bluuebunny/crossref_metadata_2025_split huggingface dataset:
The thermal physiology of the Dinosauria: direct evidence from oxygen isotopes
Authors: Barrick Reese E. , Showers William J. , Fischer Alfred G. , Genna Bernard 
Published: January 2018

The thermal physiology of extinct reptiles has been a hotly debated topic for the last two decades, with no direct evidence available to help solve the debate. Oxygen isotopes are fractionated with respect to temperature between an animal's body water and bone phosphate, thus providing avenues for deriving the first direct evidence of dinosaur thermal physiology.Multiple samples from both cortical and cancellous areas from individual bones were sampled in order to determine the heterogeneity of δ18O values within single bones. Bones from both the body core (ribs and vertebrae) and the extremities (limbs and caudal vertebrae) of known individual dinosaurs were sampled in this method. This allows for a comparison of isotopic heterogeneity from bones of all body regions. In ectothermic heterotherms or mass homeotherms the δ18O values from the extremities are expected to generally be heavier than those from ribs or dorsal vertebrae. It is also expected that there would be a greater degree of heterogeneity of δ18O values from bones in the extremities than those in the body core for these individuals. This relationship would result from the greater degree of heat loss from the extremities than body cores due to greater surface areas and distance from the heart. This relationship has been seen in analyses on bones from the modern Varanus komodoensis. On the other hand, true endothermic homeotherms should show a very narrow range of hetergeneity of δ18O values both within individual bones and between bones within single individuals as seen in modern mammals.Dinosaurs analyzed indicate isotopic heterogeneities within individual bones intermediate between modern mammals and Varanus, with the Tyrannosaurus showing the greatest isotopic variability. However, this isotopic heterogeneity is relatively small and is not significantly different for bones from the body core and extremities. This indicates that heterogeneity of the δ18O values is most likely the result of variations in drinking water δ18O values throughout an individual's lifetime rather than daily or seasonal variations in body temperatures.
The early development of tetrapod herbivory
Authors: Beerbower Richard , Olson Everett C. , Hotton Nicholas 
Published: January 2018

Herbivorous tetrapods make their first appearance in Upper Carboniferous fossil assemblages but only become abundant and diverse in Upper Permian ones. During the Late Carboniferous-Early Permian interval, herbivory appeared independently at least five times: in diadectids, bolosaurids, captorhinids, edaphosaurids and caseids. These animals ranged from small forms with aptitudes for collection and processing of low-fiber plant tissues (as well as terrestrial invertebrates) to giants particularly apt for utilization of high-fiber tissues. Our report focuses on the latter group since the development of high-fiber herbivory has had a critical impact on evolution of terrestrial plants and animals as well as on the organization of terrestrial ecosystems.The low abundance and diversity of early, high-fiber herbivores reflect on one hand, sampling biases toward habitats suboptimal for herbivory, and on the other, the limited ecological capabilities of the animals themselves. Most of the Permo-Carboniferous assemblages derive from wet-land swamp and forest ecosystems where plant tissues would have been relatively rare and/or inaccessible and predation relatively intense. The likely herbivores appear apt for life in wet-land ecosystems; there they probably utilized localized patchs of productive shrub and herb along rivers and around lakes as refuges from disturbance (desiccation, temperature extremes and predation) as well as sources of food. Their low metabolic levels and growth rates minimized nutritional requirements but along with large size provided adequately for adult maintenance and for reproduction. High adult survivorship and production of a large number of eggs through a long adult lifespan would have offset high egg and juvenile mortality.Only a few Late Carboniferous and Early Permian assemblages sample drier woodland and shrub habitats where conditions would have been more favorable for high-fiber herbivory, but by Late Permian such assemblages occur in much greater numbers and diversity. The high-fiber herbivores in these dry-land ecosystems had ecological aptitudes comparable to wet-land forms but were relatively more abundant and diverse, reflecting both a greater abundance and extent of shrubby vegetation and a lower incidence of predation.
Assemblage turnovers in Mesozoic calcareous nannofossils: periodicity and distinction from the terminal Cretaceous event
Authors: Bergen James 
Published: January 2018

