Neritic dinoflagellates from periplatform (slope) carbonates of the Clino borehole, located on the western, leeward margin of the Great Bahama Bank, record environmental fluctuations on the platform top. A lower Pliocene interval (3.6–4.2 Ma) contains platform-top sediments shed onto the lower slope when the platform was open and ramplike. Despite this open topography, abundant Polysphaeridium zoharyi indicate the presence of restricted marine environments on the platform top. Terrestrial palynomorphs are rare throughout this interval and imply a mostly or fully submergent platform top.

By late Pliocene times (about 2.1–2.3 Ma) the platform had become flat-topped and steep-sided, with the Clino site located on its upper slope. Samples characteristic of sea-level highstands and lowstands were selected for analysis. Polysphaeridium zoharyi is abundant only in lowstand samples and may have thrived in proximity to terrestrial vegetation. In highstand samples Lingulodinium machaerophorum replaces P. zoharyi, perhaps in response to less restricted marine environments on the platform top. This change in assemblages, along with apparent variations in cyst influx, reflects a fluctuating history of currents and salinities over the platform top in the late Pliocene. Upper Pliocene lowstand samples contain anomalously high proportions of terrestrial palynomorphs, allowing the identification of two phases of emergence and vegetation of the platform top. Palynology therefore appears to be a sensitive indicator of short-term (4th-order) sea-level change on carbonate platforms.

Dinoflagellate concentrations correlate positively with carbonate compaction, and infer that compacted layers have undergone dissolution of their metastable constituents. Dinoflagellate concentrations therefore can be useful in the often difficult task of assessing compaction and dissolution in fine-grained limestones where other indicators are absent.

The following dinoflagellate species are formally proposed: Operculodinium bahamense Head new species, Operculodinium? megagranum Head new species, and Spiniferites rhizophorus Head new species.

Sponges have an unrealized potential importance in biogeographic analysis. Biogeographic patterns determined from our analysis of all published data on distribution of Ordovician genera indicate Early Ordovician sponge faunas have relatively low diversity and are completely dominated by demosponges. Early Ordovician (Ibexian) faunas are characterized by the widespread co-occurrence of Archaeoscyphia and the problematic Calathium. This association is commonly found in biohermal structures. Middle Ordovician faunas show an increase in diversity, and two broad associations are differentiated: Appalachian faunas (including Southern China and the Argentine Precordillera) and Great Basin faunas.

Late Ordovician faunas show important changes in diversity and provincialism. Hexactinellid and calcareous sponges became important and new demosponge families appeared. Four Mohawkian-Cincinnatian associations are recognized here, including: 1) Midcontinent faunas; 2) Baltic faunas; 3) New South Wales faunas; and 4) Western North American (California and Alaska) faunas. However, two separate biogeographic associations are differentiated based on faunal differences. These are a Pacific association (western North American and New South Wales) and an Atlantic association (Midcontinent Laurentia and Baltica).

Distribution of sponge genera and migration patterns are utilized to consider paleogeographic dispositions of the different continental plates, climatic features, and oceanic currents. Such an analysis points to close paleogeographic affinities between the Argentine Precordillera and Laurentian Appalachian faunas. However, significant endemicity and the occurrence of extra-Laurentian genera suggest a relative isolation of the Precordillera terrane during the Late Ibexian-Whiterockian. The study also shows a faunal migration from the Appalachian region to South China during the Middle Ordovician and the migration of faunas from Baltica to Laurentia in the Late Ordovician. The occurrence of Laurentian migrants in New South Wales during the Late Ordovician could be related to inferred oceanic current circulation between these two areas, although other paleogeographic features may be involved.

The ‘granular’ wall microstructure of the Ordovician stenolaemate bryozoan Dianulites Eichwald, 1829, has been studied using ultrathin sections, scanning electron microscopy (SEM), analytical SEM, and cathodoluminescence. The timing of recrystallization and the presence of microdolomite inclusions in the skeletal walls implies that the original skeleton consisted of high-magnesium calcite (HMC). Although found in some modern cheilostomes, HMC has not been recorded in living stenolaemate bryozoans, but appears to have also been present in Nicholsonella and a few other Ordovician genera traditionally assigned to the trepostomes or cystoporates. The Russian type species of Dianulites, D. fastigiatus Eichwald, 1829, is revised and recorded for the first time in North America from the Fillmore Formation (Lower Ordovician) of Utah. Unusually among bryozoans, D. fastigiatus has turbinate, cone- or horn-shaped colonies, straight to slightly curved, with zooids opening on the flat, broad end of the cone; the sides of the cone comprise calcified exterior walls. This growth-form resembles some solitary rugose corals and other benthic animals thought to have lived with all but their tops buried in soft sediment. Such an interpretation is supported in Dianulites by the scarcity of epibionts on the exterior walls of the cone and by the occurrence of specimens comprising stacks of subcolonies, suggesting periods of partial burial of the living tissues by sediment.

