Dimeropygidae Hupé, 1953 is a family of highly vaulted and small trilobites from the paleotropics of the uppermost Cambrian through the Ordovician. Specimens are known from Laurentia, Baltica, Avalonia, Siberia, Australia, North China, and South China. Dimeropygids are difficult to recover because of their small size and vaulted, tuberculate, and often spiny exoskeletons. Thus, most of their diversity is known from secondarily silicified material which preserves remarkable amounts of detail on the sclerites. Such faunas, while often rare, are common in the Great Basin of the western USA. Trilobite research has been conducted in the Great Basin has been since the late 1800s. Recent high intensity sampling and collection of larger sample sized from silicified horizons has increased the known diversity of trilobites from Lower Early Ordovician. New collections from the Lower Ordovician are providing crucial new insight into the groups early evolutionary history (e.g., Adrain & Westrop, 2007, McAdams & Adrain, 2009, Adrain et al., 2014a). Skullrockicurus n. gen. is a new genus of dimeropygid trilobites including at least seven new species. Five of the new species are well known enough from silicified material to formally name: S. greeni (Garden City Formation, Idaho and House Formation, Utah), S. plummeri (House Formation, Utah), S. judyi (House Formation, Utah), S. massarellai (House Formation, Utah), and S. brocki (House Formation, Utah). Synapomorphies of the new genus include four pairs of tubercles on the glabella, a posteriorly bowed glabella, long preglabellar field, and semilunate pygidium with a corona of tubercles or spines at the fulcrum.

The Middle Cambrian Spence Shale Member of the Langston Formation of northern Utah and southern Idaho is a fossil-rich unit that exhibits distinct cyclicity at the parasequence (meter) scale. At least seven discrete, shallowing-upwards parasequences, or cycles, can be found at the Miners Hollow and Antimony Canyon localities, each composed of calcareous shale capped by limestone. Within each cycle and within the member as a whole, predictable patterns of faunal distribution are evident. Sampling and identification of fossils from two localities have revealed that observed changes in fauna track changes in sea level throughout the section. Through cluster and principal components analyses it has been determined that those rocks of the Spence Shale representing a transgressive systems tract are home to a particular community of organisms, while those rocks of the highstand systems tract are home to another. It logically follows that the rocks of the transgressive tract represent a distinct biofacies, while those of the highstand tract represent another. The transgressive biofacies is composed of species such as agnostid and oryctocephalid trilobites and inarticulate brachiopods that are commonly found in deeper ramp settings. The highstand biofacies is distinguished by such taxa as Zacanthoides and other larger trilobite genera such as Glossopleura and Kootenia, and the eocrinoid Gogia, among others. The difference in ramp position between the Miners Hollow and Antimony Canyon localities implies a water depth gradient, with Antimony Canyon representing shallower water and Miners Hollow representing deeper water. This relationship is also reflected in the biofacies and community assignments. The stratigraphic trends explored in this study may be applied to other Spence Shale localities and possibly other Cambrian fossil deposits, such as the Burgess Shale of British Columbia. (151 pages)

The Laurentian trilobite genus Clelandia Cossmann, 1902, is represented by 12 named species that range from the late Cambrian to Early Ordovician. Species of Clelandia have been described from many localities in the United States, Canada, Scotland, and Greenland and attempts have been made to employ them as tools in biostratigraphic correlation. Nevertheless, important questions persist regarding the taxonomy and phylogeny of the group. No species-level phylogenetic analysis has been attempted for the genus and its family affinity has been unclear. Previous work often has produced limited numbers of small photographs which tend to mask subtle, but critical, morphological details and confuse taxonomic identification. New collections from the Great Basin of the western United States have resulted in material representing five new species of Clelandia, three of which are formally named. Other species of Clelandia are illustrated and the type species is redescribed. C. aspina and C. bispina are reported from a new locality in east-central Nevada. The first articulated specimens from a species of Clelandia are illustrated and demonstrate multiple synapomorphies of the thorax and pygidium that strongly indicate a unique, low-diversity clade of trilobites which persisted from the late Cambrian into the Early Ordovician with similarities to the Kingstoniidae. Phylogenetic analysis shows Clelandia to contain two distinct components. One component is characterized by species with glabellar furrows, widely flared posterior projections, and exsagittal pits of the occipital furrow. A more derived component consists of species with long glabellar spines, relatively narrow posterior fixigenae, bacculae, and a unique glabellar-occipital spine structure.

