‘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.

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.

Pregnant tyrannosaur discovered?


This video says about itself

An excerpt from the “Clash of the Dinosaurs” series episode “Extreme Survivors” featuring the mighty TYRANNOSAURUS REX produced by Discovery Channel in 2009.

By Ed Mazza in the USA:

Science Answers An Age-Old Question: How Can You Spot A Pregnant T. rex?

“We know next to nothing about sex-linked traits in extinct dinosaurs.”

03/16/2016 05:31 am ET

Scientists have discovered what they believe is a pregnant Tyrannosaurus rex — and it might even still contain dino DNA.

Tests conducted on the fossilized femur of a 68-million-year-old T. rex revealed the presence of medullary bone, or a type of bone that forms only in female birds before or during egg-laying, according to a news release from North Carolina State University.

“It’s a dirty secret, but we know next to nothing about sex-linked traits in extinct dinosaurs,” Lindsay Zanno, assistant research professor of biological sciences at the university and co-author of the new study, said in the release.

“Dinosaurs weren’t shy about sexual signaling, all those bells and whistles, horns, crests, and frills, and yet we just haven’t had a reliable way to tell males from females,” Zanno said. “Just being able to identify a dinosaur definitively as a female opens up a whole new world of possibilities.”

N.C. state paleontologist Mary Schweitzer spotted what she believed to be the medullary bone in the T. rex sample in 2005.

“All the evidence we had at the time pointed to this tissue being medullary bone,” Schweitzer, who is lead author of the new study, said in the release. “But there are some bone diseases that occur in birds, like osteopetrosis, that can mimic the appearance of medullary bone under the microscope. So to be sure we needed to do chemical analysis of the tissue.”

The new study focused on that analysis, comparing the dino bones to the medullary tissue of ostriches and chickens.

It was a match.

One test looked for a substance called keratan sulfate, which is found in medullary bone but not other types of bone.

Scientists thought this substance might not survive the passage of millions of years, but it turns out it did.

And if that can still be detected, there may be hope that a sample of dino DNA is still waiting to be found.

“Yes, it’s possible,” Lindsay Zanno told Discovery News. “We have some evidence that fragments of DNA may be preserved in dinosaur fossils, but this remains to be tested further.”

Tyrannosaur relative, new discovery


This video says about itself:

Scientists Dicover Small T. Rex Ancestor

14 March 2016

Scientists announced Monday they have discovered a new, smaller ancestor to the T. rex. The Timurlengia euotica was roughly the size of a horse and posessed many of the same features as the T. rex.

By Jacqueline Howard, Senior Science Editor, The Huffington Post in the USA:

Meet T. Rex’s Fierce, Fleet-Footed Relative

The newly discovered species is being called a missing link.

03/14/2016 03:00 pm ET

Scientists have discovered a nimble, meat-eating dinosaur with blade-like teeth that fills an important gap in Tyrannosaurus rex’s family tree.

The newly named creature, Timurlengia euotica, sheds light on how a family of dinosaurs called tyrannosaurs advanced from being small predators to clever giants at the top of the food chain — within the span of about 70 million years.

The long-legged, 600-pound T. euotica lived some 90 million years ago. It was around this time that tyrannosaurs developed impressive cognitive abilities and sharp senses, such as the ability to detect low-frequency sounds, according to a study published Monday in the Proceedings of the National Academy of Sciences.

Soon after, tyrannosaurs began to get bigger. By the late Cretaceous period, massive tyrannosaur species would emerge, such as T. rex, which lived around 66 to 68 million years ago, said Dr. Hans-Dieter Sues, the chairman of the paleobiology department at the Smithsonian’s National Museum of Natural History and a co-author of the study.

“Timurlengia has already evolved the sophisticated senses and many bone features of T. rex but was a much smaller animal,” Sues said. “The new discovery fills in a multimillion-year gap in the evolution of one particularly successful group of dinosaurs.”

Sues and Dr. Alexander Averianov, a senior scientist at the Russian Academy of Sciences, unearthed the T. euotica fossils in the Kyzylkum Desert of Uzbekistan during a series of expeditions between 1997 and 2006.

Sues and an international team of paleontologists reanalyzed the remains and found that they belonged to a previously unknown species, T. euotica, which they determined was a relative but perhaps not an ancestor of T. rex.

“As few dinosaur fossils are known from 90 million-year-old rocks, we hoped to find fossils that would tell us something about dinosaur evolution at this point in time,” Sues said. “Still, Timurlengia showed unexpected features.”

