mammoths in North America south of the ice.

Columbian mammoth discovery in Oklahoma, USA


This video says about itself:

BBC: Columbian Mammoth, Death by Tar – Ice Age Death Trap

26 August 2008

With the help of CGI and animal puppetry, BBC’s Ice Age Death Trap team bring the … mammoth back to life to explain how such a giant creature could be killed by tar.

By Dominique Mosbergen, Senior Writer, The Huffington Post in the USA:

Bulldozer Operator Stumbles Upon Mammoth Skull In Oklahoma

The remains are at least 11,000 years old.

04/05/2016 05:21 am ET

Imagine being at work and stumbling, completely by chance, upon a mammoth discovery — a literal one, at that.

That’s what happened last month to a bulldozer operator in northwestern Oklahoma, who found the remains of a Columbian mammoth while on the job.

According to the Oklahoma Archeological Survey, the man was working at a sand pit near Alva when he made the surprise find. A partial mammoth skull, along with two tusks, have since been unearthed from the area.

“We don’t know the cause of death. There is no sign that people killed or butchered it,” archeologist Lee Bement told Live Science of the animal remains, which have yet to be dated. “Its skull was washed around in the river. The rest of the animal could be anywhere.”

Mammoth discoveries in the U.S. are not entirely unusual. Earlier this year, a mammoth femur was found under Oregon State University’s football field, and last September, two Michigan farmers stumbled upon mammoth remains in a soybean field.

Bement told Live Science that Oklahoma is home to about three “mammoth sightings” a year. Still, each new discovery brings hope of something new and unexpected.

“Archeological fieldwork is always exciting. You never know what you are going to find,” he said.

As The Associated Press noted, Columbian mammoths were a common sight across the Plains until they — along with many large Ice Age animals, including mastodons, giant sloths and giant bears — went extinct at the end of Pleistocene era about 11,000 years ago. Scientists are still unsure as to what prompted this mass die-off, though hunting by humans and climate change have been floated as possible culprits.

How many dinosaurs lived?


This 2015 video is called Dinosaur Evolution | Dinosaurs Documentary National Geographic HD.

By Jon Tennant:

How many dinosaurs were there?

March 30, 2016

There are more than 10,000 species of bird living on Earth today. If you recognise that birds are living dinosaurs, which overwhelming evidence indicates that they are, then this makes them more diverse than their living mammalian counterparts. So if you take the number of species to mean anything, this means we’re still in the reign of the dinosaurs! These days they’re just mostly a bit smaller and fluffier than their Mesozoic ancestors.

But one massive question still remains for Palaeontologists and Neontologists: Why are there so many bird species around today, when we have relatively so few dinosaurs in the fossil record? This disparity is even more extreme when you consider that while non-avian dinosaurs were around for about 170 million years, there were only ever about 800 or so species of dinosaur, based on current records. The actual number fluctuates through time, as new species are discovered, and others are shown to be invalid through research broadly known as ‘taxonomy’.

Recently, Jostein Starfelt and Lee Hsiang Liow of the University of Oslo made a major step forward in answering one of the key questions related to this: Just how many dinosaur species were there in reality?

Most previous studies of dinosaur diversity have only looked at relative diversity, which assess proportional changes from one time to another. But how do you actually estimate the real total number of dinosaurs through time?

How do Palaeontologists read the fossil record?

One of the major problems in calculating diversity is that the fossil record is a poor representation of the biological part of ecosystems. Animals are preserved differently due to differences in their anatomy. Also, not all animals have the same chance of becoming fossils, based on where they happen to find their final resting place.

Furthermore, the geological record is preserved differently through space and time, due to where seas and rivers were to deposit sediment, and due to processes of mountain building and erosion.

Once you get past these two hurdles, humans have then sampled this record differently through time, for example by collecting only from rocks where they know there is a high probability of finding new fossils, also known as the ‘bonanza effect’.

Dinosaurs be TRiPSin’..

All of this variation is broadly known as sampling bias. While many methods have been developed to account for these biases in different ways, Starrfelt and Liow developed a brand new one called TRiPS, which stands for True Richness estimated using a Poisson Sampling Model. This accounts for variation in the sampling of the dinosaur record by estimating both the bias and the overall diversity (richness) based on variation in the number of times each dinosaur species occurs at different points in time. For example, if we know lots of specimens of a particular dinosaur species, we can infer that it has a relatively high preservation potential and collection probability. The authors used this to investigate the dynamics of dinosaur diversity through time, and to assess possible extinction events in their history.

