bluuebunny/crossref_metadata_2025 huggingface dataset:
Shell-crushing by two duck species,

Tadorna tadorna

and

Somateria mollissima

in the Wadden Sea. Paleoecologic implications
Authors: Cadee Gerhard C
Published: January 2018

Shell fragments from faeces of the mollusc-eating eider (Somatera mollissima) and shelduck (Tadorna tadorna) were studied in the Dutch Wadden Sea. Both species crush shells internally in their gizzard.

Shelducks feed mainly on the small gastropod Hydrobia ulvae, which they do not always succeed in breaking: in some cases even surviving Hydrobia were collected from the faeces. This indicates that shelduck may help dispersion of Hydrobia and that not only Hydrobia fragments but also intact empty shells are contributed to the sediment by this predator.

Eiders feed mainly on mussels (Mytilus edulis) and cockles (Cerastoderma edule). When these are scarce, they take shorecrabs or the gastropod Littorina littorea. Their crushing method is usually successful; only some Littorina shells were found intact but not alive in their faeces. Shells are crushed to fragments ranging from less than 0.1 to 8 mm, with a peak in the 2 – 4 mm size fraction, 20% was < 1 mm.

Annual shell carbonate production in the Dutch Wadden Sea is ca 150.000 tonnes. The annual average number of eiders is 63.000 with a maximum of up to 200.000 in winter. Annually they consume 3200 tonnes meat (ash-free dryweight). If they fed fifty/fifty on mussels and cockles they would produce ca 75.000 tonnes shell-fragments. As they feed partly on non-molluscan food this is an upper limit, but it implies that they are the main producers of shell-fragments (of all sizes, even the smallest) in the Wadden Sea. The typically square shell-fragments they produce, are easily recognisable in Wadden Sea sediments.

Others predators (shorecrabs, shrimps, flatfish, other mollusc-eating birds like knot and curlew) produce additional shell-fragments. However, some predators e.g. seastars (Asterias rubens) leave intact the shells they consumed.

Shell-fragments in sediments, therefore, may give an indication of predation pressure, but as non-crushed shells may be left over by some predators, total predation pressure on molluscs cannot be estimated in fossil faunas.
Time averaging and temporal persistence in chemoautotrophic molluscan-dominated death assemblages on the Louisiana continental slope
Authors: Callender W. Russell , Powell Eric N.
Published: January 2018

Petroleum seeps on the Louisiana continental slope produce luxurious communities based on chemoautotrophic symbiotic bacteria. Petroleum seeps are typical cold seep communities and generate classic autochthonous death assemblages. Fossil cold seep communities are well-known, common and widespread. Most fossil analogues are dominated by lucinids, but petroleum seeps are not. A combination of sample collection and in situ experimentation has been used to determine rates of taphonomy and time averaging in petroleum seep assemblages.

Cores were obtained and sectioned from seep sites in Green Canyon lease blocks 272, 234, and 184 and Garden Banks lease block 386. Lucinids and thyasirids were selected for dating time-since-death to determine the importance of time averaging in these assemblages. Dating was accomplished by measuring the free amino acid content of the shells. Time-since-death became progressively older with depth; accordingly little time averaging had occurred in these autochthonous assemblages. Lucind and mussel shells were placed on the sea floor and recovered 3 yr later. Comparison of each species to the controls left on a laboratory shelf for 3 yr shows that taphonomic alteration was rapid. Mussels were more severely altered than lucinids. Mussels were more heavily dissolved, had more altered edges, were more prone to fragmentation and exhibited greater weight loss than lucinids. The rapid taphonomic loss of the mussels suggests that the preponderance of lucinids in the fossil record is an artifact of preservation. Taphofacies analysis suggests the same; thus verifying an important assumption of taphofacies analysis that taphonomic signatures record biases in preservation by identifying inter-species differences in the rates of important taphonomic processes. Significant variability in taphonomic rates exists between shells from locations 10 m apart indicating significant local variation in the taphonomic process. Local variability in taphonomic and community attributes is characteristic of many autochthonous assemblages.
A new phylogenetic lineage (Radiolaria) from the uppermost Triassic of the Queen Charlotte Islands, British Columbia
Authors: Carter Elizabeth S.
Published: January 2018

The Upper Triassic spumellarian genus Ferresium Blome ranges from upper Norian to Rhaetian, a relatively short period of geologic time equivalent to three ammonoid zones. During this time Ferresium undergoes rapid evolutionary change on a scale far exceeding the gradual change observed among other radiolarian genera of this age. Evolutionary progression is based on the changing shape of the ferresid cortical shell, a morphological feature easily traced from species to species. By the middle to upper Rhaetian, shell shape changes sufficiently to warrant the establishment of a new genus. In the uppermost Rhaetian, Ferresium is less common and the new genus dominates all assemblages. At the end of the Triassic all members of this lineage are extinct.
Morphometric description of cosmopolitan Early Cretaceous inoceramid bivalves
Authors: Crampton James S.
Published: January 2018

