The last and longest segment of the Mesozoic era was the final one. The K-Pg extinction event took place 66 million years ago, from the minor extinction event that took place about 140 million years ago. According to the National Park Service, the name comes from the Latin word for chalk, which means "widespread chalk deposits."
According to the Australian Museum, the continents were very different in the early days of the dinosaur era. The parts of Pangaea that were still together were drifting apart. Laurasia and Gondwana were separated by the Tethys ocean. The North and South Atlantic were still closed, even though the Central Atlantic was opening up. Most of the landmasses we are familiar with were underwater by the middle of the century. The continents were close to their modern configuration by the end of the period. The shapes of Africa and South America were different. India and Australia were not part of the same place.
According to the National Park Service, the development and radiation of flowering plants was one of the hallmarks of the Cretaceous period. This radiation "gave rise suddenly and mysteriously to exquisite angiosperm diversity in the mid-Cretaceous," an evolutionary development that troubled Charles Darwin, according to a review in the journal. According to William E. Friedman, an evolutionary biologist at Harvard University, flowering plants must have started developing long before the end of the last Ice Age. The burst of floral development may show how evolution can happen very fast.
Recent research shows that some flowering plants may have appeared in the dinosaur period.
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The flowering plants of the dinosaurs would have been rare and may have been evolutionary links between older plants that looked similar to angiosperms. According to the Brooklyn Botanic Garden, the earliest angiosperm fossils are 125 million to 130 million years old. Plants of the genera Archaefructus and Montsechia show the first evidence of ovary in plants but may lack petals.
Scientists believe that pollinating insects, such as bees and wasp, played a key role in the explosion of flowering plants. The Washington Native Plant Society says that this is an example of co- evolution.
The mid-Cretaceous saw abundant populations of both insects and flowering plants. The first direct fossil evidence of insect pollination in the mid-Cretaceous was found in the amber of a tumbling flower beetle. The beetle has body parts that are specialized for feeding on flowers and the pollen grains have characteristics associated with pollination.
The 100 million-year-old Discoscapa apicula was reported on in a 2020 paper by scientists. The insect encased in amber had some similarities with modern bees such as hind legs laden with pollen and wing vein features.
According to the Illinois Extension at the University of Illinois, pollination by insects gave flowering plants an advantage over plants that only spread pollen by wind. Competition for insect attention may have led to the development of many different size, shapes, colors and fragrances of flowers we see today. As diverse flower forms lured insects to pollinate them, insects adapted to different ways of gathering nectar and moving pollen, thus setting up the intricate co- evolutionary systems found to this day.
Some finds have estimated that some insects arrived before flowers. According to a report in the journal Science, in 2009, researchers found that 11 species of scorpion flies had the same mouth parts as bees. The study said that these likely pollinating insects were fed on non flowering plants. Around the time of the global gymnosperm-to-angiosperm turnover, these creatures went extinct. In the 1990s, researchers reported that bee- or wasp-like insects built hive-like nest in Arizona, dating back to more than 200 million years ago. According to the journal Palaeogeography, Palaeoclimatology, Palaeoecology (opens in new tab), the structures most likely came from beetle chambers or other creatures. The evaluation shows that the bee origins are not related to the angiosperms.
Dinosaurs ate flowers. Two dinosaur coprolites found in Utah contain pieces of angiosperm wood, according to a study presented at the Society of Vertebrate Paleontology annual meeting. A prehistoric ankylosaur had fruit in its gut.
According to the University of Bristol researchers, the evidence shows that dinosaurs ignored angiosperms in the late 70s and early 80s. Betsy Kruk used to be a volunteer researcher at the Field Museum in Chicago and is now a principal investigator and project manager at Material Culture consulting.
The dinosaurs were an age of animals. Dinosaurs dominated the land, while mosasaurs swam in the ocean. The largest flying animal of all time, Quetzalcoatlus, had a wingspan of over 30 feet.
The largest land predator of all time was the tyrannosaurus rex. The large sauropods, such as Apatosaurus and Diplodocus, went extinct at the end of the dinosaurs' existence. The titanosaurs were the most successful sauropods of the period, and the past two decades have seen a boom in titanosaur discoveries.
The large herds of herbivorous ornithischians flourished during the last century. Iguanodon, Ankylosaurus, and the ceratopsians are related to the duck-billed dinosaurs. A group of mostly herbivorous dinosaurs with bird-like hips were the most common type of ornithischians. Theropods were the apex predator until the end of this period.
Birds joined the pterosaurs in the air. The origin of flight has been a topic of debate for a long time. Small reptiles may have evolved flight from behaviors. According to the ground up hypothesis, flight evolved from the ability of small theropods to leap high to grab prey. Early research indicated that the primary function of feathers was thermoregulation. According to a 1975 study in The Quarterly Review of Biology, they could be moved to protect themselves from the sun when it was hot. According to a study in the International Journal of Organic Evolution, signaling and sense may have been involved in the evolution of these feather.
