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"Paleontology Eocene."
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Rhinoceros giants : the paleobiology of Indricotheres
Introduces the giant hornless rhinoceros, Indricotherium. These massive animals inhabited Asia and Eurasia for more than 14 million years, about 23 to 37 million years ago. They had skulls 6 feet long, stood 22 feet high at the shoulder, and were twice as heavy as the largest elephant ever recorded, tipping the scales at 44,100 pounds. Fortunately, the big brutes were vegetarians.
Book
Rhinoceros Giants
Written for everyone fascinated by the huge beasts that once roamed the earth, this book introduces the giant hornless rhinoceros, Indricotherium. These massive animals inhabited Asia and Eurasia for more than 14 million years, about 37 to 23 million years ago. They had skulls 6 feet long, stood 22 feet high at the shoulder, and were twice as heavy as the largest elephant ever recorded, tipping the scales at 44,100 pounds. Fortunately, the big brutes were vegetarians. Donald R. Prothero tells their story, from their discovery just a century ago to the latest research on how they lived and died.
eBook
Cretaceous and Eocene decapod crustaceans from Southern Vancouver Island, British Columbia, Canada
A large collection of fossil decapod crustaceans from Cretaceous and Eocene rocks of Vancouver Island, British Columbia, Canada, has yielded a remarkably diverse fauna. The Cretaceous decapod fauna, including previously described and new taxa, contains 17 genera in 14 families, represented by as many as 22 species. The Eocene fauna is less robust, with 7 species and 6 genera in 6 families. This publication includes one new family; three new genera; eight new species; and nine new combinations.
eBook
Pliocene and Eocene provide best analogs for near-future climates
As the world warms due to rising greenhouse gas concentrations, the Earth systemmoves toward climate states without societal precedent, challenging adaptation. Past Earth system states offer possible model systems for the warming world of the coming decades. These include the climate states of the Early Eocene (ca. 50 Ma), the Mid-Pliocene (3.3–3.0 Ma), the Last Interglacial (129–116 ka), the Mid-Holocene (6 ka), preindustrial (ca. 1850 CE), and the 20th century. Here, we quantitatively assess the similarity of future projected climate states to these six geohistorical benchmarks using simulations from the Hadley Centre Coupled Model Version 3 (HadCM3), the Goddard Institute for Space Studies Model E2-R (GISS), and the Community Climate System Model, Versions 3 and 4 (CCSM) Earth system models. Under the Representative Concentration Pathway 8.5 (RCP8.5) emission scenario, by 2030 CE, future climates most closely resemble Mid-Pliocene climates, and by 2150 CE, they most closely resemble Eocene climates. Under RCP4.5, climate stabilizes at Pliocene-like conditions by 2040 CE. Pliocene-like and Eocene-like climates emerge first in continental interiors and then expand outward. Geologically novel climates are uncommon in RCP4.5 (<1%) but reach 8.7% of the globe under RCP8.5, characterized by high temperatures and precipitation. Hence, RCP4.5 is roughly equivalent to stabilizing at Pliocene-like climates, while unmitigated emission trajectories, such as RCP8.5, are similar to reversing millions of years of long-term cooling on the scale of a few human generations. Both the emergence of geologically novel climates and the rapid reversion to Eocene-like climates may be outside the range of evolutionary adaptive capacity.
Journal Article
Timing of India-Asia collision: Geological, biostratigraphic, and palaeomagnetic constraints
A range of ages have been proposed for the timing of India‐Asia collision; the range to some extent reflects different definitions of collision and methods used to date it. In this paper we discuss three approaches that have been used to constrain the time of collision: the time of cessation of marine facies, the time of the first arrival of Asian detritus on the Indian plate, and the determination of the relative positions of India and Asia through time. In the Qumiba sedimentary section located south of the Yarlung Tsangpo suture in Tibet, a previous work has dated marine facies at middle to late Eocene, by far the youngest marine sediments recorded in the region. By contrast, our biostratigraphic data indicate the youngest marine facies preserved at this locality are 50.6–52.8 Ma, in broad agreement with the timing of cessation of marine facies elsewhere throughout the region. Double dating of detrital zircons from this formation, by U‐Pb and fission track methods, indicates an Asian contribution to the rocks thus documenting the time of arrival of Asian material onto the Indian plate at this time and hence constraining the time of India‐Asia collision. Our reconstruction of the positions of India and Asia by using a compilation of published palaeomagnetic data indicates initial contact between the continents in the early Eocene. We conclude the paper with a discussion on the viability of a recent assertion that collision between India and Asia could not have occurred prior to ∼35 Ma.
Journal Article
A Paleolatitude Calculator for Paleoclimate Studies
Realistic appraisal of paleoclimatic information obtained from a particular location requires accurate knowledge of its paleolatitude defined relative to the Earth's spin-axis. This is crucial to, among others, correctly assess the amount of solar energy received at a location at the moment of sediment deposition. The paleolatitude of an arbitrary location can in principle be reconstructed from tectonic plate reconstructions that (1) restore the relative motions between plates based on (marine) magnetic anomalies, and (2) reconstruct all plates relative to the spin axis using a paleomagnetic reference frame based on a global apparent polar wander path. Whereas many studies do employ high-quality relative plate reconstructions, the necessity of using a paleomagnetic reference frame for climate studies rather than a mantle reference frame appears under-appreciated. In this paper, we briefly summarize the theory of plate tectonic reconstructions and their reference frames tailored towards applications of paleoclimate reconstruction, and show that using a mantle reference frame, which defines plate positions relative to the mantle, instead of a paleomagnetic reference frame may introduce errors in paleolatitude of more than 15° (>1500 km). This is because mantle reference frames cannot constrain, or are specifically corrected for the effects of true polar wander. We used the latest, state-of-the-art plate reconstructions to build a global plate circuit, and developed an online, user-friendly paleolatitude calculator for the last 200 million years by placing this plate circuit in three widely used global apparent polar wander paths. As a novelty, this calculator adds error bars to paleolatitude estimates that can be incorporated in climate modeling. The calculator is available at www.paleolatitude.org. We illustrate the use of the paleolatitude calculator by showing how an apparent wide spread in Eocene sea surface temperatures of southern high latitudes may be in part explained by a much wider paleolatitudinal distribution of sites than previously assumed.
