Tag Archives: mammal

Fossil Friday: Adalatherium, the largest mammal to run with the dinosaurs

New research sheds light on a 66-million-year-old mammal that lived alongside the dinosaurs. The findings help us better understand the evolutionary history of mammals from the southern supercontinent Gondwana — today’s Africa, South America, Australia, Antarctica, India, and Arabian Peninsula.

Adalatherium huiA, photograph of skull and skeleton with BC, skeletal reconstructions in left lateral and dorsal views. Image credits David W. Krause et al., (2020), Journal of Vertebrate Paleontology.

Christened Adalatherium hui, which is a combination of Malagasy and Greek meaning “crazy beast,” the paper describes this new species based on an almost complete, excellently-preserved fossil skeleton. The authors explain that this specimen is the most complete for any mammal yet discovered in the southern hemisphere from the time of the dinosaurs.

Oldboy

Research on the fossil specimen was carried out over a period of 20 years or so. In its day, the opossum-sized animal was a giant of its family, as most mammals at the time were mouse-sized. It lived on Madagascar near the end of the Cretaceous period (145-66 million years ago). At first glance, it looks quite like a badger, but that similarity is only skin-deep, the team explains.

Adalatherium is simply odd. Trying to figure out how it moved, for instance, was challenging because its front end is telling us a completely different story than its back end” says Dr David Krause of the Denver Museum of Nature & Science, co-lead author of the paper.

“Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal like Adalatherium could have evolved; it bends and even breaks a lot of rules”.

The bizarre features Dr Krause makes mention of include a greater number of vertebrae in the animal’s torso than in other mammals, a strange limb arrangement — crocodile-like hind legs with sprinting front legs that could be tucked underneath the animal as in modern mammals — front teeth like those of rabbits but back teeth that are completely unique. It was all topped off with a strange gap in the bones at the top of the animal’s snout.

Adalatherium belongs to an extinct group of mammals known as gondwanatherians, known since around the 1980s. We’ve only known the group from small fragments such as teeth and bits of jawbone, but even these showed that the gondwanatherians were strikingly different from today’s mammals. But we didn’t know where they fit in the larger tree of life due to this lack of material.

The discovery of Adalatherium thus represents a massive break for our understanding of gondwanatherians. It is the first reliable evidence of the shape and structure of this family of mammals, and will help us piece together how they went about their lives. For example, its hind legs seem tailored to digging, but its front legs are indicative of an animal that evolved to run at great speeds.

Its teeth are indicative of a herbivore lifestyle, computer micro-tomography imaging revealed, but the structure of its back teeth is unlike that of any mammal, fossil or alive, ever seen. The authors admit that they have no clue why they’re shaped the way they are, or for what purpose.

All in all, the animal likely grew to about 3.1kgs in its adult years. While it lived, Madagascar had already been separated from Africa for over 150 million years and from the Indian subcontinent for over 20 million years.

“Islands are the stuff of weirdness,” says Krause, “and there was therefore ample time for Adalatherium to develop its many extraordinarily peculiar features in isolation.

Adalatherium is an important piece in a very large puzzle on early mammalian evolution in the southern hemisphere, one in which most of the other pieces are still missing,” adds Hoffmann.

The paper “Introduction to Adalatherium hui (Gondwanatheria, Mammalia) from the Late Cretaceous of Madagascar” has been published in the Journal of Vertebrate Paleontology.

Paleontologists uncover 66-million-year-old bizarre mammal that shouldn’t exist

 Artist impression of Adalatherium hui. Image credit: Andrey Atuchin / Denver Museum of Nature & Science.

During the Cretaceous, the dinosaurs were in their heyday, whereas mammals were confined to certain ecological niches. Usually, they weren’t bigger than a modern mouse. On the island of Madagascar, however, ancient mammals were allowed to evolve in weird directions. Such is the case of Adalatherium hui, a housecat-sized creature with a mosaic of features, distinct from other mammals that we know of.

The ‘oddest of the odd’

Adalatherium literally means “crazy beast” in Greek, while hui is a nod to Yaoming Hu, a Chinese paleontologist renowned for his work on early mammals who passed away in 2008.

The name is fitting since the ancient mammal “bends and even breaks a lot of rules,” said lead researcher David Krause, curator at the Denver Museum of Nature & Science.

“Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal-like Adalatherium could have evolved,” he added.

The fossils were found preserved in pristine condition in a Mesozoic geological formation in northwestern Madagascar.

Credit: Nature.

Although it may look like a small badger on the outside, Adalatherium had a mix of never-before-seen features. ‘Behind the hood’, paleontologists found that the ancient mammal had more vertebrae in its vertebral column than any of its contemporaries. Its leg bones were strangely curved and its peculiar teeth haven’t been encountered in any other mammal, living or extinct.

“Trying to figure out how it moved is nearly impossible because, for instance, its front end is telling us a different story than its back end,” said Simone Hoffmann of the New York Institute of Technology, a co-author of the study.

What’s more, the 3.1-kg-creature had a nasal cavity unlike any other mammal before it. It had more holes — which served as passageways for nerves and blood vessels — on its face than any known mammal.

Adalatherium belongs to a lesser-known group of mammals known as Gondwanatheria. This rare group of mammals was only known from the ancient supercontinent of Gondwana and previous members were described based on a single skull and isolated jaws and teeth.

The discovery of a complete Gondwanatherian specimen now enables scientists to understand the early evolution of this strange group of extinct mammalian species in the southern hemisphere.

“Gondwanatherians were first thought to be related to modern-day sloths, anteaters, and armadillos but now are known to have been part of a grand evolutionary experiment, doing their own thing, an experiment that failed and was snuffed out in the Eocene, about 45 million years ago,” Krause said.

According to the study published in the journal Nature, the plate tectonics of Gondwana offer hints as to how this bizarre mammal evolved.

Adalatherium hui was found in rocks dated to near the end of the Cretaceous period, at 66 million years ago. Madagascar, with the Indian subcontinent attached to the east, separated from Africa over a hundred million years before and finally became isolated as an island in the Indian Ocean when the Indian subcontinent detached at approximately 88 million years ago and drifted northward,” Dr. Krause said.

“That left the lineage that ultimately resulted in Adalatherium hui to evolve, isolated from mainland populations, for over 20 million years — ample time to develop its many ludicrous features.”


Drought and human expansion are driving the platypus extinct

Woes seem to keep piling onto poor Australia: new research shows that the continent’s iconic and unique platypus is at risk of extinction.

Image credits hobvias sudoneighm / Flickr.

The intense and prolonged drought plaguing the land down under is placing enormous strain on the platypus, a new study reports. The rivers and waterways that make up this species’ natural habitat are drying up, leaving the animals stranded, the researchers explain.

Going through a lot

Although not much is known about their natural distribution or abundance (the species is nocturnal and quite shy), platypuses were once considered widespread throughout eastern Australia and Tasmania. However, new research led by members from the University of New South Wales (UNSW) in collaboration with the Taronga Conservation Society showcases that the species is in dire need of help. It is experiencing heavy pressure from both natural and man-made factors including severe drought, water resource development, land clearing, and changing climate. The team warns that action is urgently needed to save the platypus from potential extinction.

Lead author Dr Gilad Bino, a researcher at the UNSW Centre for Ecosystem Science, said action must be taken now to prevent the platypus from disappearing from our waterways.

“There is an urgent need for a national risk assessment for the platypus to assess its conservation status, evaluate risks and impacts, and prioritise management in order to minimise any risk of extinction,” says Dr. Bino.

“These dangers further expose the platypus to even worse local extinctions with no capacity to repopulate areas.”

The species is most impacted by current climate conditions and habitat destruction through land clearing and fragmentation from dams and weirs, the team reports. They further explain that platypus numbers have almost halved since European colonists first settled Australia, with local populations going extinct across 40% of the species’ range. Considering the current drought and the likely increase in drought frequency and duration in the future (due to climate change), things are only going to get worse for the platypus.

While the International Union for Conservation of Nature (IUCN) recently downgraded the platypus’ conservation status to “Near Threatened”, it remains entirely unlisted under most local jurisdictions except in South Australia, where it is considered endangered.

