ALBERT

Description: Zigzagopora wigleyensis n. gen. n. sp. is an Upper Ordovician (Sandbian, early Caradoc) cyclostome bryozoan from the Arbuckle Mountains of Oklahoma, USA. It has runner-type colonies characterized by a mostly uniserial, geniculate arrangement of monomorphic zooids that bud alternately left and right, producing a zig-zag pattern of growth. This new genus has calcified interior walls and non-pseudoporous exterior walls. It is thus most likely affiliated with the paleotubuliporine family Sagenellidae, despite superficial similarities with the corynotrypid cyclostomes with which it co-occurs.

Description: Fossil catostomids were very rare prior to the Eocene. After the Eocene, they suddenly decreased in diversity in Asia while becoming common fishes in the North American fauna. Knowledge of the taxonomy, diversity, and distribution of Eocene catostomids is critical to understanding the evolution of this fish group. We herein describe a new catostomid species of the genus Amyzon Cope, 1872 from the Eocene Kishenehn Formation in Montana, USA. The new species, Amyzon kishenehnicum , differs from known species of Amyzon in having hypurals 2 and 3 consistently fused to the compound centrum proximally, and differs from other Eocene catostomids in that the pelvic bone is intermediately forked. All our phylogenetic analyses suggest that the new species is the sister group of A . aggregatum Wilson, 1977 and that Amyzon is the most basal clade of the Catostomidae. We reassessed the osteological characters of the North American species of Amyzon from a large number of well-preserved specimens of the new species, as well as A . gosiutense Grande et al., 1982 and A . aggregatum . Osteological characters newly discovered indicate that A . gosiutense is not a junior synonym of A . aggregatum , but should be retained as a distinct species.

Description: A bstract A new species of Apiocrinites is described from the Matmor Formation (Middle Jurassic, upper Callovian) of Hamakhtesh Hagadol, southern Israel. Apiocrinites feldmani n. sp. is a small species associated with the larger A. negevensis in a calcareous sponge and coral patch reef community. During life the columns of A. feldmani were commonly and preferentially infested with a soft-bodied parasite that grew with the crinoid and became embedded in its skeleton. These parasites embedded at the articulation between columnals, forcing the columnals to grow around them and producing with time a conical pit surrounded by swollen stereom. If the parasite died while the crinoid was still growing, the conical pit was roofed over by continued growth of columnals, resulting in a swelling with no external opening. Because the crinoids invested energy in forming extra skeleton around these parasites and because the crinoid stems were consequently deformed and likely lost flexibility, we consider these parasites to have caused significant harm. Curiously, these parasites apparently did not infect the larger and more common contemporaneous A. negevensis that lived in the same community.

Description: The influence of individual clay minerals on formation damage of reservoir sandstones is reviewed, mainly through the mechanism of fine particle dispersion and migration leading to the accumulation and blockage of pore throats and significant reduction of permeability. The minerals discussed belong to the smectite, kaolinite, illite and chlorite groups respectively. These minerals usually occur in an aggregate form in reservoir sandstones and the physicochemical properties of these aggregates are reviewed in order to reach a better understanding of the factors that lead to their dispersion in aqueous pore fluids. Particularly significant properties include the surface charge on both basal and edge faces of the clay minerals and how this varies with pH, external surface area of both swelling and non-swelling clays, porosity and pore size distribution in the micro- and meso-pore size range and overall aggregate morphology. For non-swelling clays, and perhaps even for swelling clays, dispersion is thought to be initiated at the micro- or meso-pore level, where the interaction between the pore solution and the charged clay surfaces exposed on adjacent sides of slit- or wedge-shaped pores brings about expansion of the diffuse double electric layer (DDL) and an increase in hydration pressure. Such expansion occurs only in dilute electrolyte solutions in contrast to the effect of concentrated solutions which would shrink the thickness of the DDL and so inhibit dispersion. Stable dispersions are formed, particularly where the solution pH exceeds the isoelectric pH of the mineral, which is often at alkali pH values, so that both basal face and edge surfaces are negatively charged and the particles repel each other. The osmotic swelling of smectitic clays to a gel-like form, so effectively blocking pores in situ , is often invoked as an explanation of formation damage in reservoir sandstones. Such swelling certainly occurs in dilute aqueous solutions under earth surface conditions but it is uncertain that stable smectitic gels could form at the temperatures and pressures associated with deeply buried reservoir sandstones.

