bluuebunny/crossref_metadata_2025 huggingface dataset:
Ideas for Creating a Stimulating Undergraduate Paleobiology Course: Emphasis on Student-Directed Learning, Evolution, and the Chronological Succession of Phanerozoic Life
Authors: Sunderlin David
Published: June 2019

It is commonly noted that students with no prior coursework in paleobiology are intrigued with it. Whatever the reason, many students look forward to an undergraduate course in the subject, even if they are not earth or life science majors. We, as instructors, can seize on this interest and build on it with careful course design. Here I describe a deliberate pedagogical approach in my undergraduate paleobiology course using repeated student-directed learning (SDL) activities. I also detail two course design strategies that I have found to be particularly successful: 1) placing uncommonly heavy emphasis on evolutionary processes, and 2) studying fossil groups according to their general chronological succession through the Phanerozoic. Specifically, SDL in this course involves a suite of activities that the students have some role in designing, such as choosing the study organism for an analysis or developing hypotheses for testing with data collected from the field. SDL activities are integrated into each course module, helping to create a learning environment of scientific inquiry that balances prescribed readings and lecture components with individual, interest-driven research investigations into captivating aspects of the discipline. The course design highlights evolutionary processes early in the term, then follows an unorthodox, chronological approach to organismal paleobiology in the course's second half. The strategies described here have met with success over many course iterations, both in terms of student evaluations of their own learning and in assessment of how students reach learning outcomes regarding the acquisition of knowledge and scientific research skill-sets.
Strategies for Teaching Evolution in a High-Enrollment Introductory Paleontology Course for Non-Science Majors
Authors: Kelley Patricia H.
Published: June 2019

The high-enrollment introductory paleontology course, “Prehistoric Life,” taught at the University of North Carolina Wilmington fulfills general-education life-science credit. Most students enter the course with little knowledge of evolution (90% are non-science majors). Some assume evolution and religion are incompatible, and as non-science students, they have little incentive to learn about topics perceived to threaten their faith. Nevertheless, such students need to be prepared to make informed decisions on public-policy issues related to teaching evolution. Five principal strategies have been effective in teaching evolution to such students: 1) creating a student-centered classroom in which active/ collaborative learning engages student interest and prevents them from tuning out a threatening topic; 2) building a foundation for evolution by fostering understanding of the fossil record and geologic time; 3) in discussing evolution, focusing not only on the evidence for and mechanisms of evolution, but also clarifying the nature of science and differentiating it from religion, reinforcing that science and religion need not conflict; 4) giving students the opportunity to respond in writing to one of the position statements on evolution available from professional societies; this approach helps students formulate their own views, reassures them that their religious beliefs are respected, and fends off potential hostility during class; and 5) cultivating evolutionary thinking throughout the course (e.g., discuss evidence for evolutionary transitions and role of natural selection in evolution of various groups). These strategies have been successful in fostering student learning about evolution as indicated by teaching evaluations, student attendance, and comments in student reflection papers on evolution.
How Undergraduate Students Misread Cladograms
Authors: Kortz Karen M. , Swaddle John P. , Fastovsky David E.
Published: June 2019

Although phylogenetic systematics is used to reconstruct evolutionar 123y relationships, undergraduates have a difficult time mastering its fundamental concepts. Because it is a key part of the mainstream professional thinking, we explored in what ways students misread cladograms, which are the abstract and synthetic diagrams of phylogenetic systematics. We developed a questionnaire to examine the following four hypotheses as to how introductory college-level students (n=51) read cladograms: 1) students read cladograms correctly; 2) students infer that proximity of tips equals relatedness; 3) students read cladograms as they might an evolutionary tree, reading left to right as primitive to more advanced, and perceiving organisms as branching off; and 4) students infer ancestors at the nodes. Most responses fell into one of the four hypotheses, with 55% following the scientific (‘correct’) hypothesis. Most students answered between six and eight of the ten questions correctly. Slightly more than half of the students generally followed the scientific hypothesis, while others applied both the scientific and proximity (hypothesis 2, above) hypotheses together. A few students followed the primitive hypothesis (hypothesis 3, above). Our recommendation is that instructors address discrepancies between the scientific and proximity hypotheses in particular. For undergraduates, generally, cladograms require focused teaching, explanation, and active-learning approaches to be successfully used to teach phylogenetic systematics.
Teaching Through Investigative Case Studies: Lessons from Invertebrate Paleontology
Authors: Schiappa Tamra A.
Published: June 2019

Students in traditional invertebrate paleontology courses typically are required to identify, sketch morphologic features, and memorize chronostratigraphic ranges of major fossil taxa. This traditional approach is viewed as mundane and unnecessary by many students. Integrating new learning strategies involving specific case studies into an invertebrate paleontology course creates a dynamic learning environment. This improves students' observational and critical-thinking skills as well as their understanding of the utility of the fossil record and key geologic concepts. New teaching strategies, such as investigative case studies, provide students with opportunities to develop good deductive reasoning and metacognitive skills. Strengthening these types of skills, which include comprehension, the ability to problem-solve, and the analysis and interpretation of data, will prepare students to be more successful as scientists.
The Taphonomy Experiment: Reinforcing Science Process Skills with a Class-Based Student Independent Research Project
Authors: Koy Karen A.
Published: June 2019

