Triassic crocodiles, dinosaur look-alikes


This 9 June 2020 video says about itself:

When Dinosaur Look-Alikes Ruled the Earth

There were a huge number of croc-like animals that flourished during the Triassic Period. Dinosaurs had just arrived on the scene but it was these animals that truly ruled the Earth, becoming both abundant and diverse.

Dinosaur age crocodile relatives, new research


This 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!

From the Forschungsverbund Berlin in Germany:

High-tech CT reveals ancient evolutionary adaptation of extinct crocodylomorphs

They transitioned from land to water during the Mesozoic era

June 18, 2020

The tree of life is rich in examples of species that changed from living in water to a land-based existence. Occasionally, some species took the opposite direction. New insights into the anatomy of the inner ear of prehistoric reptiles, the thalattosuchians, revealed details about one of these evolutionary turning points.

During the Mesozoic era, these now-extinct crocodile relatives ventured into the ocean after a long semiaquatic phase. During this process, the skeleton of the thalattosuchians gradually adapted to the new pelagic habitat. In particular, the changes to the inner ear vestibular system of these reptiles enhanced their ability to swim. Compared to whales, which adapted quickly to life in water without a prolonged semiaquatic stage, this is a strikingly different evolutionary path for the same transition. These new findings of an international research team were made possible by the use of a Canon high-tech computed tomography (CT) scanner from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW). The results have been published in the Proceedings of the National Academy of Sciences.

Thalattosuchians lived during the Mesozoic about 182 to 125 million years ago and evolved from their land-living relatives to become fast-swimming marine predators. An international research team led by scientists from the School of Geosciences at the University of Edinburgh studied the evolutionary changes which these crocodylomorphs went through during their transition from land to the ocean. The team focused on one of the most important vertebrate sensory systems — the inner ear.

Using high-resolution computed tomography (CT), the skulls of 18 thalattosuchians from the late Triassic to the Early Cretaceous were scanned to span much of the evolutionary history of crocodylomorphs. The CT scans were compared with the scans of modern crocodiles. Some of the scans were performed at the Leibniz-IZW in Berlin.

The x-ray scans reveal detailed changes in the vestibular system of the inner ear, particularly in the bony labyrinth, which plays a crucial role in sensing balance and spatial orientation. “As they transitioned from land to water, thalattosuchians developed a strikingly compact, reduced and thickened bony labyrinth reminiscent of the reduced labyrinths of other marine reptiles and whales,” explains Guido Fritsch, scientist and CT expert at the Leibniz-IZW. “Extinct land crocodiles, on the other hand, had a taller and narrower bony labyrinth. The labyrinths of semiaquatic crocodiles, which also include modern crocodiles, are longer and more compact than those of their land-living relatives.” These results illustrate that the inner ear morphology of an animal is strongly linked to its habitat.

Interestingly, thalattosuchians developed the reduction of their inner ear labyrinth only after a long semiaquatic phase that lasted tens of millions of years. First, their skeleton changed during this phase — limbs became flippers, the body became streamlined, which allowed them to move efficiently in the water and improved their ability to swim. Only then did the changes in the inner ear develop, possibly as a response to changing sensory requirements, when the thalattosuchians moved into deeper, more open waters. This adaptation process distinguishes them from whales, whose inner ear labyrinth was miniaturised soon after their transition from land to water, without a prolonged semiaquatic phase. Thus, thalattosuchians and whales took different evolutionary routes for the same type of transition.

Future studies will examine the advantages of a reduced inner ear labyrinth for water-living animals, investigate how quickly thalattosuchians developed the adaptations in their inner ear as they entered the water, and how other sensory organs changed during this transition.

Jurassic marine crocodiles, video


This 11 June 2020 video says about itself:

When Crocodiles Swam The Oceans

Crocodiles are good swimmers and often live near river mouths near the ocean and some of them even make brief excursions into the ocean. This means they are always at a tipping point of becoming marine animals. This is known because it has happened on several occasions throughout prehistory, but in the Jurassic, one group of crocs called the thalattosuchians would take this a step further in following whales and other marine reptiles in becoming fish-like.

