bluuebunny/crossref_metadata_2025_split huggingface dataset:
A series of sheet-structured alkali metal uranyl oxalate hydrates: structures and IR spectra
Authors: Giesting Paul Arthur , Porter Nathan J. , Burns Peter Carman 
Published: July 2006

Abstract
The novel compounds K[(UO2)2(C2O4)2OH] · 2 H2O (KUrOx), Rb[(UO2)2(C2O4)2OH] · 2 H2O (RbUrOx), and Cs[(UO2)2(C2O4)2OH] · H2O (CsUrOx) have been synthesized by mild hydrothermal methods. Single crystal diffraction data collected at 125 K using MoK
α radiation and a CCD-based area detector were used to solve and refine the crystal structures by full-matrix least-squares techniques to agreement indices (KUrOx, RbUrOx, CsUrOx) wR
2 = 0.045, 0.062, 0.042 for all data, and R1 = 0.023, 0.030, 0.022 calculated for 1834, 1863, 1821 unique reflections respectively. The compounds KUrOx, RbUrOx, and CsUrOx are all monoclinic, space group P21/m, Z = 2. The unit cell of KUrOx has the dimensions a = 5.6427(4), b = 13.7123(9), c = 9.2669(6) Å, β = 98.7490(10)°, V = 708.68(8) Å3. The unit cell of RbUrOx has the dimensions a = 5.6225(4), b = 13.8339(9), c = 9.3308(6) Å, β = 98.1590(10)°, V = 718.41(8) Å3. The unit cell of CsUrOx has the dimensions a = 5.4688(3), b = 13.5710(8), c = 9.5408(5) Å, β = 97.5830(10)°, V = 701.90(7) Å3. The structures consist of chains of uranyl pentagonal bipyramids connected by oxalate groups and hydroxyl groups, and are isotypic with the compound NH4[(UO2)2(C2O4)2OH] · 2 H2O studied by Artem’eva et al. (2003); all four of these compounds are structurally composed of sheets made by polymerizing the chains of UO2C2O4(H2O) · 2 H2O (Jayadevan and Chackraburtty, 1972; Mikhailov et al., (1999), this being achieved by removing a H atom from an H2O group in the coordination sphere of the uranyl ion to form a hydroxyl vertex that is shared by two uranyl ions. Compensating positive charges are provided by the inclusion of large monovalent cations in channels that run through the sheets; these channels also contain hydrogen-bound H2O groups. The positions of the cations and H2O groups change in relation to the uranyl oxalate sheets and to each other through the series. The infrared spectra of these materials collected at room temperature are also presented and compared with previous work.
Fluorescence Resonance Energy Transfer Between Polyphenolic Compounds and Riboflavin Indicates a Possible Accessory Photoreceptor Function for Some Polyphenolic Compounds
Authors: Chandrakuntal Kumar , Thomas Neena Mary , Kumar Pradeep G. , Laloraya Malini , Laloraya Manmohan M. 
Published: July 2006

ABSTRACTThe photoreceptive extreme tip of the wheat coleoptile exhibits intense green‐yellow fluorescence under UV light, suggesting the presence of UV‐absorbing materials. Fluorescence spectra of the intact coleoptile tip and tip homogenate showed the presence of the known photoreceptor pigments flavin and carotene, and a preponderance of phenolic compounds. Absorption spectra and fluorescence spectra of various phenolic compounds showed close overlap with the absorption and fluorescence spectra of the wheat coleoptile tip homogenate. Fluorescence spectra of several phenolic compounds showed close overlap with the absorption bands of flavin, carotene and pterine, suggesting possible energy transduction from phenols to these photoreceptors. Excitation of gentisic acid and ferulic acid with 340 nm light in the presence of flavin showed enhancement of flavin fluorescence in a concentration‐ and viscosity‐dependent fashion, indicating fluorescence resonance energy transfer between them and riboflavin. Furthermore, several phenolic compounds tested generated superoxide anion on excitation at 340 nm, suggesting that superoxide‐dependent signal cascades could operate in a polyphenol‐mediated pathway. Phenolic compounds thus may act as accessory photoreceptors bringing about excitation energy transfer to the reactive photoreceptor molecules, or they may take over the function of the normal photoreceptor in genetic mutations lacking the system, or both processes may occur. The responses of plants to UV‐B and UV‐A light in mutants may be explained in terms of various phenolics acting as energy transducers in photoreceptor functioning.
Sponges from the Park City Formation (Permian) of Wyoming
Authors: Rigby J. Keith , Boyd Donald W. 
Published: July 2006

