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532 results for “Middle Eocene”
Fig. 5 in Middle and late Eocene fish otoliths from the eastern and southern USA
Fig. 5. Measured section at the Dobys Bluff locality, Mississippi (after Dockery 1986a).
Data from: Small but mighty: how overlooked small species maintain community structure through middle Eocene climate change
<p>Understanding current and future biodiversity responses to changing climate is pivotal as anthropogenic climate change continues. This understanding is complicated though by the multitude of available metrics to quantify dynamics, and by biased sampling protocols. Here, we investigate the impact of sampling protocol strategies using a data-rich fossil record to calculate effective diversity using Hill numbers for the first time on Paleogene planktonic foraminifera. We sample 22,830 individual tests, in two different size classes, across a seven-million-year time slice of the Middle Eocene featuring a major transient warming event, the Middle Eocene Climatic Optimum (MECO; ~40 million years ago (Ma)), at study sites in the mid-latitude North Atlantic. Using Generalized Additive Models (GAMs), we investigate community responses to climatic fluctuations. After correcting for any effects of fossil fragmentation, we show a peak in generic diversity in the early and mid-stages of the MECO as well as divergent trajectories between the typical size-selected community (> 180 µm) and a broader selection including smaller genera (> 63 µm). Assemblages featuring smaller genera are more resilient to the climatic fluctuations of the MECO than those assemblages that feature only larger genera, maintaining their community structure at the reference Hill numbers for Shannon's and Simpson's Index. These results raise fundamental questions about how communities respond to climate excursions. In addition, our results emphasise the need to design studies with the aim of collecting the most inclusive data possible, to allow detection of community changes and determine which species are likely to dominate future environments. </p>
Progress in understanding middle Eocene nassellarian (Radiolaria, Polycystinea) diversity; new insights from the western equatorial Atlantic Ocean
<p>Middle Eocene deep-sea sediment sequences cored at Ocean Drilling Program Site 1260 (Leg 207; equatorial Atlantic Ocean), yielded diverse and abundant radiolarian faunas which are conducive to biostratigraphic and palaeoceanographic researchs, as well as to the study of radiolarian diversity dynamics during this epoch of dramatic climate changes. However, many species present in these sediments still have not been formally described and are therefore neglected in most biodiversity surveys. In an effort to improve the taxonomic resolution of middle Eocene radiolaria, 15 new species of nassellarian are described and illustrated. The species are: Cymaetron ? dilatatus n. sp., Eucyrtidium levisaltatrix n. sp. (Eucyrtidiidae), Siphocampe pollen n. sp., Spirocyrtis ? renaudiei n. sp. (Artostrobiidae), Pterocyrtidium eep n. sp. (Rhopalosyringiidae), Petalospyris cometa n. sp., Petalospyris castanea n. sp. (Cephalospyrididae), Velicucullus armatus n. sp. (Theophormididae), Lychnocanium nimrodi n. sp. (Lithochytrididae), Aphetocyrtis zamenhofi n. sp., Aphetocyrtis ? columboi n. sp., Aphetocyrtis ? spheniscus n. sp. (Lophocyrtiidae), Albatrossidium regis n. sp., Albatrossidium annikasanfilippoae n. sp. and Phormocyrtis lazari n. sp. (Pterocorythidae). Stratigraphic range data are provided for each new species, as well as the orbitally tuned ages for their first and last occurrences. In addition to these new species, we also illustrated and documented the stratigraphic distribution of three species described in early radiolarian studies and rarely reported since.</p>
Fig. 19 in A New Protocetid Whale (Cetacea: Archaeoceti) from the Late Middle Eocene of South Carolina
Fig. 19. Anterior views of sixth (A) and seventh (B) cervical vertebrae of Carolinacetus gingerichi
Morphometric data of the late middle Eocene to early Oligocene (~40 - 31 Ma) Coccolithophore Reticulofenestra (Order Isochrysidales)