Dinosaur-age crocodiles walked on two legs


This 2018 BBC video says about itself:

Sarcosuchus: the Dinosaur Killing Crocodile

Steve Backshall needs the most powerful jaw in the dinosaur kingdom… the giant croc Sarcosuchus might have what he’s looking for.

Sarcosuchus walked on four legs. But other crocodiles …

From the University of Queensland in Australia:

Ancient crocodiles walked on two legs like dinosaurs

June 11, 2020

An international research team has been stunned to discover that some species of ancient crocodiles walked on their two hind legs like dinosaurs and measured over three metres in length.

University of Queensland palaeontologist Dr Anthony Romilio said the researchers first thought the similar-shaped fossilised footprints were from other ancient animals known as pterosaurs.

“At one site, the footprints were initially thought to be made by a giant bipedal pterosaur walking on the mudflat, we now understand that these were bipedal crocodile prints,” Dr Romilio said.

“The footprints measure around 24 centimetres, suggesting the track-makers had legs about the same height as human adult legs.

“These were long animals that we estimate were over three metres in length.

“And while footprints were everywhere on the site, there were no handprints.”

The research team, led by Professor Kyung Soo Kim from Chinju National University of Education, soon found clues as to why there were no handprints.

“Typical crocodiles walk in a squat stance and create trackways that are wide,” Professor Kim said.

“Oddly, our trackways are very narrow looking — more like a crocodile balancing on a tight-rope.

“When combined with the lack of any tail-drag marks, it became clear that these creatures were moving bipedally.

“They were moving in the same way as many dinosaurs, but the footprints were not made by dinosaurs.

“Dinosaurs and their bird descendants walk on their toes.

“Crocodiles walk on the flat of their feet leaving clear heel impressions, like humans do.”

The footprints dated between 110-120 million years ago and were discovered after analysing animal track sites in what is now known as South Korea.

Researchers initially questioned the absence of hand impressions from the trackways, given that today’s typical crocodiles are ‘four-legged’ or quadrupedal.

Fossil crocodile tracks are quite rare in Asia, so finding an abundance of nearly one hundred footprints was extraordinary,” Dr Romilio said.

“As an animal walks, the hind feet have the potential of stepping into the impression made by the hand and ‘over-printing’ it, but we find no evidence of this at these Korean sites.

“It isn’t due to poor preservation either, because these fossils are spectacular, they even have the fine details of the toe-pads and scales on their soles preserved.”

Crocodiles, from dinosaur age till today


This 2 June 2020 video from England says about itself:

Crocodiles Rock | Live Talk with London Natural History Museum Scientist

This live talk with palaeontologist Lorna Steel answers these croc questions and more: How ancient are these creatures? What was the earliest croc and how have they changed throughout history?

Dinosaurs, male or female?


This video says about itself:

Dinosaur mating rituals | Walking with Dinosaurs in HQ | BBC

Watch the savage and deadly mating rituals that signaled which Diplodocus had earned the right to mate.

Broadcast in 1999, Walking with Dinosaurs set out to create the most accurate portrayal of prehistoric animals ever seen on the screen. Combining fact and informed speculation with cutting-edge computer graphics and animatronics effects, the series took two years to make.

From Queen Mary University of London in England:

Can we really tell male and female dinosaurs apart?

May 12, 2020

Scientists worldwide have long debated our ability to identify male and female dinosaurs. Now, research led by Queen Mary University of London has shown that despite previous claims of success, it’s very difficult to spot differences between the sexes.

In the new study, researchers analysed skulls from modern-day gharials, an endangered and giant crocodilian species, to see how easy it is to distinguish between males and females using only fossil records.

Male gharials are larger in size than females and possess a fleshy growth on the end of their snout, known as a ghara. Whilst the ghara is made from soft tissue, it is supported by a bony hollow near the nostrils, known as the narial fossa, which can be identified in their skulls.

The research team, which included Jordan Mallon from the Canadian Museum of Nature, Patrick Hennessey from Georgia Southern University and Lawrence Witmer from Ohio University, studied 106 gharial specimens in museums across the world. They found that aside from the presence of the narial fossa in males, it was still very hard to tell the sexes apart.

