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Sabertooth cats and dire wolves were not in competition for similar prey
Sabertooth cats scavenged more intensively during cooler intervals
Coyote diets were substantially affected by the extinction of megafauna
Rancho La Brea fossils reveal that diets of carnivorans are not always conserved
Summary
The fossils preserved in the Rancho La Brea "tar" seeps in southern California span the past â50,000 years and provide a rare opportunity to assess the ecology of predators (e.g., the American lion, sabertooth cats, cougars, dire wolves, gray wolves, and coyotes), including clarifying the causes and consequences of the terminal Pleistocene extinction event. Here, a multi-proxy approach elucidates dietary responses of carnivorans to changing climates and megafaunal extinctions. Using sample sizes that are unavailable anywhere else in the world, including hundreds of carnivoran and herbivore specimens, we clarify the paleobiology of the extinct sabertooth cats and dire wolves--overturning the idea that they heavily competed for similar prey. Canids (especially the dire wolf) consumed prey from more open environments than felids, demonstrating minimal competition for prey throughout the latest Pleistocene and largely irrespective of changing climates, including just prior to their extinction. Coyotes experienced a dramatic shift in dietary behavior toward increased carcass utilization and the consumption of forest resources (prey and/or plant resources) after the terminal Pleistocene megafaunal extinction. Extant predatorsâ ability to effectively hunt smaller prey and/or utilize carcasses may have been a key to their survival, especially after a significant reduction in megafaunal prey resources. Collectively, these data suggest that dietary niches of carnivorans are not always static and can instead be substantially affected by the removal of top predators and abundant prey resources.
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Saber-tooth surprise: Fossils redraw picture of the fearsome big cat
Intense look at La Brea Tar Pits explains why we have coyotes, not saber-toothed cats
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Large numbers of bird species went extinct in New Zealand after human colonization
We reconstruct diversity dynamics of New Zealandâs birds
It would take 50 million years (Ma) to recover the diversity of bird species lost
If threatened species go extinct, up to 10 Ma needed to return to todayâs levels
Summary
Islands are at the frontline of the anthropogenic extinction crisis. A vast number of island birds have gone extinct since human colonization, and an important proportion is currently threatened with extinction. While the number of lost or threatened avian species has often been quantified, the macroevolutionary consequences of human impact on island biodiversity have rarely been measured. Here, we estimate the amount of evolutionary time that has been lost or is under threat due to anthropogenic activity in a classic example, New Zealand. Half of its bird taxa have gone extinct since humans arrived and many are threatened, including lineages forming highly distinct branches in the avian tree of life. Using paleontological and ancient DNA information, we compiled a dated phylogenetic dataset for New Zealandâs terrestrial avifauna. We extend the method DAISIE developed for island biogeography to allow for the fact that many of New Zealandâs birds are evolutionarily isolated and use it to estimate natural rates of speciation, extinction, and colonization. Simulating under a range of human-induced extinction scenarios, we find that it would take approximately 50 million years (Ma) to recover the number of species lost since human colonization of New Zealand and up to 10 Ma to return to todayâs species numbers if currently threatened species go extinct. This study puts into macroevolutionary perspective the impact of humans in an isolated fauna and reveals how conservation decisions we take today will have repercussions for millions of years.
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Birds driven to extinction in New Zealand will take 50 million years to recover
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Yaminuechelys sulcipeculiaris sp. nov.Â
A new species of a long-necked chelid from the uppermost Cretaceous (CampanianâMaastrichtian) is presented in this contribution. Yaminuechelys sulcipeculiaris sp. nov. is found in outcrops of the La Colonia Formation in the northeast part of Chubut province, Argentina. This new species is mainly represented by carapacial, plastral, and postcranial remains (vertebrae and long bones). It was assigned to Yaminuechelys because it presents characters shared with the species Yaminuechelys gasparinii de la Fuente, Lapparent de Broin, and Manera de Bianco, 2001 and Yaminuechelys maior (Staesche, 1929). Those characters are a large shell with irregular polygons distributed on the external surface, the difference in length between the anterior and posterior peripheral bones, and the neural series separated from the suprapygal bones. Other characters, like the position of the sulcus between vertebral 5 and marginal 12 crossing the suprapygal and the location of the sulcus between the vertebral 5 and the marginal 11 crossing the costal 8 and suprapygal, suggest it is a new species. According to the phylogenetic analysis performed, the new species forms a monophyletic group together with Y. maior, and Y. gasparinii. The survival of Yaminuechelys to the K/Pg extinction event is also discussed.
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