An enteletid brachiopod genus Peltichia Jin and Liao, 1981, is reviewed and emended based on specimens from the Permian sequences of Japan, South China, Vietnam, and Transcaucasia. New and revised taxa are Peltichia akasakensis (Ozawa), P. kwangtungensis (Zhan), P. ruzhencevi (Sokolskaja), P. sinensis (Huang), P. subtriangularis new species, P. transversus (Huang), and P. zigzag (Huang). The genus Peltichia, consisting of 10 species, ranges from Kungurian to Changhsingian, and is distributed geographically in the Tethyan Realm and its surrounding areas and probably as well as in the western Panthalassan region.

Upon restudy, Quasidentalium Shimansky, 1974, is transferred to the Coleolidae, a group of “Vermes” that form a calcareous tube.

A new and unusually well preserved bivalve fauna of Late Ordovician age was recovered from pebbles within the Late Ashgill (Hirnantian) glacigenic diamictite of the Don Braulio Formation, in the Argentine Precordillera. According to the associated brachiopods and the presence of graptolites of the bicornis Zone in the matrix of the diamictite, an early Caradoc age is accepted for the bivalve fauna. The clasts contain bivalve molluscs representing nine genera, of which seven are new. Identified taxa are the following: Praenucula sp., Cuyopsis symmetricus new genus and species, Villicumia canteraensis new genus and species, Trigonoconcha acuta new genus and species, Concavodonta ovalis new species, Hemiconcavodonta minuta new genus and species, Hemiconcavodonta sp., Emiliania cuerdae new genus and species, and Concavoleda braulense new genus and species. Two new subfamilies are proposed: Praenuculinae and Concavodontinae. The genera Praenucula Pfab, Cuyopsis new genus, Villicumia new genus, and Trigonoconcha new genus are included in the new subfamily Praenuculinae. The genera Concavodonta Babin and Melou, Hemiconcavodonta new genus, and Emiliania new genus are included in the new subfamily Concavodontinae.

Description of two new species of the brachyuran genus Xanthosia Bell, 1863, from the upper Albian to Cenomanian Weno and Pawpaw formations from Tarrant County, Texas, increases the number of species in the genus to fifteen. Xanthosia has been recognized in England, the Netherlands, Madagascar, and in in the states of New Jersey, South Dakota, and Texas. The geologically oldest species from England gave rise to species from North America, Europe, and Madagascar. One group of species, with representatives from South Dakota, New Jersey, and Madagascar, may represent a separate taxon. The species “Xanthosia” robertsi Secretan is herein removed from the genus and placed within the Portunidae, not the Xanthidae.

Mass mortality surfaces and bioclastic lags in Turonian siliceous shales of the San Rafael and La Frontera formations in Colombia have yielded two species of decapod crustaceans, Opthalmoplax spinosus new species and Pinnotheres? species indeterminate, as well as one stomatopod, Sculda sp. All represent first records for the country. Remains of the swimming carcineretid crab, Opthalmoplax spinosus, in association with fish fragments and pelagic ammonites, cover mass mortality surfaces. The occurrence suggests that the high density living population of the crabs, exploiting abundant food resources in areas of topography-controlled upwelling, was periodically reduced catastrophically, perhaps by advection of toxic trace elements or by oxygen starvation. Two other taphofacies, characterized by current oriented appendage fragments and scattered skeletal elements represent normal accumulations of fossil material in the San Rafael and La Frontera formations.