<p><span>The first size reduction (FSR) in the <em>Reticulofenestra-Gephyrocapsa-Emiliania (RGE)</em> lineage (Order Isochrysidales) which occurred in the early Oligocene (~ 32 Ma), is of great significance for understanding the lilliput effect that has affected the coccolithophore communities from late Eocene to this day. We conducted a morphologic analysis on the coccoliths of <em>Reticulofenestra</em> species that lived during the late middle Eocene to early Oligocene (~40-31 Ma), using marine sediments from the South Atlantic Ocean. Our data show increasing size and decreasing abundance of the large species during the late Eocene, leading to their disappearance at the FSR, and a concurrent decrease in the size variability of the small-medium-sized coccoliths whose diameter of the central opening had become very reduced. Although the cosmopolitan late Paleogene through Neogene size decrease in coccolithophores has been linked to the concomitant long-term decline in global <em>p</em>CO2, we suggest here that the FSR was the result of environmental destabilization caused by the expansion of eutrophic environments following the late Eocene establishment of overturning circulation associated with ice build-up on Antarctica. This study also leads us to propose a hypothetical model that links coccolith morphology of species of the <em>RGE </em>lineage and trophic resources in the upper ocean: the small- to medium-sized, r-selected coccolithophores with smaller coccolith central opening live in nutrient-rich waters where they rely mostly on photosynthesis and little on mixotrophy; whereas the larger, K-selected species with larger coccolith central opening live in oligotrophic waters where they are more dependent on mixotrophy.</span></p>
Paleohydraulic Reconstructions, Geochemical Signals and Intermittency Estimates from the Middle Eocene Escanilla Formation, Spain
<p>The Earth’s surface undergoes changes over time due to various factors such as changes in climatic processes, sea level, and tectonic activity. These changes occur gradually and often go unnoticed to the human eye but are left behind as evidence in the form of sedimentary layers and erosional patterns that can be studied over geological time periods. For instance, ancient fluvial deposits are important archives of past changes and investigating their different aspects has implications for understanding past climate and landscape evolution. This doctoral thesis is focussed on the Middle Eocene (∼40 Ma) aged Escanilla Formation in the south-central Pyrenees, Spain, and is a compilation of 4 different studies. The first study documents how ancient riverbed systematically evolved from lower slopes in coarser-grained high amalgamation (HA) intervals, and higher slopes in finer-grained low amalgamation (LA) intervals. These changes were primarily driven by climate-controlled water discharge variations rather than base level changes. The second study presents a comprehensive geochemical record of the Middle Eocene Climatic Optimum (MECO), a global warming event that occurred at ∼40 Ma, using a suite of sampled paleosols, fluvial stromatolites, and pedogenic nodules. Geochemical proxies include carbon and oxygen stable isotopes, weathering indices, mean annual precipitation, clumped isotope temperature and clay mineralogy. Based on the regional preservation of the MECO and the climate, this study highlights fluvial sedimentary successions as interesting terrestrial archives of past changes in global climate. The third study explores a relationship between water discharge, sediment flux variability, and changing fluvial stratigraphic architecture with results indicating that HA intervals were most likely deposited under more intermittent and short-lived, intense precipitation events, while LA intervals were the result of less intermittent flows throughout the year. These estimates are consistent with values from modern ephemeral rivers typically found in arid to semi-arid climatic conditions, and highlight the connection between hydroclimate, river morphodynamics, and landscape evolution. Finally, the fourth study, explores a potential relationship between the MECO and a continental arc flare-up as a source of pCO2. An increase in mercury content relative to the MECO likely suggests a link between the two. Collectively, these studies provide new insights into the complex dynamics of past climate and landscape evolution, and have implications for interpreting ancient sedimentary deposits such as changes in fluvial stacking patterns, highlighting the importance of fluvial sedimentary successions as key archives of past global climate evolution and perturbations.</p>
Fig. 6 in Middle Eocene ungulate mammals from Myanmar: A review with description of new specimens
Fig. 6. Cenogram of the Pondaung fauna.