Apart from climate change and its associated extremes in weather and precipitation patterns, the chief threat to platypus’ long-term viability is humans, the team explains. The animals live or have traditionally lived in areas that are still experiencing extensive human development.

“These include dams that stop their movements, agriculture which can destroy their burrows, fishing gear and yabby traps which can drown them and invasive foxes which can kill them,” says study co-author Professor Richard Kingsford, also from the UNSW Sydney Centre for Ecosystem Science.

Luckily for the strange mammal, it’s not yet extinct. If preventative measures are taken now, says Professor Brendan Wintle, a study co-author from The University of Melbourne, we can turn their fortunes around. He explains that mitigating or stopping new threats (such as new dams) from impacting the species’ range can help “even a presumed ‘safe’ species such as the platypus”.

Still, the paper highlights the “urgent need” for national conservation efforts focusing on the platypus. However, they add that many other native Australian species are also threatened with extinction.

“[Preventive measures are] likely to be more effective than waiting for the risk of extinction to increase and possible failure,” Prof Wintle said. “We should learn from the peril facing the koala to understand what happens when we ignore the warning signs.”

Such measures include “increasing monitoring, tracking trends, mitigating threats, and protecting and improving management of freshwater habitats.”

Meanwhile, the team plans to continue researching the ecology and possible conservation practices for the platypus to help guide effective policy and management programs in the future.

The paper “A stitch in time – Synergistic impacts to platypus metapopulation extinction risk” has been published in the journal Biological Conservation.

What’s the difference between birds and mammals

There is a huge variety of organisms on the planet and among them, members of the animal kingdom tend to captivate us humans the most. Birds and mammals are equally remarkable, but very different.

Numerically speaking, only a handful of living organisms have skeletons and an even smaller fraction of vertebrates can regulate their own body temperature. The classes Aves and Mammalia are the only groups that have this special warm-blooded trait and that often leads people to think that birds and mammals are very related—sometimes even that birds are a type of mammal.

The truth is, however, that these two classes are very different in a lot of ways. It’s quite a bit more than the fact that we can’t fly.

“I don’t think this will work out. You’re cute but we’re just too different.” Image credits: Pixabay.

 

Defining the Problem

To start with, mammals and birds are quite different through their very definitions. The definition of a bird requires feathers, a toothless beak, wings (usually allowing for flight), and the ability to lay hard-shelled eggs. Meanwhile, mammals have hair, give birth to live young, and the females produce milk from mammary glands — the structures for which the class is named.

That being said, there are a few species that blur the definitions a little bit.

On the issue of wings, care is taken to not focus too much on the flight itself as several bird species, like penguins, have modified wings specialized for movement through water. Of course, there are also many flightless birds. Meanwhile, there are mammals that have wings and can fly, bats. At the same time, monotremes (a group including the platypus and the echidna) make things even more complicated,

Monotremes defy mammalian definitions in favor of bird-like habits. Although they’re mammals, they lay eggs rather than giving birth to live young — although it has to be said that the platypus and echidna are extremely odd mammals and we shouldn’t generalize based on them (but that is a discussion for a different article).

With those facts noted, however, even the bat’s modified forelimb doesn’t possess feathers and even after laying eggs monotreme mamas are going to feed their growing young on a milk diet.

Judging books by covers

Being humans, it’s fair to assume we get the gist of what mammals are — at least the basics.

But, very few of us have taken the time to consider the specialized form of a bird. To start with, while there is quite a variety in mammalian silhouettes, the basic structure of the bird body is fairly consistent and generally quite different from a mammal’s. Even considering only the most standard mammal form, with four similarly-sized limbs and a tail, there is a notable difference in overall structure from birds.

Image credits: Karen Arnold.

Now, let us take a closer look. If you have a pet bird, feel free to smile at it and maybe it will return an excited stare.

Some mammalian smiles sport fangs, and the bird’s mouth can be just as sharp, but it will never quite be able to give you back that excited grin—because, unlike mammals, birds don’t have any teeth. The next thing to note is the most obvious, the nice somewhat rounded feathery bodies and, where a mammal would have forelimbs, birds sport wings. But that’s okay, while they don’t have hands to hold things, if you look a little lower they are sporting a lovely pair of wrinkly clawed feet.

Birds typically possess four toes, three facing forward and one facing backward — this is the part we typically think of as the bird’s feet. However, birds are typically digitigrade meaning that they are actually walking on their toes. What we think of as their knees are actually their ankles. Canines and felines are also digitigrade but, of course, the feet look quite different. And that is just an outside look. Let us get even closer.

 

An Even Closer Look

We really need to appreciate how specially a bird must be built to live its extraordinary life in the air.

The typical internal structure of a pneumatized bird femur.

 

Because they so well adapted for flight, their internal structures can be quite different from our own. Flying requires you to be both strong and lightweight and while we may be able to accomplish the first, no amount of arm flapping will ever get us off the ground.

Since they need to be so lightweight, airborne members of the class Aves have decided to drop the weight in the densest structures in the mammalian body, their bones. Birds possess many bones which are pneumatized (hollow), with crisscrossing struts, like columns on a building, to maintain their shape and structure. Those specialized for swimming like puffins and penguins have none, however. A bit of density helps when you need to go underwater and can’t simply fall from the sky.

But, this is just one of the major ways birds and mammals differ internally to aid in flight. Another fascinating structural difference between birds and mammals is the extraordinary avian respiratory system. Flight takes energy—a lot of it. Try flapping your arms all the way up and down just ten to fifteen times, exhausting isn’t it? Birds need to do this simply to get off the ground and many bird species are not adapted for gliding so they must ­always do this to stay above ground. Hummingbirds flap their wings up to twelve times each second. How can they even keep up with all this exertion?

 

Inhalation: the air sacs expand, pulling oxygenated air from outside into the posterior sacs and deoxygenated air out of the lungs into the anterior air sac. Exhalation: The air sacs contract, the posterior sacs pushing oxygenated air into the lungs and the anterior air sacs pushing oxygen-free air away from the lungs and back up the trachea. In this way, oxygenated air is always in the lungs. Image credits L. Shyamal via Wikimedia Commons.

 

Well, unlike in mammals, birds don’t have a simple system with two neat lungs in the chest. Their respiratory system takes up a large percentage of their bodies. What moves air though bird bodies aren’t their lungs, which don’t expand and contract as ours do. Instead, they have a complex system of air sacs which move air constantly in a cyclical system far more efficient than our own.

As a point of comparison, how the mammalian system works is that we inhale and our lungs fill with air.  Deep in the lungs, there are air sacs called alveoli, covered in capillaries, in which oxygen is exchanged for carbon dioxide in the blood. When this exchange takes place to a sufficient extent we exhale, then inhale again. This system means that air must reverse direction and there is a time when our lungs are devoid of usable oxygen. This, however, is not the case with birds. For them, air goes in one direction at all times, maximizing efficiency so that the lungs always have oxygen to process.

The last thing to mention is the cloaca. While most mammals—again, monotremes are weird—possess distinct regions for defecation, urination, and reproduction (the urethra and vagina actually have distinct exit points), birds work with a one-for-all approach. For these purposes, birds have a single structure called a cloaca. Avian waste is a combination of all solid waste products, leaving their waste two-toned. Instead of liquid urea, they release semi-solid uric acid which is the reason why bird feces left on a car erodes the paint.

So, though there are mammals that can fly and lay eggs, they can never quite be as birds are. Though we haven’t gone to great detail here, birds breathe, give birth, digest and even sing using structures different from those found in mammals. Interesting and complex though mammals are, they are mostly lacking the intricate anatomy needed for flight. Though mammals and birds are all warm-blooded creatures, with four-chambered hearts, that is roundabout where the similarity between mammals and birds ends. Altogether, birds and mammals are entirely different animals.

A figure representing the 38 Kayentatherium babies found with an adult specimen. Credit: University of Texas.

Jurassic-era mammalian relative found with 38 of its babies’ skulls

Mammals today give birth to relatively few offspring with larger brains than other vertebrate species. However, this strategy wasn’t always popular. According to a new study performed at the University of Texas, a mammalian precursor no bigger than a small dog would give birth to as many as 38 babies at a time.

