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A molecular evaluation of bulk organic carbon-isotope chemostratigraphy for terrestrial correlations: An example from two Paleocene-Eocene tropical sequences

Smithsonian Libraries
The dynamics associated with the carbon cycle and the linkage between the oceans, the atmosphere, and land plants provide an opportunity to correlate marine and terrestrial sedimentary sequences using stable isotopes of carbon ([delta]13C), but few studies have tested this approach. For instance, it has been proposed that changes in plant community (e.g., gymnosperm-dominated vs. angiosperm-dominated) could have significantly altered/amplified the carbon-isotope ratios of bulk sedimentary organic matter derived from land plants ([delta]13CTOM), compared to that of the marine carbonates ([delta]13Ccarbonate). Here, [delta]13CTOM values in a terrestrial sequence of the Colombian tropics are compared to the composite Paleocene-Eocene [delta]13Ccarbonate curve from Zachos et al. (2001) to evaluate the use of [delta]13CTOM values as a reliable chronostratigraphic tool. Sediments of the studied terrestrial sequences were deposited in a transitional setting dominated by mudstones, coals, and small lenses of sandstones (Late Cretaceous-Middle Paleocene sediments) and in a mixture of deltaic and fluvial conditions (Late Paleocene-Early Eocene sediments). The biostratigraphic control was based on palynological zones for the region. The [delta]13CTOM values for the studied terrestrial sequence show three carbon-isotope excursions, which correlate closely with those present in the marine record. The [delta]13CTOM values decreased from - 24.2[per mille sign] to - 26.5[per mille sign] in sediments accumulated during Early to Middle Paleocene, increased from - 26.5[per mille sign] to - 23.8[per mille sign] during the Late Paleocene, and decreased from - 23.8[per mille sign] to - 26.5[per mille sign] near the Paleocene-Eocene boundary (52-50 Ma). Selected biomarkers indicate that most of the organic matter derived from both gymnosperms and angiosperms. Moreover, the analyses of selected biomarker ratios (CPI, Pr/Ph, Paq, and [beta][beta]/[beta][beta] + [alpha][beta] hopanes) show some diagenetic transformation in the preserved organic matter. However, no correlation between diagenesis and [delta]13CTOM values was detected, thus suggesting that [delta]13CTOM could be correlated with [delta]13Ccarbonate values. The close correspondence that was found between [delta]13CTOM and [delta]13Ccarbonate values ([Delta]13CTOM-carbonate ~ - 27[per mille sign]) provides support to the hypothesis that a tight land-plant-oceans linkage exists through geologic timescales via atmospheric carbon dioxide.

A monograph of the terrestrial Carboniferous Arachnida of Great Britain / By Reginald Innes Pocock

Smithsonian Libraries
Each plate preceded by leaf with descriptive letterpress.

Added t.-p.: The Palæontographical Society.

"The Palæontographical Society ... volume for 1910."--Added t.p.

Also available online.


A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic

Smithsonian Libraries
Non-avian theropod dinosaurs attained large body sizes, monopolising terrestrial apex predator niches in the Jurassic-Cretaceous. From the Middle Jurassic onwards, Allosauroidea and Megalosauroidea comprised almost all large-bodied predators for 85 million years. Despite their enormous success, however, they are usually considered absent from terminal Cretaceous ecosystems, replaced by tyrannosaurids and abelisaurids. We demonstrate that the problematic allosauroids Aerosteon, Australovenator, Fukuiraptor and Neovenator form a previously unrecognised but ecologically diverse and globally distributed clade (Neovenatoridae, new clade) with the hitherto enigmatic theropods Chilantaisaurus, Megaraptor and the Maastrichtian Orkoraptor. This refutes the notion that allosauroid extinction pre-dated the end of the Mesozoic. Neovenatoridae includes a derived group (Megaraptora, new clade) that developed long, raptorial forelimbs, cursorial hind limbs, appendicular pneumaticity and small size, features acquired convergently in bird-line theropods. Neovenatorids thus occupied a 14-fold adult size range from 175 kg (Fukuiraptor) to approximately 2,500 kg (Chilantaisaurus). Recognition of this major allosauroid radiation has implications for Gondwanan paleobiogeography: The distribution of early Cretaceous allosauroids does not strongly support the vicariant hypothesis of southern dinosaur evolution or any particular continental breakup sequence or dispersal scenario. Instead, clades were nearly cosmopolitan in their early history, and later distributions are explained by sampling failure or local extinction.

A phylogenetic estimation of trophic transition networks for ascomycetous fungi: Are lichens cradles of symbiotrophic fungal diversification?