Inoceramidae (Bivalvia) was a diverse, cosmopolitan family of large Cretaceous bivalves which occupied a wide range of marine environments, and experienced high rates of speciation. For biological and taphonomic reasons inoceramid taxonomy has been based almost exclusively on only two characters: shape and ornament. These characters commonly display high degrees of intraspecific variability. Previous biometric studies, using linear and angular measurements (eg. shell length, umbonal angle), have successfully discriminated between closely related species, and have overturned earlier qualitative taxonomies. Even comprehensive linear and angular measurements suffer from several disadvantages. They are restricted by instrumental limitations, are time consuming to gather, and neglect much information inherent in outline shape. Hence, the present study attempts to quantify differences in inoceramid shape and ornament using outline shape analysis complemented by a few simple distance measures. A digitised outline can be exactly described by a set of elliptic Fourier coefficients, and sets of such coefficients are treated as variables in a multivariate analysis of shape.

These methods have been used to examine the cosmopolitan, morphologically highly plastic, and highly subdivided Albian species Birostrina concentrica (Parkinson) and related forms. Collections from New Zealand (southern high latitude), England (northern high latitude), and Switzerland (Tethyan) show significant differences in the shape and maximum size of individuals. Preliminary analyses, however, have shown that within any region it is difficult to identify distinct sub-groupings based on shape or ornament. Furthermore, the total volume of morphospace occupied by B. concentrica (s.l.) can be accounted for largely by changes in morphology through ontogeny. In other words, for example, the change in shape of an individual through ontogeny can exceed the morphological distance between described subspecies. Ongoing morphometric examination of populations from different stratigraphic horizons is helping to unravel evolutionary and biogeographic patterns which are otherwise difficult to demonstrate.

Shape analysis is a tool that is largely underexploited by macropalaeontologists, and is particularly useful for the description of taxa with few landmarks or easily defined characters.
Onshore-offshore patterns in Late PreCambrian and Lower Palaeozoic trace fossils
Authors: Crimes T. Peter , Hunt N. Chris
Published: January 2018

There was a dramatic increase in abundance and diversity of trace fossils in Upper Precambrian and Lower Cambrian shallow water seas. The trace-producing animals rapidly filled all the available niches and in low energy, muddy, environments they evolved winding, meandering and patterned habits. Traces such as Taphrhelminthopsis, Helminthoida, Nereites, Paleodictyon and Squamodictyon had all evolved in clastic shelf seas during the pre-trilobite Lower Cambrian.

Significant colonisation of the deep oceans seems to have mostly been delayed until the Ordovician. A recently described suite of trace fossils from a flysch sequence in Eire includes such deep water types as: Glockerichnus, Helminthopsis, Lorenzinia, Paleodictyon and Taphrhelminthopsis. This migration into the deep sea is accompanied by a virtual absence of such traces from shallow water sequences after the Cambrian.

Deep water trace fossils therefore seem to have evolved initially in shallow water clastic seas and then migrated in to the deep ocean, thereby providing an exciting example of an onshore-offshore pattern. This may be of particular significance in that it is presumably mimicked by body fossil migrations in these early seas.
The pliocene record of climatic change: equator-to-pole biotic response
Authors: Cronin Thomas M. , Dowsett H.J.
Published: January 2018

Pliocene faunal events in tropical and subtropical regions of the Americas and the Caribbean have been causally linked to global climatic events, particularly, progressive cooling and increased amplitude of climatic cycles between 3.5 and 2.0 Ma. However, the rate and magnitude of Pliocene temperature changes has been determined in only a few climate proxy records. Our study contrasts paleoceanographic conditions at 3 Ma, an extremely warm period in many areas, with conditions 2.4 Ma, a much cooler interval, in equator-to-pole transects for the North Atlantic and the North Pacific Oceans. By using microfaunal data (ostracodes from ocean margin environments and planktic foraminifers from deep sea cores), quantitative factor analytic and modern analog dissimilarity coefficient analyses were carried out on faunas from the following sections.

Our studies lead to the following conclusions: (1) Equator-to-pole thermal gradients in the oceans at 3.0 Ma were not as steep as they are today, but thermal gradients at 2.4 Ma were steeper than those today; (2)At 3 Ma middle to high latitudes were substantially warmer than today, but tropical regions were about the same; (3)Substantial cooling occurred in middle and high latitudes in the western North Pacific Ocean and the western North Atlantic between 3 Ma and 2.4 Ma; (4)Ocean water temperatures off the southeastern U.S. remained the same or cooled only slightly between 3 Ma and 2.4 Ma. Our results support the hypothesis that ocean circulation changes, probably resulting from the closure of near surface water by the Isthmus of Panama, had significant impact on equator-to-pole heat transport and global climate between about 3 and 2.4 Ma. They also argue against the hypothesis that climatically induced ocean temperature changes were directly linked to a major marine extinction in the southwestern North Atlantic and Caribbean.
IGCP 272 - Late Palaeozoic and Early Mesozoic circum-Pacific events and their global correlation
Authors: Dickins J. M.
Published: January 2018

IGCP 203 - Permo-Triassic events of eastern Tethys and their intercontinental correlation - focussed on the Permian-Triassic boundary sequences and in particular there was a consensus that the distinctive biological changes were associated with strong sea-level and tectonic change, strong volcanic activity and a harsh climate. These factors were connected with an important change in the environment and with the exception perhaps of the climate, reflected deep-seated changes within the earth. The project also resulted in improving the physical understanding of the sequences and their biostratigraphy and correlation.

