Prehistoric crocodiles, video

This 23 June 2019 video says about itself:

5 of the Strangest Prehistoric Crocs

Over the years, scientists have found evidence for a lot of weird prehistoric animals, but some of the strangest have been the crocodyliformes!


Entelodonts, prehistoric ‘hell pigs’

This 5 June 2019 video says about itself:

Despite the name, we don’t know where the so-called “hell pigs” belong in the mammalian family tree. They walked on hooves, like pigs do, but had longer legs, almost like deer. They had hunched backs, a bit like rhinos or bison. But as is often, if not always, the case, there is some evolutionary method to this anatomical madness.

Thanks to Ceri Thomas for the excellent Entelodont illustrations!

Cambrian life explosion, because of volcanoes?

This 2016 video says about itself:

Right at the beginning of the Paleozoic, there was a huge explosion of more complex life. And that’s when things started to get really interesting.

From the University of Exeter in England:

Plate tectonics may have driven ‘Cambrian Explosion’

June 19, 2019

The quest to discover what drove one of the most important evolutionary events in the history of life on Earth has taken a new, fascinating twist.

A team of scientists have given a fresh insight into what may have driven the “Cambrian Explosion” — a period of rapid expansion of different forms of animal life that occurred over 500 million years ago.

While a number of theories have been put forward to explain this landmark period, the most credible is that it was fuelled by a significant rise in oxygen levels which allowed a wide variety of animals to thrive.

The new study suggests that such a rise in oxygen levels was the result of extraordinary changes in global plate tectonics.

During the formation of the supercontinent ‘Gondwana’, there was a major increase in continental arc volcanism — chains of volcanoes often thousands of miles long formed where continental and oceanic tectonic plates collided. This in turn led to increased ‘degassing’ of CO2 from ancient, subducted sedimentary rocks.

This, the team calculated, led to an increase in atmospheric CO2 and warming of the planet, which in turn amplified the weathering of continental rocks, which supplied the nutrient phosphorus to the ocean to drive photosynthesis and oxygen production.

The study was led by Josh Williams, who began the research as an MSc student at the University of Exeter and is now studying for a PhD at the University of Edinburgh.

During his MSc project he used a sophisticated biogeochemical model to make the first quantification of changes in atmospheric oxygen levels just prior to this explosion of life.

Co-author and project supervisor Professor Tim Lenton, from the University of Exeter’s Global Systems Institute said: “One of the great dilemmas originally recognised by Darwin is why complex life, in the form of fossil animals, appeared so abruptly in what is now known as the Cambrian explosion.

“Many studies have suggested this was linked to a rise in oxygen levels — but without a clear cause for such a rise, or any attempt to quantify it.”

Not only did the model predict a marked rise in oxygen levels due to changes in plate tectonic activity, but that rise in oxygen — to about a quarter of the level in today’s atmosphere — crossed the critical levels estimated to be needed by the animals seen in the Cambrian explosion.

Williams added: “What is particularly compelling about this research is that not only does the model predict a rise in oxygen to levels estimated to be necessary to support the large, mobile, predatory animal life of the Cambrian, but the model predictions also show strong agreement with existing geochemical evidence.”

“It is remarkable to think that our oldest animal ancestors — and therefore all of us — may owe our existence, in part, to an unusual episode of plate tectonics over half a billion years ago” said Professor Lenton.

From mammal-like reptiles to mammals

This 19 June 2019 video says about itself:

Synapsids were the world’s first-ever terrestrial megafauna but the vast majority of these giants were doomed to extinction. However, some lived on, keeping a low profile among the dinosaurs. And now our world is the way it is because of the time when the synapsids struck back.

Thanks to Ceri Thomas for the excellent Synapsid illustration (including Bulbasaurus!)!

Antarctic marine life recovery after dinosaurs’ extinction

This August 2016 video says about itself:

Fossil hunters want to know what life was like when dinosaurs became extinct 66 million years ago. We join an Aussie [Australian] palaeontologist on a US expedition searching for dinosaur fossils in Antarctica, the most challenging place to explore the end of their ancient world.

From the British Antarctic Survey:

Antarctic marine life recovery following the dinosaurs’ extinction

June 19, 2019

A new study shows how marine life around Antarctica returned after the extinction event that wiped out the dinosaurs.

A team led by British Antarctic Survey studied just under 3000 marine fossils collected from Antarctica to understand how life on the sea floor recovered after the Cretaceous-Paleogene (K-Pg) mass extinction 66 million years ago. They reveal it took one million years for the marine ecosystem to return to pre-extinction levels. The results are published today (19 June 2019) in the journal Palaeontology.

The K-Pg extinction wiped out around 60% of the marine species around Antarctica, and 75% of species around the world. Victims of the extinction included the dinosaurs and the ammonites. It was caused by the impact of a 10 km asteroid on the Yucatán Peninsula, Mexico, and occurred during a time period when the Earth was experiencing environmental instability from a major volcanic episode. Rapid climate change, global darkness, and the collapse of food chains affected life all over the globe.

The K-Pg extinction fundamentally changed the evolutionary history of life on Earth. Most groups of animals that dominate modern ecosystems today, such as mammals, can trace the roots of their current success back to the aftermath of this extinction event.

A team of scientists from British Antarctic Survey, the University of New Mexico and the Geological Survey of Denmark & Greenland show that in Antarctica, for over 320,000 years after the extinction, only burrowing clams and snails dominated the Antarctic sea floor environment. It then took up to one million years for the number of species to recover to pre-extinction levels.

Author Dr Rowan Whittle, a palaeontologist at British Antarctic Survey says:

“This study gives us further evidence of how rapid environmental change can affect the evolution of life. Our results show a clear link in the timing of animal recovery and the recovery of Earth systems.”