Long-term cycles are evident in the stratigraphic distribution(appearances/extinctions) and dominance changes of Mesozoic calcareous nannofossils. These assemblage turnovers correspond to major episodes of biological extinction recognized in inverterbrate genera and families. The identified Mesozoic nannofossil assemblage turnovers are gradual, in contrast to the well-documented and geologically instantaneous terminal Cretaceous event. Such continuity indicates a non-catatrophic cause and suggests that these turnovers are unrelated to the terminal Cretaceous “accident”. Their timing instead corresponds to interpreted sea level trends and paleoceanographic changes in the sections studied.Current evidence is based on a limited number of sections spanning the Pliensbachian to Cenomanian, although published literature and a thorough analysis of the Cenomanian show that these turnovers can be recognized over a wide geographic area. These preliminary conclusions are based on detailed sample analyses of marine sections selected for their nannofossil content. This has eliminated any taxonomic or preservational bias and problems related to compiled literature ranges.Major dominance changes are recorded in the Pliensbachian, Bajocian, Tithonian, and Aptian. The Pliensbachian turnover is evident at the family and ordinal level, whereas the younger dominance changes occur at the generic level. A major diversification during the Pliensbachian resulted in the replacement of the Jurassic Family Crepidolithaceae by the important Jurassic placolith families. The Bajocian and Tithonian turnovers were initiated by dominance changes within the common imbricate placolith family, Ellipsagelosphaeraceae. The Tithonian turnover was most dramatic including: (1) a major diversification near the Jurassic/Cretaceous boundary; (2) the extinction of several genera; and (3) the establishment of a dominant low latitude assemblage (Nannoconus, Conusphaera, Micrantholithus). Species appearances and extinctions characterize the Cretaceous turnovers. There was an increase in species extinctions during the Hauterivian, Aptian, and Cenomanian. The Aptian also includes the extinction of the aforementioned low latitude assemblage and the subsequent diversification and radiation of more cosmopolitan floras, which continued until the end of the Albian. The highest number of nannofossil species extinctions within any Mesozoic stage (except for the terminal Cretaceous) are recorded in the Cenomanian. Although several of these species extinctions are associated with the Cenomanian/Turonian boundary anoxic event, most preceeded this event.
Underprints of vertebrate and invertebrate trackways in the Coconino Sandstone (Permian) in northern Arizona
Authors: Brand Leonard R. , Kramer Jon 
Published: January 2018

The Coconino Sandstone is a Permian deposit of cross-bedded sandstone which is distributed over much of northern Arizona. Vertebrate fossil trackways are abundant in the Coconino Sandstone, and invertebrate trackways are present but less abundant. No other fossils have been found in this formation.A number of papers dealing with the systematics and paleoecology of these tracks have been published, but underprints have not previously been reported from the Coconino Sandstone. A slab from north of Seligman, Arizona bears intersecting trackways of an invertebrate and two tetrapods. A portion of the slab contains the surface on which the animals were walking. On the remainder of the slab a thin layer bearing that upper surface has broken away to reveal another surface with well preserved underprints of both invertebrates and tetrapods (systematic and behavioral aspects of these trackways will be described in a separate paper).The underprints are very distinct, deep depressions with uniformly rounded edges, while the original tracks are shallower and much less distinct because some sand slumped into them. It appears that as the animal lifted its foot out of a track the sand partly filled in the depression, but in underlying laminae the contour of the underprint was protected by the sand pushed down from above by the animal's foot.Comparison of this slab with other fossil trackways from the Coconino Sandstone suggests that a number of these trackways may be underprints. Evidence favoring that interpretation are the clarity and depth of the footprints and their uniformly rounded edges. This interpretation also suggests an explanation for some footprints that are so deep that the sand on the front edge of the track overhangs the footprint impression. The Coconino Sandstone is composed of fine sand and does not show evidence of clays or other material that could provide the cohesion to retain such steep, even overhanging, surfaces. If these footprints are underprints, the deep, undercut impressions may have been preserved by the continuity of the overlying laminae while the surface depressions were partly filled by slumping sand.It might be expected that underprints would be less distinct and detailed than the actual print. That may be true for tracks made in a substrate with an ideal consistency for preserving the tracks, but in pure, fine sand slumping of sand at the surface can apparently obliterate footprint details that are preserved in the underprints.
Oligocene carbonate platform evolution and reef development in the eastern Gulf Coastal Plain
Authors: Bryan Jonathan R. 
Published: January 2018