IGCP 272 was developed, and was approved in 1988, to apply these results to understanding the Late Palaeozoic and Early Mesozoic and was focussed on the Pacific as integration around this region seemed to offer especially fruitful possibilities.

Working group meetings up to the end of 1991 have been held in Australia (Newcastle and Hobart), New Zealand (Dunedin), South America (Sao Paulo and Buenos Aires) and North America (Washington). Meetings are planned in North America, Japan, Eastern Siberia or Thailand and western Europe (France-Spain-Austria).

Special cooperation has developed with the Carboniferous, Permian and Triassic Subcommissions of IUGS and with IGCP 214 - Global Bio-events. Using the more exact time correlations developed it has now been possible to show that major geological and biological events (of different levels of significance) are associated with major boundaries already recognized in the World Standard Stratigraphical Time Scale. These comprise the Carboniferous-Permian, the mid-Permian (twofold subdivision, the Permian-Triassic (already recognized in earlier work), the Lower-Middle and Middle-Upper Triassic and the Triassic-Jurassic boundaries.

A special achievement of the project has been to show the similar significance of the Midian-Dzhulfian boundary within the Upper Permian but corresponding closely to the traditional Lower-Upper Permian of China and the Middle-Upper Permian of Japan.

Although there are also other events at levels which have not been investigated by the project, those outlined all seem to reflect important changes within the earth.
The interpretation of Ordovician, Silurian and Devonian paleoenvironments utilizing the distribution of acritarch associations and organic palynofacies
Authors: Dorning Ken J.
Published: January 2018

Paleozoic acritarch and marine phytoplankton associations clearly interpret paleoenvironments within marine shelf and oceanic depositional areas. Marginal marine sediments are characterized by low diversity acritarch assemblages, while shelf areas contain a higher diversity of forms. Areas with significant terrestrial runoff tend to have higher phytoplankton abundance together with terrestrial palynomorphs in contrast to restricted circulation carbonate shelf areas with distinctive low abundance acritarch associations. Deep water basinal and oceanic areas with low phytoplankton nutrient availability are characterized by very low diversity acritarch associations of moderate to very low abundance. Within the Paleozoic, changes in relative sea level are indicated by the record of a series of acritarch associations reflecting changing depositional environments comparable to depositional sequences and parasequences.
Graphic correlation of deep sea and shallow marine deposits from the Central American Isthmus region: implications for Late Neogene paleoclimatology
Authors: Dowsett Harry J.
Published: January 2018

The stratigraphic record in Panama and Costa Rica preserves the biologic and climatic changes associated with the formation of a major barrier to marine migration and ocean circulation. Creating a high resolution temporal framework within which stratigraphic sections found on the Isthmus can be interpreted is fundamental to our understanding the history and importance of these units.

The Isthmus contains rich marine macro- and microfaunas and floras on both the Pacific and Atlantic margins. Planktic foraminifers and calcareous nannofossils are common and often well preserved. Preliminary analysis of these fossils reveals a rich sedimentary record spanning the Late Miocene to Pleistocene. Multivariate statistical analyses of these assemblages provide environmental estimates. Unfortunately, traditional methods of biostratigraphy are limited in their ability to create a high resolution temporal framework for the region. For example, a majority of deposits analyzed can be placed in planktic foraminiferal zone N19 (early Pliocene). In order to answer paleobiologic and paleoclimatic questions one requires more precise correlations between sections and some indication of duration of sedimentation represented by various sections.

In an attempt to overcome the shortcomings of traditional biostratigraphic methods, the Graphic Correlation method has been applied to selected sequences on the Central American Isthmus. Graphic correlation (GC) is a procedure by which two sequences can be compared and correlated using a wide variety of stratigraphic information simultaneously. A GC model of late Neogene planktic foraminifer, calcareous nannofossil, and paleomagnetic reversal events has been produced through compositing of more than 26 deep sea cores and ocean margin sequences. Following routine GC procedures the positions of all fossil first and last occurrences from a number of sections on the Caribbean and Pacific sides of the Central American Isthmus (Panama and Costa Rica) have been recorded. These sections have been correlated to the GC model and hence, to each other, providing a temporal framework for the Isthmus units.