Dr David Hone, Senior Lecturer in Zoology at Queen Mary University of London and author of the study, said: “Like dinosaurs, gharials are large, slow-growing reptiles that lay eggs, which makes them a good model for studying extinct dinosaur species. Our research shows that even with prior knowledge of the sex of the specimen, it can still be difficult to tell male and female gharials apart. With most dinosaurs we don’t have anywhere near that size of the dataset used for this study, and we don’t know the sex of the animals, so we’d expect this task to be much harder.”

In many species, males and females can look very different from each other. For example, antlers are largely only found in male deer and in peacocks, males are normally brightly-coloured with large, iridescent tail feathers whereas females are much more subdued in their colouration. This is known as sexual dimorphism and is very common within the animal kingdom. It is expected that dinosaurs also exhibit these differences, however this research suggests that in most cases this is far too difficult to tell from the skeleton alone.

Dr Hone said: “Some animals show extraordinarily high levels of sexual dimorphism, for example huge size differences between males and females. Gharials sit somewhere in the middle as they do possess these large narial fossa that can help with identification. Our study suggests that unless the differences between the dinosaurs are really striking, or there is a clear feature like the fossa, we will struggle to tell a male and female dinosaur apart using our existing dinosaur skeletons.”

The new research also challenges previous studies that have hinted at differences between the sexes in popular dinosaur species such as the Tyrannosaurus rex (T. rex), and led to common misconceptions amongst the general public.

“Many years ago, a scientific paper suggested that female T. rex are bigger than males. However, this was based on records from 25 broken specimens and our results show this level of data just isn’t good enough to be able to make this conclusion,” Dr Hone added.

South African crocodile fights five lions, video


This 28 April 2020 video from South Africa says about itself:

Cornered Crocodile is Forced to Attack 5 Lions

These lions left their waterbuck scraps lying around, which a crocodile thought was an easy meal. But, no, these lions weren’t giving up their scraps so easy.

Watch the shocking moment a crocodile finds himself completely surrounded by a pride of lions, and has no other option but to use his jaw strength and speed to get away!

This video was taken one early morning, by Vernon Cresswell (61) in Buffelshoek in the Sabi Sands area, Greater Kruger Park. He managed to capture a pride of lionesses and cubs trying to corner a crocodile that was about to steal their waterbuck meal.

Vernon told LatestSightings.com of the drive that led up to this sighting:

“We managed to track a pride of lions in that area that is called the Talamati Pride. This had taken down a male waterbuck just a few hours before. All of them had fed on the buck and left the carcass about 100m from the dam.”

“A crocodile obviously sensed that there was a carcass nearby, so he left the water to investigate and maybe get an easy meal.”

“When the croc got onto land, it was only a few meters from the waters’ edge. Some of the younger lions (9 cubs) showed some interest and moved closer to see what this creature was up to. After a little while, some of the adult females (5 in total) noticed what was happening and came to the scene.”

“At first, it seemed they toyed with the crocodile to test his reflex and speed. Soon after this toying, the crocodile let off a massive snap as it clenched its jaw. The croc snapped his jaws at the lions in an attempt to defend itself. This caused the lions to launch a full-on mob at the crocodile.”

“The lions were all taken by surprise, but their reflexes were faster than the speed of the crocodile, and they soon got the upper hand. The crocodile sensed it has no chance and scurried back towards the water, finally disappearing into the dam.

“With the hippos snorting madly in the distance, we were amazed by the sighting, and we were excited to see how it would play out. We’ve been going to the bush regularly for 30 years, and not once have we seen something like this. Always anticipate what can happen, and put yourself in the right place and just be patient. Nature usually pays off!”

Why Jurassic crocodiles were big


This 2009 video says about itself:

Paul Sereno and his team of scientists and artists show us what the world looked like in an age when crocs ate dinosaurs.

From the University of Nebraska-Lincoln in the USA:

Water pressure: Ancient aquatic crocs evolved, enlarged to avoid freezing

Study pinpoints minimum survivable size of Jurassic crocodiles

March 30, 2020

Summary: Ancient crocodilian ancestors that abandoned land for water nearly 200 million years ago supposedly got larger because they were released from the constraints of gravity, territory and diet. But a new study suggests that the upper bounds of size in aquatic vs. landlocked crocs were similar — and that smaller aquatic species got larger mostly to avoid freezing in the frigid, heat-stealing depths.