Journal Article
The delayed rise of present-day mammals
Did the end-Cretaceous mass extinction event, by eliminating non-avian dinosaurs and most of the existing fauna, trigger the evolutionary radiation of present-day mammals? Here we construct, date and analyse a species-level phylogeny of nearly all extant Mammalia to bring a new perspective to this question. Our analyses of how extant lineages accumulated through time show that net per-lineage diversification rates barely changed across the Cretaceous/Tertiary boundary. Instead, these rates spiked significantly with the origins of the currently recognized placental superorders and orders approximately 93 million years ago, before falling and remaining low until accelerating again throughout the Eocene and Oligocene epochs. Our results show that the phylogenetic 'fuses' leading to the explosion of extant placental orders are not only very much longer than suspected previously, but also challenge the hypothesis that the end-Cretaceous mass extinction event had a major, direct influence on the diversification of today's mammals.
Journal Article
Effect of the deepening of the Tasman Gateway on the global ocean
End Eocene deepening of the Tasman Seaway cools deep ocean Antarctic climate cools only moderately Result robust with respect to wind scenarios We examine the effect of the deepening of the Tasman Seaway at the end of the Eocene in a climate model with realistic late Eocene bathymetry and winds. For this, we have constructed an Eocene numerical model based on the University of Victoria climate model with wind forcing derived from a fully coupled Eocene simulation. The model climate state is characterized by an oceanic meridional overturning circulation (MOC) involving Southern Hemisphere sinking and a northward atmospheric moisture transport across the equator. The deepening of the Tasman Seaway in the presence of an open Drake Passage and the associated establishment of the Antarctic Circumpolar Current (ACC) have a limited climatic impact on Antarctica. Nonetheless, the Antarctic deep sinking regions cool sufficiently to lead to a global deep ocean cooling of 3°C. No initiation of Northern Component Water is found, indicating that this may require the development of a more mature ACC. Previous studies suggest that the Ross Sea gyre cools the east coast of Australia, and expected the deepening of the Tasman Seaway to lead to a warming east of Australia due to the introduction of warmer water from the Australo-Antarctic Gulf. We here find that this warming is limited to close to the Australian coast, and that widespread cooling prevails further off shore.
Journal Article
Paleoenvironmental and paleobiogeographical significance of Paleocene – early Eocene ostracods in Wadi Tarfa, North Eastern Desert, Egypt
This study investigates ostracod faunas from the well-preserved Paleocene to lower Eocene sedimentary succession at Wadi Tarfa, North Eastern Desert, Egypt. A total of 22 species and subspecies across 16 genera and 8 families were identified across 57 samples. Three zones were identified:
Doricythereis jordanica jordanica
Zone,
Cytheropteron toshkaensis
Zone, and
Phalcocythere horraensis
Zone, based on the stratigraphic distribution of ostracod fauna. However, correlations with other sections revealed inconsistencies in the first and last occurrences of ostracod species, indicating complexities in regional biostratigraphic correlation by ostracod fauna and the influence of localized depositional factors. Both R-mode and Q-mode clustering analyses were applied to ostracod assemblages, identifying four distinct faunal clusters and five biofacies, reflecting depositional changes from outer neritic to upper bathyal environments. The late Paleocene revealed reduced ostracod diversity, correlating with a deepening marine environment, particularly in the Tarawan Formation. Non-Metric Multidimensional Scaling (NMDS) analyses indicated significant paleobiogeographic connections between North African and Levantine sites, while faunal differentiation was greater in West African and Middle Eastern regions due to marine barriers.
Journal Article
A Late Cretaceous amber biota from central Myanmar
Insect faunas are extremely rare near the latest Cretaceous with a 24-million-year gap spanning from the early Campanian to the early Eocene. Here, we report a unique amber biota from the Upper Cretaceous (uppermost Campanian ~72.1 Ma) of Tilin, central Myanmar. The chemical composition of Tilin amber suggests a tree source among conifers, indicating that gymnosperms were still abundant in the latest Campanian equatorial forests. Eight orders and 12 families of insects have been found in Tilin amber so far, making it the latest known diverse insect assemblage in the Mesozoic. The presence of ants of the extant subfamilies Dolichoderinae and Ponerinae supports that tropical forests were the cradle for the diversification of crown-group ants, and suggests that the turnover from stem groups to crown groups had already begun at ~72.1 Ma. Tilin amber biota fills a critical insect faunal gap and provides a rare insight into the latest Campanian forest ecosystem.
The amber deposits from Kachin, Myanmar have provided numerous insights into life in the Cretaceous ~99 million years ago. Here, Zheng and colleagues describe a new Late Cretaceous amber biota from Tilin, Myanmar, dating from ~72 million years ago and preserving a diverse insect assemblage.
Journal Article