Selected sections were then correlated to other sequences such as near-by deep sea cores which have been analyzed for sea surface temperature and salinity to gain a better understanding of the overall paleoceanographic development of the region between 5 and 2 Ma. For example, correlation of units on the Caribbean side of the Isthmus with DSDP Site 502 indicates little to no change in sea surface temperatures during the entire time the Isthmus was reaching closure. Mid-to-high latitude sites exhibit amplification of warming with increasing latitude. The shoaling Isthmus, while having negligible effects on tropical marine temperatures, was responsible for increased meridional heat transport which resulted in a North Atlantic warming about 3 Ma. A general model for paleoceanographic changes during the time of closure will be discussed.
Morphometric and phylogenetic analyses of the Paleozoic Subulitoidea (Gastropoda)
Authors: Erwin Douglas H.
Published: January 2018

The gastropod superfamily Subulitoidea first appeared during the Early-Middle Ordovician gastropod radiation, seemingly from within the pleurotomarid family Lophospiridea, and persisted with low diversity and generally low abundance through the Paleozoic. One species survived the end-Permian mass extinction, but like many other Paleozoic remnants, the clade became extinct in the mid-Triassic. Many members of the clade are homeomorphic with later ‘neogastropods' and have frequently been fingered as the ancestors of these later, predatory gastropods. There is however, no direct evidence for an ancestor-descendent relationship. Addressing this possibility and understanding of the systematics and evolutionary history of the clade has been complicated by relatively simple shell form and apparent paucity of shell characters. The strength of the morphological and probable ecologic similarities between subulitids and ‘neogastropods' raises the question why this clade was unable to capitalize on their position as perhaps the only predatory gastropods during the Paleozoic. Such questions of evolutionary history are best addressed within the context of a combination of morphometric and phylogenetic analyses which may resolve the systematic questions and reveal something of the evolutionary relationships of the clade.

Morphometric analyses were performed on some 40 specimens covering the 13 described genera (and several undescribed forms). Both linear and angular measurements of external shell form and internal structure from axial thin sections were measured and apertures were analyzed using elliptical Fourier analysis (EFA). The number of specimens analyzed was intentionally limited because of difficulties obtaining specimens with sufficient preservation of the aperture. The results demonstrate the necessity, for this clade at least, of including a more complex description of apertural morphology than simple maximum length and width. Principle component analyses of the EFA data distinguishes complexity of the columellar folds along the first axis and basal rounding along the second - both biologically meaningful aspects of apertural form. Moreover, the occupation of a taxon-specific apertural space defined by the PCA increases through the Paleozoic. Further, the analyses suggest that the two traditionally recognized subfamilies of the Subulitidae (Ordovician-Devonian and Devonian-Triassic) each exhibit increased variance in the occupation of morphologic space, but additional data is required to confirm this pattern and determine if any temporal trends exist.

Analyzing patterns of occupation of morphologic space requires a rigorously constructed phylogeny. A cladistic (parsimony) analysis of the superfamily was performed using 16 taxa and over 30 discrete morphologic characters. The resulting cladograms were plotted within the taxon-specific morphospaces produced by the morphometric analyses.
Bioturbational structures in the North Atlantic: new approaches for studying cores
Authors: Fu Shaoping , Werner Friedrich
Published: January 2018

General environmental correlation, established for trace fossils, is hard to apply to modern sediment cores, for which environmental factors can be measured directly - at least with regard to the top layers. Reasons for this difficulty are obvious: (1) Outcrop volume is limited by the core diameter. (2) Biogenic structures are hard to see, because they have not yet been “developed” by diagenetic processes. (3) Cores are traditionally studied in vertical cuts, in which search patterns parallel to bedding plane - typical for deep-sea environment - are poorly expressed. Therefore cores from the North Atlantic were studied not only by traditional X-ray radiography (both vertical and horizontal cuts), but by computer tomography (CT), which renders series of sections parallel to the bedding plane, as well as a three-dimensional picture, without destroying the valuable core.

On the Iceland-Faeroe Ridge, the distribution of ichnocoenoses appears to be largely controlled by microenvironments in connection with local channel systems and their lateral migration. In a local, ridge-parallel channel system at the southern slope, a core from the NE flank shows a vertical alternation of Zoophycos, Trichichnus, and Planolites communities correlating with fluctuations of CaCO3 and the fraction >63μm. In contrast to this, on the opposite slope, sediments are uniform and dominated by Scolicia. On the colder N slope of the ridge, topography is more uniform and the water motion is sluggish. The characteristic and dominant ichnogenus is Chondrites. On top of the ridge the sediment cover becomes very thin, contains large amounts of dropstones, but still Chondrites is dominant.
The stapedial morphology of the Xenarthra and its implications for higher-level mammalian relationships
Authors: Gaudin Timothy J. , Turnbull William D.
Published: January 2018

The mammalian order Xenarthra (including the living Neotropical armadillos, anteaters, and tree sloths) has figured importantly in recent hypotheses of interordinal relationships among eutherian mammals. It has been suggested that the group shares a common ancestry both with the extant Old World order Pholidota (i.e. the pangolins or scaly-anteaters) and the extinct North American group Palaeanodonta. Furthermore, these three groups have been linked together into a monophyletic Cohort Edentata, which has been hypothesized to represent the sister-group to all other eutherians. This placement of edentates relative to the remainder of Eutheria has been supported in part by a purported difference in the morphology of the stapes in the two groups- edentates possessing a primitive, imperforate/columelliform morphology, other placentals a derived, perforate/stirrup-shaped morphology.

