Giant Ice Age species including elephant-sized sloths and powerful sabre-toothed cats that once roamed the windswept plains of Patagonia, southern South America, were finally felled by a perfect storm of a rapidly warming climate and humans, a new study has shown.
Research led by the Australian Centre for Ancient DNA (ACAD) at the University of Adelaide, published today in Science Advances, has revealed that it was only when the climate warmed, long after humans first arrived in Patagonia, did the megafauna suddenly die off around 12,300 years ago.
The timing and cause of rapid extinctions of the megafauna has remained a mystery for centuries.
"Patagonia turns out to be the Rosetta Stone - it shows that human colonisation didn't immediately result in extinctions, but only as long as it stayed cold," says study leader Professor Alan Cooper, ACAD Director. "Instead, more than 1000 years of human occupation passed before a rapid warming event occurred, and then the megafauna were extinct within a hundred years."
Climate change is by definition a global phenomenon, but there are few locations feeling its immediate impacts like Australia's Great Barrier Reef. Just a month after local scientists were left reeling as warming seas triggered the worst coral bleaching event in its history, researchers are now reporting the reef's only endemic mammal species has become extinct as a result of rising sea levels, describing its demise as the first mammal species to be killed off by human-induced global warming.
Implications of lemuriform extinctions for the Malagasy flora
Authors:
Federman et al
Abstract:
Madagascar’s lemurs display a diverse array of feeding strategies with complex relationships to seed dispersal mechanisms in Malagasy plants. Although these relationships have been explored previously on a case-by-case basis, we present here the first comprehensive analysis of lemuriform feeding, to our knowledge, and its hypothesized effects on seed dispersal and the long-term survival of Malagasy plant lineages. We used a molecular phylogenetic framework to examine the mode and tempo of diet evolution, and to quantify the associated morphological space occupied by Madagascar’s lemurs, both extinct and extant. Using statistical models and morphometric analyses, we demonstrate that the extinction of large-bodied lemurs resulted in a significant reduction in functional morphological space associated with seed dispersal ability. These reductions carry potentially far-reaching consequences for Malagasy ecosystems, and we highlight large-seeded Malagasy plants that appear to be without extant animal dispersers. We also identify living lemurs that are endangered yet occupy unique and essential dispersal niches defined by our morphometric analyses.
The beautiful title "Siberian unicorn" belongs to Elasmotherium sibiricum - an elasmotherium Siberian rhinoceros, which as previously thought became extinct 350,000 years ago. Nowadays the researchers of Tomsk State University (TSU) figured out that the "unicorn" found his last refuge "only" 29,000 years ago in Kazakhstan. The article, describing the new location of the fossil mammals in the Pavlodar Irtysh, was published in February 2016 in the American Journal of Applied Science.
"Most likely, in the south of Western Siberia it was a refúgium, where this rhino had preserved the longest in comparison with the rest of its range. There is another option that it could migrate and dwell for a while on the more southern areas," said Andrey Shpanski, a paleontologist at TSU. These conclusions were made due to research of the rhinocero's skull, found near Kozhamzhar village in Pavlodar region (Kazakhstan). The skull is well preserved: there are some cracks but no trace of pelletization, gnawing, and exfoliation. The fossils of the "unicorn" were examined by radiocarbon AMS-method analysis in the laboratory 14CHRONO Centre for Climate, the Environment, and Chronology (School of Geography, Archaeology and Palaeoecology; Queen's University Belfast; Belfast, UK). It turned out that the skull belonged to the animals that died 29,000 years ago. "Most likely, it was a very large male of very large individual age (teeth not preserved). The dimensions of this rhino today are the biggest of those described in the literature, and the proportion are typical," said the University's scientist.
Extrinsic forcing of plant ecosystems in a large igneous province: The Columbia River flood basalt province, Washington State, USA
Authors:
Ebinghaus et al
Abstract:
Volcanism associated with large igneous provinces (LIPs) has been implicated in both global climate and environmental change. To determine the impact of LIP volcanism on plant ecology we have examined plant community succession in sedimentary interbeds of the Columbia River flood basalt province (CRBP; northwest United States). Interbasaltic vegetation is characterized by primary succession communities that inhabit fresh lava surfaces until terminated by the next eruptive event, and it is assumed that longer volcanic hiatuses should lead to more mature plant communities. This expected succession trajectory is contradicted by palynological data that show that seral succession declines during the phase of waning CRPB volcanism and prolonged interbed intervals. Frequent volcanic activity and increased deposition of Snake River Plain hotspot ashes during this phase resulted in ecological disturbance of intralava field vegetation. Together with geochemical proxies from interbed sediments, this suggests that CRBP flora was largely driven by extrinsic forcing, and implies that LIP volcanism of similar scale and magnitude to that of the CRBP had a limited environmental impact. This study supports the theory that past biotic extinctions were triggered by numerous factors rather than a single geological event.