A figure representing the 38 Kayentatherium babies found with an adult specimen. Credit: University of Texas.

A figure representing the 38 Kayentatherium babies found with an adult specimen. Credit: University of Texas.

The 185-million-year-old creature in question, known as Kayentatherium wellesi, was a cynodont (“dog teeth”) — the closest reptile relatives of mammals

Cynodonts predate dinosaurs, first appearing in the fossil record about 260 million years ago, during the Permian period. Their descendants include marsupial and placental mammals (the ‘default‘ mammals), as well as monotremes — mammals that lay eggs instead of giving birth to live young, such as the platypus and echidna.

Despite their mammal-like skulls and jaws, cynodonts were still reptiles. K. wellesi is a prime example of just how different pre-mammalian animals could be from the lineage they spawned.

This particular fossil specimen — recently described by researchers at the University of Texas — was discovered 18 years ago in the Kayenta Formation of northeastern Arizona. In wasn’t until 2009 that Sebastian Egberts, at the time a fossil preparator at the University of Texas, recognized the excavated chunk of rock for its real worth. Protruding specks of tooth that looked like they belonged to some fish or primitive reptile later turned out to be something far more exciting.

The skull of a baby Kayentatherium, which is only about 1 centimeter long. Credit: Eva Hoffman / The University of Texas at Austin.

The skull of a baby Kayentatherium, which is only about 1 centimeter long. Credit: Eva Hoffman / The University of Texas at Austin.

Using micro-computed tomography (micro-CT) scans, researchers were able to resolve the fine features of the fossils encased in the slab without actually having to cut it open. Inside it, researchers found the fossils of a mother and the tiny jaws, teeth, skulls, and partial skeletons of its babies — no fewer than 38 individuals. The babies’ skulls were proportional to the mother’s, like miniature versions of adult K. wellesi. This is the first evidence of a mammal precursor’s babies on record.

The skulls of the cynodont’s babies are just 0.4 inches (1 cm) long, a tenth of the size of their mothers. However, modern mammal babies have disproportionately bulbous heads, that encase their big brains. Modern mammals also have much smaller litter sizes.

Credit: Eva Hoffman / The University of Texas at Austin.

Credit: Eva Hoffman / The University of Texas at Austin.

It makes sense to birth fewer offspring when switching strategies to big-brained babies — it’s simply far more energy intensive to bear and raise them. These findings suggest that a critical step in the evolution of mammals was trading big litters for big brains.

Kayentatherium is an extinct mammal relative that lived during the Early Jurassic. Credit: Eva Hoffman / The University of Texas at Austin.

“Just a few million years later, in mammals, they unquestionably had big brains, and they unquestionably had a small litter size,” study co-researcher Timothy Rowe, a professor of geoscience at the University of Texas, said in a statement.

K. wellesi’s impressive litter of 38 offspring likely developed inside eggs, akin to reptiles, or had just hatched when they perished.

Ultimately, following the development of mammalian reproduction relates to human development. This way, we can learn more about the evolutionary processes that shaped our species.

“These babies are from a really important point in the evolutionary tree,” study lead researcher Eva Hoffman, a graduate student of geosciences at the University of Texas, said in a statement. “They had a lot of features similar to modern mammals, features that are relevant in understanding mammalian evolution.”

The findings appeared in the journal Nature and were presented at the 78th annual Society of Vertebrate Paleontology meeting.

Early mammal fossil shows how the Pangaea supercontinent split up

A 130-million-year-old fossilized skull found in Utah is shaping up to be a groundbreaking discovery. Not only does it show how reptile-like mammals bridged the transition between the two groups but it also shows that Pangaea might have split up a bit slower than we thought.

Nasty little guy! The new species Cifelliodon wahkarmoosuch is estimated to have weighed 2.5 pounds and probably grew to be about the size of a small hare. Image credits: Keck School of Medicine of USC/Jorge A. Gonzalez.

Some 300 million years ago, a group called the synapsids started splitting from the reptilian and avian lineages. Synapsids are important as they include mammals, as well as their extinct relatives. The Permian-Triassic extinction event, which took place about 252 million years ago, likely created the necessary niches for other creatures to emerge, and synapsids took advantage of this. The first true mammals emerged 225 million years ago, as nocturnal insect-eating creatures. At this point, the entire landmass of Earth was clumped together into a supercontinent we now call Pangaea.

Fast forward to 130 million years ago, you have the creature you see above. Mammals were still in their early stages of evolution, but they were already starting to disperse. The new fossil finding allows researchers to better understand how this group of animal evolved and spread through Pangaea.

“Based on the unlikely discovery of this near-complete fossil cranium, we now recognize a new, cosmopolitan group of early mammal relatives,” said Adam Huttenlocker, lead author of the study and assistant professor of clinical integrative anatomical sciences at the Keck School of Medicine of USC.

Pangaea.

Using high-resolution computed tomography (CT) scans, the researchers calculated that the creature weighed up to 2.5 pounds (1.1 kg) and was probably the size of a small hare. That might seem like a small creature, but for its contemporaries, it was probably a giant. The fossil shows that the creature had large olfactory bulbs, which suggests that it had a keen sense of smell. However, its eye sockets were tiny, so it likely had poor vision. Its teeth resembled those of fruit-eating bats and could nip, shear and crush. It might have incorporated plants into its diet, but this is not clear. Its brain was also fairly small. These characteristics suggest that the animal was probably a nocturne creature, using its sense of smell to sniff out food.

The new species Cifelliodon wahkarmoosuch is estimated to have weighed 2.5 pounds and probably grew to be about the size of a small hare. Credit: Keck School of Medicine of USC/Jorge A. Gonzalez.

But most remarkably, the creature shows that at the time, mammals were already a diverse group and occupied numerous ecological niches.

“For a long time, we thought early mammals from the Cretaceous (145 to 66 million years ago) were anatomically similar and not ecologically diverse,” Huttenlocker said. “This finding by our team and others reinforce that, even before the rise of modern mammals, ancient relatives of mammals were exploring specialty niches: insectivores, herbivores, carnivores, swimmers, gliders. Basically, they were occupying a variety of niches that we see them occupy today.”

Paleontologists were also able to derive another important piece of information from the fossil. Remember how we said the entire landmass at the time was concentrated into a supercontinent? Well at one point, that continent split up, and the fossil might show that the split occurred later than it is generally thought.

The creature belongs within a group called Haramiyida, an extinct branch of mammal ancestors. Most of the Jurassic and Cretaceous fossils of Haramiyidans are from the Triassic and Jurassic of Europe, Greenland and Asia. But its particular subgroup was only known through fossils in northern Africa. So this means that during this creature’s lifetime, North American and Africa were still corrected — in other words, Pangaea was still together.

“But it’s not just this group of haramiyidans,” Huttenlocker said. “The connection we discovered mirrors others recognized as recently as this year based on similar Cretaceous dinosaur fossils found in Africa and Europe.”

Journal Reference: Late-surviving stem mammal links the lowermost Cretaceous of North America and GondwanaNature (2018). DOI: 10.1038/s41586-018-0126-y , www.nature.com/articles/s41586-018-0126-y.

10 of the Weirdest Prehistoric Creatures

Eons ago, many millennia before written history, bizarre animals roamed the Earth. The most renowned of these prehistoric creatures were the dinosaurs. Countless films have been made featuring these great reptiles. But during the various epochs of our world’s prehistory there existed many other weird and wonderful beasts. And many of them had names that were even weirder.

You will find some of these to be even more fascinating than dinosaurs. It was in this era before the dominance of mankind that life on Earth underwent a great deal of evolution. And, in fact, the Earth itself, its land masses and oceans, also evolved drastically.

Ichthyostega

Credit: Wikimedia Commons.

Credit: Wikimedia Commons.

Living in the late Devonian period, Ichthyostega was one of the earliest amphibian-like animals. It had the head and tail of a fish, and it needed to return to the water in order to breed. The feature which differentiated Ichthyostega from lobe-finned fish was the limbs. In Ichthyostega, the fins were jointed, with leg and toe bones. Ichthyostega‘s foot was odd by modern standards. It had eight toes.