A recent study of stapedial morphology among mammals by Novacek and Wyss (1986) suggests that within the Xenarthra itself a perforate stapes is found among armadillos, but that the pilosa in particular (the clade including anteaters and sloths) and the order as a whole are characterized primitively by an imperforate stapes. Our studies of the xenarthran ear region (Patterson et al., in press) have uncovered new ontogenetic and paleontological evidence which contradict the findings of Novacek and Wyss. Among adults of the two extant tree sloth genera, the stapes lacks a stapedial foramen. However, in both genera, this adult imperforate morphology is derived from a perforated juvenile stapes. Novacek and Wyss ignored fossil species in their consideration of the xenarthran stapes. It has long been known that extinct ground sloths of the family Mylodontidae possessed a large stapedial foramen. Unfortunately, until now no stapes were known from the remaining ground sloth families, the Megatheriidae and the Megalonychidae. We have uncovered a complete left stapes of an early Miocene megatheriid ground sloth Eucholoeops ingens. This stapes possesses a well-developed stapedial foramen. We believe that this new paleontological evidence, combined with our information on the ontogeny of the stapes in the living genera, clearly indicates that a perforate stapes is primitive for sloths. Moreover, when we plot distributions of stapedial morphologies of both living and fossil edentates onto a phylogeny of the Edentata, we can demonstrate that the a large stapedial foramen is primitive for the Xenarthra as a whole, and probably for the entire Cohort Edentata. Such a distribution makes it unlikely that stapedial morphology can be used to separate edentates from other eutherian mammals.
The isotopic record of Miocene-Recent environmental changes in shallow marine habitats on either side of the Panamanian isthmus
Authors: Geary Dana H. , Teranes Jane L. , Bemis Bryan E.
Published: January 2018

The Pliocene uplift of the Panamanian isthmus isolated previously contiguous Caribbean and eastern Pacific marine faunas, and initiated the development of different selective regimes on opposing sides of the barrier. Contrasting environmental conditions provided the context for different rates and kinds of evolutionary change on either side of the isthmus. The goal of our study is to characterize the rates and types of these paleoenvironmental changes; we employ stable isotopic profiles of venerid bivalve shells from the Miocene-Recent deposits of Panama and Costa Rica.

We analyzed geographic and depth variation in Recent shells as a means of calibrating the fossil analyses. Results from Recent venerids highlight the differences between the Caribbean and eastern Pacific shallow marine environments. Pacific shells typically exhibit strong annual fluctuations in δ18O, associated with seasonal upwelling and its associated cool waters. In shallow, near-shore habitats, freshwater runoff during the rainy season also contributes significantly to annual δ18O cycles. Caribbean shells exhibit negligible annual cyclicity.

We analyzed fossil shells from the Miocene Gatun Formation, and the Pliocene Cayo Agua, Escudo de Veraguas, and Rio Banano Formations from the Caribbean coast, and the Plio-Pleistocene Charco Azul Group from the Pacific coast. Results from fossil shells indicate that annual cycles are well-preserved, and not obscured by diagenesis or other alteration. A strong annual signal in δ18O (amplitude >1.5‰) is found back at least to the Early Pleistocene along the Pacific coast. Some post-uplift Caribbean samples exhibit stronger seasonality than that observed in similar habitats today.
Response of North American mammal communities to late Quaternary environmental fluctuations
Authors: Graham Russell W.
Published: January 2018

The late Quaternary was a time of rapid environmental fluctuations. The last glacial maximum was reached about 20 ka with continental glaciers covering most of Canada as well as the northeastern and upper midwestern United States (U.S.). Glacial ice physically displaced entire terrestrial biomes and the cooler climates altered distributions of species outside of the glacial limits. About 14 ka, the climate began to warm rapidly and glacial ice retreated northward, opening new landscapes for colonization by terrestrial biotas. Maximum warmth was reached between 9–5 ka with a time transgressive progression from west to east.

Radiocarbon chronologies allow for fine scale (100's to 1000's of years) resolution of mammal responses to these changes. Mammal communities did not respond as intact units but individual species shifted diachronically along environmental gradients. As a result, many late Pleistocene mammal communities contain associations of extant species that do not occur together today and appear to be ecologically incompatible. Pleistocene mammal communities also had a greater diversity of species than either Holocene or modern ones. This greater diversity was, in part, due to the existence of a diverse megafauna that became extinct at the end of the Pleistocene (10 ka). However, Pleistocene small mammal guilds with extant species, especially insectivores and microtine rodents, were also more diverse. Rapid changes in small mammal species distributions, diversity patterns, and clinal shifts around 10 ka strengthens environmental models for the end-Pleistocene extinction.