Using this new method, applied to the whole known dinosaur record through the whole of the Mesozoic (Triassic to the end of the Cretaceous), they estimated that 1543-2468 species existed altogether around the globe. While the authors acknowledge that this is a crude estimate, it is largely convergent on previous calculations too.

Importantly, this number is much higher than what is currently known from the fossil record. If you break this down into the three major dinosaur groups, a slightly different pattern emerges. Theropods, the mostly carnivorous group leading to modern birds, had almost twice as many species (1115) than either the long-necked sauropods (513) or bird-hipped ornithischians (508).

Steve Brusatte of the University of Edinburgh is sceptical though: “I would take these numbers with an ocean full of salt”, he said. “There are over 10,000 species of birds – living dinosaurs – around today. So saying there were only a few thousand dinosaur species that lived during 150+ million years of the Mesozoic doesn’t pass the sniff test. That’s not the fault of the authors. They’ve employed advanced statistical methods that take the data as far as it can go. The problem is the data. The fossil record is horrifically biased. Only a tiny fraction of all living things will ever be preserved as fossils. So what we find is a very biased sample of all dinosaurs that ever lived, and no amount of statistical finagling can get around that simple unfortunate truth.”

Jostein Starrfelt also thinks that there is more work to be done in this domain: “Our estimate of total dinosaur richness of approximately 2000 species was done attempting to combine the sampling probabilities from all stages of the Mesozoic and should be interpreted with caution, and my gut feeling is that the total number of dinosaur species for the whole Mesozoic is higher than our total estimate suggests.”

The future of dinosaur hunting

So what does all of this mean for dinosaur hunters? Well, it suggests that there are still hundreds more to be found out there! So get your hiking boots out and go track some dinosaurs!

Brusatte said “There are huge swaths of the planet and huge stretches of the Mesozoic that have yielded few or no dinosaur fossils. The Middle Jurassic and mid Cretaceous are notoriously poorly sampled, as are Antarctica, Australia, and much of Africa. It’s only been over the last few decades that we’ve come to appreciate the bounty of Chinese dinosaurs, and they keep coming at a furious pace. We still have a lot to find.” Indeed, Starrfelt agreed that their method could be used to “get a better picture of which continents are under-sampled and for which periods (and could thus deserve some more human effort).”

It also hints that there might be something fundamentally different about the evolutionary biology of bird-line dinosaurs, and non-avian dinosaurs. Many studies are beginning to unravel the origins and diversification of modern birds, but these will only truly shed light if they are considered in the wider context of dinosaur diversity through time.

Starrfelt also hinted at his future plans with this line of research. “As with most scientific endeavours I wouldn’t say that TRiPS has solved the major problems of using the fossil record as a source of information about the dynamics of clades; but that it might be a good start. The approach lends itself easily to being extended; in the future we might be able to include information about the ‘human effort’ part of fossil bias by interpreting the sampling rate as the product of a fossilization rate and a ‘discovery probability’, for instance. We’re also in the process of putting TRiPS in a Bayesian framework.” How exciting!

Only by being able to estimate diversity with greater accuracy through space and time can we begin to understand the forces that have shaped the evolutionary history of animals.

As always, Brian Switek has also written an excellent post on this study.

Reference

Starrfelt, J., Liow, L. H. (2016) How many dinosaur species were there? Fossil bias and true richness estimated using a Poisson sampling model. Philosophical Transactions of the Royal Society Series B: Biological Sciences. doi: 10.1098/rstb.2015.0219. The data and code are all available via Dryad.

305 million-year-old spider relative discovered


This video says about itself:

The ancient creature that was ‘nearly a spider’

30 March 2016

The ancient creature that was ‘nearly a spider’: 305-million-year-old arachnid had similar legs and jaw but couldn’t spin a web.

Spiders predate the dinosaurs, scurrying along 315 million years ago – but their precise origins remain a mystery.

Now scientists believe they have filled a ‘gap’ in the evolutionary story of arachnids, with the discovery of a fossil that’s the closest relative to spiders ever discovered.

The creature, dubbed Idmonarachne brasieri, measured less than one inch long and lived alongside the oldest known ancestors of modern spiders 305 million years ago.