A new small twiglike anthaspidellid sponge, Virgaspongiella
ramosa new genus and species, and an incrusting lithistid
sponge have been recovered from silicified residues of etched limestone
blocks from the Middle Permian Franson Member of the Park City Formation in
western Wyoming. Virgaspongiella n. gen. has a
skeleton of upwardly and outwardly divergent trabs formed of merged tips of
runglike dendroclone spicules in ladderlike series. One to a few oxeas
function as coring spicules in the trabs and project as fine spines from the
dermal surface, and other monaxial spicules project from pores of the
canals.
The incrusting sponge, Incrustatospongia
superficiala new genus and species, forms a distinct,
thin, uniform lithistid skeletal layer, composed largely of X-shaped
dendroclones, incrusted on both the inner and outer surfaces of productoid
brachiopod valves. Separated monaxial spicules locally protrude from the
sponge's dermal surface apparently as spinose defensive elements.
Shark-bitten protostegid turtles from the Upper Cretaceous Mooreville
Chalk, Alabama
Authors: Shimada Kenshu , Hooks G. E. 
Published: July 2006

Protostegids are Cretaceous marine turtles. Fossil materials assignable
to the family Protostegidae range from early Albian to Late Campanian in age
and have been described from all continents except Antarctica (Hirayama,
1995). The group includes two gigantic forms,
Archelon Wieland and
Protostega Cope, that reached maximum
carapace lengths in excess of 2 m and rank among the largest turtles that
ever lived.
In this paper, we describe two specimens of Protostega
gigas Cope housed in the Field Museum of Natural History
(FMNH), Chicago, Illinois: FMNH P27452 and FMNH PR58. Both are from the
Mooreville Chalk (Upper Santonian to Lower Campanian: Mancini et al., 1995)
in Greene County, Alabama, and are noteworthy because they show tooth marks
from at least one large shark. One of the specimens also exhibits five
embedded teeth of the Late Cretaceous cretoxyrhinid shark
Cretoxyrhina mantelli (Agassiz). This note
constitutes the first report of protostegid turtles bitten by
C. mantelli.
Beyond competition
Authors: Gould Stephen Jay 
Published: July 2006

In a rare lapse of judgment, T. H. Huxley defined science as “organized common sense.” Huxley's motivation cannot be faulted, for he wished, by this definition, to stress the accessibility of science to any well-educated person. In the first paragraph of his most famous work on popular science (The Crayfish: An Introduction to the Study of Zoology, 1880), Huxley stated the fallacy that he wished to dispel with this definition:Many persons seem to believe that what is termed Science is of a widely different nature from ordinary knowledge, and that the methods by which scientific truths are ascertained involve mental operations of a recondite and mysterious nature, comprehensible only by the initiated, and as distinct in their character as in their subject matter, from the processes by which we discriminate between fact and fancy in ordinary life.
The muricid gastropod subfamily Rapaninae: phylogeny and ecological history
Authors: Vermeij Geerat J. , Carlson Sandra J. 
Published: July 2006