Modern mammal communities began to appear at the end of the Pleistocene and into the Holocene. In the eastern U.S., the species composition of these communities has been stable for the last 10 ka, although vegetational communities have shown change throughout the Holocene. In other parts of the U.S., middle Holocene warming caused some species to shift their geographic ranges. However, species composition of communities was not significantly altered. Understanding these changes not only provides a better perspective for viewing mammal communities of the past but it may also give insight into those of the future as climate will continue to vacillate, whether induced naturally or anthropogenically.
Reconciling the lithologic and paleobotanic records of climatic change during the Pennsylvanian
Authors: Gyllenhaal Eric D.
Published: January 2018

Both lithologic and paleobotanic data have been used to construct climatic curves for the Pennsylvanian of the Appalachian Basin (Figure 1). The strengths and weaknesses of each type of evidence must be considered when reconciling these data into a composite curve. (1) The calibrated lithologic curve is based ultimately on the geographic ranges of sediments and soils relative to modern precipitation. Although it provides quantitative estimates of precipitation, the calibrated curve cannot detect minor fluctuations in climate, and time-averaging of range data can lead to an over-estimate of the rate of climatic change. (2) The geochemical model, although uncalibrated, uses essentially the same data as the calibrated curve. It avoids some of the problems of time-averaging by incorporating rough estimates of abundance. Although the long-term curve portrays a uniform climate during the earlier Pennsylvanian, lithologic data may be insensitive to climatic fluctuations in extremely wet climates. (3) The abundance of arborescent lycopods in coal may be a useful climatic indicator through much of the Pennsylvanian, but its usefulness in the Mississippian (before the evolution of non-lycopod swamp trees) and the latest Pennsylvanian (after a major extinction of arborescent lycopods) must be questioned. (4) The abundance of coal resources (as with any other climatic indicator) depends on many factors other than climate. The lack of congruence between the coal abundance curve and the other curves emphasizes the importance of including non-climatic factors in any model that predicts coal resources based on paleoclimate.

The composite curve takes its overall shape from the geochemical model, quantifies it using the calibrated curve, and details climatic trends in the wet lower Pennsylvanian based on lycopod abundance data. The major weakness of the composite curve is that it ignores potential variations in seasonality of precipitation.
Changes in predatory behavior & efficiency: gastropod drilling patterns in Miocene-Pliocene Turritella (Gastropoda)
Authors: Hagadorn James W. , Boyajian George E.
Published: January 2018

The escalation of predator-prey interactions over the Phanerozoic is described as an “arms race” among the Gastropoda. Examples of escalation have been extensively documented on the scale of hundreds of millions of years, however, these patterns are not well documented on shorter time scales. Effective escalation of prey defenses should cause a drop in predatory efficiency. We study the efficiency of Naticid and Muricid predation upon Turritelline gastropods from the Miocene to the Pliocene. These predators leave a well preserved trace of predation in the form of a borehole in the shell of the prey. This study focuses on 18 species of Miocene and Pliocene Turritella from the southeastern United States. Over five thousand individual shells were examined and measured, collected from 13 localities from Maryland to southern Florida.

Predatory efficiency is determined by a number of factors: shell thickness at drillhole site, vertical location of drillhole, percent of shells that have multiple drillholes, and percent of shells that contain incomplete drillholes. Shell thickness at drillhole and location of drillhole are measured because predators would benefit by expending less energy drilling into the thinnest part of the shell that is nearest the visceral mass of the prey. Multiple complete boreholes represent at least one failure to obtain food. Incomplete boreholes represent a drilling attempt which has failed to produce food at the cost of metabolic energy.

While the intensity of Naticid and Muricid predation of Turritella increases (χ2, α<.01), predators become less efficient from the Miocene to the Pliocene. Decreased predatory efficiency is indicated by an increase in the number of shells with multiple and incomplete drilling sites (χ2, α<.01). Although predators appear to have little radial preference, they indicate strong vertical preference for centrally located drilling sites (t-test, α<.01). Predators appear to be drilling into thicker parts of Turritelline shells and thus expending more energy in drilling -however, this pattern is not statistically significant (χ2, α>.20).

We show that the efficiency of Naticid and Muricid predators decreased from the Miocene to Pliocene. Decreased efficiency of predators might result from newly evolved structural changes in prey shells, new prey escape responses or problems in predator recognition of live versus dead prey shells resulting from high densities of both living and dead individuals.

