An eocene hystricognathous rodent from Texas: its significance in interpretations of continental drift

The earliest known representative of the fundamentally South American and African hystricognathous rodents has recently been found in the middle or late Eocene of southwestern Texas; this discovery supports the postulate of a northern and independent origin for the two southern groups and increases the evidence against mid-Tertiary trans-Atlantic migration of these rodents at a time when the South Atlantic was narrower than it is at present. The fossil seems to be related to the North American Eocene family Sciuravidae.     

Mite-plant associations from the eocene of southern australia

Acarodomatia or "mite houses" are located on leaves of many present-day angiosperms and are inhabited by mites that may maintain leaf hygiene. Eocene deposits in southern Australia have yielded acarodomatia on fossil leaves of Elaeocarpaceae and Lauraceae and also contain oribatid mites with close affinities to those that inhabit the acarodomatia of the closest living relatives of the fossil plant taxa. The data indicate that mite-plant associations may have been widespread in southern Australia 40 million years ago.     

Iguanid lizard from the upper cretaceous of Brazil

Pristiguana brasiliensis, new genus and species, from the Upper Cretaceous Baurú Formation of Brazil, is the oldest fossil referable to the living lizard family Iguanidae. It resembles living primitive South American iguanids in some features, but also shows similarity to members of the related family Teiidae. Iguanid fossils do not appear in North America until the early Eocene, probably by waif dispersal from South America during the late Paleocene or early Eocene. A southern continental (Gondwanan) origin of iguanids is more plausible than the northern one often suggested.     

小兴安岭菊科植物区系地理与多样性研究

[目的]为小兴安岭菊科植物资源的保护和合理开发利用提供理论依据。[方法]采用野外调查和标本鉴定的方法,对小兴安岭菊科植物物种多样性、区系地理成分和经济用途多样性等进行了研究。[结果]该区共有菊科植物126种,隶属48属,且优势属明显,少种属和单种属占总属数的比例分别为37.50%和56.25%。从属层次上表现出典型的温带性质,以北温带成分为主,且没有我国特有属。[结论]小兴安岭菊科植物组成丰富,区系地理成分多样,经济用途多样。     

Middle and late eocene mammal communities: a major discrepancy

The multituberculate Parectypodus lovei has been found in late Eocene rocks in Montana, together with 11 other mammal species similar to those found in the late Eocene Tepee Trail Formation in Wyoming.The multituberculate and six other species are unknown in rocks of equivalent age or of middle Eocene age elsewhere.It is suggested that the known middle Eocene faunas are all taken from a similar ecological situation and do not reflect the true diversity of middle Eocene life. Middle Eocene faunas of different ecological aspect may be recovered from sediments along, and in, the mountain fronts of northwestern Wyoming.     

Origin of whales in epicontinental remnant seas: new evidence from the early eocene of pakistan

Pakicetus inachus from the early Eocene of Pakistan is the oldest and most primitive cetacean known. The dentition of Pakicetus resembles that of carnivorous mesonychid land mammals as well as middle Eocene cetaceans. The otic region of the cranium lacks characteristic specializations of whales necessary for efficient directional hearing under water. Pakicetus occurs with a land-mammal fauna in fluvial sediments bordering epicontinental Eocene remnants of the eastern Tethys seaway. Discovery of Pakicetus strengthens earlier inferences that whales originated from terrestrial carnivorous mammals and suggests that whales made a gradual transition from land to sea in the early Eocene, spending progressively more time feeding on planktivorous fishes in shallow, highly productive seas and embayments associated with tectonic closure of eastern Tethys.     

Antarctic Glaciation during the Tertiary Recorded in Sub-Antarctic Deep-Sea Cores

Study of 18 Cenozoic South Pacific deep-sea cores indicates an association of glacially derived ice-rafted sands and relatively low planktonic foraminiferal diversity with cooling of the Southern Ocean during the Lower Eocene, upper Middle Eocene, and Oligocene. Increased species diversity and reduction or absence of ice-rafted sands in Lower and Middle Miocene cores indicate a warming trend that ended in the Upper Miocene. Antarctic continental glaciation appears to have prevailed throughout much of the Cenozoic.     