Since the mid-20thcentury, science education has focused on active inquiry rather than direct transmission of knowledge. The National Research Council's National Science Education Standards direct that inquiry-based activities be incorporated at all levels of education. The application of inquiry-based activities at the college level should include faculty-student research programs. This paper presents a class-based faculty-student research project conducted by teams of students over the course of a semester. The advantage of inquiry-based learning for undergraduates is outlined in a review of the educational literature. While there has not been much in the way of quantitative assessments of inquiry-based learning, it is clear that students with a good foundation in the subject benefit from open-ended inquiry. This information was used to create an inquiry-based approach to teaching science-process skills, which was used successfully in an upper-level undergraduate paleontology course at Missouri Western State University, a four-year institution located in northwest Missouri. Students worked in groups to design an original experiment addressing some aspect of taphonomic processes. After online class discussions of the research proposals and final approval from the instructor, students independently ran the experiments, monitoring and collecting data outside of class. During the final week of classes, the groups presented their experiments in a 20-minute, conference-style PowerPoint presentation that placed their experiment within the context of the literature.
Engaging Paleontology Undergraduates in Collaborative Research Experiences
Authors: Savarese Michael , Schmidt Diane
Published: June 2019

Undergraduate research is rightfully viewed as a valuable educational endeavor, yet few students have the time or incentive to avail themselves of the opportunity. Those students who do obtain research experience typically do so during their senior year, at a time too late to best benefit from the experience. Finally, requiring students to conduct independent research can be unsustainable, drawing on limited resources and faculty time. We have developed a collaborative undergraduate research model that unites students as a research team in their standard courses. The method is applicable to all course levels, from introductory science courses to upper-division, discipline-specific courses. At the introductory level, students work on longer-term research problems that require regular monitoring, with each successive class adding to an iterative database. Students in upper-division classes design group projects that are completed in the course of the semester. The benefits of the model are numerous. Students develop a sense of ownership and stewardship; they obtain a thorough experience practicing science while their curriculum is applied to real problems; and students learn to work cooperatively. Results from many of these experiences are of a high enough quality to be presented at scientific meetings and eventually published. Projects often help students focus their discipline-based interests and spawn senior theses, and faculty members have a vehicle to vicariously increase their research productivity. Examples from an upper division paleobiology course are presented. Overall, this model has been highly successful, especially when employed at the upper-division levels.
The Meaning of Evolution
Authors: Bambach Richard K.
Published: June 2019

In 1950, the great vertebrate paleontologist George Gaylord Simpson published a book titled “The Meaning of Evolution.” Simpson divided his work into three parts: (a) the Course of Evolution, (b) Interpretation of Evolution, and (c) Evolution, Humanity, and Ethics. I will take a different approach. Rather than detailing the course of evolution (topics of which are covered elsewhere in this volume), or interpreting patterns seen in the history of life, or trying to construct an ethical program, I will just consider three aspects: (1) what we mean by evolution, (2) the status of the theory of evolution, and (3) what evolution means to understanding the natural world. Some ideas about the importance of human existence and its implications do emerge, however, from the third topic, and several of my points do parallel some of Simpson's conclusions.
The Age of Things Found in the Earth
Authors: McKinney Frank K.
Published: June 2019

One of my favorite places to collect fossils is a steep, high railway cut in a rural part of southern Kentucky, where a ridge made of limestone sat right across the most efficient route the railway could take. When that cut was first made, professional paleontologists and amateur fossil collectors came by to have a look at the newly exposed rock; but although the fossils could be seen, we could get hardly anything out because they were almost all too firmly locked within the rock. Within just a couple of years, weathering had caused some of the weaker, clay-rich layers to break down a little, yielding loads of fossils. The rock around the fossils broke apart into small grains, and the fossils themselves, skeletal remains of marine animals, could be picked up by the hundreds of thousands: crinoids, blastoids, brachiopods, screw-shaped parts of bryozoans, trilobites, individual cone-shaped corals, strange conical snails, even rare starfish.
The Nature of the Fossil Record
Authors: Kidwell Susan M. , Sepkoski J. John
Published: June 2019

The term “fossil record” is used in two ways: to mean either the totality of fossils preserved in all rocks or the sum of human knowledge of those fossils. In both cases, the term carries the connotation also of the geologic context of the fossils—their distribution in time and space and their relationship to the enclosing rock. One of the primary scientific interests of the fossil record is what it can teach us about the history of life and the processes of large-scale transformation, or evolution, in the forms, diversities, and biological interactions of living things.
Evolution and Systematics
Authors: Carlson Sandra J.
Published: June 2019