Sharovipteryx

Sharovipteryx. Credit: Wikimedia Commons

Scientists believe Sharovipteryx to be an ancestral link to the winged reptiles the pterosaurs. Not classified as a true pterosaur itself, it lived in the early Triassic period over 240 million years ago. It’s in a class of its own. The creature’s remains have been unearthed at the Madygen Formation in Kyrgyzstan, Central Asia. It was a mere one foot in length. It had four appendages which seem to have possessed thin flaps of skin like wings. The two forelimbs were quite short, and the rear limbs were much longer. Some theorize this design enabled Sharovipteryx to jump with ease. Paleontologists believe its mode of transportation was more like gliding than true flying.

Longisquama

Longisquama. Credit: Wikimedia Commons.

Longisquama. Credit: Wikimedia Commons.

This creature was what has been called a diapsid. The diapsids were a reptilian subclass which eventually would evolve into the most important reptile subclass. But it began as a small group of climbing and gliding reptiles. The diapsids lived in forests located on the supercontinent Pangea during the Triassic period. Thus, Pangea was the place Longisquama would have called home.

The skeleton’s most stunning feature is a double row of long scale-like structures running along its back, forming six to eight pairs. It had one pair of scales for each of its pairs of ribs. The scales had a central hollow vein, like bird feathers. But unlike feathers, Longisquama‘s scales seem to have been formed of flat sheets and not genuine plumes. This is the creature featured in this article’s header image.

Stagonolepis

Illustration of an Aetosaur. Credit: Wikimedia Commons.

 

Stagonolepis was an aetosaur, sometimes also synonymically referred to as a stagonolepid. The Triassic world was filled with a vast variety of crocodilian species. The aetosaurs were unique among the early crocodiles since they were herbivorous. Unlike modern crocs, they were vegetarians. And Stagonolepis was one of the most prevalent of the stagonolepids at the close of the Triassic. Its long, narrow body was armor-coated, and it was capable of reaching a length of nine feet. Some artist renderings depict a creature which rather resembles a modern armadillo.

Casea

Credit: Wikimedia Commons.

Credit: Wikimedia Commons.

The caseids were another group of early reptiles. No reptile living today looked as odd as the Casea. The massive pig-like body, tiny head, overhanging upper jaw with peg-like teeth, and lower jaw with no teeth gave Casea a goofy look. These prehistoric creatures had large ribcages and were capable of reaching four feet long. Their prime occurred in the late Permian period. The term “casea” means “cheesy.”

Nothosaurus

Nothosaurus. Credit: Wikimedia Commons.

Nothosaurus. Credit: Wikimedia Commons.

Nothosaurs were related to the plesiosaurs but did not always have the best physical capabilities for coping with marine life. These reptiles did not have gills. So they had to come up to the surface for fresh air. Their long necks which would have easily been able to sneak into a school of fish were a big asset when it came to catching their prey.

Nothosaurus is one example of a nothosaur. Others such as Ceresiosaurus, Pachypleurosaurus, and Lariosaurus are also classified as nothosaurs. A good deal of our basic understanding of these marine reptiles comes from Dr. Oliver Rieppel of the Field Museum, Chicago, Illinois. Nothosaurus itself lived in the mid-Triassic, and its name’s meaning is translated as “false lizard.” Scientists have considered two possibilities as to how the animals gave birth to their offspring. The eggs were laid on the sandy shores like modern sea turtles. Or a Nothosaurus would give live birth to its young at sea just as some sharks do today.

Stegosaurus

3D Model of Stegosaurus

You know, it would be kind of unfair not to include at least one dinosaur in this list. (Although, cinema and literature have almost made them overrated.) What is so special or weird about Stegosaurus apart from the fact that it was a dinosaur? Well, it isn’t really. It is primarily included on this top ten list in order to clear up some misconceptions and mysteries surrounding its public consideration. Dwelling in the prehistoric Americas in the late Jurassic period, Stegosaurus had bony plates along its back and small ossicles covering its throat.

In relation to the creature’s mass, it has the smallest brain of all dinosaurs. Speaking of brains, here is another fun fact which some people still may have never heard. For a time, scientists were throwing out the hypothesis that a certain organ located in the tail of a Stegosaurus was responsible for performing some actions in the dinosaur’s posterior end.

However, the mass of nerves or whatever organ it may have been is no longer considered to have been a true brain. As for its renowned plates, scientists have made several speculations as to their function. They could have been for simple body defense when sparring with its peers or evading predators. They might have been for storing up heat during the day to then “burn up” after the sun went down. Or the plates even could have a means to attract mates.

Thylacosmilus

 

 

Artist Rendering of Thylacosmilus

 

Thylacosmilus obviously has the body style of a saber-toothed tiger. Interestingly enough, the animal also happened to be a marsupial. A marsupial is simply an animal which has a pouch of skin in which to carry its newborn young for a period. Modern marsupials include kangaroos and opossums. Living in the late Tertiary period, Thylacosmilus had strong, long-lived family relationships. Any restoration is far from perfect since a full skeleton has never been found.

Tsaidamotherium

Credit: Frontiers of Zoology.

Credit: Frontiers of Zoology.

Considered a pronghorn, Tsaidamotherium lived in the late Tertiary and bears some resemblance to the musk ox of present-day. Its body shape seems related to that of bovines. Tsaidamotherium was a grazing creature like many of its Miocene peers and lived on the Mongolian plains. It possessed one great cylindrical horn ontop its forehead and directly in the center. Another much smaller horn was located directly adjacent to it.

The likely function that its larger horn is supposed to have carried out was perhaps for display to attract a counterpart of the opposite gender. At first glance then, this creature could resemble the description of the mythical beast the unicorn. Dougal Dixon states this same relation in The World Encyclopedia of Dinosaurs and Prehistoric Creatures.

Megatherium

Artist Depiction of Megatherium. Credit: Wikimedia Commons.

 

As the name implies, this brute was a pretty large mammal. It was actually a giant ground sloth related to modern sloths. An inhabitant of South America during the Quaternary period, an adult standing on its hind legs could reach a height of 20 feet. Megatherium was previously regarded as a slow tree ripper. But recent studies show that its great claws might have been used for stabbing and killing. If this was the purpose of its claws, it would make the giant sloth the largest predator of the South American plains.

This rat-like creature is the earliest ancestor of mankind

Fossil teeth belonging to a small rat-like mammal were discovered in the coast of Dorset, in England. Paleontologists believe that the animal is the first known creature belonging to the line that led to human beings.

Juramaia, the mammal ancestor. Fossil found in a previous study in China. Composite: Zhe-Xi Luo/Mark Klingler/Carnegie Museum of Natural History.

A sweet tooth

Researchers from the University of Portsmouth have been analyzing that particular coast for quite a while now, but, ironically, it was an undergrad who made the impressive finding. Grant Smith was sifting through previously extracted samples from early Cretaceous rocks, in the hopes of finding something interesting for his dissertation. At some point, Grant realized he found something remarkable — not one, but two teeth from a small mammal — but he wasn’t quite sure what to make of it, until Dr. Steven Sweetman, a research fellow at the university who led the research, stepped in. Sweetman was contacted by Dave Martill, Grant’s supervisor.

Sweetman realized that the teeth are evolved enough to belong to an advanced mammal, and it didn’t take long for him to understand what he was dealing with. The animal from which the teeth originated turned out to be the earliest ancestor of an extremely diverse group of mammals, ranging from blue whales to pygmy shrews and humans.

“The teeth are of a type so highly evolved that I realised straight away I was looking at remains of Early Cretaceous mammals that more closely resembled those that lived during the latest Cretaceous – some 60 million years later in geological history,” he says. “In the world of palaeontology there has been a lot of debate around a specimen found in China, which is approximately 160 million years old. This was originally said to be of the same type as ours but recent studies have ruled this out.”

“That being the case, our 145 million year old teeth are undoubtedly the earliest yet known from the line of mammals that lead to our own species.”