From NPR in the USA:

305 Million-Year-Old Fossil A Glimpse Into The Origins Of Spiders

March 30, 20166:53 PM ET

Merrit Kennedy

Scientists have discovered a well-preserved 305 million-year-old arachnid that is “almost a spider” in France. In a new journal article, they say the fossil sheds some light on the origins of “true” spiders.

The main point of distinction: This newly discovered arachnid very likely could produce silk but lacked the spinnerets used by true spiders to, well, spin it, the scientists say. The researchers say it belongs to a “sister group” to the real-deal spiders.

The species, which they described in a new article in the journal Proceedings of the Royal Society B, is named Idmonarachne brasieri. That’s after Idmon, the father of Arachne in Greco-Roman mythology. Appropriately, Arachne was a master weaver who was transformed into a spider.

The paper says Idmonarachne “does not fit comfortably into the established orders.” National Geographic reports that it “acts as a bridge between early spider-like creatures brewing up blobs of silk and the skilled weavers that we see today.”

Here’s more from National Geographic on the comparatively clumsy beginnings of spiderly silk production:

“While delicately constructed webs seem synonymous with spiders, we know from the fossil record that the ability to secrete silk came before the ability to carefully control it. Spider relatives called uraraneids, which lived from 385 million years ago through the time of Idmonarachne, could produce silk but could not build webs.”

University of Manchester’s Russell Garwood, who was one of the article’s authors, told the BBC, “This fossil is the most closely related thing we have to a spider that isn’t a spider.”

The specimen was found in a deposit in Montceau-les-Mines in France and then included in what the article’s co-author described as a “box of fossils” borrowed by the University of Kansas, as the BBC reported. It had been sitting there for decades — the BBC says the box came from Paris’ Museum National d’Histoire Naturelle in the 1980s.

The scientists used laboratory and synchrotron scans of the fossil to produce digital 3-D imagery of Idmonarachne. The arachnid predated the first appearance of the dinosaurs by some 80 million years.

New Ice Age rhino discovery in Kazakhstan


This video says about itself:

18 August 2015

Elasmotherium” is an extinct genus of giant rhinoceros endemic to Eurasia during the Late Pliocene through the Pleistocene, documented from 2.6 Ma to as late as 50,000 years ago, possibly later, in the Late Pleistocene, an approximate span of slightly less than 2.6 million years.

Three species are recognised. The best known, “E. sibiricum”, was the size of a mammoth and is thought to have borne a large, thick horn on its forehead. This horn was used for defense, attracting mates, driving away competitors, sweeping snow from the grass in winter and digging for water and plant roots. Like all rhinoceroses, elasmotheres were herbivorous. Unlike any others, its high-crowned molars were ever-growing. Its legs were longer than those of other rhinos and were adapted for galloping, giving it a horse-like gait.

From LiveScience:

‘Unicorns’ Lumbered Across Siberia 29,000 Years Ago

by Mindy Weisberger, Senior Writer

March 29, 2016 04:24pm ET

Large, four-legged beasts, each with a single horn growing from its head, once ambled across part of western Siberia, in what is now Kazakhstan.

Sometimes referred to as “unicorns” because of their single horns, these animals were originally thought to have gone extinct 350,000 years ago. However, fossils from a new dig site place the hefty creatures in the region as recently as 29,000 years ago, according to a recent study.

In spite of their magical-sounding nickname, these bruisers share little in common with the graceful and delicate horselike creatures described in song and story and pictured in medieval tapestries. A 1923 publication by paleontologist Henry Fairfield Osborn estimated the creatures to be larger than any of the modern rhino species. Artists’ reconstructions hint at a burly build and body plan that resemble that of the animals’ extant cousins. And the beasts go by an equally cumbersome name: Elasmotherium sibiricum (ee–laz–moh–THEER–ee–um sih–BIH–rih–cum). [6 Extinct Animals That Could Be Brought Back to Life]

A well-preserved skull

The partial skull that the researchers found was well-preserved and in very good condition overall, though the teeth were missing, the scientists said. Dimensions of features in the skull fragment were considerably bigger than those in any other E. sibiricum specimen yet discovered in Eastern Europe, hinting that the skull most likely belonged to a large, older male, said study co-author Andrey Shpanski, a paleontologist at Tomsk State University in Russia.

“The dimensions of this rhino [described] today are the biggest of those described in the literature,” Shpanski said in a statement.