Five new bivalved arthropods are described from the Lower Cambrian Chengjiang fauna, Yunnan, China. All of them are rare in the fauna, represented by one or two individuals among thousands of specimens. Four of the five new taxa are preserved with soft parts that show a clear distinction between them. The new taxa provide new important information concerning the soft bodied and limb characters of the early bivalved arthropods. A significant lesson is that, not knowing any soft parts, it is virtually impossible to place systematically a new type of bivalved carapace. It is often impossible even to tell if it is a crustacean or not. A second antenna in the shape of a “great appendage” is identified for the first time among the bivalved arthropods. The new taxa include representatives of the order Pectocaridida, the families Pectocarididae, Clypecarididae and Occacarididae, the genera and species Pectocaris spatiosa, Clypecaris pteroidea, Occacaris oviformis, Forfexicaris valida and Yunnanocaris megista.

The Lower Cambrian Shuigoukou Formation of Xichuan, Henan province, China, yielded phosphatized instars belonging to the protolenid Ichangia ichangensis Chang, 1957, and two undetermined taxa. With relatively simple body plans, the three larval forms resemble each other to some extent, and protaspides of I. ichangensis show general similarities to those of the ellipsocephalid Palaeolenus lantenoisi Mansuy. However, their early ontogenetic processes exhibit subtle yet distinct differences. One group of unassigned protaspides possesses a sagittal glabellar furrow and protomarginal spines with branching extremities. The other unassigned protaspides bear especially long genal and protomarginal spines. The detailed preservation of these larvae reveals delicate structural variations that help provide a framework for evaluating relationships among Early Cambrian trilobites.

Pleurocystites strimplei new species, from the Galena Group of Iowa and Minnesota, is closely related to P. squamosus Billings from the Appalachians and Michigan. Numerous specimens provide information about growth, living habits, functional morphology, and respiration. The development of P. strimplei n. sp. is largely isometric with several exceptions. New dichopores form throughout ontogeny. Length of the dichopores and the area available for respiration are characterized by strong positive allometry relative to the volume of the animal. The length of the distal stem increases with respect to the size of the theca. During life the aboral side faced up. Some animals were largely covered by a thin layer of sediment whereas others lay directly on the seafloor. The orientation of the brachioles is most consistent with deposit feeding. Quantitative models of respiration suggest that the pectinirhombs accounted for over half of the needs of youngsters but this contribution falls to about 38 percent in adults. Respiration by the surface area of the theca and the water vascular system provide small amounts of oxygen, especially for animals living on the surface of the seafloor. Cloacal pumping or a similar type of respiratory device probably furnished the remainder of the oxygen required by P. strimplei n. sp. The morphometric data in conjunction with parameters taken from Recent oceans and echinoderms produce a plausible respiration budget, which is affected by size, age, allometry, and living orientation.

Embedded thalli of Permian Ivanovia tebagaensis, a calcified, cyathiform, codiacean, Chlorophyta, were X-rayed with a medical CT (computed tomography) scanner. The two-dimensional digital X-ray image files were copied to floppy disks and transferred to an IBM-compatible personal computer. The images were cropped, and built into a data volume with a commercial three-dimensional software program. The data were color edited so that only the algae were visible. The data volume was then systematically manipulated to visualize some hitherto unknown details of the structure of the utricles, and of a vegetative propagule, a developing bud.

Molostovskaja (1979, p. 54) described without illustrations the family Darwinuloididae Molostovskaja, 1979. The following year, Molostovskaja (1980, p. 33) described the family again as new [Darwinuloididae fam. nov.]. She included the genus Whipplella Holland, 1934, in the family and illustrated Darwinuloides svijazhicus (Sharapova 1948) (Molostovskaja, 1980, p. 28, figs. 5a, b, 8). Schneider (1948, p. 29, pl. 2, figs, 1a, b) originally described and illustrated this species as “Darwinula svijazhicus Sharapova n. mns.” Two years later, Molostovskaja (1982, p. 158) illustrated cross-sections of the adductor muscle attachment scar patterns in the families of the Darwinulacea Brady and Norman, 1889. Later Molostovskaja (1990, p. 166) erected the superfamily Darwinuloidacea Molostovskaja, 1979 to include Whipplella Holland, 1934, Vymella Kalis and Mischina in Mischina and Kalis, 1975, and questionably Pruvostina Scott and Summerson, 1943. In the same paper, she illustrated Whipplella sp. (pl. 72, figs. 6a, b) [from Sohn, 1977], Vymella dobrinini (Kashevarova, 1961) (pl. 72, figs. 7a-c), Darwinuloides sentjakensis (Sharapova in Schneider, 1948) (pl. 73, figs. 5, 6), and D. svijazhicus (Sharapova in Schneider, 1948) (pl. 74, figs. 14a, b).