Latitudinal gradients in greenhouse seawater δ(18) O: evidence from Eocene sirenian tooth enamel

The Eocene greenhouse climate state has been linked to a more vigorous hydrologic cycle at mid- and high latitudes; similar information on precipitation levels at low latitudes is, however, limited. Oxygen isotopic fluxes track moisture fluxes and, thus, the δ(18)O values of ocean surface waters can provide insight into hydrologic cycle changes. The offset between tropical δ(18)O values from sampled Eocene sirenian tooth enamel and modern surface waters is greater than the expected 1.0 per mil increase due to increased continental ice volume. This increased offset could result from suppression of surface-water δ(18)O values by a tropical, annual moisture balance substantially wetter than that of today. Results from an atmospheric general circulation model support this interpretation and suggest that Eocene low latitudes were extremely wet.     

Discovery of the oldest known anthropoidean skull from the paleogene of Egypt

A group of primate fossils newly discovered in the Fayum badlands of Egypt is probably of Eocene age. The site is much older than the localities of previously known Egyptian early Tertiary primates. These finds include a crushed cranium that is the oldest skull found to date of a higher primate. This skull shows four characteristics of higher primates: a catarrhine dental formula, an ectotympanic at the rim of the auditory bulla, a fused frontal bone, and postorbital closure. Details of tooth structure (premolars and molars) and a possibly unfused mandibular symphysis resemble these parts in certain Eocene prosimians.     

Paleocene hyracothere from polecat bench formation, wyoming

A lower jaw of an eohippus (Hyracotherium cf. H. angustidens) from late Paleocene strata in Wyoming has extended the geological record of fossil horses into pre-Eocene time and suggests that the order Perissodactyla had an origin earlier than that heretofore conjectured. This specimen, together with equid teeth also possibly of late Paleocene age from Baja California, indicates that early perissodactyls were widespread on the North American continent before the Eocene epoch. Late Paleocene and early Eocene deposits of northwestern Wyoming have yielded many vertebrate rarities and "first or earliest occurrences" which require reappraisals of inter-and intracontinental dispersal patterns of the vertebrate grolups involved.     

不同绿肥品种综合利用价值的比较

比较了不同绿肥植物地上绿色体产量及肥料和饲料价值。结果表明:供试绿肥品种的地上绿色体还田量高低顺序是禾本科苋科菊科豆科十字花科;肥料价值和饲料价值高低顺序是豆科苋科禾本科菊科十字花科。     

High plant diversity in Eocene South America: evidence from Patagonia

Tropical South America has the highest plant diversity of any region today, but this richness is usually characterized as a geologically recent development (Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco in Patagonia, Argentina, paleolatitude approximately 47 degrees S, we report 102 leaf species. Radioisotopic and paleomagnetic analyses indicate that the flora was deposited 52 million years ago, the time of the early Eocene climatic optimum, when tropical plant taxa and warm, equable climates reached middle latitudes of both hemispheres. Adjusted for sample size, observed richness exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America.     

Multiple microtektite horizons in upper eocene marine sediments: no evidence for mass extinctions

Microtektites have been recovered from three horizons in eight middle Eocene to middle Oligocene marine sediment sequences. Five of these occurrences are coeval and of latest Eocene age (37.5 to 38.0 million years ago); three are coeval and of early late Eocene age (38.5 to 39.5 million years ago); and three are of middle Oligocene age (31 to 32 million years ago). In addition, rare probable microtektites have been found in sediments with ages of about 36.0 to 36.5 million years. The microtektite horizon at 37.5 to 38.0 million years can be correlated with the North American tektite-strewn field, which has a fission track age (minimum) of 34 to 35 million years and a paleomagnetic age of 37.5 to 38.0 million years. There is no evidence for mass faunal extinctions at any of the microtektite horizons. Many of the distinct faunal changes that occurred in the middle Eocene to middle Oligocene can be related to the formation of the Antarctic ice sheet and the associated cooling phenomena and intensification of bottom currents that led to large-scale dissolution of calcium carbonate and erosion, which created areally extensive hiatuses in the deep-sea sediment records. The occurrence of microtektite horizons of several ages and the lack of evidence for faunal extinctions suggest that the effects of extraterrestrial bolide impacts may be unimportant in the biologic realm during middle Eocene to middle Oligocene time.     