To learn more about the species and its cognitive abilities, the researchers took CT scans of T. euotica‘s fossilized brain case and used that data to build a model of its brain.

They concluded that, even though T. euotica‘s skull was much smaller than that of T. rex, its brain and senses were highly developed.

“The ancestors of T. rex would have looked a whole lot like Timurlengia, a horse-sized hunter with a big brain and keen hearing that would put us to shame,” Dr. Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland who led the new research, said in a statement. “Only after these ancestral tyrannosaurs evolved their clever brains and sharp senses did they grow into the colossal sizes of T. rex. Tyrannosaurs had to get smart before they got big.”

This new research is not only noteworthy for what it teaches us about the tyrannosaurs’ family tree, but also because it could provide clues about how dinosaurs evolved when faced with a changing environment, Sues said.

“Dinosaurs have been a huge evolutionary success since they first appeared about 230 millions year ago,” he said. “Learning about their evolutionary history and how they coped with environmental changes holds important lessons for the many changes seen in today’s world.”

Tyrannosaur evolution, new research


This video from the American Museum of Natural History in the USA says about itself:

2 July 2012

Fossils of two never-before-seen species of tyrannosaur are overturning long-held ideas about the diversity and evolution of this family of dinosaurs. One is an unusually slender, eight-horned tyrannosaur named Alioramus altai, unveiled by AMNH Chair of Paleontology Mark Norell and AMNH/Columbia University PhD student Stephen Brusatte. The other is an ancient, tiny version of Tyrannosaurus rex called Raptorex kriegsteini, recently described by University of Chicago paleontologist Paul Sereno.

From PLOS Paleo blog:

The evolution of tyrannosaurs

Posted February 17, 2016 by Jon Tennant

T. rex is probably the most notorious and infamous dinosaur of all time, and somewhat of an icon in both the scientific and public spheres. After all, it was a pretty fearsome and impressive carnivore, and arguably worthy of such admiration. But there were actually a lot of other dinosaurs similar to T. rex, together forming a group known as tyrannosauroids.

Recently, a whole series of new findings is helping us to unlock the secrets of these fascinating beasts, and we can now begin to answer questions about their evolutionary relationships, biogeography, and how decent their fossil record is. In fact, half of all known tyrannosauroid species have been discovered in the last decade alone!

Tyrannosauroid species were actually around way before T. rex, which only occupied the top of the food chain right at the end of the Cretaceous reign of the non-avian dinosaurs. Actually, the largest tyrannosauroids only seemed to appear around 20 million years before this. Before they achieved such terrifyingly gigantic sizes, most were actually quite small-bodied (for a dinosaur), and quite ecologically diverse.

Steve Brusatte, Thomas Carr and their colleagues visited the question of the inter-relationships of tyrannosauroids back in 2010. Forming hypotheses of relationships like this forms the basis for assessing important evolutionary factors, such as the origins and evolution of particular anatomical features, rates of evolution, diversity, anatomical disparity, and biogeography. So when another study produced alternative results to their earlier study, Brusatte and Carr decided to go back to the Mesozoic and reanalyse tyrannosauroids, but incorporating all of the recent bits of knowledge we have gained about them over the last few years.

In addition to this, Brusatte and Carr decided to approach this with a dual method. Typically, when palaeontologists create trees that form the basis of assessing evolutionary relationships, we use a method called parsimony. This looks at how many different anatomical changes have occurred between different species, and tries to provide the minimum number of changes in order to build a tree. They also decided to go Bayesian on their dataset though, something which hasn’t really taken off in palaeontology yet, and has been more widely applied to molecular analyses. This works slightly differently by analysing anatomical data (in the form of a character matrix) in a probabilistic framework, and by using more complicated models that treat characters in different ways. By using this combination of techniques, it is possible to see which results are congruent, and therefore which conclusions can be best supported.

Fortunately for Brusatte and Carr, the results of both analyses were quite similar overall, lending support to their conclusions. There are slight differences, which you can see by comparing the two trees figured here. The overall structure reveals that tyrannosauroids can be sub-divided into a basal clade of proceratosauroids, which includes taxa such as the feathered Yutyrannus and Guanlong; an intermediate grouping or grade of small- to medium-sized beasties; and the gigantic apex predators such as T. rex and Tarbosaurus that we all know thanks to the best scientific minds in Hollywood.

