Were Allosaurus dinosaurs cannibals?


This 2018 BBC video says about itself:

Steve Backshall looks at the Majungasaurus, the only know dinosaur to eat others from its own species.

From PLOS ONE, 27 May 2020:

High frequencies of theropod bite marks provide evidence for feeding, scavenging, and possible cannibalism in a stressed Late Jurassic ecosystem

Abstract

Bite marks provide direct evidence for trophic interactions and competition in the fossil record. However, variations in paleoecological dynamics, such as trophic relationships, feeding behavior, and food availability, govern the frequency of these traces.

Theropod bite marks are particularly rare, suggesting that members of this clade might not often focus on bone as a resource, instead preferentially targeting softer tissues.

Here, we present an unusually large sample of theropod bite marks from the Upper Jurassic Mygatt-Moore Quarry (MMQ). We surveyed 2,368 vertebrate fossils from MMQ in this analysis, with 684 specimens (28.885% of the sample) preserving at least one theropod bite mark.

This is substantially higher than in other dinosaur-dominated assemblages, including contemporaneous localities from the Morrison Formation. Observed bite marks include punctures, scores, furrows, pits, and striations. Striated marks are particularly useful, diagnostic traces generated by the denticles of ziphodont teeth, because the spacing of these features can be used to provide minimum estimates of trace maker size.

In the MMQ assemblage, most of the striations are consistent with denticles of the two largest predators known from the site: Allosaurus and Ceratosaurus. One of the bite marks suggests that a substantially larger theropod was possibly present at the site and are consistent with large theropods known from other Morrison Formation assemblages (either an unusually large Allosaurus or a separate, large-bodied taxon such as Saurophaganax or Torvosaurus).

The distribution of the bite marks on skeletal elements, particularly those found on other theropods, suggest that they potentially preserve evidence of scavenging, rather than active predation. Given the relative abundances of the MMQ carnivores, partnered with the size-estimates based on the striated bite marks, the feeding trace assemblage likely preserves the first evidence of cannibalism in Allosaurus.

See also here.

Dinosaurs extinct by asteroid, how?


This 2016 video says about itself:

Here’s a look at what might have caused the extinction of dinosaurs approximately 65 million years ago.

From Imperial College London in England:

Dinosaur-dooming asteroid struck Earth at ‘deadliest possible’ angle

May 26, 2020

New simulations from Imperial College London have revealed the asteroid that doomed the dinosaurs struck Earth at the ‘deadliest possible’ angle.

The simulations show that the asteroid hit Earth at an angle of about 60 degrees, which maximised the amount of climate-changing gases thrust into the upper atmosphere.

Such a strike likely unleashed billions of tonnes of sulphur, blocking the sun and triggering the nuclear winter that killed the dinosaurs and 75 per cent of life on Earth 66 million years ago.

Drawn from a combination of 3D numerical impact simulations and geophysical data from the site of the impact, the new models are the first-ever fully 3D simulations to reproduce the whole event — from the initial impact to the moment the final crater, now known as Chicxulub, was formed.

The simulations were performed on the Science and Technology Facilities Council (STFC) DiRAC High Performance Computing Facility.

Lead researcher Professor Gareth Collins, of Imperial’s Department of Earth Science and Engineering, said: “For the dinosaurs, the worst-case scenario is exactly what happened. The asteroid strike unleashed an incredible amount of climate-changing gases into the atmosphere, triggering a chain of events that led to the extinction of the dinosaurs. This was likely worsened by the fact that it struck at one of the deadliest possible angles.

“Our simulations provide compelling evidence that the asteroid struck at a steep angle, perhaps 60 degrees above the horizon, and approached its target from the north-east. We know that this was among the worst-case scenarios for the lethality on impact, because it put more hazardous debris into the upper atmosphere and scattered it everywhere — the very thing that led to a nuclear winter.”

The results are published today in Nature Communications.

Crater creation

The upper layers of earth around the Chicxulub crater in present-day Mexico contain high amounts of water as well as porous carbonate and evaporite rocks. When heated and disturbed by the impact, these rocks would have decomposed, flinging vast amounts of carbon dioxide, sulphur and water vapour into the atmosphere.

The sulphur would have been particularly hazardous as it rapidly forms aerosols — tiny particles that would have blocked the sun’s rays, halting photosynthesis in plants and rapidly cooling the climate. This eventually contributed to the mass extinction event that killed 75 per cent of life on Earth.

The team of researchers from Imperial, the University of Freiburg, and The University of Texas at Austin, examined the shape and subsurface structure of the crater using geophysical data to feed into the simulations that helped diagnose the impact angle and direction. Their analysis was also informed by recent results from drilling into the 200 km-wide crater, which brought up rocks containing evidence of the extreme forces generated by the impact.

Peak performance

Pivotal to diagnosing the angle and direction of impact was the relationship between the centre of the crater, the centre of the peak ring — a ring of mountains made of heavily fractured rock inside the crater rim — and the centre of dense uplifted mantle rocks, some 30 km beneath the crater.