Members of the neogastropod muricid subfamily Rapaninae are abundant, shallow-water predators whose phylogeny was previously investigated by Kool (1993b), who used mainly anatomical characters. In order to deepen understanding of the evolution of this important clade and to incorporate functional, ecological fossil evidence, we performed a phylogenetic analysis based on 34 shell characters in 45 genus-level taxa, including five muricid outgroups. Cladograms based on shell characters alone differed from those founded on anatomical features these analyses differed from the phylogenetic reconstruction combining all available morphological evidence. The preferred cladogram incorporates all evidence and reveals a “Thaisgroup” and an “Ergalataxclade” that both emerge from the derived portion of a more primitive, paraphyletic group of other rapanines. The Ocenebrinae, the other four outgroup taxa three ergalataxine taxa all lie outside the rapanine clade that includes the remaining ergalataxines as a derived subclade.We used the phylogenetic results to probe aspects of the ecological history of the Rapaninae. Our data imply that antipredatory shell defenses (elongated aperture, denticles on the inner side of the outer lip robust external spines and tubercles) evolved multiple times, mainly in post–early Miocene clades in the Indo–West Pacific region. These results support earlier nonphylogenetic inferences.We compared known prey types and methods of predation of living rapanines with their distribution on our phylogenetic tree. The plesiomorphic mode of feeding in the Rapaninae is drilling of hard-shelled prey. Feeding by other means and on such soft-bodied prey as sipunculan and polychaete worms evolved several times independently among post–early Miocene rapanines in the Indo–West Pacific. Methods of predation on hard-shelled prey that involve edge-drilling or attack by way of the aperture also evolved independently several times, but did so throughout the geographical range of the subfamily.Specialization for life on the upper shore occurred in at least eight lineages, all but two of which are confined to the Indo–West Pacific. Ecological diversification of the Rapaninae was therefore most common in the tropical Indo–West Pacific during and after early Miocene time. This diversification occurred in a setting of already high biological diversity and intense competition and predation.
Contrasting evolutionary flexibility in sister groups: disparity and diversity in Mesozoic atelostomate echinoids
Authors: Eble Gunther J. 
Published: July 2006

Temporal asymmetries in clade histories have often been studied in lower Paleozoic radiations. Post-Paleozoic patterns, however, are less well understood. In this paper, disparity and diversity changes in Mesozoic heart urchins were analyzed at the ordinal level, with contrasts among the sister groups Holasteroida and Spatangoida, their paraphyletic stem group Disasteroida the more inclusive clade, the superorder Atelostomata. A 38-dimensional landmark-based morphospace representing test architecture was used to describe morphological evolution in terms of total variance and total range. Discordances between disparity and diversity were evident and were expressed both as deceleration in morphological diversification in all groups and as disproportionately higher disparity early in the histories of the Atelostomata, Holasteroida Spatangoida. The finding that the early atelostomate disparity peak coincides with the origin of the orders Holasteroida and Spatangoida lends support to the perception of orders as semi-independent entities in the biological hierarchy and as meaningful proxies for morphological distinctness.A comparison of holasteroid and spatangoid responses to the end-Cretaceous mass extinction revealed morphological selectivity. Paleocene spatangoid survivors showed no change in disparity relative to the Campanian-Maastrichtian sample, suggesting nonselectivity. Holasteroids suffered a pronounced loss in disparity (despite a rather high Late Cretaceous level of disparity), indicating morphological selectivity of extinction.Partitioning of disparity into plastral and nonplastral components, reflecting different degrees of developmental entrenchment and functionality, suggests that the origin of holasteroids and spatangoids is more consistent with an exploration of the developmental flexibility of nonplastral constructions than with uniform ecospace occupation. Within groups, several patterns were also most consistent with intrinsic controls. For plastral landmarks, there is an apparent increase in developmental modularity and decrease in developmental constraint from disasteroids to holasteroids and spatangoids. For nonplastral landmarks, no substantial change in disparity was observed from disasteroids to holasteroids and spatangoids, suggesting the maintenance of a developmental constraint despite the passage of time and ecological differentiation. More generally, this study suggests that certain topologies of disparity and evolutionary mechanisms potentially characteristic of the lower Paleozoic radiations of higher taxa (e.g., developmental flexibility) need not be confined to any given time period or hierarchical level.
Fenestrate theoretical morphology: geometric constraints on lophophore shape and arrangement in extinct Bryozoa
Authors: Starcher Robert W. , McGhee George R. 
Published: July 2006

