Latest news with #Cretaceous-Paleogene
Forbes
29-04-2025
- Science
- Forbes
Life At Impact Site Of Dinosaur-Killing Asteroid Recovered Surprisingly Fast
At the Cretaceous-Paleogene transition 66 million years ago, an asteroid about 10 kilometers in diameter struck a shallow sea in what is today Southeast Mexico. The impact formed the Chicxulub crater, which is around 200 kilometers wide and one kilometer deep. The impact would have thrown trillions of tons of dust into the atmosphere, blocking the sunlight and cooling the Earth's climate significantly. Entire ecosystems collapsed and the impact caused the extinction of 75 percent of all species, including all non-avian dinosaurs. At the impact site every life form was virtually wiped out, but just 30,000 years later marine life flourished thanks to a hydrothermal system created by the asteroid shattering the seafloor. In 2016, an international team of researchers retrieved over 829 meters of cores from within the crater. A new study based on chemical traces and microfossils found in the cores presents evidence that marine life returned to the site of the crater less than a decade after the impact. This rapid recovery was likely helped by a hydrothermal system created by the asteroid impact and a steady supply of nutrients in the crater environment. "After the asteroid impact, the Gulf of Mexico records an ecological recovery process that is quite different from that of the global ocean, as continuous hydrothermal activity has created a unique marine environment," says study lead author Honami Sato, an assistant professor at Japan's Kyushu University. The study hinges on a chemical element called osmium, a metallic element common in asteroids. The researchers found evidence that osmium from the remains of the asteroid buried kilometers beneath the impact crater was continuously released in the Gulf of Mexico as hot water moved beneath the shattered seafloor and up toward the surface. The researchers analyzed the chemical composition of sediments covering the crater to determine the extent of the hydrothermal system and how long the enrichment of osmium lasted. Microfossils preserved in the same sediments allowed the scientists to reconstruct how species diversity changed after the impact. The results show that as the hydrothermal system ceased releasing osmium from the asteroid, the types of marine life living at the crater site changed. When the hydrothermal system was releasing osmium, the dominant plankton were species living in high-nutrient environments. When the osmium returned to pre-impact levels, the plankton changed to species adapted to low-nutrient environments. This finding indicates that the ecosystem was no longer being sustained by the nutrients from the hydrothermal system being released into the overlying ocean. Likely the system was buried to deep by sediments accumulating over time in the basin formed by the impact. "This study reveals that impact cratering events, while primarily destructive, can in some cases also lead to significant hydrothermal activity," concludes coauthor Steven Goderis, a research professor at the Vrije Universiteit Brussel, Belgium. "In the case of Chicxulub, this process played a vital role in the rapid recovery of marine ecosystems." The study,"Prolonged 187Os/188Os excursion implies hydrothermal influence after the Chicxulub impact in the Gulf of Mexico," was published in the journal Nature Communications. Additional material and interviews provided by the University of Texas at Austin.
Yahoo
13-03-2025
- Science
- Yahoo
How mammals avoided being eaten by dinosaurs
Early mammals had dark inconspicuous fur and only came out at night until dinosaurs became extinct, scientists believe. A study of colouration of mammals that lived in the Mesozoic era – around 150 million years ago – shows that none had developed the array of patterns and colours seen today and were a dark and dusky greyish-brown shade. The colours are similar to the hue of nocturnal animals, such as moles, mice, rats and bats. Experts say the findings support the hypotheses that early mammals were largely nocturnal and coloured to camouflage them from meat-eating dinosaurs and other predators. After dinosaurs became extinct approximately 66 million years ago, mammals were able to come out during the day and evolve the spots, stripes and brighter colours exhibited by many creatures today, experts believe. Dr Matthew Shawkey, associate professor of biology at the University of Ghent, said: 'Evidence suggests that most mammals were nocturnal in the Jurassic/Cretaceous, perhaps to avoid being eaten by dinosaurs. 'It is likely that the extinction of the dinosaurs enabled mammals to take on new habits, including daytime activity, as they were no longer threatened by dinosaurs. 'Mammals rapidly diversified and spread into new niches previously occupied by dinosaurs.' The findings were only possible because scientists have recently discovered that melanosomes – the cell machinery responsible for pigmentation – can be preserved in fossils. Scientists looked at the melanosomes from 116 living mammals and compared them to the fossilised versions from six types of Mesozoic mammals from around 158 million years ago to see which fur had the closest match. The results stand in stark contrast to the varied melanosome structures found in feathered dinosaurs, early birds, and pterosaurs. There also appeared to be no difference in coat colour between male and female mammals. Writing in the journal Science, the authors said: 'Samples taken from different integumentary locations of each fossil resulted in uniformly dark brown colour, with no evidence of colour patterns such as striping, spots, or counter-shading as seen in extant mammals. 'A nocturnal lifestyle may have enabled these species to avoid predation by diurnal carnivores and, furthermore, may have helped them to survive mass extinction. Darker hairs could help small mammaliaforms to reduce heat loss through insulation 'Our results suggest that the melanosome variation and colour expansion seen in extant mammals may have occurred during their rapid radiation and diversification after the Cretaceous-Paleogene extinction.' Researchers believe that the high melanin content in their fur could have been beneficial for thermoregulation and providing mechanical strength for protection. Broaden your horizons with award-winning British journalism. Try The Telegraph free for 1 month with unlimited access to our award-winning website, exclusive app, money-saving offers and more.
