Enlarge / Grasshoppers, beware! Robopteryx is here to flush you from your hiding place. (credit: Jinseok Park, Piotr Jablonski et al., 2024)

Scientists in South Korea built a robotic dinosaur and used it to startle grasshoppers to learn more about why dinosaurs evolved feathers, according to a recent paper published in the journal Scientific Reports. The results suggest that certain dinosaurs may have employed a hunting strategy in which they flapped their proto-wings to flush out prey, and this behavior may have led to the evolution of larger and stiffer feathers.

As reported previously , feathers are the defining feature of birds, but that wasn't always the case. For millions of years, various species of dinosaurs sported feathers, some of which have left behind fossilized impressions. For the most part, the feathers we've found have been attached to smaller dinosaurs, many of them along the lineage that gave rise to birds—although in 2012, scientists discovered three nearly complete skeletons of a "gigantic" feathered dinosaur species, Yutyrannus huali, related to the ancestors of Tyrannosaurus Rex .

Various types of dino-feathers have been found in the fossil record over the last 30 years, such as so-called pennaceous feathers (present in most modern birds). These were found on distal forelimbs of certain species like Caudipteryx , serving as proto-wings that were too small to use for flight, as well as around the tip of the tail as plumage. Paleontologists remain unsure of the function of pennaceous feathers—what use could there be for half a wing? A broad range of hypotheses have been proposed: foraging or hunting, pouncing or immobilizing prey, brooding, gliding, or wing-assisted incline running, among others.

Enlarge (credit: MARK GARLICK/SCIENCE PHOTO LIBRARY )

Classic whodunit mysteries work because just about every character ends up being a murder suspect. The demise of non-avian dinosaurs is a lot like that. The Chicxulub impact and its aftereffects created a huge range of potentially lethal suspects. Whodunit? A giant fireball and massive tsunamis? Wild swings in the climate? Global wildfires? A blackened sky that shut down photosynthesis? All of the above?

Modeling these impacts, combined with data on the pattern of extinctions, has led to various opinions on what proved decisive regarding the extermination of so many species. In the latest look at the end-Cretaceous extinction, a team of scientists largely based in Brussels has revisited deposits laid down in the aftermath of the impact and found that much of the debris came from fine dust. When that dust is plugged into climate models, global temperatures plunge by as much as 25° C, and photosynthesis shuts down for almost two years.

Dust to dust

There was a lot going on in the atmosphere in the years after the impact. Debris thrown up by the impact would have re-entered Earth's atmosphere, burning up into fine rocky and sulfur-rich particles in the process. The heat generated by this process would have set off massive wildfires, adding a lot of soot to the mix. And all of that was churned up with the debris from the impact that stayed within the atmosphere.

Enlarge / It takes careful study and the right kind of bones to determine how something like this breathed. (credit: Tito Aureliano et. al. )

Somewhere in Earth’s past, some branches on the tree of life adopted a body plan that made breathing and cooling down considerably more efficient than how mammalian bodies like ours do it. This development might not seem like much on the surface, until you consider that it may have ultimately enabled some of the largest dinosaurs this planet has ever known. It was so successful that it was maintained by three different groups of extinct species and continues to exist today in the living descendants of dinosaurs.

Because lungs don’t usually survive fossilization, one might wonder how scientists are able to ascertain anything about the breathing capabilities of extinct species. The answer lies within their bones.

In a suite of papers published in late 2022 and early 2023 , paleontologists examined fossil microstructure within some of the earliest known dinosaurs to determine just how early parts of this system evolved.

Enlarge / The two skeletons are completely intertwined. (credit: Gang Han)

A new fossil described this week captures two intertwined animals caught in a life-or-death struggle right before both were entombed in a volcanic event. Published in Scientific Reports this Tuesday, the fossil doesn’t capture one dinosaur attacking another—rather, the predator in this case is a smaller mammal known as Repenomamus robustus, and it died with its teeth clamped upon the herbivorous Psittacosaurus lujiatunensis , a dinosaur three times its size.

Gut contents from a Repenomamus fossil described in 2005 prove this same mammalian species ate very young and considerably smaller Psittacosaurus . But the remarkable fossil revealed today is the first evidence of any Cretaceous mammal attacking a larger dinosaur. It’s an astounding snapshot of ancient behavior, challenging previous assumptions of predator/prey dynamics millions of years ago.

A final struggle

These two species in the fossil couldn’t be more different. Psittacosaurus is a type of bipedal ceratopsian dinosaur—an early relative of dinosaurs such as Triceratops—with a large beak-like snout and spiky tail bristles. This was a herd animal, and it's the most commonly found fossil in the Lujiatun Member of the Lower Cretaceous Yixian Formation of China. This particular Psittacosaurus was approximately 6.5–10 years old when it died.

Enlarge (credit: Royal Tyrrell Museum of Palaeontology)

Borealopelta mitchelli found its way back into the sunlight in 2017, millions of years after it had died. This armored dinosaur is so magnificently preserved that we can see what it looked like in life. Almost the entire animal—the skin, the armor that coats its skin, the spikes along its side, most of its body and feet, even its face—survived fossilization. It is, according to Dr. Donald Henderson, curator of dinosaurs at the Royal Tyrrell Museum, a one-in-a-billion find.

Beyond its remarkable preservation, this dinosaur is an important key to understanding aspects of Early Cretaceous ecology, and it shows how this species may have lived within its environment. Since its remains were discovered, scientists have studied its anatomy, its armor, and even what it ate in its last days, uncovering new and unexpected insight into an animal that went extinct approximately 100 million years ago.

Down by the sea

Borealopelta is a nodosaur, a type of four-legged ankylosaur with a straight tail rather than a tail club. Its finding in 2011 in an ancient marine environment was a surprise, as the animal was terrestrial.