The authors do a great job of trying to work out why their results differ slightly, but as always, the devil is in the details and it can be quite difficult to figure out. Part of the reason for some of the discrepancies might be to do with missing data – we can never fully sample every organism that has lived, and palaeontologists accept that limit of the fossil record. In the case of tyrannosauroids, there is a 20 million year gap in their fossil record from just before the time when the Western Interior Seaway covered much of North America. What this means is that animals simply weren’t preserved in the right time in the right place to be preserved as fossils. Yet, at least. Discovering new tyrannosauroids from this gap might be critical in working out how more derived tyrannosauroids evolved during a clearly important time in their history.

But what does all of this mean then for the evolution of tyrannosauroids? Well, for starters, it shows that the evolution of their large body size appeared to happen more gradually, rather than a rapid burst. Accompanying this, it shows that bite forces increased incrementally too, and that their elaborate facial ornamentations gradually became more complicated along with increasing body size. The first truly gigantic tyrannosauroids, coming in at more than 1.5 tonnes in mass and 10 metres in body length, didn’t appear in the fossil record until around 80 million years ago.

In terms of their biogeography, some interesting patterns emerge. It seems like there was episodic interchange between Asia and North America during the Late Cretaceous. What this means, and I’m sure Donald Trump will love this, is that T. rex actually appears to have been an Asian immigrant that colonised North America. However, this understanding might change as we recover ever more tyrannosauroid fossils from the latest Cretaceous of Asia and North America.

So, that’s a quick update on what we know about tyrannosauroids. Despite them clearly winning a cross-dinosaur popularity contest, there is still much we can learn about these creatures, and only time and future exploration can tell what we’ll discover!

Fossil dinosaur and fossil wildebeest, discoveries and simillarities


This video says about itself:

Shared noses: Extinct wildebeest relative was remarkably dinosaur-like

5 February 2016

An artist’s interpretation of Rusingoryx atopocranion on the Late Pleistocene plains of what is now Rusinga Island, Lake Victoria.

From the Christian Science Monitor in the USA:

Weird convergence: Extinct wildebeest cousin and dinosaur shared noses

Scientists discover two unrelated, extinct animals had the same strange nose.

By Eva Botkin-Kowacki, Staff writer February 5, 2016

You might not expect to find many similarities between a mammal and a reptile, particularly if they lived millions of years apart. But scientists have found that two such extinct beasts share a rare, distinctive facial feature.

An extinct relative of the wildebeest and a duck-billed dinosaur both had bizarre crests on their heads. But it wasn’t the protruding bump that has most intrigued scientists, it’s what they found beneath.

The bony crest is hollow, forming a trumpet-shaped nasal passage unlike any seen outside these two species. No other animal, living or dead, has been found with such a feature.

So how did two beasts from two very different taxa come to have such a mysterious commonality? Convergent evolution, scientists say in a paper published Thursday in the journal Current Biology.

“We have an animal that its skeleton looks a lot like a wildebeest – it’s actually very closely related to modern wildebeests – but its face looks a lot more like something you would see if you went way back in time to the Cretaceous and looked at hadrosaur dinosaurs,” study lead author Haley O’Brien tells The Christian Science Monitor in an interview.

Rusingoryx atopocranion, the mammal, lived about 65 thousand years ago, during the late Pleistocene, while Lambeosaurine hadrosaurs, the dinosaur, lived closer to 65 million years ago, during the late Cretaceous – and yet both animals evolved the same strange nose.

And not only do their nasal passages look alike, she said, the feature also appears to develop the same way as the animals grow up from juveniles to adults, as a variety of fossils display.

“When I first saw the complete skulls, I was blown away,” vertebrate paleontologist David C. Evans, who was not part of the study, writes in an email to the Monitor. “The resemblance between Rusingoryx and some hollow-crested dinosaurs in the form of their nasal structures is truly striking, and there are clear parallels in how they evolved and grew. Both groups elongated their noses to such a degree that they evolved highly domed skulls to house their nasal passages on top of their heads, above their eyes.”

Different origins, same result

“It’s probably one of the best examples of convergence in large animals that I’ve seen in a long time,” Ali Nabavizadeh, a researcher in evolutionary biology and anatomy at the University of Chicago, who was not involved in the study, tells the Monitor.

One was a mammal and the other a reptile, and millions of years elapsed between their tenure on Earth, but still, these animals developed the same adaptation.