The biological process of evolution—descent with modification—generates and structures the remarkable diversity of life on Earth today and in the geological past. Take a moment to consider the vast number of different kinds of living things: mushrooms, koalas, sunflowers, whales, mosquitoes, kelp, bacteria, tapeworms, lichens, clams, redwoods,…the list could go on and on, seemingly forever. Without some understanding of how the diversity of life was generated, the scope of the diversity may seem overwhelming, perhaps even unknowable. Fortunately the structure of this extraordinary diversity, generated by the process of evolution, can be discovered using the methods of systematics. Evolution can be thought of as “an axiom from which systematic methods and concepts are deduced” (de Queiroz, 1988). Systematics, therefore, provides a way to organize the diversity surrounding us, and make sense of it in an evolutionary framework. Patterns of similarity and difference in morphology, genetics, and development—the evidence of evolution—can only be explained in an evolutionary context by means of systematics. No other method seeks to identify patterns that are evolutionary in origin, generated by the process of common descent.
Missing Links in the History of Life
Authors: Marshall Charles R.
Published: June 2019

Ever since Darwin proposed his theory of evolution (or more correctly, theories; see Mayr, 1991) it has been assumed that intermediates now extinct once existed between living species. For some, the hunt for these so-called missing links in the fossil record became an obsession, a search for evidence thought needed to establish the veracity of evolutionary theory. Few modern paleontologists, however, search explicitly for ancestors in the fossil record because we now know that fossils can be used to chart the order of evolution regardless of whether they are directly ancestral either to extinct organisms or to those living today.
Major Patterns in Botanical Diversity
Authors: Crane Peter R.
Published: June 2019

At a time when the popular perception of paleontology is dominated by images of dinosaurs and other spectacular vertebrates, or the mysteries surrounding the Cambrian “explosion” of animal life, it is perhaps not surprising that the rich and informative fossil record of plants has scarcely made an impact on the public consciousness. In reality, as one would expect from those organisms that comprise the bulk of the biological material in terrestrial ecosystems, the fossil record of plants is extensive (Stewart and Rothwell, 1993). Leaves, wood fragments, pollen grains, spores, fruits, seeds, and other plant parts are the most common fossils in rocks deposited in ancient flood plains, lakes, and many other environments—and they are often exquisitely preserved. This excellent fossil record provides important information about the ecology of ancient terrestrial ecosystems. The quality of the plant fossil record also makes paleobotanical data highly informative about the historical pattern of plant evolution. It is this pattern, and its congruence with patterns in the characters of living and fossil plants—as summarized in a classification—that is the focus of this chapter.
Molecules and Evolutionary History
Authors: Collins Allen G.
Published: June 2019

Paleontologists learn and tell the history of life; it is our job. You might suspect that paleontologists spend most of their time studying fossils. While fossils are an important source of information for the paleontologist, other types of evidence can also tell us about biological history. For instance, the rocks themselves provide important information, especially about past climates. It makes perfect sense that organisms are more easily understood if you know the environment in which they lived. A third important source of information is all around us.
Long / Short Term Influences on Change
Authors: Roy Kaustuv
Published: June 2019

Change has been the rule in the history of life. Mammals today dominate the terrestrial habitats where dinosaurs once held sway. In modern oceans, ecologists can study many species of arthropods, but trilobites are long gone. Using data from the fossil record, David Raup estimated that only about one in a thousand species that ever lived on this planet is still alive today (Raup, 1991). On the other hand, the number of species and higher taxa has increased steadily over geologic time. Thus the history of life is essentially a history of turnover of species, lineages, and higher taxa over time.
Rates of Evolution
Authors: Stanley Steven M.
Published: June 2019

Any two biologic groups—populations, species, or groups of species—that are separated in time but connected by evolution provide us with the opportunity to measure a rate of evolution.
The Evolution of Biodiversity: Richness and Disparity
Authors: Valentine James W.
Published: June 2019

The study of biodiversity can be divided into two major aspects. One aspect is concerned with the numbers of species, genera, families, or other taxonomic units that are present within a given group of organisms, or a given region, or during a given period of time. This measure of diversity is termedrichness. Richness may be represented at any geographic scale: local, such as the number of species in your backyard; regional, such as the number of species found in California; or global, such as the number of species in the entire world at present. Preservation of species richness in the present biosphere is clearly a matter of great social and scientific concern. Each species has a unique genetic makeup, and a distinctive place within an ecosystem. If a species is lost, the unique genes are also lost, and the effects on the ecosystem can be destabilizing, affecting the well-being of still other species.
Creating Models for Interpreting Data
Authors: Plotnick Roy E.
Published: June 2019

For many of us, the word model may trigger remembrances of long-ago afternoons spent painstakingly gluing a small plastic car or airplane model together (for others, it may conjure up images of a somewhat emaciated young woman staring out of the cover of Vogue or Elle). The model car is not the same as a real car; it is made of different materials, it has many fewer parts, and it does not move. Nevertheless, it resembles a real automobile sufficiently that we recognize it as a realistic representation. Similarly, scientists use the term model to refer to a reconstruction of nature for the purpose of study (Levins, 1966). In other words, in order to understand nature, one may not always want to study it directly. Instead, understanding may come from studying a facsimile of nature that captures what is perceived to be its essential properties. In the same way, a child may learn how a car is built by building a plastic model of it, even if this model contains no moving parts.
Science, Religion, and Evolution
Authors: Scott Eugenie C.
Published: June 2019

