Enodicalix (Diploporita, Aristocystitidae): A new echinoderm genus from the Middle Ordovician of Spain

Restudy of an Ordovician diploporite specimen from the Middle Ordovician of central Spain reveals that the species ‘Calix’ inornatus MELÉNDEZ has four ambulacra, each with two equal facets, an oval hydropore and a smooth thecal surface. In contrast, the type species of Calix has four ambulacra, each with four facets added in a clockwise direction during growth, a trilobed hydropore, and a theca with spiny plates. Other aristocystitid genera with four ambulacra have one facet per ambulacrum. ‘Calix’ inornatus differs from all other aristocystitid genera and warrants a new generic name, for which we propose Enodicalix.

An Early Ordovician (Floian) Conodont Fauna from the Eastern Cordillera of Peru (Central Andean Basin)

Late Floian conodonts are recorded from a thin limestone lens intercalated in the lower part of the San José Formation at the Carcel Puncco section (Inambari River), Eastern Cordillera of Peru. The conodont association includes Gothodus costulatus LINDSTRÖM, Protopanderodus rectus (LINDSTRÖM), Drepanoistodus basiovalis (SERGEEVA), Drepanoistodus forceps (LINDSTRÖM), Drepanodus arcuatus PANDER, Trapezognathus diprion (LINDSTRÖM), Erraticodon patu COOPER, and Ansella cf. jemtlandica (LÖFGREN). This species association can be assigned to the upper part of the well-documented Oepikodus evae Zone. It is the northernmost conodont record of late Floian age in South America. This study updates the preliminary data presented in 2001 from this fossil locality, and it has important consequences for the paleogeographic reconstruction of the Peruvian part of the Central Andean Basin. In accordance with trilobites and brachiopods documented for the same strata, the conodont association represents a relatively cold-shallow-water platform environment. The record of late Floian conodonts towards the middle part of the San José Formation shows that the base of this unit in the studied section is considerably older than other sections of the distribution area, where its lowermost part is dated as early Darriwilian by the record of graptolites from the Undulograptus austrodentatus graptolite Zone. The diachronous initiation of the marine sedimentation makes the lower part of the Carcel Puncco shales penecontemporaneous with the volcanigenic rocks related with the Arequipa Massif, which transitionally underlie the San José Formation in other places of the Altiplano and the Eastern Cordillera of Peru

Middle Ordovician harknessellid brachiopods (Dalmanellidina) from the Mediterranean margin of Gondwana

The family Harknessellidae Bancroft, 1928 (Orthida, Dalmanellidina) was designed to embrace an assemblage of species referred previously to Harknessella Reed, 1917, and included five genera known mainly from the Middle and Upper Ordovician of England. Herein, we suggest reassigning to this family the genus Cacemia Mitchell, 1974, widespread in the middle Darriwilian (upper Middle Ordovician) of the Iberian and Armorican massifs. Since its designation, Cacemia was placed among the dalmanellidin heterorthids, in spite of its strongly mucronate hinge line, which is totally unknown within this Mediterranean family. A new harknessellid has been identified from the upper Darriwilian beds of the Central Iberian Zone (Central Spain): Isabelella fascicostellata Reyes-Abril Villas gen. et sp. nov. It is similar to Horderleyella Bancroft, 1928 for its coarsely fascicostellate radial ornamentation and obtuse cardinal angles, although its convexoplane to convexoconcave profile allows discrimination from the typically dorsibiconvex Horderleyella. A phylogenetic analysis of the family places both Cacemia and Isabelella in basal positions of their clades, which fits with their early stratigraphic record. Based on our study, the family Harknessellidae appears to have originated in the high latitude Mediterranean margins of Gondwana during pre-Darriwilian times, before the detachment of Avalonia from Gondwana. The family reached its highest diversification in Avalonia throughout the Late Ordovician, keeping connections with the Mediterranean and Proto-Andean margins of Gondwana, as well as with the mid-latitude palaeocontinents of Baltica and South China.Peer Reviewe

Middle Ordovician harknessellid brachiopods (Dalmanellidina) from the Mediterranean margin of Gondwana

The family Harknessellidae Bancroft, 1928 (Orthida, Dalmanellidina) was designed to embrace an assemblage of species referred previously to Harknessella Reed, 1917, and included five genera known mainly from the Middle and Upper Ordovician of England. Herein, we suggest reassigning to this family the genus Cacemia Mitchell, 1974, widespread in the middle Darriwilian (upper Middle Ordovician) of the Iberian and Armorican massifs. Since its designation, Cacemia was placed among the dalmanellidin heterorthids, in spite of its strongly mucronate hinge line, which is totally unknown within this Mediterranean family. A new harknessellid has been identified from the upper Darriwilian beds of the Central Iberian Zone (Central Spain): Isabelella fascicostellata Reyes-Abril Villas gen. et sp. nov. It is similar to Horderleyella Bancroft, 1928 for its coarsely fascicostellate radial ornamentation and obtuse cardinal angles, although its convexoplane to convexoconcave profile allows discrimination from the typically dorsibiconvex Horderleyella. A phylogenetic analysis of the family places both Cacemia and Isabelella in basal positions of their clades, which fits with their early stratigraphic record. Based on our study, the family Harknessellidae appears to have originated in the high latitude Mediterranean margins of Gondwana during pre-Darriwilian times, before the detachment of Avalonia from Gondwana. The family reached its highest diversification in Avalonia throughout the Late Ordovician, keeping connections with the Mediterranean and Proto-Andean margins of Gondwana, as well as with the mid-latitude palaeocontinents of Baltica and South China