Throughout the Early Oligocene, the eastern Gulf Coast was characterized by three paleogeographic/carbonate facies provinces: (1) Shelf Province (Alabama/NW Florida), with foramol/bryomol limestones and local red algal pavements; (2) Gulf Trough/Apalachicola Embayment Province (N Florida/SW Georgia), a deep, current-swept structure with shallow, flanking coralgal reefs; and (3) Florida Platform Province (peninsular Florida/SE Georgia), a miliolid, peloidal, chlorozoan limestone with local patch reefs and coral thickets.During the mid-Oligocene highstand (TO1.2 depositional sequence), the Shelf Province became a drowned ramp with a shelf margin condensed section (Glendon LS). This carbonate system was unable to keep-up with sealevel rise because of the slow-growing, temperate water character of its fauna (30 °N paleolatitude). Around the Gulf Trough, however, coralgal reefs (Bridgeboro LS) kept pace with sealevel rise and formed a rimmed platform. Despite their comparatively high paleolatitude (29–32°N), the tropical fauna of these carbonates thrived because of the influence of warm Gulf Trough waters originating in the Caribbean. The Florida Platform also kept pace with sealevel rise, and was partially emergent (so-called “Orange Island”).This mosaic of adjacent tropical and temperate water carbonates, developed on rimmed platform and ramp settings, is comparable to the modern shelf margin from south Florida (Florida Reef Tract), westward to the west Florida carbonate ramp slope. A good modern analog for the Gulf Trough-Florida Platform Facies Provinces is the Florida Reef Tract-Florida Straits-Bahama Bank system.During the 30 Ma eustatic sealevel fall, coralgal reefs moved from the flanks of the Gulf Trough (Bridgeboro LS) into the Trough (Okapilco Member, Suwannee Limestone). This time-transgressive shift in reef development continued to step down the bathymetric gradient (tracking sealevel fall) until by the Late Oligocene, reefs were growing along the northern Gulf shelf margin in southern Mississippi and Alabama (Heterostegina Zone) as a rimmed shelf. Isolated, time-equivalent reefs grew on the shoals produced by emerging salt domes in Texas and Louisiana (e.g., Damon Mound).
Morphometric species recognition and phylogeny reconstruction in scleractinian reef corals
Authors: Budd Ann F. , Johnson Kenneth G. 
Published: January 2018

Scleractinian reef corals have a number of properties that are somewhat unique in morphometrics and therefore require methodologies different from those used in more structurally complex, non-colonial organisms with determinate growth. Most importantly, characters used in species recognition occur at two levels: (1) within modules and (2) among modules within colonies. Due to structural constraints imposed by radial symmetry and to the fact that growth is accomplished primarily by continuous accretion along the upper skeletal surface, most characters at the first level are continuous and consist either of architectural features related to coral lite size or to the upward growth of vertical structures forming the septa and columella. Because of high environmental variability, these features are best described using landmark based methods. Patterns of distribution of modules across colonies are best estimated using spatial statistics that can be related to underlying rules of budding and overall colony shape.Here we demonstrate how traditional multivariate statistical procedures can be applied to these two different levels of data to recognize species in the common branching and massive coral Porites, and to derive characters useful in phylogeny reconstruction. Discrete morphologic units are first identified by subdividing modules from the same colony into two groups of so-called “colony halves”, running cluster analysis on distances among halves, and using the relative positions of halves from the same colony and a modified jackknife procedure to establish cutoffs on the dendrogram for group recognition. The resulting clusters are tested using crossvalidation procedures in discriminant analysis which compare classification results for corallite level and colony level data sets, and similar results for different portions of the same colonies. Iterative procedures are then used to maximize the probability of correct group assignment for each colony. Using multiple comparisons among the resulting species, a set of independent characters that maximize group separation are selected for use in phylogeny reconstruction. Comparison with electrophoretic analyses on the same material shows high correspondence in both species assignments and phylogenetic trees based on the morphometric and allozyme approaches.
Benthonic foraminifera of the northern Monagas area, in the eastern Venezuelan basin: its implications in hydrocarbon exploration
Authors: Carrillo Marta , Intevep S.A. 
Published: January 2018

An association of benthonic foraminifera, Late Oligocene to Early Miocene in age, characteristic of the Monagas area, Eastern Venezuelan Basin, is presented in this paper.The identified assemblage could indicate a sequence boundary between a lowstand wedge and a transgressive system tract; this assemblage overlies the Naricual Formation oil sand reservoirs; therefore it is very important to have it well described.The studied assemblage has been picked out of samples analyzed from ten wells in the El Carito - El Furrial area. A total of one hundred species were identified, including twenty species turned out to be unidentifiable. Four new taxa have been described in this age interval.The fauna exhibits strong dominance, being the main species: Nonionella opima, Nonion atlanticus, Textularia cf. T. grenadana, Textularia sp., Textularia panamensis, Valvulineria sp., Ammonia beccarii, Nonionella sp., and Trochammina sp. All these species correspond to a transitional to inner neritic environment.The detailed identification of this fauna assemblage will contribute to a better understanding of the stratigraphy in the area, and in consequence to optimize hydrocarbon exploration.
Quaternary forcing of diversity in neotropical forests
Authors: Colinvaux P.A. 
Published: January 2018