A geometric analysis of fenestrate bryozoan lophophore shape and arrangement is conducted by creating a theoretical morphospace of apertural positioning within the colonial meshwork. Working from the assumption that fenestrate bryozoans needed to form a continuous filtering surface with contact between adjacent lophophores, we show that within the morphospace three regions exist for optimum close-packing of lophophores with circular projections; all other close-packing configurations in the morphospace require the existence of noncircular lophophores.Examination of the actual distribution of 251 fenestrate colonies within the morphospace reveals that the morphospace regions occupied by fenestellids and polyporids are displaced and have little overlap, but that they are very similar in size and shape that the colonies scale similarly. With increasing size, fenestrate meshworks expand laterally faster than the branches widen and the proximodistal spacing of the apertures increases, apparently because the larger zooids require disproportionately more room for their lophophores.Two of the optimum close-packing regions of the morphospace are occupied by fenestrates. The positioning of the fenestellid region within the morphospace suggests that these biserial bryozoans followed a proximodistal-row placement of the lophophores that the lophophores were generally equitentacular, with circular projections. The positioning of the polyporid region within the morphospace suggests that these polyserial bryozoans followed a diagonal-row placement of the lophophores that the lophophores were heteromorphic, with medial lophophores on the branch being more equitentacular whereas the laterally placed lophophores were obliquely truncate. The third optimum close-packing region in the morphospace, corresponding to a hypothetical lateral-row placement of the lophophores within the colony, is unoccupied. We suggest that hypothetical fenestrate morphologies in the vacant region of morphospace have branches that would be too narrow to support normally shaped zooids that the lateral-row placement of the lophophores would have required the branches of the colony to have been perfectly aligned throughout growth.
Evolution of taxonomic diversity gradients in the marine realm: evidence from the composition of Recent bivalve faunas
Authors: Crame J. Alistair 
Published: July 2006

A major new inventory of living marine Bivalvia (Mollusca) is based on 29 regional faunas. These again pick out strong latitudinal and longitudinal gradients in taxonomic diversity, but there are indications that the patterns are not so regular as previously thought. There are signs of asymmetry between the Northern and Southern Hemisphere latitudinal gradients, with the former tending to be more regular than the latter. Northern gradients are also characterized by a marked inflection at approximately 30°N, and the three Australian provinces seem to form a distinct “hot-spot” in the Southern Hemisphere. The larger of the two tropical high-diversity foci (the southern China-Indonesia-NE Australia one) appears to be much more nearly arcuate in plan view than oval and is closely associated with the world's richest development of coral reefs.A taxonomic and stratigraphic analysis reveals that the steepest latitudinal gradients are associated with the youngest bivalve clades. The most striking pattern is that shown by the heteroconchs, an essentially infaunal taxon that radiated extensively throughout the Cenozoic era. Steep gradients are also characteristic of the relatively young anomalodesmatan and arcoid clades and, somewhat surprisingly, the predominantly epifaunal pteriomorphs. Although the latter taxon falls within an older (i.e., “late Paleozoic-Jurassic”) group of clades, it is apparent that certain elements within it (and in particular the Pectinidae) radiated extensively in the latest Mesozoic-Cenozoic. A small but significant component of the later stages of the adaptive radiation of the Bivalvia comprised epifaunal taxa.The presence of the steepest latitudinal gradients in the youngest clades provides further evidence that the Tropics have served as a major center of evolutionary innovation. Even though some sort of retraction mechanism cannot be completely ruled out, these gradients are most likely the product of primary radiations. Clade history can be an important determinant of contemporary large-scale biodiversity patterns. The markedly lower diversity of some bivalve clades, such as the heteroconchs, in the high-latitude and polar regions may simply reflect the fact that they are not yet fully established there. In a way that is reminiscent of the onshore-offshore radiation of certain benthic marine invertebrate taxa, it may take periods of tens or even hundreds of millions of years for bivalve clades to disseminate fully across the earth's surface.The persistent spread of taxa from low- to high-latitude regions should perhaps come as no great surprise, as the tropical ocean is very much older than either of the polar ones. The late Cretaceous-Cenozoic evolutionary radiation of the Bivalvia was accompanied by a marked deterioration in global climates, and many new groups have yet to be fully assimilated into cool- and cold-water benthic ecosystems.
Calcified metazoans in thrombolite-stromatolite reefs of the terminal Proterozoic Nama Group, Namibia
Authors: Grotzinger John P. , Watters Wesley A. , Knoll Andrew H. 
Published: July 2006