It remains to be seen whether predatory efficiency declines over longer time scales. In light of previous studies which have concentrated on evolution in the shell shape and ornamentation of prey in response to predators, a more promising and direct measure of the efficiency of predation may lie in the study of the frequency of multiple and incompletely drilled shells. By this method we might better judge the effectiveness of defense mechanisms and the evolutionary significance of predator-prey escalation.
Ecophenotypic and geographic constraints in a microevolutionary study of a rhabdomesid bryozoan
Authors: Hageman Steven J.
Published: January 2018

Documentation of microevolutionary changes in morphologic character complexes through geologic time, especially across speciation events, is one of the most significant contributions that paleontologists can provide to evolutionary biology. Papers treating patterns of evolution have established criteria required for the study of microevolution, which include: wide geographic coverage, a sequence of closely spaced samples, well defined taxa and rigorous biometric testing of large samples. Many excellent empirical studies of microevolution have taken great steps to maximize temporal resolution and to improve numerical treatment of data. Factors of ecophenotypic and geographic variation, however, have been neglected in most microevolutionary studies.

Late Paleozoic cyclothems of the North American midcontinent, with their fine stratigraphic resolution and well documented paleoenvironments that can be correlated over large geographic distances, provide a unique opportunity to study patterns of microevolution and concomitant ecophenotypic and geographic variation. Bryozoans are well suited for studies that require large morphometric data sets, because of their relative abundance, complexity, and the fact that fragmentary material can provide tenable data. Due to their colonial nature, limits of phenotypic versus genotypic variation.

In order determine the effects of geographic variation among the rhabdomesid genus Streblotrypa (Cryptostomata, Bryozoa), specimens were collected from nine localities, all taken from the lowermost six inches of the Winzeler Shale (Virgilian) distributed along a 300 km transect from south-central Kansas to northeastern Kansas. Data were collected from five specimens per locality, all from nearly identical paleoenvironments, and of very nearly the same age. Cluster analysis and discriminant analysis demonstrate some differences among the groups, however, no morphologic trends are found to correspond to geographic distributions, nor can specimens be readily assigned to locality based on morphology.

A strong genetic control within colonies is apparent. Individual observations (composite OTU's) can be assigned to the specimen from which they were measured with a very high degree of confidence. Variation between environments at the same locality over the shortest possible time span (estimated in the magnitude of 104 years) is currently being tested by analyzing data collected from the next unit above, a limestone with interbedded shales. Data from three other localities of similar environment, but significantly different age (+3 Ma), are also being analyzed to further test the degree of morphologic variation with environment verses time.

Results obtained using standard multivariate techniques applied to morphometric data are building a composite picture of the characteristics of microevolutionary change within Streblotrypa.
Paleobiogeographic and paleogeographic significance of Permian brachiopod faunas of the Bilk Creek Limestone, Nevada, and the McCloud Limestone, California
Authors: Hanger Rex Alan
Published: January 2018

The Bilk Creek Limestone of the Black Rock Terrane in northwestern Nevada and the McCloud Limestone of the Eastern Klamath Terrane in northern California contain a diverse and abundant Permian brachiopod fauna currently under study. The composite rock record of both limestones spans the Wolfcampian and Leonardian stages of the Permian, during which both terranes were part of a volcanic arc separated from the North American continent by a marginal basin of unknown dimension. Brachiopods of this volcanic arc provide important evidence bearing on current hypotheses of Permian paleobiogeography and paleogeography.

The Bilk Creek/ McCloud brachiopods are best characterized as an endemic fauna of a unique province and not as a mixed, “Tethyan” and North American fauna. The central problem of these arc faunas is not how similar they are to faunas of the Tethyan basin but why they are so dissimilar from North American faunas. Overlying rock units in both terranes contain Guadalupian brachiopod faunas that are North American in character. The paleobiogeographic pattern is one of decreasing levels of endemism throughout the Wolfcampian and Leonardian, to ultimate deprovincialization during the Guadalupian. This is not consistent with a pantropic dispersal hypothesis.

The temporal pattern is consistent with a paleogeographic hypothesis of initial, long-distance separation of arc and continent with convergence of the arc toward the North American continental margin. The dissimilarity of the arc brachiopod faunas to coeval, same-environment faunas of North America suggests that the marginal basin that separated the two must have been several thousand kilometers wide during the Early Permian, producing the endemic fauna. A Japan-style model, with arc and continent in close proximity is not supported.
Rates of evolution and homoplasy
Authors: Hauser David L. , Boyajian George E. , Shubin N.H.
Published: January 2018

Homoplasy is present in virtually every known systematic analysis and exists at all levels of the Linnaean hierarchy. Despite the nearly universal presence of homoplasy, the patterns and causal mechanisms of it have only recently been addressed.

Sanderson and Donoghue (1989) examined the relationships between homoplasy (as measured by the consistency index) and taxonomic rank, the number of characters, and the number of taxa. Their analysis, which involved 60 data sets from the literature, showed a statistically significant and inverse correlation between the number of taxa and the amount of homoplasy exhibited.