Evolution is one the most controversial concepts for teachers to teach. The source of opposition to evolution primarily comes from the perception that acceptance of evolution is somehow incompatible with religion. In this paper, I shall discuss the sometimes bumpy relationships between science, religion, and evolution, and what this history means for teachers. First, however, I should define the critical terms evolution, science, and religion.
Evolution of Bird-Hipped Dinosaurs (Ornithischia)
Authors: Sereno Paul C.
Published: June 2019

By the end of the last century, the assortment of dinosaur skeletons that had already accumulated were classified into two groups of approximately equal size based on the divergent plan of their hip bones: Saurischia, the “lizard-hipped” dinosaurs, and Ornithischia, the “bird-hipped” dinosaurs (Seeley, 1888). Today we continue to follow this early dinosaur classification, albeit for somewhat different reasons, and consider that it captures a fundamental, ancient bifurcation in dinosaur evolutionary history.
Pachycephalosaurs and Ceratopsians (Ornithischia: Marginocephalia)
Authors: Sereno Paul C.
Published: June 2019

Explanatory scenarios for the evolution of dinosaur anatomy are often couched in terms of competitive advantage, with those animals of superior design overtaking those that are slower and less efficient. Many, if not the majority, of the most striking structural modifications, however, are the product of competition and display between conspecifics during courtship. Among dinosaurs, ornithischians evolved an elaborate array of bony crests on the skull. These often constitute the most diagnostic portions of the entire skeleton. Traditionally these bony head accessories, typically sheathed and extended by horn, were viewed as the defensive weaponry of quiescent herbivores. More recently they have been reinterpreted on the basis of living analogs (such as horned ungulates) as secondary sexual characteristics employed primarily during intraspecific rivalry (see Norman's contribution to this volume).
The Sauropod Dinosaurs: A Brief Survey
Authors: McIntosh John S.
Published: June 2019

The sauropod dinosaurs, those long-necked, long-tailed giants, burst onto the world scene in the Lower Jurassic period and lived on until the end of the Age of Reptiles at the close of the Cretaceous. From the shapes of their teeth it is clear that they were herbivorous, and what an enormous amount of plant material they must have continuously consumed to fuel their gigantic bulk. Colbert (1962) estimated the weight of an adult Apatosaurus (Brontosaurus) at 34 metric tons, and that of Brachiosaurus at 78 metric tons. Dale Russell (see Russell, Beland and McIntosh, 1980) regards these estimates as too high by perhaps a factor of two, but in any case their masses were immense. The sauropods were quadrupedal, and their limbs were oriented in a columnar position as in large mammals, and unlike those of other dinosaurs. From this fact and a bone histology more nearly like that of mammals than typical reptiles, Bakker (1975) and de Ricqlès (1968, 1980) have independently suggested that the sauropods may have been warm-blooded (endothermic). Many dinosaur experts concede that this may have been true of some of the smaller, faster-moving carnivores, but the majority seem unconvinced of endothermy in the sauropods. Instead, it seems more appropriate to regard them as inertial homeotherms: that is, their large mass ensured a fairly constant body temperature, as in large mammals. However, as in mammals, the story is probably more complex than a single fact or factor can explain (Thomas and Olson, 1980; Weaver, 1983).
Theropod Dinosaurs of the Cretaceous
Authors: Currie Philip J.
Published: June 2019

Tyrannosaurus rex is unquestionably the most famous dinosaur, probably because of its awesome size and appearance, and its apparent strength, agility and prowess. In spite of its fame, the anatomy and relationships of Tyrannosaurus and its kin remain poorly understood. By Late Cretaceous times (about 65 to 100 million years ago), carnivorous dinosaurs (theropods) had reached their peak of diversity in the Northern Hemisphere, and there were many specialized species of all sizes.
The Origin of Birds and the Evolution of Flight
Authors: Gauthier J.A. , Padian K.
Published: June 2019

One of the most salient advances in vertebrate paleontology in recent decades has been the settling of the question of the origin of birds, a problem that has vexed evolutionary biologists since well before Darwin. To be sure, the consensus is not unanimous, and many details of this branch of the phylogenetic tree are yet to be worked out, but we now have a much clearer picture of this problem than we had a decade ago. Less settled, but equally stimulating, has been the controversy over the origin of flight in birds and other flying vertebrates. Was there a gliding stage? Did flight begin from the ground up or from the trees down? Were birds initially arboreal? What selective pressures drove the ancestors of birds to take advantage of the aerial opportunity?
Time resolution in terrestrial macrofloras: Guidelines from modern accumulations
Authors: Burnham Robyn J.
Published: June 2019