Reefs containing abundant calcified metazoans occur at several stratigraphic levels within carbonate platforms of the terminal Proterozoic Nama Group, central and southern Namibia. The reef-bearing strata span an interval ranging from approximately 550 Ma to 543 Ma. The reefs are composed of thrombolites (clotted internal texture) and stromatolites (laminated internal texture) that form laterally continuous biostromes, isolated patch reefs, and isolated pinnacle reefs ranging in scale from a meter to several kilometers in width. Stromatolite-dominated reefs occur in depositionally updip positions within carbonate ramps, whereas thrombolite-dominated reefs occur broadly across the ramp profile and are well developed as pinnacle reefs in downdip positions.The three-dimensional morphology of reef-associated fossils was reconstructed by computer, based on digitized images of sections taken at 25-micron intervals through 15 fossil specimens and additionally supported by observations of over 90 sets of serial sections. Most variation observed in outcrop can be accounted for by a single species of cm-scale, lightly calcified goblet-shaped fossils herein described asNamacalathus hermanastesgen. et sp. nov. These fossils are characterized by a hollow stem open at both ends attached to a broadly spheroidal cup marked by a circular opening with a downturned lip and six (or seven) side holes interpreted as diagenetic features of underlying biological structure. The goblets lived atop the rough topography created by ecologically complex microbial-algal carpets; they appear to have been sessile benthos attached either to the biohermal substrate or to soft-bodied macrobenthos such as seaweeds that grew on the reef surface. The phylogenetic affinities ofNamacalathusare uncertain, although preserved morphology is consistent with a cnidarian-like bodyplan. In general aspect, these fossils resemble some of the unmineralized, radially symmetric taxa found in contemporaneous sandstones and shales, but do not appear to be closely related to the well-skeletonized bilaterian animals that radiated in younger oceans. Nama reefs demonstrate that biohermal associations of invertebrates and thrombolite-forming microorganisms antedate the Cambrian Period.
Bangiomorpha pubescensn. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes
Authors: Butterfield Nicholas J. 
Published: July 2006

Multicellular filaments from the ca. 1200-Ma Hunting Formation (Somerset Island, arctic Canada) are identified as bangiacean red algae on the basis of diagnostic cell-division patterns. As the oldest taxonomically resolved eukaryote on recordBangiomorpha pubescensn. gen. n. sp. provides a key datum point for constraining protistan phylogeny. Combined with an increasingly resolved record of other Proterozoic eukaryotes, these fossils mark the onset of a major protistan radiation near the Mesoproterozoic/Neoproterozoic boundary.Differential spore/gamete formation showsBangiomorpha pubescensto have been sexually reproducing, the oldest reported occurrence in the fossil record. Sex was critical for the subsequent success of eukaryotes, not so much for the advantages of genetic recombination, but because it allowed for complex multicellularity. The selective advantages of complex multicellularity are considered sufficient for it to have arisen immediately following the appearance of sexual reproduction. As such, the most reliable proxy for the first appearance of sex will be the first stratigraphic occurrence of complex multicellularity.Bangiomorpha pubescensis the first occurrence of complex multicellularity in the fossil record. A differentiated basal holdfast structure allowed for positive substrate attachment and thus the selective advantages of vertical orientation; i.e., an early example of ecological tiering. More generally, eukaryotic multicellularity is the innovation that established organismal morphology as a significant factor in the evolutionary process. As complex eukaryotes modified, and created entirely novel, environments, their inherent capacity for reciprocalmorphologicaladaptation, gave rise to the “biological environment” of directional evolution and “progress.” The evolution of sex, as a proximal cause of complex multicellularity, may thus account for the Mesoproterozoic/Neoproterozoic radiation of eukaryotes.