Smithsonian Libraries
Fungi associated with photosynthetic organisms are major determinants of terrestrial biomass, nutrient cycling, and ecosystem productivity from the poles to the equator. Whereas most fungi are known because of their fruit bodies (e.g., saprotrophs), symptoms (e.g., pathogens), or emergent properties as symbionts (e.g., lichens), the majority of fungal diversity is thought to occur among species that rarely manifest their presence with visual cues on their substrate (e.g., the apparently hyperdiverse fungal endophytes associated with foliage of plants). Fungal endophytes are ubiquitous among all lineages of land plants and live within overtly healthy tissues without causing disease, but the evolutionary origins of these highly diverse symbionts have not been explored. Here, we show that a key to understanding both the evolution of endophytism and the diversification of the most species-rich phylum of Fungi (Ascomycota) lies in endophyte-like fungi that can be isolated from the interior of apparently healthy lichens. These "endolichenic" fungi are distinct from lichen mycobionts or any other previously recognized fungal associates of lichens, represent the same major lineages of Ascomycota as do endophytes, largely parallel the high diversity of endophytes from the arctic to the tropics, and preferentially associate with green algal photobionts in lichen thalli. Using phylogenetic analyses that incorporate these newly recovered fungi and ancestral state reconstructions that take into account phylogenetic uncertainty, we show that endolichenism is an incubator for the evolution of endophytism. In turn, endophytism is evolutionarily transient, with endophytic lineages frequently transitioning to and from pathogenicity. Although symbiotrophic lineages frequently give rise to free-living saprotrophs, reversions to symbiosis are rare. Together, these results provide the basis for estimating trophic transition networks in the Ascomycota and provide a first set of hypotheses regarding the evolution of symbiotrophy and saprotrophy in the most species-rich fungal phylum.

A reassessment of carbon content in tropical trees

Smithsonian Libraries
Accurate knowledge of carbon (C) content in live wood is essential for quantifying tropical forest C stocks, yet generic assumptions (such as biomass consisting of 50% carbon on a weight/weight basis) remain widely used despite being supported by little chemical analysis. Empirical data from stem cores of 59 Panamanian rainforest tree species demonstrate that wood C content is highly variable among co-occurring species, with an average (47.4±2.51% S.D.) significantly lower than widely assumed values. Prior published values have neglected to account for volatile C content of tropical woods. By comparing freeze- and oven-dried wood samples, we show that volatile C is non-negligible, and excluding the volatile fraction underestimates wood C content by 2.48±1.28% (S.D.) on average. Wood C content varied substantially among species (from 41.9–51.6%), but was neither strongly phylogenetically conserved, nor correlated to ecological (i.e. wood density, maximum tree height) or demographic traits (i.e. relative growth rate, mortality rate). Overall, assuming generic C fractions in tropical wood overestimates forest C stocks by ∼3.3–5.3%, a non-trivial margin of error leading to overestimates of 4.1–6.8 Mg C ha−1 in a 50-ha forest dynamics plot on Barro Colorado Island, Panama. In addition to addressing other sources of error in tropical forest C accounting, such as uncertainties in allometric models and belowground biomass, compilation and use of species-specific C fractions for tropical tree species would substantially improve both local and global estimates of terrestrial C stocks and fluxes.

A remarkable new species of small falcon from the Quaternary of Cuba (Aves : Falconidae : Falco)

Smithsonian Libraries
An enigmatic small falcon, Falco kurochkini, new species, is described from postcranial bones from several Quaternary sites in western and central Cuba. It was approximately intermediate in size between F. sparverius and F. columbarius but had proportionately longer and more slender leg elements than any living species of Falco. It is hypothesized that F. kurochkini may have been terrestrial, pursuing prey on foot, and that its extinction could have been related to terrestrial nesting habits as well.

A sustained +21 m sea-level highstand during MIS 11 (400 ka): direct fossil and sedimentary evidence from Bermuda

Smithsonian Libraries
A small, protected karstic feature exposed in a limestone quarry in Bermuda preserved abundant sedimentary and biogenic materials documenting a transgressive phase, still-stand, and regressive phase of a sea-level in excess of 21.3 m above present during Marine Isotope Stage (MIS) 11 (400 ka) as determined by U/Th dating and amino acid racemization. Cobbles and marine sediments deposited during the high-energy transgressive phase exhibit rim cements indicating a subsequent phreatic environment. This was succeeded stratigraphically by a still-stand deposition of fine calcareous lagoonal sediments containing bioclasts of red algae and benthic and planktonic foraminifera that was intensely burrowed by marine invertebrates, probably upogebiid shrimp, that could not be produced under any condition other than sustained marine submergence. Overlying this were pure carbonate beach sands of a low-energy regressive phase containing abundant remains of terrestrial and marine vertebrates and invertebrates. The considerable diversity of this fauna along with taphonomic evidence from seabird remains indicates deposition by high run-up waves over a minimum duration of months, if not years. The maximum duration has yet to be determined but probably did not exceed one or two thousand years. The most abundant snails in this fauna are two species indicative of brackish water and high-tide line showing that a Ghyben-Herzberg lens must have existed at > + 20 m. The nature of these sediments and fossil accumulation is incompatible with tsunami deposition and, given the absence of evidence for tectonic uplift of the Bermuda pedestal or platform, provide proof that sea-level during MIS 11 exceeded +20 m, a fact that has widespread ramifications for geologists, biogeographers, and human demographics along the world's coastlines.

Acanthococcus minor Hansg.

NMNH - Botany Dept.
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