Author Dr James Witts, a palaeontologist at University of New Mexico says:

“Our discovery shows the effects of the K-Pg extinction were truly global, and that even Antarctic ecosystems, where animals were adapted to environmental changes at high latitudes like seasonal changes in light and food supply, were affected for hundreds of thousands of years after the extinction event.”

Arctic Ice Age hyenas discovery

This 17 January 2019 video says about itself:

Chasmaporthetes, also known as hunting or running hyena, is an extinct genus of hyenas distributed in Eurasia, North America, and Africa. It lived during the Pliocene-Pleistocene epochs, from 4.9 million to 780,000 years ago, existing for about 4.12 million years.

The genus probably arose from Eurasian Miocene hyenas such as Thalassictis or Lycyaena, with C. borissiaki being the oldest known representative. It was a fast runner and an important carnivore on 4 continents during the Pliocene.

At least nine species are currently recognised. The genus type species is Chasmaporthetes ossifragus. It was assigned to Hyaenidae by Hay (1921), Geraads (1997), and Flynn (1998).

The species C. ossifragus was the only hyena to cross the Bering land bridge into the Americas. C. ossifragus ranged over what is now Arizona and Mexico during Blancan and early Irvingtonian Land Mammal ages, between 5.0 and 1.5 million years ago.

Chasmaporthetes was one of the so-called “dog-like” hyenas (of which the aardwolf is the only survivor), a hyaenid group which, in contrast to the now more common “bone-crushing” hyenas, evolved into slender-limbed, cursorial hunters like modern canids.

The genus has entered the popular culture lexicon as a result of cryptozoologic claims, having been proposed as the likely origin of the American Shunka Warakin and the Cuitlamiztli.

Chasmaporthetes was named by Hay (1921), who noted the name to be a reference to the possibility that the beginning of the Grand Canyon was witnessed by the North American species, C. ossifragus.

The limb bones of Chasmaporthetes were long and slender like those of cheetahs, and its cheek teeth were slender and sharp-edged like those of a cat. Chasmaporthetes likely inhabited open ground and was a daytime hunter.

In Europe, the species C. lunensis competed with the giant cheetah Acinonyx pardinensis, and may have preyed on the small bourbon gazelle (Gazella borbonica) and the chamois antelope (Procamptoceras brivatense).

The North American C. ossifragus was similar in build to C. lunensis, but had slightly more robust jaws and teeth. It may have preyed on the giant marmot Paenemarmota, and competed with the far more numerous Borophagus diversidens.

A study on the genus’ premolar intercuspid notches indicated Chasmaporthetes was likely hypercarnivorous rather than durophagous as its modern cousins (excluding the aardwolf) are.

Like most of the animals of the time, reasons for its extinction are not known.

By Nicoletta Lanese, 6:00am, June 18, 2019:

Hyenas roamed the Arctic during the last ice age

Newly identified fossils confirm how the carnivores migrated to North America, researchers say

Modern hyenas stalk the savannas of Asia and Africa, but the animals’ ancient relatives may have had snowier stomping grounds: the Arctic. Two fossilized teeth, collected in Canada in the 1970s, confirm a long-held hunch that ancient hyenas ventured into North America via the Bering land bridge, scientists say.

The teeth belonged to members of the extinct genus Chasmaporthetes, also known as the “running hyena” for their unusually long legs, researchers report June 18 in Open Quaternary. Like wolves, the creatures could sprint over long distances. That ability that may have enabled the hyenas to make the long trek to America from Asia. Running hyena remains crop up across the southern United States and central Mexico. But before the Arctic discovery, a more than 10,000-kilometer gap lay between them and their closest relatives in Mongolia.

“This new Arctic find puts a dot right in the middle of that”, says paleontologist Jack Tseng of the University at Buffalo in New York. “It actually confirms previous hypotheses about how hyenas got to the New World.”

The teeth date to between 850,000 and 1.4 million years ago, Tseng says, placing the hyenas in the Arctic during the Pleistocene Ice Age, which began roughly 2.6 million years ago and lasted until about 11,700 years ago. The large carnivores may have hunted ancient caribou, horses, camels and the occasional juvenile mammoth (SN: 4/6/13, p. 9).

Paleontologists originally dug up the teeth in the Old Crow Basin in the Yukon at a site nicknamed the “supermarket of fossils”. There, rushing water dislodges fossils from their soil beds and drops them along bends in the river. The spoils can be reached only by boat or helicopter, but it’s worth the effort — over 50,000 known mammal fossils have been collected in the basin to date.

For decades, the hyena teeth lay buried among fossil specimens in the Canadian Museum of Nature in Ottawa. Few field notes referenced the finds, and an unpublished manuscript by archaeologist Brenda Beebe provided the only photographs. Tseng and his colleagues finally tracked the fossils down; they were a mere six-hour drive from his home base in Buffalo.

“Hyena are one of the groups with a really patchy fossil record in North America. This finding adds to our knowledge of how the species came over,” says paleontologist Julie Meachen of Des Moines University in Iowa, who was not involved in the study. The finding opens the door for further research on the migration of carnivores across the Bering land bridge (SN: 1/31/09, p. 5), Meachen says, and may help clarify which species competed for the same kills during the Pleistocene.

See also here.

Woolly rhinos and ice ages, video

This 30 May 2019 video says about itself:

The History of Climate Cycles (and the Woolly Rhino) Explained

Throughout the Pleistocene Epoch, the range of the woolly rhino grew and shrank in sync with global climate. So what caused the climate — and the range of the woolly rhino — to cycle back and forth between such extremes?