SciTech

The Oxford Student | Friday 10 June 2022 SciTech | 29 SciTech

Pterrifying: Fantastic beasts in a flash

Yexuan ZHU

The old king - Dinosaurs

Dinosaurs are the most canonical figures appearing in people’s heads when thinking about the pre-human past of the earth. Though none of us humans, perhaps luckily considering their destructive power, has the chance to meet these mysterious creatures in life, efforts never ceased to unveil their biology. Among palaeontologists, there remains a fundamental but controversial dispute - cold or warm, are dinosaurs’ blood? A recent fossil analysis has shifted the balance to the warm-blood hypothesis. The more scientific terms for warm-blooded and cold-blooded are endothermic and exothermic, respectively. Warm-blooded, or endothermic, animals can maintain a relatively constant body temperature and have higher metabolic rates. On the contrary, cold-blooded animals, such as reptiles, rely on the environment to maintain body temperature. As body temperature is crucial for a variety of physiological functions, warm-blooded organisms are less limited by their surroundings. Scientists have found a new marker of endothermy, the chemical outcomes of the higher metabolism, waste molecules that accumulate in dark patches in fossils. These patches are chemically stable, which makes them better markers than growth rings or isotopes used before.

After examining the thigh bones of 55 species from ancient to modern, scientists conclude that dinosaurs are highly metabolically active and thus most of them are likely to be warm-blooded. They possibly had body temperatures similar to those of modern birds, around 42 degrees celsius. This discovery also challenges current views of the massive extinction of dinosaurs - many scientists attribute this to them being cold-blooded. Now palaeontologists may need to turn to other factors to decipher the disappearance of dinosaurs.

Flying dinosaurs - Pterosaurs

During the Jurassic period, territorial dinosaurs were not the only inhabitants of the earth. They were joined by their avian pals - pterosaurs. Pterosaurs were the first vertebrates able to fly on Earth, doing so by wing membranes supported by their fingers. Earlier this year, research confirmed that pterosaurs also had feathers as modern birds do, and even surprisingly had colourful plumage. Previous analysis of pterosaur fossils had limited soft tissue remains. As a result, scientists failed to reach a consensus over whether these creatures had real feathers with their characteristic organisation of fibres. In April, a team at University College Cork published their conclusions from a part of the skull of a pterosaur named Tupandactylus imperator, with soft tissue wellpreserved. They found filaments with branching structures similar to those of modern bird feathers. They also found melanosomes, cells that secrete pigments, of different morphologies. This is an indication that they produce different colours - usually spherical melanosomes generate warm colours, while the elongated ones generate dark colours. Just imagine, pterosaurs carried feathers and showed off their flamboyance in the Jurassic sky. Now the new question for scientists is the function of these feathers - as pterosaurs already had membranous wings, it is unlikely that the feathers serve the same function. Possible explanations propose that the feathers may be used for insulation or sexual attraction.

Image credits: Jon Butterworth

Headbutting champions - Discokeryx xiezhi

Giraffes have evolved long necks and small heads to forage leaves high up in the trees, but their ancient relatives that have been recently characterised, Discokeryx xiezhi, armoured their heads and necks for violent sexual competition. The first pieces of skull and neck vertebrae of D. xiezhi were discovered by palaeontologist Jin Meng in the Junggar Basin in China. All the bone fragments appear to be substantially thickened, with the skull exceeding an inch in thickness. For palaeontologists, to find out the purpose of having strong skulls and necks does not take a hard guess: male D. xiezhi would compete for mating opportunities by headbutting. This is not an uncommon fighting strategy among males, but D. xiezhi did adapt to this in an extreme way. Meng and his colleagues conclude that D. xiezhi had one of the most defensive and sophisticated heads and necks within the animal kingdom, even stronger than those of Pachycephalosaurs, dinosaurs known to be good at headbutting. Extreme adaptations to lifestyles seen in modern giraffes and their ancient relatives highlighted the role of sexual selection, on top of natural selection, in evolution. While the need for feeding selected giraffes with longer necks and D. xiezhi with harder skulls, females also made the same choices.

Our loyal friend - Dogs

Dogs are descendants of wolves that were domesticated by humans around 15,000 to 30,000 years ago. Since then, they have been living with humans and helping us in various activities, for example, hunting and herding, as revealed by art depictions. Simultaneously, either by natural or artificial selection, dogs develop traits that adapt to their roles. A recent study surveyed domestic dog remains in eastern Adriatic sites spanning from the Neolithic era (around 8000 years ago) to the Bronze/Iron era (around 2000 years ago). Researchers found that the body weight of domestic dogs almost doubled during this period. Scientists relate this change in body size to the need for dogs to help defend livestock from the attack of larger animals, such as wolves and bears. The rationale is that body size is not as important if dogs only acted as hunting partners or food sources. In addition, isotope analysis of the dogs’ skeletons revealed that seasonal transhumance, or the seasonal movement of herdsmen, had already emerged during this period. Dogs with larger

New survey reveals evidence of urban society in the ancient Amazon

Emily HUDSON

For the first time, scientists have identified mounds in the south-west of the Amazon basin as the sites of ancient urban settlements. This contradicts the oft-thought conjecture that civilisation was bought to the Amazon by European invaders, adding to a growing body of evidence for the existence of low-density, urban societies within the vast forest.

Developed areas up to three times the size of Vatican city have been uncovered, thought to have been inhabited by the Carasabe people, who lived in the Bolivian Amazon between 500 and 1400AD. Why the civilisation disappeared after 900 years remains a mystery, but what is truly monumental is the extent and complexity of the society they developed.

Why now?

The discovery is owed primarily to developments in a technology called lidar. This technique uses lasers to create a 3D map of terrain from above, which is especially useful in densely forested areas such as the Amazon basin, and allows scientists to survey an area without disturbing it. It is also far more efficient than sending people out on foot; lidar investigations of six sites in Honduras yielded results that, according to researchers, would have taken 400 years to obtain by conventional means. The discoveries indicate a strong network of mounds and causeways, indicative of urban settlements. Researchers doing investigations in the 1990s also found graves, walls and platforms, so they knew that society had been present—but until this lidar survey, had no indication as to the extent of it. This discovery goes against the common notion that complex societies did not exist in the Amazon, though, as one researcher put it, “given that civilizations rose and thrived in other tropical areas, why shouldn’t something like that exist here?”