Convergent evolution occurs when two species along different lineages independently evolve the same, or similar, features for the same function. One example is how insects, birds, and bats can all fly.

Convergence typically occurs when different species face the same ecological pressures. So what did Rusingoryx and the hadrosaurs have in common?

Both animals were herbivores and lived in herds. Rusingoryx was a ruminant and hadrosaurs have been called the cows of the Cretaceous, but the similarities, besides the shared nose, stop there.

Rusingoryx lived on the savanna, a dry wide open plain, while Lambeosaurine hadrosaurs were thought to have lived in a tropical rainforest.

Understanding this mysterious convergence might hinge on the purpose that these strange nasal passages served.

Inner trumpets

Without looking inside the animals’ skulls, the crest might appear to be simply for visual display or some other external use.

“We have known for decades that visual display and physical combat have strongly shaped skull evolution in many groups of animals with elaborate horns and crests,” Dr. Evans says. But the long, trumpet-shaped interior suggests a more complex purpose.

The hollow cavity, part of the respiratory tract, loops up over the animal’s head and seems to connect to the vocal tract.

To determine the purpose behind this strange nose, scientists focused on the mammal’s living cousins, wildebeests and antelopes. While researchers can look at their soft tissue for clues, all that’s left of the dinosaurs is bone.

The unusual nose could have helped the animals smell, bugle, or even regulate their temperature, Evans says. “The case for vocalization as the primary function of the nasal dome in Rusingoryx is by far the most convincing, as the authors advocate.”

The Rusingoryx are very social, says Ms. O’Brien. “They live in herds and they use a lot of vocal signals to communicate. When we looked into the function of what this skull type might be doing in Rusingoryx, we really couldn’t prescribe a function outside of that social vocalization.”

“There are obviously a lot of things that animals do with their faces,” she says. “But we don’t think that this crazy nasal dome would have really changed those more normal functions for this animal. We think that it was using the nasal crest to modify the way that it’s producing these vocalizations and communicating.”

That makes sense, says Thomas E. Williamson, curator of paleontology at the New Mexico Museum of Natural History and Science, who was not part of the study.

“When you have any kind of a tubing, it becomes naturally resonant,” he explains. “So the idea that it’s being used somehow to amplify certain frequencies of sound, it will do that,”

Not your average moo

O’Brien and her colleagues suggest that Rusingoryx, and perhaps the dinosaurs by extension, used this bizarre nasal dome to communicate at frequencies other animals cannot hear. This is called infrasound, and animals like elephants and cassowaries use it to communicate under the radar.

That’s possible, says Dr. Nabavizadeh. “If you have a very gregarious group of animals and they’re in a big arid, open environment, as these bovids are, then you are under the selective pressure to start to create more lower bellowing sounds that are possibly outside of the hearing range of carnivores, so they can communicate without being found in big open environments.”

But the environment doesn’t preclude the dinosaurs from needing this ability too, says Dr. Williamson. “Infrasound … is able to travel over great distances and open areas and in closed environments. It pretty much goes everywhere,” he says. And cassowaries, the living birds thought to communicate in infrasound, live in dense tropical rainforests.

Extremely big dinosaur discovery in Argentina


This 22 January 2016 Argentine TV video, in Spanish, is about the recent discovery of the Notocolossus gonzalezparejasi dinosaur.

From Nature:

A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot

18 January 2016

Abstract

Titanosauria is an exceptionally diverse, globally-distributed clade of sauropod dinosaurs that includes the largest known land animals. Knowledge of titanosaurian pedal structure is critical to understanding the stance and locomotion of these enormous herbivores and, by extension, gigantic terrestrial vertebrates as a whole. However, completely preserved pedes are extremely rare among Titanosauria, especially as regards the truly giant members of the group.

Here we describe Notocolossus gonzalezparejasi gen. et sp. nov. from the Upper Cretaceous of Mendoza Province, Argentina. With a powerfully-constructed humerus 1.76 m in length, Notocolossus is one of the largest known dinosaurs. Furthermore, the complete pes of the new taxon exhibits a strikingly compact, homogeneous metatarsus—seemingly adapted for bearing extraordinary weight—and truncated unguals, morphologies that are otherwise unknown in Sauropoda. The pes underwent a near-progressive reduction in the number of phalanges along the line to derived titanosaurs, eventually resulting in the reduced hind foot of these sauropods.

A Culture24 top ten of the best dinosaur museums and collections in the UK: here.