Diego Corrochano

Remarks on the cortical structure of late Paleozoic “phylloid algae”

Abstract The cortical structure of the green anchicodiacean alga Anchicodium in the Pennsylvanian Dueñas Formation of the Cantabrian Zone (northwestern Spain) is described and illustrated. Anchicodium is characterized by a broad phylloid or leaflike calcified thallus, consisting of a bilateral cortex and a poorly calcified central medulla. The organization and morphology of the cortical system have been revealed with great detail using cathodoluminescence microscopy. Anchicodium cortex is composed of up to three (four?) orders of dichotomized branched cortical siphons that are usually swollen at the center; primary siphons are bulbous and are followed by elongate cylindrical siphons. Cortical siphons are preserved as dull-bright luminescent molds filled with micrite or microsparite, and contrast sharply with the surrounding non-luminescent calcite infilling the intersiphonal spaces, originally occupied by aragonite. Anchicodium in the Dueñas Formation exhibits a variety of preservational stages. Through a compilation of the taxonomic nomenclature and morphologic re-interpretations, it is concluded that some late Paleozoic anchicodiacean algae might represent diagenetic stages of Anchicodium or Eugonophyllum without any taxonomic significance. This conclusion is suggested particularly for the taphotaxon Ivanovia.

BENTHIC FORAMINIFERA AND OSTRACODA FROM MIDDLE–UPPER MIOCENE SEQUENCES OF SOUTHERN ECUADOR

Abstract. The debate regarding a possible marine influence during the middle—late Miocene in the Loja, Malacatos-Vilcabamba and Catamayo-Gonzanamá Basins (southern Ecuador) continues. To shed light on this controversy, we present a detailed stratigraphic and micropaleontological (benthic foraminifers and ostracods) study of selected sections from these basins. The facies associations, together with the presence of several benthic foraminifer species from marginal marine and open-water environments and ostracod genera resistant to high salinity changes, verify a marine water influence and sporadic marginal marine conditions in this area during certain periods of the middle—late Miocene. Additionally, six new ostracod species are hereby described: Heterocypris ballentae, Cyprideis lojaensis, Cyprideis petersonae, Cyprideis pachamama, Cyprideis tumi and Cyprideis amaru.

A new plate-like hypercalcified chaetetid demosponge (Loiscupula bachendensi gen. nov. sp. nov) from the Cantabrian Zone (Moscovian, Pennsylvanian, NW Spain)

A new hypercalcified chaetetid sponge, Loiscupula bachendensi gen. nov. sp. nov. (Demospongiae), has been recovered from the Bachende Formation (late Kashirian/early Myachkovian) in the Cantabrian Zone, NW Spain. Loiscupula has a circular, concentric, platy basal skeleton, some with cylindrical features and chimneys, which sometimes branch on the upper surface. The basal skeleton is composed of polygonal (commonly hexagonal) to rounded tubules perpendicular to the surface of the skeleton producing the characteristic honeycomb pattern of chaetetids. Cathodoluminescence microscopy revealed non-luminescent calcite pseudomorphs of monoaxon and polyaxon spicules, rarely styles, which are irregularly distributed although there are occurrences that suggest that a spicular network existed. The basal skeleton is composed of neomorphic low-Mg calcite (1.7 mol% MgCO3) and is strongly recrystallized; the tentative penicillate microstructure with relics of aragonite needles, and the high Sr content (up to 3456 ppm), suggest an original aragonite composition. Loiscupula is interpreted as primarily a gregarious organism with an inferred central point of attachment. This mode of growth produced small cryptic cavities between Loiscupula and the substrate, which were inhabited by encrusting organisms, mostly fistuliporid bryozoans. Based on the associated fossils and sedimentological features, it is suggested that Loiscupula inhabited an environment with a muddy bottom in the euphotic zone, where the water was well-oxygenated, of normal salinity, and the energy regime low to moderate. Diego Corrochano. Facultad de Ciencias, Departamento de Geología, Universidad de Salamanca, Plaza de los Caídos s/n, 37008, Salamanca, Spain. dcf@usal.es Ronald R. West. 1014 Houston Street, Manhattan, Kansas, 66502, USA. rrwest@ksu.edu