Evolving mammals

This is a reconstruction of the small, rat-like creatures that lived 145 million years ago in the shadow of the dinosaurs. Dr Mark Witton, palaeo-artist, University of Portsmouth.

Mammals emerged early in the Triassic age, around 200 million years ago (between 225 and 167, depending on which study you choose to believe). They emerged around the same time as the dinosaurs. However, until the end of the Cretaceous, mammals lived in the shadow of the mighty dinosaurs. The catastrophic event that brought the end of the Cretaceous (and the Mesozoic) wiped off the non-avian dinosaurs but allowed some mammals to prosper. Several mammal groups survived and diversified. Among these groups, there are monotremes (platypus and echidna), the marsupials (such as kangaroos and koalas), the multituberculates (which then died off around 35m years ago), and the eutherians — the so-called placental mammals. Out of the lot, eutherians are the most successful group on Earth so far, and these fossils represent the earliest eutherian we know of. It’s not easy to know when they, as a group, originated, since the fossil record is often lacking.

The animal itself was likely a small, nocturnal, furry creature, somewhat similar to today’s rodents. It may have eaten insects and plants.

“The teeth are of a highly advanced type that can pierce, cut and crush food. They are also very worn which suggests the animals to which they belonged lived to a good age for their species. No mean feat when you’re sharing your habitat with predatory dinosaurs!”

Two fossil teeth of the Purbeck Mesozoic mammals. These Jurassic mammals are ancestors to placental mammals, and are oldest of their kind found in Europe. Photograph: SCS/Sweetman et al. 2017.

It’s uncommon for such fossil to be found at all, especially in Great Britain, which makes Grant’s finding even more impressive.

“Steve made the connection immediately, but what I’m most pleased about is that a student who is a complete beginner was able to make a remarkable scientific discovery in palaeontology and see his discovery and his name published in a scientific paper,” Martill adds. “The Jurassic Coast is always unveiling fresh secrets and I’d like to think that similar discoveries will continue to be made right on our doorstep.”

To give things an extra-British spin, one of the creatures was named Durlstotherium newmani — not after a particular trait or a famous person, but rather after Charlie Newman, the landlord of the Square and Compass pub in Worth Matravers, close to where the fossils were discovered.

Journal Reference: Steven C. Sweetman, Grant Smith, and David M. Martill. Highly derived eutherian mammals from the earliest Cretaceous of southern BritainActa Palaeontologica Polonica in press available online 07 Nov 2017 doi:https://doi.org/10.4202/app.00408.2017

The American pika is being killed off by climate change

The American pika, “one of the cutest animals” in the country, is feeling the heat as a hotter, drier summers threaten its habitat.

I brought you a gift! Don’t kill us please.
Image credits NPS Climate Change / Flickr.

Whole populations of the tiny rabbit-like mammal known as the American pika are vanishing from the animal’s historic range in the mountainous areas of the western USA. The main culprit seems to be loss of habitat powered by climate change, according to findings by the US Geological Survey. After observing the animal from 2012 to 2025, the Survey found that the pika’s range is shrinking in southern Utah, north-east California, and in most of Nevada, parts of Utah, Oregon, Idaho and California — almost the entire Great Basin.

The study provides more conclusive evidence to the effect of global warming on the tiny mammal, building on earlier research which found that climate change was at least partly contributing to the animal’s decline. It did not measure how many total American pika still exist, but studied several areas where it has historically roamed eating grass, weeds and wildflowers. While the pika overall seems to be struggling, the study found that it’s thriving in a few places — most notably the Columbia River Gorge in Oregon and Grand Teton National Park in Wyoming.

But don’t rest easy just yet. The American pika (all species of pika are extremely cute) has completely disappeared from the Zion National Park in Utah, despite sightings as recently as 2011. In the nearby Cedar Breaks National Monument, the animal was nowhere to be seen on three-quarters of their historical range according to Erik Beever, a research ecologist with the USGS and lead author of the study. In north-eastern California, the pika was only found in 11 of the 29 sites of confirmed habitat. In the Great Basin, which stretches from Utah’s Wasatch mountains in the east to the Sierra Nevada and Cascade mountains in the west, the population is down about 44% compared to historical records.

“The longer we go along, the evidence continues to suggest that climate is the single strongest factor,” said Beever.

Essentially, the pika are dying of exposure in their own burrows, and it’s all because of us.

The pika are tailored to live in a very specific conditions, and are very sensitive to changes in temperature and humidity. The animals make their home on mountain slopes, known as talus, where they search for open spaces in the ground to burrow. But the talus fields are becoming a much hotter, drier place in summer and a very harsh place in winter, with less snowfall to insulate the critter from cold.

The historical range of the American Pika. The animal resides in cool, moist microhabitats on high peaks or watercourses. Distribution data from IUCN Red List.
Image credits Wikimedia user Chermundy.

The study is the latest argument in the long-running efforts of wildlife advocacy groups, which have been trying to get the pika on the endangered species list for a few years now. In 2010, the US Fish and Wildlife Service rejected one such request, citing that not all populations are declining. The latest petition was made this April by a high school student in New York state. This situation isn’t singular — ZME Science reported the other day that the average waiting time for a species to make the Endangered Species list is 12 years, or six times more than the designated timeline. 

A preliminary ruling is due this September, but the new study won’t be taken into account because the agency’s staff only takes into consideration information submitted with the petition, said Serena Baker, a USFWS spokeswoman. Hopefully, the ruling will be in favor of the pika. But, should the USFWS turn it down, the study should help future petitions to have the animal declared endangered, as the study confirms that climate change is putting the animal at real risk, says endangered species director at the Center for Biological Diversity in Arizona Noah Greenwald. Without such a ruling, future generations of mountain enthusiasts may not have the chance to see these lovable critters on their hikes, he adds.

“It’s gotta be one of the cutest animals in North America. It’s like a cross between a bunny rabbit and prairie dog,” Greenwald said. “Part of what makes our world interesting is the diversity of animals and plants that you can see when you go to different species.”

President Barack Obama is a big supporter of the issue. During his Yosemite National Park speech in June this year, he talked about the damage climate change is inflicting on the country’s national parks. He said the pika was being forced further up-slope at Yosemite to escape the heat.

“It’s not that they’ve just moved, they are gone all together,” Beever said.

 

Bramble Cay melomys. Credit: Wikimedia Commons

Great Barrier Reef rodent becomes first extinct mammal at the hand of climate change

Bramble Cay melomys. Credit: Wikimedia Commons

Bramble Cay melomys. Credit: Wikimedia Commons

Great Barrier Reef’s only endemic mammal, the Bramble Cay melomys, is now officially extinct, scientists say. The rat-like rodent occupied a very confined habitat spanning an area no larger than a football field called Bramble Cay, a minuscule atoll in the northeast Torres Strait, Australia. Although pressured by human hunting and competition with other species, what ultimately killed off the species were surging sea waters and rising tides triggered by man-made climate change — the first mammalian species wiped out of the evolutionary history books in this manner.

The small coral cay where the rodent used to live was just 340m long and 150m wide, sitting only three meters above the sea level, off the north coast of Queensland, Australia. When Europeans first settled Queensland around 1845, records show they proceeded hunting the ‘rats’ with bow and arrow. By 1978, only a couple hundred specimens were recorded during field surveys, which were quite accurate given the minute area. Around this time the rodent was listed as endangered.

The last melomys were sighted in 2009, and despite extensive surveys in the area, no specimen was found even to this day. There might still be some odd rodents lurking in some crevices, but that seems unlikely given that their habitat is often flooded nowadays, which left them without food, shelter or any kind of livelihood. Natalie Waller and Luke Leung from the University of Queensland now claim with high confidence that the melomys are extinct, in a recent review.

“For low-lying islands like Bramble Cay, the destructive effects of extreme water levels resulting from severe meteorological events are compounded by the impacts from anthropogenic climate change-driven sea-level rise,” the authors said in their report.

“Significantly, this probably represents the first recorded mammalian extinction due to anthropogenic climate change,” they added.

