No matter whether they ate meat or plants, theropod dinosaur species had one thing in common. Over time, they evolved thicker jaws for bigger bites, a new analysis concludes.

Theropods were a very diverse group of dinosaurs. They were descended from a carnivorous ancestor, but not all lineages stayed that way. Some eventually evolved into charismatic apex predators like tyrannosaurs and velociraptors, while others took different paths and became omnivores or herbivores.

“Because of these drastic dietary changes, I was interested in how their feeding mechanics changed with their diets,” says at the University of Birmingham, UK.

Ma and her colleagues used computer simulations of more than 40 theropod jawbones representing most known major groups. Through techniques very similar to those an engineer might use to estimate the strength of a bridge from its structure, Ma unearthed a general trend of jaw strengthening in theropods over time.

Early theropods like Guanlong, a 4-metre-long ancestor to the tyrannosaurs that lived about 160 million years ago, were carnivores with straight, slender jaws that experienced a lot of stress when clamping down on prey. As time progressed, later dinosaurs like Velociraptor and T. rex evolved deeper and wider jaws that gave them a stronger bite. This was true regardless of the dinosaur’s size.

It was also true no matter what the dinosaurs ate. All theropods generally trended towards deeper, more robust jaws with more powerful bites.

This doesn’t mean their jaws evolved to be the same. Herbivores like therizinosaurs and oviraptorosaurs sported jaws that angled slightly downwards, while the jaws of their meat-eating relatives curved upwards.

According to Ma and her colleagues, the downturned jawbone was an acquired feature that helped herbivorous theropods protect the jaw from damage by dissipating stress.

“Herbivores require really strong jaws because they need to crop plants repetitively,” says Ma. The downturned jaw allows the stress of chewing to dissipate evenly across the bone so that it is less likely to break.

The upturned jaw of the carnivores had a significant purpose as well. Ma’s simulations suggest that it shored up bite strength, while also improving the jaw’s overall stability.

The general deepening of the jaw, along with the carnivorous upturn and the herbivorous downturn, seems to have played a key role in the evolution of this diverse group of dinosaurs.

“Although theropod dinosaurs are depicted as fearsome predators in popular culture, they are in fact very diverse in terms of diet,” says Ma. “Studying how their feeding mechanics changed is key to understanding the dietary transitions in other vertebrates, too.”

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The standard for good cephalopod fathers might be a pretty low bar, but bigfin reef squid swim right over it. Male cephalopods, such as squids and octopuses, aren’t known for their parenting due to the fact that they often die soon after mating. But bigfin reef squid might be the exception to this rule, as they have now been seen investigating potential nest sites to make sure they are safe before their female counterparts lay eggs.

Typically, female cephalopods are left to care for their eggs alone. “Usually, the only thing the male does before and after mating is mate guarding,” says at the University of Lisbon in Portugal. After a male courts a female and mates with her, his only other job is to guard her against the sperm of rival males.

But this might not be the case for some squid species. Sampaio and his collaborator, at the American Museum of Natural History, filmed squid mating rituals at two sites, one in the Red Sea and the other off the coast of Indonesia.

In their recordings from both locations, a male bigfin reef squid (Sepioteuthis lessoniana) that has just mated raises his arms up while pushing his tentacles downward. At the same time, he dons a moving colour pattern that is similar to zebra stripes.

“This is really awkward for the squid, because the tentacles are usually held with the arms to protect them,” said Sampaio, “But the whole display is really obvious for other males to see.”

After the zebra display but before his mate lays her eggs, the male dives into a crevice in a reef or rocks on the sea floor, possibly checking for signs of predators. “Typically, the male just copulates and goes, but here we saw that he actually checks out the nest site first,” said Sampaio. “Only then does the female enter the location.”

The male does this despite the risk of predators lying in wait and of rival males sweeping in on his unguarded mate. “One cool thing to consider is that we were able to document this behaviour in populations 10,000 kilometres apart from each other,” said Sampaio. This suggests the behaviour is widespread among bigfin reef squids.

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Illicit drug use is a growing global health concern that causes a financial burden of hundreds of billions of dollars in the US alone. But hidden beneath the societal costs of this human epidemic is a potential ecological crisis. As methamphetamine levels rise in freshwater streams, fish are increasingly becoming addicted.

“Where methamphetamine users are, there is also methamphetamine pollution,” says  at the Czech University of Life Sciences.

Humans excrete methamphetamines into wastewater, but treatment plants aren’t designed to deal with such substances. Because of this, as treated wastewater flows into streams, so do methamphetamines and other drugs.

In some streams in the Czech Republic, methamphetamine concentrations have been measured at hundreds of nanograms per litre, according to Horký and his colleagues, but the effect of these levels on aquatic animals has been unclear.

To investigate, they set up an experiment to detect possible adverse side effects of this hidden ecological epidemic. They divided 120 hatchery reared brown trout (Salmo trutta) into two 350 litre tanks. The water in one tank contained methamphetamines matching concentrations measured in wild streams while the other was left uncontaminated as a control.

After eight weeks, the researchers removed the methamphetamine from the experimental tank. During the following 10-day “withdrawal” period, Horký tested fish selected at random from both groups for signs of addiction and withdrawal. To do this, he constructed a tank in which water could flow in on one side and out the other as if a stream were passing through the enclosure. One side of the flow, however, contained the same level of methamphetamine that the experimental tank had contained.

The control fish showed no preference for one side of the simulated stream or the other, but the methamphetamine-exposed fish repeatedly chose to stay in the drugged water.

What’s more, the methamphetamine-exposed fish had elevated levels of methamphetamine in their brain tissue and were also less active than normal – which might reduce their chances of surviving and reproducing.

“Drug reward cravings by fish could overshadow natural rewards like foraging or mating,” says Horký. “Such contamination could change the functioning of whole ecosystems.”

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A tiny bird-like dinosaur with long legs and muscular, clawed arms was quite the night owl. Shuvuuia deserti lived around 75 to 81 million years ago and not only had remarkable hearing, but also well-honed night vision – much better than that of other dinosaurs and most modern birds.

This odd creature was first discovered in the mid-1990s, but a new analysis of its inner ear bones shows that it may have been a nocturnal hunter, like modern owls.

Jonah Choiniere at the University of the Witwatersrand in South Africa and his colleagues analysed 3D scans of S. deserti’s inner ear and found that it had a very large lagena, a structure responsible for hearing. The larger the lagena relative to the skull, the more sensitively an animal can hear – and this one was bigger than researchers had ever seen in a dinosaur.

“When we stumbled onto this structure, it just immediately prompted all these questions,” said Choiniere. He and his team compared the dinosaur’s inner ear with those of more than 100 species of modern birds.

They found that the only bird with a lagena even approaching the same size as S. deserti‘s was the barn owl (Tyto alba), a nocturnal hunter with extraordinary hearing and night vision. If S. deserti has such sensitive hearing, they wondered, how well could it see?

The researchers then examined 3D scans of skull fossils of S. deserti, including an eye structure called the scleral ring, which gives clues as to how well an animal can see at night. It turned out that the animal seems to have had fantastic night vision.

Most birds and dinosaurs have ears and eyes adapted for daytime foraging. Because the common ancestor of birds and lizards was also active in the day, nocturnal traits evolved independently within these lineages. Now, S. deserti seems to indicate that nocturnal traits may have evolved independently in non-bird dinosaurs too.

“Studying the past really requires studying the present, too,” said Choiniere. “The biodiversity we see today is an extraordinary window to the lifestyles of animals from long ago.”