Swimming beaver under water video


This 15 November 2018 video shows a swimming beaver.

Diver Jos van Zijl made this video in the Netherlands.

Advertisements

South American rodents’ ancestry


This 6 November 2018 video says about itself:

When Rodents Rafted Across the Ocean

The best evidence we have suggests that, while Caviomorpha originated in South America, they came from ancestors in Africa, over 40 million years ago. So how did they get there? Thanks to Ceri Thomas for the Josephoartigasia monesi reconstruction.

Oldest flying squirrel fossil discovered


This video says about itself:

9 October 2018

At Can Mata Landfill (els Hostalets de Pierola, Catalonia, Spain), scientists discovered fossil remains of the oldest-known flying squirrel – Miopetaurista neogrivensis. Based on the reconstructions, researchers estimate a weigh between 1.1 and 1.6 kilos, length of almost one meter and a wingspan around 40 centimeters.

From eLife:

Oldest fossil of a flying squirrel sheds new light on its evolutionary tree

October 9, 2018

The oldest flying squirrel fossil ever found has unearthed new insight on the origin and evolution of these airborne animals.

Writing in the open-access journal eLife, researchers from the Institut Català de Paleontologia Miquel Crusafont (ICP) in Barcelona, Spain, described the 11.6-million-year-old fossil, which was discovered in Can Mata landfill, approximately 40 kilometers outside the city.

“Due to the large size of the tail and thigh bones, we initially thought the remains belonged to a primate“, says first author Isaac Casanovas-Vilar, researcher at the ICP. In fact, and much to the disappointment of paleoprimatologists, further excavation revealed that it was a large rodent skeleton with minuscule specialised wrist bones, identifying it as Miopetaurista neogrivensis — an extinct flying squirrel.

Combining molecular and paleontological data to carry out evolutionary analyses of the fossil, Casanovas-Vilar and the team demonstrated that flying squirrels evolved from tree squirrels as far back as 31 to 25 million years ago, and possibly even earlier.

In addition, their results showed that Miopetaurista is closely related to an existing group of giant flying squirrels called Petaurista. Their skeletons are in fact so similar that the large species that currently inhabit the tropical and subtropical forests of Asia could be considered living fossils.

With 52 species scattered across the northern hemisphere, flying squirrels are the most successful group of mammals that adopted the ability to glide. To drift between trees in distances of up to 150 metres, these small animals pack their own ‘parachute’: a membrane draping between their lower limbs and the long cartilage rods that extend from their wrists. Their tiny, specialised wrist bones, which are unique to flying squirrels, help support the cartilaginous extensions.

But the origin of these animals is highly debated. While most genetic studies point towards the group splitting from tree squirrels about 23 million years ago, some 36-million-year-old remains that could belong to flying squirrels have previously been found. “The problem is that these ancient remains are mainly teeth”, Casanovas-Vilar explains. “As the dental features used to distinguish between gliding and non-gliding squirrels may actually be shared by the two groups, it is difficult to attribute the ancient teeth undoubtedly to a flying squirrel. In our study, we estimate that the split took place around 31 and 25 million years ago, earlier than previously thought, suggesting the oldest fossils may not belong to flying squirrels.

“Molecular and paleontological data are often at odds, but this fossil shows that they can be reconciled and combined to retrace history”, he adds. “Discovering even older fossils could help to retrace how flying squirrels diverged from the rest of their evolutionary tree.”

An exceptional site in a rubbish dump

The Can Mata landfill holds a set of more than 200 sites ranging in age between 12.6 and 11.4 Ma (middle to late Miocene). In the last 20 years, excavations carried out by the ICP in Can Mata have led to the identification of more than 80 species of mammals, birds, amphibians and reptiles. A remarkable number of primate remains from the site have revealed three new species of hominoids, nicknamed ‘Pau’ (Pierolapithecus catalaunicus), ‘Laia’ (Pliobates cataloniae) and ‘Lluc’ (Anoiapithecus brevirostris). Various studies of mammal remains recovered from the site, including the current work in eLife, indicate the existence of a dense subtropical forest.

South American rodent evolution, new study


This video says about itself:

Today the largest land mammals in South America are wild camelids, tapirs, jaguars, and capybaras.

Yet, as recently as 10,000-17,000 years ago the landscape of South America contained remarkable beasts—massive mammals that dominated their environment, many of which have no modern analog for comparison. These enigmatic animals were decimated during the Quaternary—all South American mammal species larger than 100 kg were lost.

The mystery surrounding their extinction has yet to be fully resolved, and is a topic of considerable debate.

List of these giants vanished forever is very large but here is the mention of 10 such beasts which roamed in South America until recently when earlier humans reached these lands and made interactions with them.

1- Megatherium 2- Macrauchenia 3- Cuvieronius 4- Doedicurus clavicaudatus 5- Hippidion 6- Toxodon 7- Notiomastodon 8- Arctotherium 9- Smilodon populator 10- Terror Birds

From Florida State University in the USA:

Family of rodents may explain how some groups of animals become so diverse

October 3, 2018

Summary: Scientists have developed a new model that shows how geography can play a major role in how families of animals evolve and result in many species.

How did a single species of rodent invade South America and then quickly branch off into 350 new species?

The answer is simple — the rodents were able to move quickly across the continent unencumbered by geographic boundaries that can’t be easily crossed such as an ocean.

FSU Professor of Biological Science Scott Steppan and his former postdoctoral researcher John Schenk, now at Georgia Southern University, developed a new model that shows how geography can play a major role in how families of animals evolve and result in many species. The research was part of a $500,000 grant from the National Science Foundation to understand why the superfamily Muroidea (which includes the subfamily Sigmodontinae) is the most diverse branch of the mammal family tree.

The research is published in the journal American Naturalist.

“Biologists have long been fascinated by the process of adaptive radiations, which occurs when a lineage undergoes rapid speciation that is correlated with variation in habitats that species evolve into, resulting in numerous species that differ in the environments in which they live”, Schenk said. “Our study was the first to directly measure how movement across the landscape facilitated the speciation process.”

Scientists in the past had believed that when species evolved in a short period of time they diverged because of different ecological niches, not necessarily because of the ability to cross geographic boundaries.

Schenk and Steppan found that the … Sigmodontinae moved into South America and quickly diversified across all the regions within the continent. In about 8 million years, they diversified into about 400 new species that covered South America.

“That’s really fast”, Steppan said. As time passed, the movement between regions and diversification slowed because the regions and their associated ecological niches were essentially full.

“This [geography] largely tracks with what speciation is doing,” Steppan said. “After that initial burst, it slows down.”

Steppan studies evolutionary biology and has always been interested in how species diversify. Most studies of species diversification involve islands where different groups of terrestrial species are walled off from competing interests by ocean water allowing for animals to diversify based simply on the ecology of the island.

But little is known about how species diversify across the continuous geography of a continent.

Steppan said that he and Schenk are looking at several possibilities for follow-up studies that focus on DNA work and measuring other aspects of the rodents, such as the structure of their limbs and skulls, to see how these structures adapted to new environments over time. Steppan said.