Description: The instability of shales in drilled formations leads to serious operational problems with major economic consequences for petroleum exploration and production. It is generally agreed that the nature of the clay minerals in shale formations is a primary causative factor leading to their instability, although the exact mechanism involved is more debateable. Currently, the principal cause of shale instability is considered to be volume expansion following the osmotic swelling of Na-smectite. However, illitic and kaolinitic shales may also be unstable, so that interlayer expansion cannot therefore be considered as a universal causative mechanism of shale instability. This review considers alternative scenarios of shale instability where the major clay minerals are smectite, illite, mixed-layer illite-smectite (I/S) and kaolinite respectively. The influence of interacting factors that relate to shale clay mineralogy such as texture, structure and fabric are discussed, as are the pore size distribution and the nature of water in clays and shales and how these change with increasing depth of burial. It is found from the literature that the thickness of the diffuse double layer (DDL) of the aqueous solutions associated with the charged external surfaces of clay minerals is probably of the same order or even thicker than the sizes of a significant proportion of the pores found in shales. In these circumstances, overlap of the DDLs associated with exposed outer surfaces of clay minerals on opposing sides of micropores (〈2 nm in diameter) and mesopores (2–50 nm in diameter) in a lithostatically compressed shale would bring about electrostatic repulsion and lead to increased pore/hydration pressure in smectitic, illitic and even kaolinitic shales. This pressure would be inhibited by the use of more concentrated K-based fluids which effectively shrink the thickness of the DDL towards the clay mineral surfaces in the pore walls. The use of soluble polymers would also encapsulate these clay mineral surfaces and so inhibit their hydration. In this scenario, the locus of action with respect to shale instability and its inhibition is moved from the interlamellar space of the smectitic clays to the charged external surfaces of the various clay minerals bounding the walls of the shale pores.

Description: A bstract Teeth of a new freshwater dasyatoid ray recovered from the latest middle Eocene Brian Head Formation of southern Utah represent the youngest freshwater stingray so far known in the fossil record of North America. The crown morphology of Saltirius utahensis n. gen. n. sp. exhibits strong sexual dimorphism, with the presumed males bearing two prominent margino-labial protuberances and a bifid cusp that produces a saltire-like outline. This unique crown separates this genus and species from any known extinct or extant myliobatiform, but does have some resemblance to the crown of Asterotrygon maloneyi from the lower Eocene Green River Formation of Wyoming. The occurrence of S. utahensis in the Brian Head Formation provides additional evidence for the persistence of warm subtropical temperatures during the late Eocene in southern Utah.

Description: A bstract A new species of Apiocrinites is described from the Middle Jurassic (Callovian) Matmor Formation of the Negev, Israel. Apiocrinites negevensis is from the tropical latitudes in the Tethys, in contrast to all other reported species of this genus. With a narrow radial facet and adjacent arms not in lateral contact and large aboral cup plates, A. negevensis is quite unusual for this genus.

Description: A bstract Pywackia baileyi Landing in Landing et al., 2010 , from the upper Cambrian Yudachica Member of Oaxaca State, southern Mexico, consists of small, phosphatic, proximally tapering cylindrical rods covered by shallow polygonal calices. The bryozoan-like morphology of this fossil prompted its interpretation as the first bryozoan known from the Cambrian. However, restudy of some of the original material, employing scanning electron microscopy for the first time, questions the assignment of Pywackia to the Bryozoa. Striking similarities between Pywackia and the modern pennatulacean octocoral Lituaria lead to an alternative hypothesis interpreting Pywackia an early fossil octocoral. While Pywackia is probably not a true pennatulacean, a group with a definitive fossil record stretching back only to the Late Cretaceous, it can be envisaged as having had a similar skeletal structure and ecology to Lituaria , the rods representing mineralized axes of tiny colonies that lived with their proximal ends buried in the sediment and distal ends covered by feeding polyps. Landing et al. (2010 ) considered the phosphatic composition of Pywackia specimens to be the result of diagenetic replacement, but the evidence is equivocal. If Pywackia had a primary phosphatic skeleton, this would support the hypothesized existence of phosphatic biomineralization early in the evolutionary history of Cnidaria, as well as providing further evidence that Pywackia is not a bryozoan.

Description: Rhuddanian crinoid faunas are poorly known globally, making this new fauna from the Hilliste Formation of western Estonian especially significant. The Hilliste fauna is the oldest Silurian fauna known from the Baltica paleocontinent, thus this is the first example of the crinoid recovery fauna after the Late Ordovician mass extinction. Hiiumaacrinus vinni n. gen. n. sp., Protaxocrinus estoniensis n. sp., Eomyelodactylus sp., calceocrinids, and five holdfast types are reported here. Although the fauna has relatively few taxa, it is among the most diverse Rhuddanian faunas known. Similar to other Rhuddanian crinoid faunas elsewhere, the Hilliste crinoid fauna contains crinoids belonging the Dimerocrinitidae, Taxocrinidae, Calceocrinidae, and Myelodactylidae; most elements of the new fauna are quite small, perhaps indicative of the Lilliput Effect.

Description: Study of new collections of the Wenlock and Pridoli, Silurian, crinoids from Saaremaa, western Estonia, result in taxonomic revision, expanded ranges, and new taxa. Eucalyptocrinites regularis and Periechocrinus laevis are recognized outside of Sweden for the first time. Desmidocrinus laevigatus Ausich et al., 2012 is reassigned to Methabocrinus . Because the type species of Methabocrinus was previously known only from glacial sediments, the age and provenance of this genus are constrained for the first time. A new crotalocrinitid, Velocrinus coniculus new genus and species, is described. Although the Pridoli faunas of western Estonia contain only twelve species-level taxa assigned to nine genera, this fauna is one of the four richest Pridoli faunas known.