THE CONODONTS FROM THE EL HÍGADO FORMATION AND ITS CONTRIBUTION TO THE KNOWL-EDGE OF METAMORPHISM AND ORDOVICIAN PALEOGEOGRAPHY IN THE CENTRAL CORDILLERA OF COLOMBIA

En la Formación El Hígado aforante en la vertiente oriental de la Serranía de Las Minas, a 9.5 km al NW del municipio de Tarqui (Departamento del Huila), se encontró en su miembro inferior, en niveles de caliza bioclástica formados por acumulaciones lumaquélicas de braquiópodos rinconeliformes, una asociación de conodontos del Ordovícico Medio, junto con microelementos reelaborados del Ordovícico Inferior y Medio basal. El conjunto involucra una mezcla tafonómica de dos o más horizontes ordovícicos. Las formas más antiguas son de edad Tremadociano (biozonas de Paltodus deltifer a Paroistodus proteus). El rango de la asociación más moderna abarca las biozonas de Lenodus variabilis a Eoplacognathus suecicus y es de edad Darriwiliano. Otras formas retrabajadas parecen sugerir asociaciones adicionales de edades Floiano, Piso Tercero y Darriwiliano basal. El descubrimiento de estos conodontos implica que el Tremadociano llegó a depositarse en esta zona y fue erosionado prácticamente in situ en tiempos arenigianos, por lo que el Terreno Chibcha ya quedaría adyacente por aquél entonces a la cuenca pericratónica del este de Colombia. El índice de alteración del color de los co-nodontos (CAI), con valores 2 a 4, descarta el metamorfsmo regional de la Formación El Hígado, afectada localmente por hidrotermalismo (CAI 6).   Palabras clave: Conodontos, Ordovícico, Cordillera Central de Colombia, Metamorfsmo, Paleogeografía      Conodonts are rare fossils in northern South America, and this work reports their frst occurrence in the Ordovician of Colombia. The studied sample come from a thin brachiopod coquina interstratifed in storm-generated sandstone deposits, 20 m above the base of the El Hígado Formation (Darriwilian) in its type section in the Central Cordillera. The conodont assemblage contains fairly well preserved elements with different states of mechanical fragmentation, corrosion and even bacterial alteration. CAI values are between 2 and 6, in absence of regional metamorphism and with evidence of local hydrothermalism. The sample involved a taphonomic mixture of two or more Ordovician horizons. The older conodont assemblage is of Tremadocian age and range from the Paltodus deltifer to the Paroistodus proteus conodont biozones. The youngest assemblage range through the Lenodus variabilis and Eoplacognathus suecicus conodont biozones and is of Darriwilian age. A number of reworked conodont taxa seem to suggest additional assemblages of Floian, Third Stage and lowest Darriwilian intermediate ages. The studied conodonts indicate the existence of older and previously unknown Ordovician sedimentation in Central Colombia, where reworked specimens were probably winnowed from condensed successions ranging from the lower Tremadocian to the lower Darriwilian, and are indicative of a pre-Ordovician accretion fro the Chibcha terrane.   Key words: Conodonts, Ordovician, Central Cordillera of Colombia, Metamorphism, Palaeogeography.   &nbsp

Revisión bioestratigráfica de las pizarras del Ordovícico Medio en el noroeste de España (zonas Cantábrica, Asturoccidental-leonesa y Centroibérica septentrional)

A complete review of more than one hundred Middle Ordovician fossil localities, distributed within the north western part of the Hesperian Massif, shows that the sedimentation of the dark shales (Luarca Fo rmation and equivalents) that overlie Arenig quartzites with Cruziana (the 'Armorican Quartzite' facies) was not as uniform as it has been supposed for the whole NW Spain. These shales were mainly deposited during the Oretanian in the West Asturian-Leonese Zone and in nort h e rn Central-Iberian Zone (Domain of the Ollo de Sapo Antiform). In these zones, the top of the unit is close to the Oretanian/Dobrotivian boundary, without any fossils with proved Dobrotivian age. In the Cantabrian Zone, clay sedimentation started in the latest Oretanian and continued during the Dobrotivian. Several local or regional stratigraphic gaps are proposed and characterized for the whole study area. In addition, the most recent paleog e ographical reconstructions proposed are discussed, in accordance with new paleoecological and paleobiog e ographical data. These data indicate that sedimentation took place in open shelf areas, relative ly deeper than in the southern Central Iberian shelf, and with trough areas where some mesopelagic elements are recorded. We identified a total of 97 different fossil taxa (67 from Oretanian rocks and 45 from Dobrotivian rocks), remarkable among which are the first known appearance of certain trilobites and ostracodes, the latest record of other taxa, and also the presence of some taxa in common with Avalonia and Baltica, that were previously unknown from any area of SW Europe