E. sibiricum is thought to have ranged from the Don River in southern Russia to the eastern part of Kazakhstan, and prior findings showed that the animal had long inhabited the southeastern part of the West Siberian Plain.

Other fossils found alongside the E. sibiricum skull include two upper teeth from a mammoth, the lower jaw of a steppe elephant and pieces of a bison‘s horn stem.

Dating a “unicorn”

To find out how old the fossils were, the scientists used a method known as radiocarbon dating, which they employed to analyze the amount of carbon-14 in the skull pieces. Carbon-14 is a carbon isotope, a variation of carbon with a different number of neutrons in its nucleus (14, in this case). Living plants and animals absorb carbon-14 from the atmosphere as long as they’re alive.

But once an organism dies, the carbon-14 in its body begins to decay at a regular rate that can be tracked over time, until about 60,000 years have passed and all the carbon-14 is gone. By analyzing bones to see how much carbon-14 is left, scientists can tell when the animal was still alive.

Radiocarbon dating told researchers that the E. sibiricum individual died 29,000 years ago, a dramatic divergence from previous estimates placing the species’ extinction at 350,000 years ago.

If the new calculation is correct, the “Siberian unicorn” could have crossed paths with modern humans. An earlier study suggested that humans inhabited the Siberian Arctic as far back as 45,000 years ago, based on the evidence of a butchered mammoth carcass that was likely cut up by hunters.

The new findings were published in the Feb. 2016 issue of the American Journal of Applied Sciences.

New Australopithecus fossil discovery in Kenya


This video from the USA says about itself:

Walking With Lucy | California Academy of Sciences

19 September 2013

Appearing next to a full–scale recreation of the famous “Lucy” skeleton (Australopithecus afarensis) in Tusher African Hall, this computer animation compares the distinctive gaits of a chimpanzee, A. afarensis, and modern human, highlighting the trait of upright walking that the latter two share.

From Science Daily:

Australopithecus fossils found east of the Great Rift Valley

New remains demonstrate early hominid’s adaptability

March 24, 2016

Source: Kyoto University

Summary: New fossils from the outskirts of Nairobi reveal that Australopithecus afarensis lived far eastward beyond the Great Rift Valley, demonstrating how adaptable the early hominid species were to new environments.

New fossils from Kenya suggest that an early hominid species — Australopithecus afarensis — lived far eastward beyond the Great Rift Valley and much farther than previously thought. An international team of paleontologists led by Emma Mbua of Mount Kenya University and Masato Nakatsukasa of Kyoto University report findings of fossilized teeth and forearm bone from an adult male and two infant A. afarensis from an exposure eroded by the Kantis River in Ongata-Rongai, a settlement in the outskirts of Nairobi.

“So far, all other A. afarensis fossils had been identified from the center of the Rift Valley,” explains Nakatsukasa. “A previous Australopithecus bahrelghazali discovery in Chad confirmed that our hominid ancestor’s distribution covered central Africa, but this was the first time an Australopithecus fossil has been found east of the Rift Valley. This has important implications for what we understand about our ancestor’s distribution range, namely that Australopithecus could have covered a much greater area by this age.”

A. afarensis is believed to have lived 3,700,000-3,000,000 years ago, as characterized by fossils like “Lucy” from Ethiopia.

Stable isotope analysis revealed that the Kantis region was humid, but had a plain-like environment with fewer trees compared to other sites in the Great Rift Valley where A. afaransis fossils had previously appeared. “The hominid must have discovered suitable habitats in the Kenyan highlands. It seems that A. afaransis was good at adapting to varying environments,” notes Nakatsukasa.

The team’s survey also turned up masses of mammal fossils, including a few that probably belong to new species of bovids or baboons.

The authors write that the Kantis site was first noted in a 1991 geological survey. At that time, a farmer said that he and his family had come across fossilized bones from Kantis in the 1970s, although they did not recognize their importance. Following airing of Kenyan television programs on paleontological research, locals gradually started to appreciate the fossils. Since then, Kantis and other sites have been identified thanks to fossil notifications from the local population.

The team welcomes this achievement not only for its academic implications, but also for the benefits to the local community. “Kantis is in the vicinity of Nairobi, a major city,” said Nakatsukasa. “We hope that the discovery of the new site and the fossils will aid in increasing tourism, and in improving educational awareness of the local community.”