Taking the evolutionary plunge into water and abandoning land for good, as some crocodilian ancestors did nearly 200 million years ago, is often framed as choosing freedom: from gravity, from territorial boundaries, from dietary constraints.

Water might inflict more pressure in the pounds-per-square-inch sense, the thinking went, but it also probably relieved some — especially the sort that kept crocs from going up a size or 10. If they wanted to enjoy the considerable spoils of considerable size, water seemed the easy way.

A recent study from the University of Nebraska-Lincoln’s Will Gearty, who compiled a database of 264 species stretching back to the Triassic Period, says that freedom was actually compulsion in disguise.

After analyzing the database of crocodyliforms — a lineage of crocodile-like species that share a common ancestor — Gearty found that the average weights of aquatic crocodyliforms did easily surpass their semi-aquatic and landlocked counterparts, sometimes by a factor of 100.

But the study suggests that this disparity represented a response to, not a release from, the pressures of natural selection. Rather than expanding the range of crocodyliform body sizes, as some longstanding theories would predict, taking to the water instead seemed to compress that range by raising the minimum size threshold needed to survive its depths. The maximum size of those aquatic species, by contrast, barely budged over time.

And when Gearty derived a set of equations to estimate the largest feasible body sizes under aquatic, semi-aquatic and terrestrial conditions?

“All three habitats had roughly the same upper limit (on size),” he said. “So even though it seems like you’re released from this pressure, you’re actually squeezed into an even smaller box than before.”

Two major factors — lung capacity and body heat — seem to have helped initiate the squeeze play. Prior research had proposed that aquatic crocodyliforms got big in part because they needed to dive deeply for food, including the choice prey that would sustain a larger size. Upon digging into the literature, though, Gearty learned that lung volume increases more or less in lockstep with body size.

“So you actually don’t have much excess lung volume to spare,” said Gearty, a postdoctoral researcher in biological sciences. “When you get bigger, (lung capacity) is just basically scaling up with your body size to accommodate that extra size. The amount of time you could stay underwater increases a little bit, but not that much.”

At larger sizes, the evolutionary tradeoff between the benefits of longer, deeper dives and the energy demands of finding more food probably also reached a stalemate, he said, that helped cement the aquatic ceiling on size.

As for the higher floor? That’s where the thermal conductivity of water cranked up the evolutionary heat, Gearty said. Unfortunately for the aquatic crocs, water steals heat far faster than air does. The issue was likely compounded by the fact that temperatures in the waters they occupied were lower than the air temperatures enjoyed by their land-dwelling counterparts.

That would have left smaller aquatic crocodyliforms with only bad options: limit the duration and depth of their dives so that they could regularly return to the surface and warm themselves in the sun, or risk freezing to death during deeper hunts for food. Whether by starvation or hypothermia, either would eventually spell doom.

“The easiest way to counteract that is to get bigger,” Gearty said.

Getting bigger was especially appealing because the volume of body tissue, which generates heat, increases faster than the surface area of the skin that surrenders it. But the unforgiving consequences of heat loss still limited the pool of ancestors from which aquatic crocodyliforms could evolve.

“They actually needed to start at a larger size,” Gearty said. “So it’s not like a marine crocodile could have just evolved from anywhere. It had to be evolving from some non-marine crocodile that was already a little larger than normal.”

The fossil records of the crocodyliforms allowed Gearty and Jonathan Payne, his former doctoral adviser at Stanford University, to pinpoint the minimum weight threshold for aquatic survival: 10 kilograms, or about 22 pounds. And when they plotted the relationships of heat loss and lung capacity to body mass, they discovered that the two slopes crossed at almost exactly the same value: 10 kilograms.

“We were able to explain, with these physiological equations, exactly why there were no marine crocodiles below a certain size,” Gearty said. “This indicates that these very fundamental physiological constraints and controls … actually may be some of the strongest forces for pushing animals to different body sizes through time. Not whether there’s an asteroid hitting the world, not whether you’re being (hunted) by some other animal — that just these physical and chemical properties of the world we live in are what drive this. And if you want to enter a new habitat, you need to conform to that new set of properties.”

