Latest news with #LateJurassic
Yahoo
3 days ago
- General
- Yahoo
Birds were nesting in the Arctic during age of dinosaurs, scientists discover
The Arctic might evoke images of polar bears and seals, but 73m years ago it was a dinosaur stomping ground. Now fossil hunters say these beasts shared their turf with a host of different birds. Researchers believe their discovery of more than 50 bird fossils from the Prince Creek formation in Alaska is the oldest evidence of birds nesting in polar regions, pushing back the date by more than 25m years. 'The previous oldest evidence for polar nesting is a penguin colony from the Eocene of Antarctica [that lived about 46.5m years ago],' said Lauren Wilson, first author of the work from Princeton University. More than 200 species of bird nest in the Arctic today, with the researchers saying they are crucial members of the ecosystem, helping with essential tasks such as pollination and seed dispersal. And the latest findings suggest their presence is nothing new. 'These new fossils fill a major gap in our understanding of bird evolution,' said Prof Patrick Druckenmiller, director of the University of Alaska Museum of the North and a co-author of the study published in the journal Science. While the earliest birds emerged in the Late Jurassic, about 150m years ago, the delicate nature of bird bones means such animals are rare in the fossil record. 'Prior to this work, and with the exception of a few footprints, bird fossils weren't known from Alaska,' said Druckenmiller. The discovery involved far more than mere good fortune, with the team carefully excavating bones as well as washing and sieving material from small, sandy deposits to isolate tiny fossils, many of which were less than 2mm in size. 'It was literally like panning for gold, except bird bones are our prize,' said Druckemiller. Wilson added that many of the bones were from embryos or hatchlings. At least one species of bird, she said, belonged to a now-extinct group called Ichthyornithes, and would have resembled a toothed seagull, while the researchers also found at least one member of another extinct group called Hesperornithes: foot-propelled diving birds with teeth. Many of the fossils came from toothless birds that may have resembled ducks. That, the team note, is significant because features such as a lack of teeth are a hallmark of Neornithes, the group that includes all living birds and their most recent common ancestor. It suggests the prehistoric birds nesting in the Arctic were close relatives of modern birds. Druckenmiller said that, like the Arctic today, the Prince Creek ecosystem of 73m years ago would have experienced about six months of continuous daylight in the summer, during which it would have been very green. As a result there would have been an abundance of food. However, the winter would have been chilly. 'While [winters were] not as harsh as today, year-round residents would have to endure freezing temperatures, occasional snowfall, and about four months of continuous winter darkness,' he said. Wilson said the newly discovered fossils showed the birds were breeding in the Arctic, but she said it was unclear if they spent the winter there, adding it was highly likely at least some of them were migratory. Steve Brusatte, a professor of palaeontology and evolution at the University of Edinburgh who was not involved in the work, said that while the fossils discovered by the team were 'absolutely minuscule', they told a huge story. 'These fossils show that birds were already integral parts of the these high-latitude communities many tens of millions of years ago, and thus that these communities are a long-term norm of Earth history, not a recent ecological innovation of modern times,' he said.
Yahoo
03-05-2025
- Science
- Yahoo
94 million years ago sea monsters got wiped out by boiling oceans, high CO2: Study
For millions of years, the Late Jurassic and Early Cretaceous oceans belonged to enormous and scary hunters. Among them were pliosaurs with giant jaws, toothy crocodile-like reptiles (thalattosuchia), and sleek, fast, fish-shaped predators (ichthyosaurians, or sea monsters) that dominated the seas. These were apex predators, ruling their underwater kingdoms with unchallenged power. But then, something shifted. The middle Cretaceous saw a dramatic upheaval in the marine world. The long reign of ichthyosaurs, thalattosuchians, and pliosaurids started to end abruptly. They vanished from the fossil record. In their place, a new cast of characters emerged: the mosasaurs, plesiosaurs, and even diverse kinds of sharks. The abrupt disappearance of these long-reigning marine animals and the rise of new ones has long been a mystery for experts. A new study, presented at the General Assembly of the European Geosciences Union next week, sheds light on this ancient mystery. According to Valentin Fischer of the Université de Liège and his colleagues, the culprit was likely a period of intense ocean anoxia and dramatic climate volatility. Ocean anoxia is when large parts lose most or all of their oxygen. This tumultuous era coincided with the Cenomanian/Turonian transition, which estimates suggest occurred around 93.9 million years ago. This was a relatively short but significant period of environmental stress. It is 'the hottest interval of the last 541 million years.' During this transition, carbon dioxide levels soared to their highest point in the Cretaceous. The delicate balance of ocean nutrients, like sulfur and iron, was thrown into disarray. The combination of extreme heat, widespread oxygen loss in the oceans, high CO2 levels, and nutrient imbalances created a challenging environment that likely triggered the die-off of marine life and reshaped marine ecosystems. The study suggests it triggered a major reshuffling of the oceanic food web, leading to the disappearance of established predators and the rise of new ones. 'This transition is associated with a shift in top predators, creating the unique and somewhat short-lived oceanic food webs of the Late Cretaceous,' the researchers noted. The research involved a comprehensive analysis of hundreds of marine reptile lineages. The team examined the evolutionary relationships and compiled the largest 2D and 3D marine reptile data dataset. Through this extensive analysis, they pinpointed how these extinctions unfolded and impacted the predatory capabilities of Cretaceous marine reptiles. 'Our analyses showed that the Cenomanian-Turonian transition is associated with elevated rates of extinction and that these extinctions disproportionally targeted some groups of large and fast predators, in a stepwise manner,' Fischer noted in the press release. Dr. Fischer highlights a key piece of evidence for the shift in predatory capabilities: the significant differences in skull shapes of marine reptiles before and after the Cenomanian/Turonian transition. These altered skull morphologies directly impacted their ability to hunt and consume prey. It led to 'distinct bite force.' The reign of the ancient marine giants ended not with a bang, but with a shift. This dramatic environmental upheaval paved the way for the iconic marine predators of the Late Cretaceous. However, the asteroid event led to the extinction of most of these marine creatures, including mosasaurs and plesiosaurs, approximately 66 million years ago. This new research provides insight into how Earth's forces can cause major evolutionary shifts.
