SOME RESULTS ON BIORTHOGONAL POLYNOMIALS 625

ABSTRACT. Some biorthogonal polynomials of Hahn and (q2;q)(R)(abq2;q)(R)(qz;qZ)(R)(qz-1;q)(R) (aq2;q)(R)(bq;q)(R)(qaz;q)(R)(qbz_;q2)(R

New data on the morphology of Sphenothallus Hall: implications for its affinities

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73676/1/j.1502-3931.1992.tb01378.x.pd

The position of graptolites within Lower Palaeozoic planktic ecosystems.

An integrated approach has been used to assess the palaeoecology of graptolites both as a discrete group and also as a part of the biota present within Ordovician and Silurian planktic realms. Study of the functional morphology of graptolites and comparisons with recent ecological analogues demonstrates that graptolites most probably filled a variety of niches as primary consumers, with modes of life related to the colony morphotype. Graptolite coloniality was extremely ordered, lacking any close morphological analogues in Recent faunas. To obtain maximum functional efficiency, graptolites would have needed varying degrees of coordinated automobility. A change in lifestyle related to ontogenetic changes was prevalent within many graptolite groups. Differing lifestyle was reflected by differing reproductive strategies, with synrhabdosomes most likely being a method for rapid asexual reproduction. Direct evidence in the form of graptolithophage 'coprolitic' bodies, as well as indirect evidence in the form of probable defensive adaptations, indicate that graptolites comprised a food item for a variety of predators. Graptolites were also hosts to a variety of parasitic organisms and provided an important nutrient source for scavenging organisms

The Origin and Initial Rise of Pelagic Cephalopods in the Ordovician

BACKGROUND: During the Ordovician the global diversity increased dramatically at family, genus and species levels. Partially the diversification is explained by an increased nutrient, and phytoplankton availability in the open water. Cephalopods are among the top predators of today's open oceans. Their Ordovician occurrences, diversity evolution and abundance pattern potentially provides information on the evolution of the pelagic food chain. METHODOLOGY/PRINCIPAL FINDINGS: We reconstructed the cephalopod departure from originally exclusively neritic habitats into the pelagic zone by the compilation of occurrence data in offshore paleoenvironments from the Paleobiology Database, and from own data, by evidence of the functional morphology, and the taphonomy of selected cephalopod faunas. The occurrence data show, that cephalopod associations in offshore depositional settings and black shales are characterized by a specific composition, often dominated by orthocerids and lituitids. The siphuncle and conch form of these cephalopods indicate a dominant lifestyle as pelagic, vertical migrants. The frequency distribution of conch sizes and the pattern of epibionts indicate an autochthonous origin of the majority of orthocerid and lituitid shells. The consistent concentration of these cephalopods in deep subtidal sediments, starting from the middle Tremadocian indicates the occupation of the pelagic zone early in the Early Ordovician and a subsequent diversification which peaked during the Darriwilian. CONCLUSIONS/SIGNIFICANCE: The exploitation of the pelagic realm started synchronously in several independent invertebrate clades during the latest Cambrian to Middle Ordovician. The initial rise and diversification of pelagic cephalopods during the Early and Middle Ordovician indicates the establishment of a pelagic food chain sustainable enough for the development of a diverse fauna of large predators. The earliest pelagic cephalopods were slowly swimming vertical migrants. The appearance and early diversification of pelagic cephalopods is interpreted as a consequence of the increased food availability in the open water since the latest Cambrian

There is no such thing as the ‘Ediacara Biota’

The term ‘Ediacara Biota’ (or many variants thereof) is commonly used to refer to certain megascopic fossils of Precambrian and early Palaeozoic age – but what does the term actually mean? What differentiates a non-Ediacaran ‘Ediacaran’ and an Ediacaran ‘Ediacaran’ from an Ediacaran non-‘Ediacaran’? Historically, the term has been used in either a geographic, stratigraphic, taphonomic, or biologic sense. More recent research and new discoveries, however, mean that the term cannot actually be defined on any of these bases, or any combination thereof. Indeed, the term is now used and understood in a manner which is internally inconsistent, and unintentionally implies that these fossils are somehow distinct from other fossil assemblages, which is simply not the case. Continued use of the term is a historical relic, which has led in part to incorrect assumptions that the ‘Ediacara Biota’ can be treated as a single coherent group, has obscured our understanding of the biological change over the Precambrian–Cambrian boundary, and has confused research on the early evolution of the Metazoa. In the future, the term ‘Ediacaran’ should be restricted to purely stratigraphic usage, regardless of affinity, geography, or taphonomy; sufficient terminology also exists where reference to specimens on a geographic, taphonomic, or biologic basis is required. It is therefore time to abandon the term ‘Ediacara Biota’ and to instead treat equally all of the fossils of the Ediacaran System