Unfortunately, this might just be one of the first in many yet to come. A 2013 report notes 17 percent — one in six — of threatened and endangered species are at risk from rising sea levels in the United States alone. As for Australia’s coral reef, things are pretty bleak. Half of the Northern Great Barrier Reef is now dead at the hand of global warming which triggered massive coral bleaching.

Brilliant GIF shows how Humans, Birds and Insects Breathe

Three different ways to breathe:

Mammals, birds and insects breathe in different ways, as exemplified above. Humans, as mammals, inhale by moving the diaphragm to lower the air pressure in the chest cavity and pull air into the lungs. The human chest cavity is always at a lower pressure than the outside environment.

Birds on the other hand, have air sacs that reach into the bones, and have no diaphragm, respiratory infections can spread to the abdominal cavity and bones. Bird lungs do not expand or contract like the lungs of mammals. Unlike in mammals, air flows only in one direction and this allows birds to take in oxygen even as they exhale.

Insects have no lungs. Instead of lungs, insects breathe with a network of tiny tubes called tracheae. Air enters the tubes through a row of holes along an insect’s abdomen. The air then diffuses down the blind-ended tracheae. Since the biggest bugs have the longest tracheae, they should need the most oxygen to be able to breathe. Grasshoppers use different breathing methods when they are resting, alert, hopping or flying. Here, an alert grasshopper is depicted.

Credits: Eleanor Lutz

 

colugo

Colugo (flying lemur): the most accomplished and cutest mammalian glider

It seems like us mammals were never meant to fly. Sure, bats can fly, but that’s kind of it. Even so, some mammals have learned alternative means of skipping at an altitude: gliding (feather-tailed possums, sifaka) or parachuting (cats). Yes, cats parachute, but enough of them. Chances have it you’ve seen on average 17 cats already since morning. Today’s post is about a gliding mammal that’s in much more need of attention: the adorable colugos.

A colugo baby. Image: Flickr

A colugo baby. Image: Flickr

Also called a  flying lemur, despite it’s not a lemur, nor can it fly. The colugo’s  distinguishing hallmark is a gliding membrane (patagium) surrounding almost the entire body margin. This  stretches from its face to the tips of its digits all the way back to its tail, even between fingers and toes (hence the name ‘mitten-gliders’). “Geometrically, it has the greatest surface area that you can have between those limbs without actually evolving an entire wing like bats did,” said conservation biologist Jan Janecka of Duquesne University.

The most accomplished mammalian glider. Photo: Norman Lim

The most accomplished mammalian glider. Photo: Norman Lim

This long patagium makes them fantastic gliders. They’re so good, that mums glide their fragile-boned young along from tree to tree. And as if their long cape wasn’t enough, the colugo has an unique set of dentures: the lower incisors are shaped like combs. Colugos are strict herbivores, predominantly eating young leaves from many tree species, and in the gastrointestinal tract the caecum is greatly enlarged.

Colugo

Source: ImgKid

Two colugo species exist in the world, both confined to evergreen tropical rainforests of South-East Asia:  Galeopterus variegatus (Malayan colugo, formerly known as Cynocephalus variegatus) and Cynocephalus volans (Philippine colugo). Elusive and shy, there’s little documentation pertaining to their habitat or way of life. Important genetic research, however, was carried out in the last couple of years. Apparently, classifying the animal is no easy feat.  Previously, a sister-group relationship between colugos and primates seemed likely, but most recently researchers suggest  colugos and tree-shrews constitute a monophyletic group. Such a group, labeled Sundatheria, was, for example, indicated by cladistic analysis of dental features, and several authors have reported molecular evidence linking colugos to tree-shrews.

 

age of dinosaurs

Earliest tree-clinging and burrowing mammals show they weren’t afraid of dinosaurs

Although mammals surfaced only 20 million years after the first dinosaurs evolved, there’s a general consensus that mammals were shadowed and reclusive in the face of dinosaurs, seeing how they were the dominant animals on the planet back then. As such, early mammals are thought to have been mostly nocturnal with minimal interaction with dinosaur environments, occupying very limited ecological niches. This conventional thinking might be toppled by recent findings made by Chinese paleontologists who discovered two highly sophisticated early mammals each at least 160 million years old: the first tree-clinging mammal and the first burrowing mammal. These creatures munched on the same plants dinosaurs did, proving they seemingly coexisted in the same ecological framework.

Mammals and dinosaurs

age of dinosaurs

Early mammals were surprisingly adapted and sophisticated at times when dinosaurs were at a their prime. The image shows the tree clinging Agilodocodon (top), the swimming Castorocauda (in the water) and the burrowing Docofossor (bottom). Image: University of Chicago

Zhe-Xi Luo, a renowned Chinese paleontologist now affiliated with the University of Chicago, first sent waves in the paleontology community when he first reported the discovery in China of a 164-million-year-old docodont named Castorocauda lutrasimilis, which apparently not only swam but might also have eaten fish. This was the first time such a mammal was discovered, an unlikely creature by the dinosaur overlord dictum. Although unknown before the Middle Jurassic, and therefore not among the oldest known mammals, docodonts are considered to be one of the most archaic mammalian groups. Their remains were first discovered more than a century ago in the Late Jurassic Morrison Formation of Wyoming and Colorado, where they are found together with the bones of giant sauropod dinosaurs. Most docodonts are known solely from the dentition, which includes complex, broad cheek teeth. The teeth of these shrew-sized mammals – a cross between a rat and a squirrel – showed they were well adapted for shearing, crushing and grinding plants, but also other foods, as Castorocauda lutrasimilis shows.

Now, Luo and fellow paleontologist Qing-Jin Meng of the Beijing Museum of Natural History published two papers in Science which document two new docodonts. One, called Agilodocodon scansorius, is the earliest known tree-climbing mammal. It had specialized teeth which likely helped it feed on tree sap. The other is 160-million-year-old Docofossor brachydactylus, which judging from its shortened, shovel-like paws is considered the first burrowing mammal.

The early mammal records were found by farmers in the fossil-rich shale outcrops called the Tiaojishan Formation in northeast China.

The delicate fossils were encased in shale slabs. To be sure they wouldn’t ruin them, the paleontologists used CT scans – the same used to image bones and soft tissue in the human body – to image the fossils in high resolution. The images suggest Agilodocodon scansorius (meaning “agile docodon” with a scansorial, or climbing, adaptation) was about 13 centimeters from head to tail and weighed about 27 grams, roughly the size of a house mouse. Docofossor brachydactylus (“Doco” for docodont; “fossor” for fossorial, or digging, adaptations; and “brachydactylus” for short, broad fingers) had a striking resemblance to the modern African golden mole, a burrowing mammal that lives underground. It was about 7 centimeters long and weighed about 16 grams, the size of a small shrew, and had a wide stance typical of burrowing animals, according to Michael Balter writing for Science.

Some 160 million years ago when these mammals lived, dinosaurs were the dominant genus on Earth. Only after they went extinct 65 million years ago did mammals catch ground and really started to diversify, occupying the now empty ecological niches. From rat-sized animals, mammals grew tremendously in size. Examples include Megatherium, a giant ground sloth found in South America which weighed up to four tons and was twenty feet (6m) in length from head to tail.

However, considering how sophisticated these early mammals were, it is likely that the evolutionary groundwork for this surprising diversity and adaptiveness among early mammals was laid down much earlier than researchers suspected. Luo is cautious, however. He’s careful to note that while these fascinating clinging and burrowing mammals seem to counter the stereotypical image of cowering mammals, it is very much true that mammals were only at a fraction of their potential during the dinosaur age.

New fossils throw mammalian family tree into disarray

A fossil of a small, forest-floor-dwelling animal called Megaconus puts a big question mark on the evolution of mammals – it suggests that its group predated animals, while another one, from its tree dwelling ‘cousing’ Arboroharamiya shows the group belonged to the mammals.

megaconus

Megaconus

The two fossils have paleontologists scratching their heads, not knowing where to place them in the family tree. A team analysing one fossil claims that the group belongs in mammals, but researchers looking at the other propose that its evolutionary clan actually predates true mammals. The situation requires more analysis, and, as both teams agree, more fossils.