The climate of the Amazon during the last northern glaciation may be taken to represent the normal climate of the basin throughout the Quaternary, since boundary conditions for Amazon and neotropical environments had not otherwise changed since the Andean orogeny and emplacment of the Isthmus of Panama late in the Teritary.The few radiocarbon dated data describing the climate of the ice age Amazon suggest that the principal climatic forcing was cooling in excess of 6 o C, associated with modest reductions in precipitation. Unlike Africa, the New World tropics were not noticeably arid. The evidence for cooling comes from paleoecological data at the foot of the Equatorial Andes, where temperature sensitive taxa had descended 1500 m into elevations that now support rain forest. Pollen data from all elevations of the Andes show that climates continued moist throughout glacial cycles, thus making appropriate the application of moist air lapse rates to substantial evidence for cooling in the high Andes also. Evidence that reductions in precipitation were modest in the lowlands come from new pollen records from 2-300 m elevation in the central Amazon of Brazil.A long record of lake sediments from lowland Panama possibly represents a complete glacial cycle. Pollen, phytolith, and other paleoecological data show both cooling and modest reductions in precipitation, in parallel with the Amazon records.At all stages in glacial cycles, neotropical forests have been subjected to intermediate disturbance tending to prevent competitive exclusion. But the forests have never been fragmented or displaced into “refugia”. Vicariance has always been provided by the scales of geography and local disturbance. The forests are dynamic systems of species whose adaptive norms are appropriate to climates of the ice age earth, but which are able to form temporary accomodations in response to climatic change.The modern Amazon rain forest was formed as an ephemeral response to the short-lived warm episode of the Holocene. Local concentrations of species, like those noted on elevated regions surrounding the Amazon basin by refugial theorists, can best be explained because occupying regions of greatest environmental change, with the consequent pattern of invasion and reinvasion necessary with each climatic shift.
Whither

Anomalocaris

? The search in the Burgess Shale continues
Authors: Collins Desmond 
Published: January 2018

A hundred years ago, Anomalocaris canadensis Whiteaves, 1892, was described as the body of a Phyllopod Crustacean. At NAPC III in Montreal in 1982, Whittington and Briggs showed that Anomalocaris canadensis was a claw, one of a pair at the front of an extraordinary predatory animal, whose jaws had previously been described as a jellyfish (Peytoia). The search to understand Anomalocaris and its relatives continues. So does the mistaken allocation of separated parts.In 1991, the first complete Anomalocaris canadensis was collected. It has a fan tail, much like the tail of another Burgess Shale conundrum, Opabinia. Another new specimen shows that its head and claws were more flexible than previously realized, and its eyes were on stalks.The large feeding claw, Appendage F, was allocated first to the arthropod, Sidneyia, by Walcott, then to the other Anomalocaris species, A. nathorsti, by Whittington and Briggs. The small size and lack of strong cross spines on the claws of A. nathorsti suggest that Appendage F probably came from another anomalocarid. Another puzzling feature on A. nathorsti is the thin, segmented structure running across the abdomen, one per body segment, ending in a club-shaped extremity on each side.A third anomalocarid is now recognized in the Burgess Shale. Its front half is composed of 3 or 4 carapace like parts previously named Hurdia and Proboscicaris. Two small sheathed claws on stalks are attached at the rear of the “carapaces”. Hanging below the rear of the “carapaces” is a grasping, feeding organ composed of a pair of claws and Peytoia jaws with an inner set of teeth. It is connected to the body which has 11 segments and a tail. The two “oblique compressions” and the Peytoia jaws with the extra group of “spines” within the mouth allocated by Whittington and Briggs (1985) to Anomalocaris nathorsti almost certainly belong to the Hurdia anomalocarid.It is evident that attempting to allocate anomalocarid parts to a particular anomalocarid is much like a Pin-the-Tail-on-the-Donkey game. In both cases the players are operating in the dark. The differences are that there is an unknown number of anomalocarids in the Burgess Shale and not only do they disarticulate easily, but they often have similar parts. As a consequence, our understanding of the anomalocarids is almost completely dependent on finding articulated specimens with the parts in place. This in turn depends on the success of field excavation. It took 100 years and 12 seasons of excavation to get the first complete Anomalocaris canadensis.