The evidence available for determining time resolution in plant fossil deposits can be subdivided easily into two general categories: the information provided by the biological properties of the plants and the information provided by the physical properties of the sediments and accumulation styles. Accordingly, this contribution is divided into two sections, covering these two aspects of time resolution from modern plant accumulations. From a standpoint of modern macrofloral accumulation, there are four ideas that have guided this chapter.
Mathematical models of temporal mixing in the fossil record
Authors: Cutler Alan H.
Published: June 2019

In December 1969 officials from the U.S. Selective Service System conducted a draft lottery to establish the order in which nineteen-year-old men were to be called for military service. Three hundred sixty-six capsules, one for each possible birthday, were placed in a large wooden box. As the capsules for each month were added to the box, the contents of the box were mixed. Once all 366 capsules were in the box, it was shaken several times and emptied into a deep bowl. Capsules were then drawn from the bowl to determine the draft number corresponding to each date. Observers were satisfied that the capsules had been thoroughly mixed, but, as it turned out, the results were anything but random. The Spearman rank correlation between birth date and draft number was significant at the.001 level – men with December birthdays had a significantly higher probability of being called than did those with January birthdays (Fienberg, 1971).
Summary: Estimates of Time-Averaging
Authors: Kidwell Susan M. , Behrensmeyer Anna K.
Published: June 2019

Figure 1 summarizes estimates for the time-scales over which fossil assemblages accumulate, based on the findings summarized by the various authors of this volume, and organized according to major taxonomic groups in terrestrial and marine environments. For each group, actualistic estimates are based primarily on field evidence for the durability of organic remains, either from time-lapse tracking of carcasses or from direct-dating of individuals in Recent death assemblages; other methods include extrapolating from known rates of sediment accumulation and rates and depths of mixing. Estimates from the fossil record are based almost exclusively on indirect evidence, such as bracketing of assemblages by biostratigraphic and other chronostratigraphic datums, and actualistic rates of formation for the kinds of beds and facies that contain assemblages. The reader should see individual chapters for details and original sources of data.
Status of Ordovician and Silurian Radiolarian Studies in North America
Authors: Noble P. J. , Aitchison J. C.
Published: June 2019

Polycystine radiolaria that produce siliceous tests are known to range from Cambrian to Holocene. They have proven to be enormously useful in providing age control for siliceous marine sequences of Middle Devonian and younger ages, particularly for cherts and shales that are commonly devoid of other biostratigraphically useful fossils. The utility of radiolarian biostratigraphy became widely recognized in the 1970s and 1980s when it was applied in dating deformed marine siliceous sequences in orogenic belts around the world, most notably in Cordilleran North America and other areas along the Pacific rim (e.g., Jones and Murchey, 1986; Aitchison and Murchey, 1992; Ichikawa et al., 1990).
Cretaceous Diatoms: Morphology, Taxonomy, Biostratigraphy
Authors: Harwood David M. , Nikolaev Vladimir A.
Published: June 2019

The Cretaceous record of the diatoms presented here outlines our understanding of their early morphological development. Recent documentation of well preserved Lower Cretaceous (Aptian/Albian) diatom assemblages provides a window into the early history of the diatoms and serves as a base for comparing their subsequent morphological changes. A brief review of diatom biology and morphology is provided to introduce this paper and that of Barron and Baldauf (this volume). Additional background information on the diatoms can be found in the works of Schrader and Schuette (1981), Tappan (1980), Bach and Burkhardt (1984), Barron (1985a, 1993), Fenner (1985), Ricard (1987), Bradbury (1988), Round et al. (1990), and Picket-Heaps et al. (1990).
Fossil Continental Diatoms: Paleolimnology, Evolution, and Biochronology
Authors: Bradbury J. P. , Krebs W. N.
Published: June 2019

Diatoms are golden brown algae (class Bacillariophyceae) whose cellular contents are enclosed between two valves or shells of silica. They are classified into groups with radial symmetry (centric diatoms) and axial symmetry (pennate diatoms). The latter are subdivided as raphid and araphid diatoms according to the presence or absence of raphes (slit-like structures) that allow diatoms to move along firm surfaces. Many centric and some araphid diatoms are planktonic, maintained by turbulence in the limnetic region of a lake, whereas raphid diatoms live on the lake bottom or are attached to objects in the illuminated zone.
Ebridians and Endoskeletal Dinoflagellates
Authors: Ernisse John J. , McCartney Kevin
Published: June 2019

General.—Ebridians, in many ways, are “neglected step-children” in the family of siliceous microplankton. Reduced to only three living species and never particularly abundant througout their history, ebridians do show up in marine, diatom-bearing sediments from practically every region of the globe.
The Arthropod Fossil Record: Biologic and Taphonomic Controls on its Composition
Authors: Mikulic Donald G.
Published: June 2019

It is difficult to overestimate the importance of arthropods in the history of life. In terms of diversity and abundance, modern arthropods embody the ultimate success of the metazoa. Their prominence stems from an innovative, durable body plan, allowing mobility and adaptability for almost any environment in the earth's biosphere. Arthropods have been able to exploit an enormous range of lifestyles, becoming a conspicuous biotic component of many marine and terrestrial settings.
Mass Extinction in the Cambrian Trilobite Faunas of North America
Authors: Westrop Stephen R.
Published: June 2019