According to the Australian Museum, the earliest bird was 150 million years ago and resembled small dinosaurs more than birds today. A number of birds arrived on the scene with features that could be similar to current birds. The Australian Museum said that "bird-like dinosaurs, primitive birds and early modern birds all co-existed" for a stretch of the dinosaur period.
About 125 million years ago, there was a bird. It was a crow-size bird with a toothless beak, similar to the tree-dwelling birds, and flight-worthy feathers. According to the California Academy of Sciences, the ancient birds probably had dark feathers on their torsos and lighter-colored wings.
Birds are dinosaurs.
Many marine groups reached their peak levels of diversity during the Cretaceous period. There were mollusks that built reefs similar to today's coral reefs, as well as sharks, lobsters and crabs, sand dollar-like creatures known as echinoids, and a type of fish called ray-finned fish.
Early mammals existed in the world at the time. The view of scientists has been that mammals couldn't evolve many species types because dinosaurs were the most popular. After the mass extinction of dinosaurs, mammals were able to evolve into many different forms. According to a study published in the journal Trends in Ecology and Evolution, mammals may have been exposed to radiations during the dinosaur age. Evolutionary suppression of therians, the ancestors of today's mammals, may have come from ancient relatives of mammals known as mammaliaforms.
In one of Earth's five great mass extinction events, nearly all large vertebrates and many tropical invertebrates became extinct. The mass extinction is thought to have been caused by an asteroid that crashed into Mexico. The American Museum says that the event killed off all nonavian dinosaurs, all pterosaurs, and many marine reptiles. Most of the species were dead at the time.
What happened when the asteroid hit?
The K-Pg extinction event is called a mass die-off because it marks the boundary between the two periods. The event used to be called the Cretaceous-Tertiary (K-T) event, but the group that sets standards for geologic terminology now considers tertiary out of date.
The crater in the Yucatn Peninsula is believed to be the site of the asteroid's landing. The K-Pg event took place within 30,000 years of this crater. "We've shown the impact and the mass extinction coincide as much as one can possibly demonstrate with existing dating techniques," Paul Renne, the lead scientist in the study, told Live Science.
The K-Pg extinction was associated with an extraterrestrial impact by scientists. The thin layer of clay was found to contain high concentrations of iridium. In meteorites and asteroids, this element is more common than on Earth, according to the lunar and planetary science institute. Other researchers found a form of mineral called "shocked quartz" and tiny glass-like globes called tektites that form from droplets of melted rock. When an alien object strikes Earth, there are geological features.
According to Live Science, research in 2020 found that the object that carved out Chicxulub hit Earth at the most destructive angle. The 7.5 mile-wide (12 km) asteroid, traveling at about 27,000 mph (43,000 km/h), would have caused a lot of damage.
A shock wave with "hurricane-force winds" rippling across the Americas would have been caused by the asteroid's impact. As debris from the impact fell back to Earth, it would have caused the atmosphere to cook, causing forest fires, and painting the sky red. The heat pulse was burning vegetation and cooking living things that were unable to burrow or dive.
Kruk said that the rain of hot dust raised global temperatures for hours after the impact. Small animals may have been able to survive the initial heat blast.
Part of the sun's rays may have been blocked for months or years because of the asteroid's impact. It may have lasted as long as 16 years with a 30 year recovery period. According to the Natural History Museum in London, if the sun were to go down, plants would die and the food chain would be disrupted.
Live Science previously reported that reduced sunlight would have caused global temperatures to plunge from 81 F to 41 F in the tropics. Large active animals with high energy needs would have been affected by the new cold climate.
Smaller, omnivorous animals, like mammals, lizards, turtles or birds, may have been able to survive as scavengers feeding on the carcasses of dead dinosaurs, while smaller animals with lower metabolisms were best able to wait the disaster out
According to the University of Maryland, greenhouse warming could have lasted 100,000 years. The carbonite rocks would have released a lot of carbon dioxide into the atmosphere. According to the American Museum of Natural History, there was a series of eruptions at the Deccan traps just before the impact. According to the University of Maryland, these catastrophes combined with the asteroids to heat up the planet.
Climate Policy Watcher says that the world was a warmer place before global warming started. Kruk said that the poles were cooler than the lower latitudes. This idea is supported by fossils of tropical plants. According to Climate Policy Watcher, warm ocean currents, unfrozen poles and levels of CO2 that were relatively high before the extinction event all combined to create a hot planet.
The animals lived all over the place. The Hadrosaur fossils were found in Alaska and the rainforest was found in the mid-Cretaceous.
There is a cast of titanosaurs at the American Museum of Natural History and you can learn about them. There is a chance that we've entered a new mass extinction event at the Natural History Museum.
Mary Bagley and Laura Geggel contributed to the original article.
The original article was published on Live Science on January 8, 2016
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