At Chicxulub, these centres are aligned in a southwest-northeast direction, with the crater centre in between the peak-ring and mantle-uplift centres. The team’s 3D Chicxulub crater simulations at an angle of 60 degrees reproduced these observations almost exactly.

The simulations reconstructed the crater formation in unprecedented detail and give us more clues as to how the largest craters on Earth are formed. Previous fully 3D simulations of the Chicxulub impact have covered only the early stages of impact, which include the production of a deep bowl-shaped hole in the crust known as the transient crater and the expulsion of rocks, water and sediment into the atmosphere.

These simulations are the first to continue beyond this intermediate point in the formation of the crater and reproduce the final stage of the crater’s formation, in which the transient crater collapses to form the final structure. This allowed the researchers to make the first comparison between 3D Chicxulub crater simulations and the present-day structure of the crater revealed by geophysical data.

Co-author Dr Auriol Rae of the University of Freiburg said: “Despite being buried beneath nearly a kilometre of sedimentary rocks, it is remarkable that geophysical data reveals so much about the crater structure — enough to describe the direction and angle of the impact.”

The researchers say that while the study has given us important insights into the dinosaur-dooming impact, it also helps us understand how large craters on other planets form.

Co-author Dr Thomas Davison, also of Imperial’s Department of Earth Science and Engineering, said: “Large craters like Chicxulub are formed in a matter of minutes, and involve a spectacular rebound of rock beneath the crater. Our findings could help advance our understanding of how this rebound can be used to diagnose details of the impacting asteroid.”

The work was supported by the International Ocean Discovery Program (IODP), International Continental Scientific Drilling Program (ICDP), (STFC) DiRAC High Performance Computing Facility and the Natural Environment Research Council.

Scipionyx baby dinosaur discovery


This 24 March 2020 video says about itself:

The Baby Dinosaur With Fossilised OrgansScipionyx

The discovery that this baby dinosaur fossil had preserved large parts of the internal organs for over 110 million years was one of the greatest revelations in recent palaeontology. So what can this amazing fossil tell us about extinct dinosaur biology?

Dinosaur’s anti-predator armour, how strong?


This 19 May 2020 video says about itself:

Mechanical Dinosaur Jaws Vs. Replica Borealopelta Body

Scientists have created powerful mechanical jaws, modeled after the mid-Cretaceous predator known as Acrocanthosaurus. Now it’s time to test it out on a recreation of Borealopelta’s armored body.

Why Tyrannosaurus rex had long legs


This May 2019 video is called Was the T-Rex really as fierce as its legend says? | T Rex: An Evolutionary Journey.

From the University of Maryland in the USA:

T. rex was a champion walker, highly efficient at lower speeds

Research finds leg length gave giant predatory dinosaurs the advantage of efficiency, not speed as previously thought.

May 13, 2020

Long legs may make good runners, but they’re great for walking, too. Scientists have generally assumed that long-limbed dinosaurs evolved their leggy proportions for speed to catch prey and avoid predators.

But a new study by the University of Maryland’s Thomas Holtz and his colleagues suggests that long legs evolved among the biggest dinosaurs to help them conserve energy and go the distance as they ambled along searching for prey. The study was published in the journal PLOS ONE on May 13, 2020.

“The assumption tends to be that animals with adaptations for running, such as long legs, are adapted for a higher maximum speed, but this paper shows that there’s more to running than top speed,” said Thomas Holtz, principal lecturer in the UMD Department of Geology. “When you’re a bigger animal, those adaptations may also be for endurance and efficiency. It may be about being a marathoner rather than a sprinter.”

Holtz and his colleagues analyzed a variety of metrics like limb proportions, size ratio, body mass and gaits to estimate the top speeds of more than 70 species from a group of dinosaurs called theropods. Theropods ranged in size from less than a half-pound to more than nine tons. They included Tyrannosaurus rex and the many other two-legged predators that dominated the age of dinosaurs for 180 million years. Bipedalism and running speed have often been cited as major contributors to their success.

The study revealed a more nuanced story. According to the new analysis, longer legs were associated with higher top speeds in small and medium-sized dinosaurs, but that didn’t hold true for dinosaurs weighing over 2,200 pounds. Scientists have known that larger body size can limit speed, and the study showed that large dinosaur species with longer legs were no faster than their stubby-limbed brethren. But they moved more efficiently.

By calculating how much energy each dinosaur expended while moving at walking speeds, the researchers found that among the largest dinosaurs, those with longer legs needed less energy to cruise around.

“That’s actually a very beneficial savings, because predators tend to spend a great deal of their time foraging, searching for prey,” Holtz said. “If you are burning less fuel during the foraging part of the day, that’s an energy savings that dinosaurs with shorter leg forms didn’t get.”

These results highlight the often-overlooked impact of body proportions on running ability and the limiting effect of large body size on running speed. Clearly, there are different kinds of runners. This work should broaden the discussion about what it means to be adapted for running.

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.