Interestingly enough, both species were previously unknown to science; both are members of the haramiyids, a group of animals that first appeared around 212 million years ago first studied in the 1840s. Until now, the only available fossils of this group of animals were isolated examples of distinctive teeth and a single jawbone. But both fossils described today include not only the distinctive teeth, but also vertebrae and bones from the limbs, feet, and even tails.

“It’s remarkable, for such an incredibly obscure group, to have two fairly complete skeletons pop up at the same time,” says Richard Cifelli, a vertebrate palaeontologist at the Oklahoma Museum of Natural History in Norman, who co-authored a related News & Views3. “These new fossils change everything.”

Fossil no. 1

The first fossil lived about 160 million years ago in (what is today) Northern China, being well adapted for life in the trees; it easily climbed and had exceptionally long digits. Its bones also suggest it had a tail.

After investigating the fossil and its evolutionary relationships, the team concluded that the animal is well in the mammal tree, and suggested that mammals, as a group, first appeared somewhere between 228 million and 201 million years ago.

Arboroharamiya probably preferred feeding on seeds, but it was omnivorous.

Fossil no. 2

arborohayama

The second fossil was found in today’s Mongolia and probably lived on the forest floor: in each of its rear legs, the two lower bones were fused together at the top and bottom, similar to those of the modern armadillo.

Unlike Arboroharamiya, ground dwelling Megaconus and its evolutionary relationships suggest that the common ancestor of all extant mammals lived about 180 million years ago — and that the haramiyids, including Megaconus, branched away from the family tree some 40 million years before the true mammals evolved.

But here’s the kicker – neither one of the two creatures and interpretations fills in with the current mammal family tree! Megaconus and Arboroharamiya may or may not be mammals, and they may or may not be related – but they’re really shaking a big chunk of what paleontologists thought they knew about mammals.

Mammals Can ‘Choose’ Sex of Offspring, Study Finds

An extremely challenging study published by a team of researchers from the Stanford School of Medicine claims that through some unknown mechanism mammals can bias  the sex of their offspring in order to win the genetic lottery and produce extra grandchildren.

The holy graal of modern evolutionary biology

fertilizationAfter analyzing 90 years of breeding records from the San Diego Zoo, the researchers were able to prove (or at least give a strong indication of) one of the most debated theories in evolutionary biology – mammals rely on some unknown physiologic mechanism to manipulate the sex ratios of their offspring, as part of a subtle, but highly adaptive evolutionary strategy.

“This is one of the holy grails of modern evolutionary biology — finding the data which definitively show that when females choose the sex of their offspring, they are doing so strategically to produce more grandchildren,” said Joseph Garner, PhD, associate professor of comparative medicine and senior author of the study, published July 10 in PLOS ONE. The results applied across 198 different species.

Female power… for the sons!

In order to reach this conclusion, the team assembled three-generation pedigrees of more than 2,300 animals and found that grandmothers and grandfathers were able to strategically influence the sex of their offspring, choosing to give birth to sons if this seems more likely to reward them with more high quality offspring. The process is thought to be largely controlled by females.

“You can think of this as being girl power at work in the animal kingdom,” he said. “We like to think of reproduction as being all about the males competing for females, with females dutifully picking the winner. But in reality females have much more invested than males, and they are making highly strategic decisions about their reproduction based on the environment, their condition and the quality of their mate. Amazingly, the female is somehow picking the sperm that will produce the sex that will serve her interests the most: The sperm are really just pawns in a game that plays out over generations.”

The study builds on a theory initially proposed in 1973 by scientists Robert Trivers and Dan Willard, founders of the field of evolutionary sociobiology. They challenged the traditional belief, that the sex of mammal offspring is random, claiming that the odds arent 50-50, but rather hypothesized that mammals are selfish creatures with a significant control over their body. Thus, parents in very good conditions, more healthy and better adapted will often choose to produce sons whose inherited strength and bulk could help them better compete in the mating market – giving them a significant avantage in the “race for grandchildren”.

New Sumatran Tigers

“This paper was a huge leap forward, providing the first suggestion that the idea might work in mammals,” Garner said. “But because it relied on data from only two generations, it couldn’t show whether females that produced more sons also gained more grandchildren from those sons.” In fact, this key prediction of the hypothesis has remained untested, because complete three-generation pedigrees are so hard to obtain in the wild, Garner said.

Daughters and sons

The researchers ended up with a pool of 1,627 granddams (female grandparents) and 703 grandsires (male grandparents) for whom they did a complete report that went back 3 generations. They analyzed all major mammal groups: big carnivores, primates, cloven-hoofed and odd-toed grazing animals. They results showed that when females produced mostly sons, those sons had 2.7 times more children per capita than those whose mothers bore equal numbers of male and female offspring. This raises some pretty interesting questions.

“The question is, within each species, among females who had more sons, did those sons do better in terms of producing more grandchildren per capita? And the answer is yes,” Garner said. “Females are choosing and being very Machiavellian about it. They’re doing it for their own benefit.”

The same was true for grandsires, though it’s unlikely that they can control this process.

“A grandfather producing more male offspring also has more success. But that could be entirely determined by the female,” as she may be deciding the sex ratio to produce based on the quality of the male, Garner said.

Apparently – mating and ensuring offspring are like gambling, and sons are the “high risk, high reward” bet, while daughters are safety.

“I’m gambling on how many grandchildren I’m going to produce. If I’m producing nothing but daughters, I’m making a safe bet — I’m going to make the average.”

“Think about lions,” Garner said. “Most male lions don’t reproduce. There may be 10 or 15 females but only one male that fathers everybody. The same is true with baboons. There is one alpha male. If you are the parent of that harem-holding male, then you have hit the genetic jackpot because he might produce tens or hundreds of offspring. If you have a bachelor male, who never produces offspring, he produces zero. So males are a high-risk, high-payoff bet. Who would take the bet unless they knew they could rig it?”

But how is it that mammals control this? The honest answer is – we don’t know. The only half decent theory is that females can somehow detect ‘male’ and ‘female’ sperm due to their different shapes and decide on which they ‘let pass’. But how they control this remains a total mystery.

As for any possiility of this happening, it’s already suggested that humans likely adapt their offspring sex-ratio in response to social cues.

Scientific article

The earliest placental mammal probably ate insects, and weighed no more than a few hundred grams. (c) Carl Buell

Earliest mammal pinpointed suggests the ancestry expanded after dinosaurs died off

For the past twenty years there’s been a debate whether the mammal explosion that eventually made the class of animals dominant on Earth happened before or after the end of the dinosaur reign. Scientific papers and various evidence supporting both views have surfaced along the years, but a recent massive study conducted by a collaborative team of scientists may have finally sealed this debate – according to their findings, the oldest placental mammal appeared some 200,000 years after the extinction event that saw the end of the dinosaurs. It was a rat-sized, insect-eating mammal.

Typically, paleontologists derive ancestry and links between species by studying phenotype – diet, lengths of limbs, shapes of teeth, length of fur if any, and so on. This is an extremely laborious process which implies manually measuring bones , detecting features and comparing anatomy with other species in order to move down the evolutionary tree – a process that hasn’t changed too much since the XIXth century.

“Anatomy and research in palaeontology had a very 19th Century veneer to it – that we would sit in small groups in a lab with a fossil describing it,” said lead author of the study Maureen O’Leary of Stony Brook University in New York, US.

“That is a very effective and important part of what we do, but by trying to bring this into the 21st Century and using new software, we were able to really band together as a group of experts and tackle a much larger problem,” she told BBC News.

Meet your oldest ancestor

The earliest placental mammal probably ate insects, and weighed no more than a few hundred grams. (c) Carl Buell

The earliest placental mammal probably ate insects, and weighed no more than a few hundred grams. (c) Carl Buell

The scientists gathered more than 4,500 details of phenotype from 86 different species that are around today, and from 40 fossils of extinct animals. In addition  12,000 detailed images and genetic information for all of the current species have been used and compiled in a massive database that is ten times larger than the nearest runner-up .