Sepkoski (1981a,b, 1988) has characterized the Cambrian fauna as unique, both in terms of taxonomic composition and in environmental distribution of taxa. Compared with the rest of the Phanerozoic, the frequency of mass extinction in the Cambrian must also rank as a distinctive feature which had a profound impact on macroevolutionary patterns. Three well-documented extinctions occurred in the Upper Cambrian of North America (Figure 1; Palmer, 1979; Westrop and Ludvigsen, 1987) and are best expressed in the trilobite faunas. Possible older extinctions may be present at the top of theOlenellusZone and near the base of theBolaspidellaZone (e.g., see Palmer, 1982) but more data are required.
Trilobite Larvae, Larval Ecology and Developmental Paleobiology
Authors: Speyer Stephen E. , Chatterton Brian D.E.
Published: June 2019

Since Barrande (1852) first illustrated a trilobite larva, aspects of trilobite ontogeny and early development have received a great deal of attention (see Beecher, 1895; Størmer, 1942; Whittington, 1957; Hu, 1971; Chatterton, 1980). Much of this literature, however, is purely descriptive and very little has been done to incorporate these works into a biological synthesis. During the past several decades a great deal has been learned about the role of larval ecology in monitoring biogeographic distributions, cohort survivorship and taxonomic longevity among modern marine invertebrates. This growing body of knowledge has provided the basis for many new insights regarding patterns of extinction and survivorship and macroevolution evident within the fossil record (see Jablonski, 1986; Jablonski and Lutz, 1983).
The Future of Analytical Paleobiology
Authors: Raup David M.
Published: June 2019

In the past few decades, we have come a long way in making paleobiology more rigorous. We have accumulated an impressive array of quantitative techniques – statistical and otherwise – and these are in use with the full range of paleobiological problems. Also striking is the way the added rigor of our science has spilled over into non-quantitative judgments and interpretations. No longer is the Just-So Story allowed to stand unchallenged. Rather, we respond to these bald assertions and ad hoc theories with: “Can you prove it?” or “Can this be tested?”
Vertebrate Trace Fossils
Authors: Schult Mark F. , Farlow James O.
Published: June 2019

The study of fossil footprints began soon after the birth of vertebrate paleontology. The Reverend Henry Duncan started a study of footprints from the New Red Sandstone (Permian) of Scotland in 1824 (Sarjeant, 1987). Even earlier reports of footprints are known, but the fossils were not studied until later (Sarjeant, 1975). The first experiment in making trackways occurred around 1830, when the Reverend William Buckland walked a turtle across pie crust, wet sand, and soft clay.Chirotherium, one of the most famous ichnogenera, was described by J. F. Kaup in 1835. In 1836, Edward Hitchcock published the first of many papers describing dinosaur and other footprints from the Triassic and Jurassic of the Connecticut Valley (Sarjeant, 1987). The first Carboniferous footprints were discovered in 1841 in Nova Scotia by William Logan, and provided the first evidence of terrestrial vertebrate life older than the New Red Sandstone (Sarjeant and Mossman, 1978). Tertiary footprints were described by Jules Desnoyers in 1859 (Sarjeant, 1987). Studies continued through the nineteenth and the first three decades of the twentieth centuries. Permian trackways from the Grand Canyon were found in 1915 and extensively described by Gilmore (Gilmore, 1926, 1927, 1928; Spamer, 1984). Soon after this, however, the study of vertebrate trace fossils fell into disrepute. In the last decade or two, a resurgence of interest has occurred, primarily spurred by an interest in using dinosaur footprints to learn more about these animals (Sarjeant, 1987).
Bioerosion: Eating Rocks for Fun and Profit
Authors: Bromley Richard G.
Published: June 2019

“Bioerosion” was coined by Neumann (1966) as an abbreviation of “biologic erosion”, and describes every form of biologic penetration into hard substrates, i.e., lithic (including skeletal) and woody. An extremely wide range of organisms causes bioerosion (see Bromley, 1970; Warme, 1970, 1975; Ekdale et al., 1984, p. 108–139). The work of these organisms produces trace fossils at all scales, from microscopic to gigantic. Minute scars etched by brachiopod pedicles have a paleoecologic story to tell; at another scale, cliff sapping by communities of boring bivalves and rasping limpets can cause major geographic changes. For example, the work of pholad bivalves played a leading role in the separation of England from the European continent; and had the great armada, sent against England by Philip II of Spain in 1588, not been annihilated by wood-boring shipworms (bivalves), the language of this short-course would have been Spanish.
Quo Vadis, Ichnology?
Authors: Seilacher Adolf
Published: June 2019