In order to expand on Sanderson and Donoghue's important contribution, we attempt to dissect the causal mechanisms of homoplasy. As a working hypothesis, we assume that if the number of character states is limited, homoplasy should be a function of at least three factors: 1) the number of cladogenetic events (which is directly related to the number of taxa), 2) the percentage of characters that undergo change at each node, and 3) the probability of any one character changing at any one node. Because the absolute, or even relative, values of the last two factors are rarely known for a given taxonomic group, we used computer generated data sets in order to quantitatively determine the relative importance of these three factors to patterns of homoplasy. Characters were allowed to “evolve” on a preset tree topology; this process was repeated for a wide variety of values for each of the above factors. The correlation of each factor with the consistency index was then examined. In order to control for results that were unique to a given tree topology, the same data sets were generated onto two very different tree topologies (a extensively bifurcated tree and a Hennigian comb).

Our preliminary results indicate that homoplasy is much more sensitive to the percentage of characters that change at a given node then to the number of taxa involved (as determined by the amount of variance explained by a regression line). In addition, the nature of the above procedure allows for the analysis of the dynamic relationship between evolutionary rate and constraint (defined as a limitation in the number of character states possible). These two factors conspire to produce homoplasy. The effect of high rates of evolution on homoplasy is magnified by successively greater constraints on character states; conversely, high rates of evolution in conjunction with low degrees of constraint lead to lesser levels of homoplasy.
The characterization of fossil and modern sporopollenins using 13-C solid state nuclear magnetic resonance
Authors: Hemsley Alan R. , Chaloner William G. , Scott Andrew C. , Barrie Patrick J. , Butler David A.
Published: January 2018

Recent 13C solid state nuclear magnetic resonance studies have demonstrated differences in the composition of sporopollenins (the inert biomolecule forming spore and pollen walls) from the major groups of extant plants. This substance is also the main constituent of fossil spore walls.

We have obtained 13C NMR spectra from three species of Carboniferous lycopod megaspores, and in one case, the associated microspores. Additionally, spores from the Devonian plant Parka decipiens Fleming have been analyzed. The spectra obtained are relatively similar although at present it is unclear how much of this similarity results from diagenesis.

The spectra of the fossil spores have been compared to those obtained from extant lycopods and from other plant groups. The fossil lycopod spores share some of the distinctive features of modern lycopod sporopollenin but are, none the less, very different. The spectra of the fossil species also demonstrate the loss of constituents known to form a significant part of the sporopollenin in extant species. Our studies show that some of the chemical characteristics of sporopollenins are retained in fossil spores, allowing the investigation of evolutionary changes of sporopollenin within a group and facilitating the assignment of taxonomically enigmatic fossil species. Further investigation of a range of fossil material, combined with data obtained from pyrolysis, should provide further information on the composition of sporopollenin from different plant groups and on its diagenesis.
The importance of paraphyletic groups in mammalian paleobiology
Authors: Janis Christine
Published: January 2018

The introduction of cladistic techniques in phylogenetic systematics have revolutionized many concepts in mammalian taxonomy: most notably, many early groups have been relegated to the status of paraphyletic or polyphyletic assemblages (e.g. the “Condylarthra” or “stem ungulates” and the “Proteutheria” insectivorans.). While it is important to recognize truly polyphyletic groups (e.g. the “Amblypoda” or Paleogene “pachyderm” analogs), all non-monophyletic groups are now commonly assigned to a similar “wastebasket” status, rendering all events associated with their evolution as “pseudo-events” on the grounds of taxonomic impurity.

I am uncomfortable with this tendency for two reasons. The first is philosophical. Monophyly is a time-dependent system of classification: all taxa were monophyletic at their inception and the more successful (i.e. generative) ones must inevitably pass into paraphyly. Cladistic taxonomy claims to be independent of stratigraphic bias, but seemingly has no problem with using an arbitrary cut-off point in the geological record (the Recent) as a means of imposing taxonomic nomenclature. The second is for practical reasons concerning information contained in many of these paraphyletic taxa that is relevant to issues other than phylogenetic systematics.

I examine closely the evolutionary histories of early Paleogene “miacoid” carnivores and late Paleogene “gelocid” artiodactyls. The extinction of miacoid species in the Late Eocene (giving rise to families of larger, apparently more actively hunting carnivores) and the extinction of gelocid species in the Late Oligocene (giving rise to families of larger ruminants apparently better equipped to ingest and process fibrous vegetation) were both coincident with major climatic and environmental changes. The change from non-seasonal to seasonal climates in the Northern hemisphere in the late Eocene may have influenced a change in predator adaptive strategies; likewise, the drying trend and spread of more open habitats in the early Neogene may have influenced ruminant foraging strategies. I submit that while not all paraphylectic groups may be useful in this fashion, at least in the above instances much paleobiological information is lost if these groups are dismissed because of their paraphyletic status: their demise reflects not artificial “pseudoextinction” but rather a real loss of archaic adaptations in a changing world.