Still, we’re in the XIX century and besides making good use of genetics to establish and compare similarities across species, the researchers also employed a software that helped them put the pieces of the puzzle together. In the end, by noting which traits have been preserved down the lineage and how they are expressed, the researchers found that all placental mammals today – no marsupials (kangaroo) or egg laying mammals (platypus) – sprung from a common ancestor some 200,000 years after the dinosaurs went extinct. At its own end, this placental mammal most likely branched from  older marsupial-like mammal types in South America and North America, rather than in Africa, given the geologic timing of events.

After the dinosaurs died off, a lot of open space and evolutionary niches were left right for the taking, and the mammals didn’t think twice about it. So, roughly 24 million generations later mammals went from mouse-size to elephant-size.

“With regards to evolution, it’s critical to understand the relationships of living and fossil mammals before asking questions about ‘how’ and ‘why,’ ” says Jonathan Bloch of the Florida Museum of Natural History.

“This gives us a new perspective of how major change can influence the history of life, like the extinction of the dinosaurs – this was a major event in Earth’s history that potentially then results in setting the framework for the entire ordinal diversification of mammals, including our own very distant ancestors.”

This common ancestor hasn’t been actually found, fossils and all, but based on the same information that allowed them to pinpoint the age, the scientists were also able to make some guesses on to how this animal might have looked like. By mapping the traits most strongly supported by the data, the researchers believe the oldest placental mammal ancestor had a two-horned uterus, a brain with a convoluted cerebral cortex and a placenta in which maternal blood came in close contact with membranes surrounding the fetus, as in humans.

Findings were documented in the journal Science.

Dracula mammal lived with the dinosaurs in Transylvania

Well it may be a bit of overreaction, but with the Halloween and all, you just have to call it: 70 million year old mammal had long, oversized, blood-red teeth, scurrying at the feet of dinosaurs. The discovery of a new skull now gives new insight into his diet and habits.

Barbatodon transylvanicus lived in what is today Transylvania, Romania, but it wasn’t much bigger than an average rat, belonging to a well known group of mammals that outlived the dinosaurs by over 30 million years, the little rascals they are. Thierry Smith of the Royal Belgian Institute of Natural Sciences in Brussels and Vlad Codrea of the University of Babes-Bolyai in Romania explained that its strange, blood red tooth enamel actually contains 3 per cent iron, which made it more resistant to abrasion, while also giving it this eerie look.

Now, just because you lived during the dinosaur period doesn’t mean it’s all bad for you – on the contrary. At the end of the late Cretaceous, approximately 65.5 million years ago, a massive extinction event took place, virtually eliminating any dinosaur species, as well as many others. The entire biosphere suffered from this event, but some species took it much harder than others. For plants it was a dramatic period, as energy from the Sun was decreased due to atmospheric particles blocking the sunlight. Many animals which relied on these plants for food also perished as a result, and consequently, even top predators like the T-Rex fell. Some paleontologists went as far as saying that at the end of the extinction period, there were no purely herbivorous or carnivorous mammals or birds: all the species that survived adapting to a more omnivorous diet. Mammals and birds which survived the extinction fed on plants, insects, larvae, worms, and snails, which in turn fed on dead plant and animal matter.

But mammals like the Barbatodon transylvanicus indirectly profited from this event, because it was the exact window of opportunity they needed. Their food of preference was insects, as suggested by the massive teeth, which were used for crushing the bugs. The species went on to live another 30 million years after the extinction.

Sabre tooth ferret like mammal unearthed in Patagonia

A recent discovery of an extinct mammal called Cronopia promises to help scientists trace the ascent and spread of mammals.

Even though it looks rather taken from a cartoon than from reality, Cronopio dentiacutus was the real deal. It had a long snout, huge sharp canines, and a powerful set of jaw muscles to bite and chew its prey.

The animal lived 94 million years ago, well into the age of the dinosaurs, in today’s South America, and it had quite a lot of competition in the fight for survival. Its fossilized remains were found in Patagonia by a team of researchers led by Guillermo Rougier of the University of Louisville; the results were published in Nature.

The finding is extremely important because mammal fossils from the age of the dinosaurs are extremely rare, and they yield valuable information. Even when they are found – it is usually just jaws or some scattered bones; full skeletons are indeed extremely rare.

“Our knowledge of the first two-thirds of mammalian evolution, which extends from the first record of a mammal about 220m years ago to the end of the Cretaceous period 65.5m years ago, is therefore terribly incomplete,” wrote De Muizon.

Mammals, half way extinct??

The previous 5 mass extinctions wiped out more than three quarters of the world’s animals, and if things continue to move in the same way, the same thing will happen in North America, according to a University of California, Berkeley, and Pennsylvania State University analysis.

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Numerous scientists have warned that the direction things are moving in is way more dangerous than believed by most authorities, and the combined effect of habitat destruction, global warming and environmental degrading will lead to a global catastrophe, yet fully accurate estimations were not done, due to the inability to compare species that live today with species that live in the past. However, the researchers from the above mentioned universities teamed up in order to overcome that obstacle, and using data from three catalogs of mammal diversity they were able to conclude the study.

“The optimistic part of the study is that we haven’t come all that far on extinction in the past 10,000 years,” said co-author Anthony Barnosky, UC Berkeley professor of integrative biology. “We have this pulse when humans had their first effect about 13,000 years ago, but diversity has remained pretty steady for about 10,000 years.”

In the last 100 or so years, however, “we are seeing a lot of geographic range reductions that are of a greater magnitude than we would expect, and we are seeing loss of subspecies and even a few species. So it looks like we are going into another one of these extinction events.”

But there are still things that can be done.

“I’m optimistic that, because we haven’t lost those species yet, if we redouble our conservation efforts we can stem the tide of extinctions and have those species around in the future,” he added.

Double our efforts to conserve species – do you really see that happening? I would be absolutely thrilled to see this happening, or even a less significant intensification, but it makes me sad to think how unlikely this is. Just this month massive distress calls were launched about koalas and siberian tigers. The thing is, we are responsible for this, and this is why it’s our responsibility to do something. Everytime mammals (and not only) had such problems, they would eventually get over it, but all that changed ~13.000 years ago, when humans entered the scene.

“The bottom line is, mammals in general were able to deal with these changes in the past. Only when humans arrive do the numbers fall off a cliff.”

That’s something to think about when you go to sleep at night, or when you’re complaining about bad weather.

Blue whales singing lower every year, baffled scientists say

Blue whales are not only the biggest living creatures in the world right now, but the biggest ever to have ‘walked’ the face of the earth; they’re also the loudest for that matter. After recovering from near extinction in the beginning of the 20th century, blue whales are finally getting a part of the respect they deserve.

However, researchers cannot understand what is causing these majestic creatures to ‘sing’ at lower frequencies year after year. No one is fully sure of all the uses of the blue whale songs, but it’s known they are used to communicate and as a mating ritual. However, ever since the 1960s, the frequencies which these giants use are getting lower and lower, without anybody being able to give an explanation.

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Of course, some theories have emerged, the two most likely being that it’s a direct result of the water pollution or a sign that an almost extinct population is recovering. Mark McDonald, president of Whale Acoustics, a company that specializes in recording the songs of blue whales (yeah, really) originally thought the cause could be noise pollution caused by intensified traffic; however, if this would be the case and they would want to make themselves heard louder, they would use higher, and not lower frequencies. This may be a bit weird because generally lower frequency transmissions are used for long distances, but mister McDonald explains:

Across the frequencies of blue whale song, the underwater transmission losses are nearly the same regardless of frequency. It is absorption which is the primary cause of frequency dependent transmission losses, rather than dispersion in this case, and the absorption loss only begins to become significant when ranges reach thousands of kilometers. Theory tells us the whales can produce higher amplitude songs at higher frequencies, based on given lung volume.

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Another possible reason could be a change in the mating rituals. Scientists have long known that only male blue whales sing, and larger (which are usually more mature) specimens sing at lower frequencies. The hypothesis is that the younger guys are trying to emulate the older ones in order to attract females (that seems familiar). Either way, there are many we have yet to understand about the way these marine mammals act. The only good thing is that the blue whale populations is nearing a normal limit; let’s set this as an example for other species too, instead of treating them with less care now that they’re not on the brink of extinction anymore.