Nobody knows exactly when and where Lady Ichnology was born; but everybody would agree that she is coming of age. There are unmistakable signs of this: social acceptance, for instance, or its own journal, and a progeny that can only be estimated from the yearly flow of publications and from a regular newsletter sent out in numbers that make book publishers greedy.
Effects of Particle Nonsphericity on Dust Optical Properties in a Forecast System: Implications for Model‐Observation Comparison
Authors: Hoshyaripour G. A. , Bachmann V. , Förstner J. , Steiner A. , Vogel H. , Wagner F. , Walter C. , Vogel B.
Published: June 2019

Mineral dust is a key player in the Earth system that affects the weather and climate through absorbing and scattering the radiation. Such effects strongly depend on the optical properties of the particles that are in turn affected by the particle shape. For simplicity, dust particles are usually assumed to be spherical. But this assumption can lead to large errors in modeling and remote sensing applications. This study investigates the impact of dust particle shape on its direct radiative effect in a next‐generation atmospheric modeling system ICON‐ART (ICOsahedral Nonhydrostatic weather and climate model with Aerosols and Reactive Trace gases) to verify if accounting for nonsphericity enhances the model‐observation agreement. Two sets of numerical experiments are conducted by changing the optical shape of the particles: one assuming spherical particles and the other one assuming a mixture of 35 randomly oriented triaxial ellipsoids. The simulations are compared to MISR (Multiangle Imaging Spectroradiometer), AERONET (Aerosol Robotic Network), and CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations (with focus on North Africa). The results show that consideration of particle nonsphericity increases the dust AOD (Aerosol Optical Depth) at 550 nm by up to 28% and leads to slight enhancement of the agreement between modeled and measured AOD. However, the model performance varies significantly when focusing on specific regions in North Africa. These differences stem from the uncertainties associated with particle size distribution and emission mechanisms in the model configuration. Regarding the attenuated backscatter, the simulated profile assuming nonsphericity differs by a factor of 2 to 5 from the experiment assuming spherical dust and is in a better agreement with the CALIPSO observations.
Modeling the Subsurface Hydrology of the Greenland Ice Sheet
Authors: Sidder Aaron
Published: June 2019

Firn aquifers—pockets of meltwater beneath the surface of an ice sheet—could have far-reaching impacts on subglacial hydrology, a new study finds.
Careers in Community Science
Authors: Johnson Anne
Published: June 2019

Community science brings scientists and communities together to solve local challenges. What are the career paths in community science, and what opportunities might the future bring?
Can Bold U.S. Federal Climate Legislation Be Enacted Now?
Authors: Showstack Randy
Published: June 2019

Nearly 10 years after the introduction of the ambitious Waxman-Markey climate change bill, experts assess the chances of climate legislation.
An inkjet printing paper-based immunodevice for fluorescence determination of immunoglobulin G
Authors: Guo Xiaoyan , Chen Ying , Zhang Liu , Liu Wei
Published: June 2019

A sequential inkjet printing strategy was utilized on a microfluidic paper-based fluorescence (FL) immunodevice for immunoglobulin G (IgG) detection.
Oxidation and chalcogenylative disproportionation of anionic phosphide ligands in yttrium complexes with elemental sulfur and selenium
Authors: Zhang Fangjun , Yi Weiyin , Zhang Jie , You Qing , Weng Linhong , Zhou Xigeng
Published: June 2019

Rare-earth mediated oxidation and disproportionation of anionic phosphide ligand has been established by the reactions of yttrium phosphide with S or Se, providing a potential route to synthesize rare-earth mono- and di-thio/selenophosphinates.
Single-cell RT-LAMP mRNA detection by integrated droplet sorting and merging
Authors: Chung Meng Ting , Kurabayashi Katsuo , Cai Dawen
Published: June 2019

We present a droplet-based microfluidic platform that permits seamless on-chip droplet sorting and merging, which enables completing multi-step reaction assays within a short time, and demonstrate detection of specific single-cell mRNA expressions.
In situ S-doped ultrathin gC3N4 nanosheets coupled with mixed-dimensional (3D/1D) nanostructures of silver vanadates for enhanced photocatalytic degradation of organic pollutants
Authors: Joseph Subi , Abraham Sinoj , Priyanka Ragam N. , Abraham Thomas , Suresh Arya , Mathew Beena
Published: June 2019

A novel plasmonic Z-scheme sulphur doped gC3N4/Ag3VO4/β-AgVO3/Ag (SGA-x) hybrid quaternary photocatalyst was successfully fabricated via the ultrasonic assisted Kirkendall effect and diffusion processes followed by low temperature phase conversion.
How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition
Authors: Csókás Dániel , Ho Annabel Xuan Ying , Ramabhadran Raghunath O. , Bates Roderick W.
Published: June 2019

Acid catalysis delivers the cis isomer as the kinetic product via a late transition state; base catalysis delivers the trans isomer via an early transition state.
Improper Gaussian signaling scheme for the two‐users X‐interference channel
Authors: Li Dan , Gu Fanglin , Wang Shan , Xiong Jun
Published: June 2019

