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The evolution of the digestive system has formed a significant influence in mammal evolution. With the emergence of mammals, the digestive system was modified in a variety of ways depending on the animal's diet. For example, cats and most carnivores have simple large intestines, while the horse as a herbivore has a voluminous large intestine. [127]
Rapid dominance of conifers and ginkgos in high latitudes, along with mammals becoming the dominant species. First psammobiid bivalves. Earliest rodents. Rapid diversification in ants. 63 Ma Evolution of the creodonts, an important group of meat-eating (carnivorous) mammals. 62 Ma Evolution of the first penguins. 60 Ma
The Virginia opossum, Didelphis virginiana, the only marsupial in temperate North America. Armadillos, opossums and porcupines are present in North America today because of the Great American Interchange. Opossums and porcupines were among the most successful northward migrants, reaching as far as Canada and Alaska, respectively.
The North American land-mammal-age system was formalized in 1941 as a series of provincial land-mammal ages. [2] The system was the standard for correlations in the terrestrial Cenozoic record of North America and was the source for similar time scales dealing with other continents.
Local mammals diversified significantly during the Jurassic. The Morrison Formation is the best source of Jurassic mammal fossils in North America. [67] Local dinosaurs included the ornithopod Camptosaurus, the sauropods Apatosaurus and Diplodocus, and the theropod Allosaurus. [68]
The two oldest-known fossil skeletons of bats, unearthed in southwestern Wyoming and dating to at least 52 million years ago, are providing insight into the early evolution of these flying mammals ...
A microbiologist is proposing the idea that the reign of dinosaurs forced mammals to speed up their reproductive cycle, eliminating key longevity genes. Historic Dinosaur Dominance May Cause ...
The Mesozoic era followed and the dinosaurs began their rise to dominance, spreading into the country before Pangaea split up. During the latter Jurassic Morrison Formation dinosaurs lived in the western states. During the Cretaceous, the Gulf of Mexico expanded until it split North America in half. Plesiosaurs and mosasaurs swam in its waters.