Ages of fossil penguins in new zealand

The age of a New Zealand specimen generally believed to represent the oldest known penguin, hitherto considered early Eocene (Heretaungan), has been restudied by the New Zealand Geological Survey and is early Miocene. The oldest known penguins are from the late Eocene. The reported great range of a single species, Palaeeudyptes antarcticus, from late Eocene to late Oligocene or early Miocene (Kaiatan to Waitakian) is not acceptable. Dating of some other specimens is less precise than previously reported.     

An upper eocene frog from the dominican republic and its implication for Caribbean biogeography

A frog of the leptodactylid genus Eleutherodactylus is reported from Eocene amber found in the Dominican Republic. It is the first described amphibian fossil in amber, and the oldest complete lissamphibian fossil from Mesoamerica (Central America and Mexico). Dating of the amber matrix indicates that by the end of the Eocene a diverse fauna was present in the Antilles, much earlier than has generally been proposed. The presence of this and other amber fossils from this same age suggests that Tertiary patterns of landmass movements were significant in determining the present distribution of species.     

Eocene Epiphyllous Fungi

Fossil fungi belonging to the Meliolaceae and Microthyriaceae were found in Eocene deposits in Tennessee. Germinated spores for each form of fungus were identified. One of the two forms of the genus Meliola, (Meliolaceae) appears to have parasitized the leaf upon which it grew. The vegetative, sexual, and asexual reproductive structures are preserved in a member of the genus Asterina (Microthyriaceae). The discovery of these fungi indicates that Western Tennessee was warm and humid during the Eocene.     

The Eocene/Oligocene boundary event in the deep sea

Analysis of middle Eocene to early, Oligocene calcareous and siliceous microfossils shows gradual biotic changes with no massive extinction event across the Eocene/Oligocene boundary. Biotic changes in the late Paleogene appear to reflect changing paleoclimatic and paleoceanographic conditions and do not support suggestions of a catastrophic biotic event caused by a bolide impact at the Eocenel Oligocene boundary.     

Transient Middle Eocene atmospheric CO₂ and temperature variations

The long-term warmth of the Eocene (~56 to 34 million years ago) is commonly associated with elevated partial pressure of atmospheric carbon dioxide (pCO(2)). However, a direct relationship between the two has not been established for short-term climate perturbations. We reconstructed changes in both pCO(2) and temperature over an episode of transient global warming called the Middle Eocene Climatic Optimum (MECO; ~40 million years ago). Organic molecular paleothermometry indicates a warming of southwest Pacific sea surface temperatures (SSTs) by 3° to 6°C. Reconstructions of pCO(2) indicate a concomitant increase by a factor of 2 to 3. The marked consistency between SST and pCO(2) trends during the MECO suggests that elevated pCO(2) played a major role in global warming during the MECO.     

Elevated Eocene atmospheric CO2 and its subsequent decline

Quantification of the atmospheric concentration of CO2 ([CO2]atm) during warm periods of Earth's history is important because burning of fossil fuels may produce future [CO2]atm approaching 1000 parts per million by volume (ppm). The early Eocene (~56 to 49 million years ago) had the highest prolonged global temperatures of the past 65 million years. High Eocene [CO2]atm is established from sodium carbonate minerals formed in saline lakes and preserved in the Green River Formation, western United States. Coprecipitation of nahcolite (NaHCO3) and halite (NaCl) from surface waters in contact with the atmosphere indicates [CO2]atm > 1125 ppm (four times preindustrial concentrations), which confirms that high [CO2]atm coincided with Eocene warmth.     

入侵杂草小飞蓬和钻形紫菀种子风传扩散生物学特性研究

种子的风传扩散是菊科入侵杂草的主要扩散方式之一,植物自身的传播特性和外在环境因子决定了种子扩散格局。从种子释放高度、沉降速度、脱落行为等内在因子出发,研究了两种在我国广泛分布的典型菊科入侵种小飞蓬和钻形紫菀自身的传播特性与风传扩散特征的关系。结果表明,小飞蓬和钻形紫菀的沉降速度均较小,分别为41.4cm·s-1和30.7cm·s-1,在空中停留时间长,且种子的脱落方式为非随机脱落,脱落概率大致与风速的平方成正比;种子的释放高度在种群内部存在很大的差异,显著影响种子的扩散距离。相比而言,小飞蓬种子的沉降速度大、释放高度高、远距离扩散(>100m)的概率大,扩散距离更远。研究表明了植物自身的传播特性对种子风传扩散的重要性,也为其他菊科入侵杂草种子风传扩散的研究提供了科学依据。