The properties of a Rydberg atom immersed in an ultracold environment were investigated. Two scenarios were considered, one of which involves the neighbouring ground-state atoms arranged in a spatially structured configuration, while the other involves them distributed randomly in space. To calculate the influence of the multiple ground-state atoms on the Rydberg atom, Fermi-pseudopotential was used, which simplified greatly the numerical effort. In many cases, the few-body interaction can be written down analytically which reveals the symmetry properties of the system. In the structured case, we report the first prediction of the formation of ``Rydberg Borromean trimers''. The few-body interactions and the dynamics of the linear A-B-A trimer, where A is the ground-state atom and B is the Rydberg atom, were investigated in the framework of normal mode analysis. This exotic ultralong-range triatomic bound state exists despite that the Rydberg-ground-state interaction is repulsive. Their lifetimes were estimated using both quantum scattering calculations and semi-classical approximations which are found to be typically sub-microseconds. In the disordered case, the Rydberg-excitation spectra of a frozen-gas were simulated, where the nuclear degrees of freedom can be ignored. The systematic change of the spectral shape with respect to the density of the gas and the excitation of the Rydberg atom were found and studied. Some parts of the spectral shape can be described by simple scaling laws with exponents given by the basic properties of the atomic species such as the polarizability and the zero-energy electron-atom scattering length.

The properties of a Rydberg atom immersed in an ultracold environment were investigated. Two scenarios were considered, one of which involves the neighbouring ground-state atoms arranged in a spatially structured configuration, while the other involves them distributed randomly in space. To calculate the influence of the multiple ground-state atoms on the Rydberg atom, Fermi-pseudopotential was used, which simplified greatly the numerical effort. In many cases, the few-body interaction can be written down analytically which reveals the symmetry properties of the system. In the structured case, we report the first prediction of the formation of ``Rydberg Borromean trimers''. The few-body interactions and the dynamics of the linear A-B-A trimer, where A is the ground-state atom and B is the Rydberg atom, were investigated in the framework of normal mode analysis. This exotic ultralong-range triatomic bound state exists despite that the Rydberg-ground-state interaction is repulsive. Their lifetimes were estimated using both quantum scattering calculations and semi-classical approximations which are found to be typically sub-microseconds. In the disordered case, the Rydberg-excitation spectra of a frozen-gas were simulated, where the nuclear degrees of freedom can be ignored. The systematic change of the spectral shape with respect to the density of the gas and the excitation of the Rydberg atom were found and studied. Some parts of the spectral shape can be described by simple scaling laws with exponents given by the basic properties of the atomic species such as the polarizability and the zero-energy electron-atom scattering length.

An Algerian Phacopid fauna, described by Lemaître in 1952, is reexamined here. Species arereevaluated in order to be in agreement with modern taxonomy. To characterize the size and shape of our specimens, as well as inter- and intraspecific variations, a morphometric analysis was performed. Only holaspids were analyzed. Results of our analysis show that genera can be be well differentiated thanks to quantitative methods. However, at a specific level, only Austerops lemaitrii nov. sp. is well- defined. Other species can be defined, however, thanks to quantitative methods. Shape variations during growth were also defined in order to understand the evolution of our specimens. Three species show a correlation between shape and size variations for cephala, and two species for the pygidia, which show an ontogenic control of the shape. A covariate analysis was made between the shape of the cephala and the shape of the pygidia, and all of the specimens analyzed show a covariance betweencephalic and pygidial shape. / Trilobiter utgjorde en viktig del av faunun under paleozoikum. I denna artikel studeras ochomprövas en trilobitpopulation från Algeriets devon. För att bättre förstå populationstillväxt och evolution görs analyser av storlek (biometrisk analys) och form (morfometrisk analys). Resultaten visar att de olika släktena är väldefinierade och att tillväxten av somliga arter påverkar formen.Analysen visar också på en samvariation mellan cephalons och pygidiums form.

No description available.

In my dissertation thesis I made a revision of two selected groups of Lower Carboniferous arthropds from the Moravian Karst: trilobites and thylacocephalans. I studied their systematics, autecology as well as taxonomy. In the first part I mapped an occurrence of an atheloptic trilobite association in the Březina village vicinity. Based on a study the new trilobite association is erected. The second part is focused on the very first discovery of Lower Carboniferous thylacocephalan outside of US. Its specific carapace structure is studied. New species Paraconcavicaris viktoryni (Broda et al. 2020) is determined and compared to known species.

No description available.

No description available.