Mountain uplift explains differences in Palaeogene patterns of mammalian evolution and extinction between North America and Europe
Authors:
Eronen et al
Abstract:
Patterns of late Palaeogene mammalian evolution appear to be very different between Eurasia and North America. Around the Eocene–Oligocene (EO) transition global temperatures in the Northern Hemisphere plummet: following this, European mammal faunas undergo a profound extinction event (the Grande Coupure), while in North America they appear to pass through this temperature event unscathed. Here, we investigate the role of surface uplift to environmental change and mammalian evolution through the Palaeogene (66–23 Ma). Palaeogene regional surface uplift in North America caused large-scale reorganization of precipitation patterns, particularly in the continental interior, in accord with our combined stable isotope and ecometric data. Changes in mammalian faunas reflect that these were dry and high-elevation palaeoenvironments. The scenario of Middle to Late Eocene (50–37 Ma) surface uplift, together with decreasing precipitation in higher-altitude regions of western North America, explains the enigma of the apparent lack of the large-scale mammal faunal change around the EO transition that characterized western Europe. We suggest that North American mammalian faunas were already pre-adapted to cooler and drier conditions preceding the EO boundary, resulting from the effects of a protracted history of surface uplift.
Most supposed impact indicators at 29 sites are too old or too young to be remnants of an ancient comet that proponents claim sparked climate change at the end of the Ice Age, killed America's earliest people and caused a mass animal extinction
Controversy over what sparked the Younger Dryas, a brief return to near glacial conditions at the end of the Ice Age, includes a theory that it was caused by a comet hitting the Earth.
As proof, proponents point to sediments containing deposits they believe could result only from a cosmic impact.
Now a new study disproves that theory, said archaeologist David Meltzer, Southern Methodist University, Dallas. Meltzer is lead author on the study and an expert in the Clovis culture, the peoples who lived in North America at the end of the Ice Age.
Meltzer's research team found that nearly all sediment layers purported to be from the Ice Age at 29 sites in North America and on three other continents are actually either much younger or much older.
Scientists agree that the brief episode at the end of the Ice Age — officially known as the Younger Dryas for a flower that flourished at that time — sparked widespread cooling of the Earth 12,800 years ago and that this cool period lasted for 1,000 years. But theories about the cause of this abrupt climate change are numerous. They range from changes in ocean circulation patterns caused by glacial meltwater entering the ocean to the cosmic-impact theory.
The cosmic-impact theory is said to be supported by the presence of geological indicators that are extraterrestrial in origin. However a review of the dating of the sediments at the 29 sites reported to have such indicators proves the cosmic-impact theory false, said Meltzer.
Meltzer and his co-authors found that only three of 29 sites commonly referenced to support the cosmic-impact theory actually date to the window of time for the Ice Age.
The findings, "Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago," were reported May 12, 2014, in the Proceedings of the National Academy of Sciences.
Analysis of coprolites from the extinct mountain goat Myotragus balearicus
Authors:
Welker et al
Abstract:
Humans colonized the Balearic Islands 5–4 ka ago. They arrived in a uniquely adapted ecosystem with the Balearic mountain goat Myotragus balearicus (Bovidae, Antilopinae, Caprini) as the only large mammal. This mammal went extinct rapidly after human arrival. Several hypotheses have been proposed to explain the extinction of M. balearicus. For the present study ancient DNA analysis (Sanger sequencing, Roche-454, Ion Torrent), and pollen and macrofossil analyses were performed on preserved coprolites from M. balearicus, providing information on its diet and paleo-environment. The information retrieved shows that M. balearicus was heavily dependent on the Balearic box species Buxus balearica during at least part of the year, and that it was most probably a browser. Hindcast ecological niche modelling of B. balearica shows that local distribution of this plant species was affected by climate changes. This suggests that the extinction of M. balearicus can be related to the decline and regional extinction of a plant species that formed a major component of its diet. The vegetation change is thought to be caused by increased aridity occurring throughout the Mediterranean. Previous hypotheses relating the extinction of M. balearicus directly to the arrival of humans on the islands must therefore be adjusted.
Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans
Authors:
Mark A. Loewen, Randall B. Irmis, Joseph J. W. Sertich, Philip J. Currie and Scott D. Sampson
Abstract:
The Late Cretaceous (~95–66 million years ago) western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah—including a new taxon which represents the geologically oldest member of the clade—to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades.
Mammal disparity decreases during the Cretaceous angiosperm radiation
Authors:
David M. Grossnickle and P. David Polly
Abstract:
Fossil discoveries over the past 30 years have radically transformed traditional views of Mesozoic mammal evolution. In addition, recent research provides a more detailed account of the Cretaceous diversification of flowering plants. Here, we examine patterns of morphological disparity and functional morphology associated with diet in early mammals. Two analyses were performed: (i) an examination of diversity based on functional dental type rather than higher-level taxonomy, and (ii) a morphometric analysis of jaws, which made use of modern analogues, to assess changes in mammalian morphological and dietary disparity. Results demonstrate a decline in diversity of molar types during the mid-Cretaceous as abundances of triconodonts, symmetrodonts, docodonts and eupantotherians diminished. Multituberculates experience a turnover in functional molar types during the mid-Cretaceous and a shift towards plant-dominated diets during the late Late Cretaceous. Although therians undergo a taxonomic expansion coinciding with the angiosperm radiation, they display small body sizes and a low level of morphological disparity, suggesting an evolutionary shift favouring small insectivores. It is concluded that during the mid-Cretaceous, the period of rapid angiosperm radiation, mammals experienced both a decrease in morphological disparity and a functional shift in dietary morphology that were probably related to changing ecosystems.