Different from conventional proper Gaussian signalling (PGS), whose achievable rate depends on the input signals' covariances only, the capacity of channels with improper Gaussian signalling (IGS) is a function with the signals' covariances and pseudo‐covariances. Thus, the additional degree of freedom provided by pseudo‐covariance is available to improve the achievable rate. In this study, the authors investigate the achievable rate region of two‐users X‐interference channel (IC) in the condition of applying IGS. By treating the interference as additive Gaussian noise, the authors analyze the mathematical expression of capacity based on Shannon's theorem. Specifically, for the two‐users simple input, simple output (SISO)‐IC, they propose two optimal signalling schemes to achieve the Pareto boundary in situations of employing PGS and IGS, respectively. In these optimal signalling schemes, the transparent geometric model which takes less computational complexity is applied to calculate the optimal transmission parameters for the Pareto boundary. Numerical simulation results show that the proposed IGS strategies can achieve larger achievable rate region and a greater sum rate. Finally, the authors give an in‐depth discussion about the structure of the Pareto boundary, which is characterised by the degree of impropriety measured by the covariance and the pseudo‐covariance of signals.
Joint source and relay precoder design for energy‐efficient MIMO‐cognitive relay networks
Authors: Maurya Shikha , Bansal Matadeen , Trivedi Aditya
Published: June 2019

This study addresses the energy efficiency (EE) maximisation problem in multi‐input multi‐output cognitive relay networks, where a secondary transmitter–receiver pair communicates through an amplify‐and‐forward relay using the licenced spectrum of a primary user. The authors aim to maximise the EE of the secondary system by jointly designing the source and relay precoding matrices, subject to transmit power, interference, and quality‐of‐service constraints. The resultant problem is non‐convex in the precoding matrices; it is converted into a much simpler vector‐valued problem using singular value decomposition. A combination of iterative optimisation, fractional programming, and Lagrangian multiplier is used to further tackle the problem. Numerical results are presented to evaluate the EE performance of the proposed scheme. Impact of transmit power, interference threshold, and minimum rate requirement on the EE is analysed.
Hybrid precoding with phase shifter reduction for 5G massive antenna multi‐user systems in millimetre wave
Authors: Zhao Xiongwen , Zhang Yu , Geng Suiyan , Du Fei , Fu Zihao , Zhou Zhenyu
Published: June 2019

In this study, the performances of commonly used precoding schemes are evaluated based on channel measurements carried out at 28 GHz in a railway station for a massive antenna system configuration. And a hybrid precoding algorithm for a fifth generation (5G) multi‐user antenna system is proposed and its performance is evaluated based on real measured channels. Specifically, An upper bound for achievable sum‐rate of phased zero forcing (PZF) algorithm is derived and a precoding technique by reduction of phase shifters (PSs) named reduced‐PZF (RPZF) is proposed, which can obviously reduce power consumption in hybrid precoding systems. In addition, the authors give the closed‐form expression for achievable sum‐rate when RPZF is used. There are no requirements in the authors’ proposed scheme with complicated matrix decomposition and optimisation techniques. The simulation results show that it is possible to reduce 30 and 50% of the PSs by using the proposed hybrid precoder with better system performance in the line‐of‐sight (LoS) and non‐LoS scenarios, respectively. In addition, the digital PSs with 3 bits low resolution can achieve the similar performance when using analogue ones.
Ellipsoidal state estimation based on sum of squares for non‐linear systems with unknown but bounded noise
Authors: Massioni Paolo , Salnikov Nikolay N. , Scorletti Gérard
Published: June 2019

This brief concerns the set‐theoretic recursive state estimation of non‐linear systems with polynomial dynamics, making use of ellipsoidal bounds. The sum of squares approach is used to construct an optimal ellipsoid containing the intersection of sets obtained with the use of non‐linear system equations and measurement equations. The properties of the proposed filter are illustrated with two examples, one concerning the simultaneous estimation of parameters and state of a linear system, and the other on the Euler equations of the rigid body rotational motion.
Unscented Kalman filtering for target tracking systems with packet dropout compensation
Authors: Ma Kemao , Xu Long , Fan Hongxia
Published: June 2019

The unscented Kalman filtering problem is investigated for a class of non‐linear discrete‐time stochastic systems subject to random packet dropout. Here, a random variable, which obeys Bernoulli distribution with known conditional probability, is introduced to depict the phenomenon of packet dropout occurring in a stochastic way. Based on the compensation technology of packet dropout, the one‐step prediction value of observer instead of zero‐input is used as a compensator when packet dropout occurs. Owing to taking the phenomenon of random packet dropout into account, the authors need to compute parameters to reduce the effects of the compensator. Then, based on the minimum mean square error principle, a new unscented Kalman filtering algorithm is proposed such that, for the random packet dropout, the filtering error is minimised. By solving the recursive matrix equations, the filter gain matrices and error covariance matrices can be obtained and the proposed results can be easily verified by using the standard numerical software. They finally provide two examples, one is a numerical example to show the performance of the proposed approach, and the other is to solve the problem of target estimation for a tracking system with random packet dropout.