Telegraph
13-03-2025
- Science
- Telegraph
How mammals avoided being eaten by dinosaurs
Early mammals had dark inconspicuous fur and only came out at night until dinosaurs became extinct, scientists believe. A study of colouration of mammals that lived in the Mesozoic era – around 150 million years ago – shows that none had developed the array of patterns and colours seen today and were a dark and dusky greyish-brown shade. The colours are similar to the hue of nocturnal animals, such as moles, mice, rats and bats. Experts say the findings support the hypotheses that early mammals were largely nocturnal and coloured to camouflage them from meat-eating dinosaurs and other predators. After dinosaurs became extinct approximately 66 million years ago, mammals were able to come out during the day and evolve the spots, stripes and brighter colours exhibited by many creatures today, experts believe. Dr Matthew Shawkey, associate professor of biology at the University of Ghent, said: 'Evidence suggests that most mammals were nocturnal in the Jurassic/Cretaceous, perhaps to avoid being eaten by dinosaurs. 'It is likely that the extinction of the dinosaurs enabled mammals to take on new habits, including daytime activity, as they were no longer threatened by dinosaurs. 'Mammals rapidly diversified and spread into new niches previously occupied by dinosaurs.' The findings were only possible because scientists have recently discovered that melanosomes – the cell machinery responsible for pigmentation – can be preserved in fossils. Scientists looked at the melanosomes from 116 living mammals and compared them to the fossilised versions from six types of Mesozoic mammals from around 158 million years ago to see which fur had the closest match. The results stand in stark contrast to the varied melanosome structures found in feathered dinosaurs, early birds, and pterosaurs. There also appeared to be no difference in coat colour between male and female mammals. Writing in the journal Science, the authors said: 'Samples taken from different integumentary locations of each fossil resulted in uniformly dark brown colour, with no evidence of colour patterns such as striping, spots, or counter-shading as seen in extant mammals. 'A nocturnal lifestyle may have enabled these species to avoid predation by diurnal carnivores and, furthermore, may have helped them to survive mass extinction. Darker hairs could help small mammaliaforms to reduce heat loss through insulation 'Our results suggest that the melanosome variation and colour expansion seen in extant mammals may have occurred during their rapid radiation and diversification after the Cretaceous-Paleogene extinction.'
Yahoo
11-03-2025
- Science
- Yahoo
This extinct tree-dwelling mammal may be among humans' closer relatives
The planet's earliest mammals are an important part of our evolutionary history, yet remain shrouded in mystery. One of them, Mixodectes pungens lived in western North America during the early Paleocene–about about 66 to 56 million years ago. It was first discovered over 140 years ago by paleontologist–and 1881 Popular Science profile subject–Edward Drinker Cope. But most of what we know about them came from tiny jawbone fragments and fossilized teeth collected in the years since. Now, we may have some answers, thanks to a well-preserved 62 million-year-old skeleton. This particular Mixodectes pungens specimen represents a mature adult that weighed about three pounds, lived in trees, feasted on leaves, and may be among our closer evolutionary relatives. The findings are detailed in a study published March 11 in the journal Scientific Reports. 'A 62-million-year-old skeleton of this quality and completeness offers novel insights into mixodectids, including a much clearer picture of their evolutionary relationships,' study co-author and Yale University anthropologist Eric Sargis said in a statement. 'Our findings show that they are close relatives of primates and colugos–flying lemurs native to Southeast Asia– making them fairly close relatives of humans.' Mixodectes belonged to an extinct family known as mixodectids and lived during the Paleocene epoch. This geological epoch followed the Cretaceous-Paleogene extinction event that killed off non-avian dinosaurs about 66 million years ago. Many scientists believe that this mass extinction paved the way for the rise of mammals. The skeleton in this study was collected in New Mexico's San Juan Basin by study co-author and New Mexico Museum of Natural History & Science paleontology curator Thomas Williamson. The specimen includes a partial skull with teeth, spinal column, rib cage, forelimbs, and hind limbs. By the anatomy of its limbs and claws, the team believes that it lived in trees and could vertically cling to tree trunks and branches. Its molar teeth had crests that are used to break down abrasive material, which suggests an omnivorous diet heavy on the leaves. 'This fossil skeleton provides new evidence concerning how placental mammals diversified ecologically following the extinction of the dinosaurs,' study co-author and Brooklyn College paleontologist Stephen Chester, said in a statement. 'Characteristics such as a larger body mass and an increased reliance on leaves allowed Mixodectes to thrive in the same trees likely shared with other early primate relatives.' According to the team, Mixodectes was rather large for a tree-dwelling mammal in North America during the early Paleocene. For example, the Mixodectes skeleton in this study is significantly larger than a partial skeleton of Torrejonia wilsoni. This small arboreal mammal from an extinct group of primates called plesiadapiforms was discovered alongside it. While Mixodectes primarily ate leaves, Torrejonia mostly ate fruit. The authors believe that these distinctions in both size and diet suggest that mixodectids likely occupied a unique ecological niche in the early Paleocene that set them apart from their tree-dwelling contemporaries. Mixodectids were also euarchontans, a group of mammals that consists of treeshrews, primates, and colugos. To clarify just where Mixodectes fits on the evolutionary tree, the team conducted two phylogenetic analyses. One analysis supported that they were archaic primates, while the other did not. However, the latter analysis did verify that mixodectids are primatomorphans. This group Euarchonta was made up of primates and colugos, but not treeshrews. 'While the study doesn't entirely resolve the debate over where mixodectids belong on the evolutionary tree, it significantly narrows it,' Sargis said.