The findings mostly reinforce a 2018 Gearty-led study that found similar trends among nearly 7,000 living and extinct mammal species. An elementary difference between mammals and reptiles, though, initially left the verdict in doubt.

“The whole (premise) of the marine mammal project was that these things are warm-blooded, and they have to keep their temperature up,” Gearty said. “They have to really worry about this heat loss. So the idea was, ‘Well, would the same constraint occur in cold-blooded organisms that are also living in the ocean?’

“There have been a couple papers suggesting that some of these marine crocodiles may have been somewhat warm-blooded, and so they may have been able to kind of reheat their own bodies. But even if that’s the case, they were still going to be losing heat like these marine mammals would. They were still constrained by these thermoregulatory controls.”

GREYHOUNDS AND DOLPHINS

With the help of an undergraduate student at Stanford and funding from the National Science Foundation, Gearty spent most of the summer of 2017 tracking down the fossil records that informed the new study.

“But that was to find the stuff that’s readily available online,” he said. “Then you’ve got, you know, undocumented books that you need to find, and they have to get shipped from Europe or somewhere. So there were a lot of these one-offs. I was still measuring specimen photos and getting records up until I submitted the paper in the middle of last year.”

Gearty said he was mostly spared the time and expense of traveling to museums and physically measuring fossil dimensions, as some of his colleagues have in the name of their own research. But the haphazardness of some older classifications and documentation still had him following false leads and trying to make sense of the nonsensible.

“A lot of the crocodiles that people have described in papers have never actually been documented the way they’re supposed to be,” he said. “Someone might say, ‘Here’s the Nebraska crocodile.’ It’s just a colloquial name. And you’ll be like, ‘I guess I’ve got to go find the Nebraska crocodile.’ You look this up, and you see that there’s this crocodile from Nebraska, and this one, and this one. You don’t know which one is the ‘Nebraska crocodile.’

“You need to follow this trail of breadcrumbs, sometimes, to find these papers that may or may not have ever been published on these crocodiles that may or may not have ever been found. Fortunately, I was able to get most of the specimens just from the literature. But it did take a lot of digging to find the last probably 10% of the crocodiles.”

Many of the terrestrial fossils, in particular, trace body shapes that barely resemble the low-slung profile of the modern crocodile.

“The example I like to give is: Imagine a greyhound, and then put a crocodile skull on it,” Gearty said. “There were things like that running around on land probably 200 million years ago.”

Though their maximum size remained almost constant, marine species did evolve two to three times faster than the semi-aquatic and terrestrial groups, Gearty found. Along with increasing the size of smaller aquatic species, natural selection molded body forms to surmount the challenges presented by water. Scales, plates and other drag-increasing skin deposits disappeared. Heads and tails flattened. Snouts narrowed.

“All of these were probably more dolphin-like than modern crocodiles, with even longer, thinner tails,” he said. “And some of them had very paddle-like feet, almost like flippers.”

Despite the fact that virtually all modern crocodile species are semi-aquatic, Gearty said those adaptations served the aquatic crocodyliforms well — more than 100 million years before mammals ventured into the deep.

“No one has talked about it much, but really, these things were quite successful,” he said. “And some of them weren’t even fazed by some of the big, (cataclysmic) events. When the asteroid hit that killed all the dinosaurs, one of the marine groups just kind of kept going like nothing happened. A lot of the terrestrial species went extinct, but this group just kept ticking along for a long time.”

Top 15 prehistoric crocodiles, video


This October 2019 video says about itself:

15 Largest Extinct Crocodiles and Related Species

Sarcosuchus, popularly known as “ supercroc ” is an extinct genus of crocodyliform and distant relative of the crocodile that lived 112 million years ago. It dates from the early Cretaceous Period of what is now Africa and South America and is one of the largest crocodile-like reptiles that ever lived. We also showcase to you the top 15 largest extinct crocodiles and their related species with a brief explanation. We hope you enjoy the video!!