Middle Eocene terrestrial paleoweathering and climate evolution in the midlatitude Bohai Bay Basin of Eastern China
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Data from: Carnivorous mammals from the middle Eocene Washakie Formation, Wyoming, USA, and their diversity trajectory in a post-warming world
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Data from: Small but mighty: how overlooked small species maintain community structure through middle Eocene climate change
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Morphometric data of the late middle Eocene to early Oligocene (~40 - 31 Ma) Coccolithophore Reticulofenestra (Order Isochrysidales)
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Progress in understanding middle Eocene nassellarian (Radiolaria, Polycystinea) diversity; new insights from the western equatorial Atlantic Ocean
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FIG. 8 in Late Middle Eocene bats from the Creechbarrow Limestone Formation, Dorset, southern England with description of a new species of Archaeonycteris (Chiroptera: Archaeonycteridae)
FIG. 8. Trigonids of lower molars, Creechbarrow bats. Rhinolophidae gen. et sp. indet. M35711. Trigonid left lower molar in A — occlusal, B — buccal and C — lingual views. HZM 2.38159. Trigonid right lower molar in D — occlusal, E — buccal and F — lingual views. Microchiroptera gen. et sp. indet. HZM 22.34774. Trigonid right lower molar in G — occlusal, H — buccal
F. 4. Pseudorhinolophus schlosseri, Creechbarrow. HZM 1.31792. Left M2 in Late Middle Eocene bats from the Creechbarrow Limestone Formation, Dorset, southern England with description of a new species of Archaeonycteris (Chiroptera: Archaeonycteridae)
F. 4. Pseudorhinolophus schlosseri, Creechbarrow. HZM 1.31792. Left M2: A — occlusal and B — oblique distal views. HZM IG 3.38170. Left M1/2 in C — distal, D — lingual, E — buccal and F — occlusal views. Rhinolophidae gen. et sp. indet. HZM 1.31222.
FIG. 1 in Late Middle Eocene bats from the Creechbarrow Limestone Formation, Dorset, southern England with description of a new species of Archaeonycteris (Chiroptera: Archaeonycteridae)
FIG. 1. Archaeonycteris relicta sp. nov., Creechbarrow, mandibular cheekteeth. HZM 4.37495. Right P2 in A — occlusal, B — buccal and C — lingual views. Scale = 0.5 mm. HZM 5.38291. Left M3 (holotype) D — distal, E — lingual, F — buccal and G — occlusal
FIGURE 19. Sciara gurnetensis Cockerell, 1915, USNM 61435 and S. lacoei Cockerell, 1915, USNM 61436. 1 in Diptera of the middle Eocene Kishenehn Formation. I. Documenting of diversity at the family level
FIGURE 19. Sciara gurnetensis Cockerell, 1915, USNM 61435 and S. lacoei Cockerell, 1915, USNM 61436. 1, Sciara gurnetensis (wing only). M1 and M2 labeled; 2, S. lacoei, habitus. CuA1 and distal portion of M2 labeled. "Veins" under each of the three asterisks are artifacts; the "?" denotes the vein Cockerell identified as M1. Inset: Head (Arrow points to base of antenna); 3, S. lacoei, (#7583). M1 and M2 labeled. Scale bars equal 1.0 mm (1, 2, 3).
FIGURE 21 in Diptera of the middle Eocene Kishenehn Formation. I. Documenting of diversity at the family level
FIGURE 21. Rymosia hypnolithica sp. nov., USNM 624134, male. 1, Habitus; 2, Right forewing. Scale bars equal 2.0 mm (1), 1.0 mm (2).
FIGURE 18. Sciara florissantensis Cockerell 1916, USNM 61995. 1 in Diptera of the middle Eocene Kishenehn Formation. I. Documenting of diversity at the family level
FIGURE 18. Sciara florissantensis Cockerell 1916, USNM 61995. 1, Habitus; 2, Head and antennae; 3, Right forewing. Long arrow denotes 1st abscissa of Rs; the arrowhead points to remnants of the r-m crossvein. Scale bar equals 1.0 mm (1, 3), 0.25 mm (2).
FIGURE 7. Cyttaromyia fuscula Cockerell, 1921 in Diptera of the middle Eocene Kishenehn Formation. I. Documenting of diversity at the family level
FIGURE 7. Cyttaromyia fuscula Cockerell, 1921 (new combination), USNM 66572. 1, Wing. Arrow points to a defect in the wing where the distal portion of the wing has shifted anteriorly relative to the basal portion causing an upwards curving of the basal portion of Rs; 2, Line drawing of the wing. Scale bar equals 3.0 mm (1).
FIGURE 2 in Diptera of the middle Eocene Kishenehn Formation. I. Documenting of diversity at the family level
FIGURE 2. Tipula (Trichotipula) fji sp. nov., USNM 625687. 1, Head. Arrow denotes palpus; 2, Antennae. Arrows denote boundaries between basal flagellomeres, double arrows point to verticils at the base of the terminal flagellomere. Scale bars equal 1.0 mm (1) and 0.5 mm (2).
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.