Björn Berning

Origin and geochemical evolution of the Madeira-Tore Rise (eastern North Atlantic)

The Madeira-Tore Rise, located ∼700 km off the NW African coast, forms a prominent ridge in the east Atlantic. The age and origin of the rise are controversial. This study presents major and trace element, Sr, Nd, Pb, Hf isotope and 40Ar/39Ar age determinations from volcanic rocks dredged from different sites along the rise. In addition, isotopic compositions of rock samples from Great Meteor Seamount in the central Atlantic are presented. The new radiometric and paleontologically constrained ages identify two major episodes of volcanism: The first is the base of the rise (circa 80 to >95 Ma) and the second is seamounts on the rise (0.5–16 Ma). It is proposed that interaction of the Canary hot spot with the Mid-Atlantic spreading center formed the deep basement of the Madeira-Tore Rise and the J-Anomaly Ridge west of the Atlantic spreading center in the Mid-Cretaceous. Age and geochemical data and plate tectonic reconstructions suggest, however, that the recovered Late Cretaceous volcanic rocks represent late stage volcanism from the time when the Madeira-Tore Rise was still close to the Canary hot spot. Long after moving away from the influence of the Canary hot spot, the Madeira-Tore Rise was overprinted by late Cenozoic volcanism. Miocene to Pleistocene volcanism at the northern end of the rise can be best explained by decompression mantle melting beneath extensional sectors of the Azores-Gibraltar Fracture Zone (African-Eurasian plate boundary). The geochemical compositions of these volcanic rocks suggest that the magmas were variably contaminated by enriched material within or derived by melting of enriched material underplated at the base of the lithosphere, possibly originating from the Cretaceous Canary plume. Alternatively, these late Cenozoic volcanic rocks may have derived from decompression melting of enriched pyroxenitic/eclogitic material in the upper mantle. Isotopically more depleted Pliocene to Pleistocene volcanism at the southern end of the Madeira-Tore Rise may be related to the nearby Madeira hot spot.

Revision of the north‐eastern Atlantic and Mediterranean species of the genera Herentia and Therenia (Bryozoa: Cheilostomata)

The cheilostome genera Herentia Gray and Therenia David and Pouyet, placed in the recently established family Escharinidae Tilbrook, were hitherto generally regarded as synonyms of Escharina Milne Edwards. Here we resurrect and define both genera, and revise their eastern Atlantic and Mediterranean species, which turn out to be species complexes. Besides presenting a re‐description of the genotype of Herentia, H. hyndmanni (Johnston) from the British Isles, new species from Madeira (Herentia andreasi n. sp.) and the Adriatic Sea (Herentia majae n. sp.) are introduced. The ancestrula of H. hyndmanni, a kenozooid with an almost completely calcified, gymnocystal frontal shield, is here documented for the first time. For Therenia it can be shown that the type species T. porosa (Smitt) from Florida differs from the eastern Atlantic and Mediterranean congeners, all of which were hitherto referred to as this species. Consequently, three new species (Therenia cryptooecium n. sp. from Ghana, Therenia peristomata n. sp. from Madeira, and Therenia rosei n. sp. from the Mediterranean Sea) are described. Both genera show a Paleogene origin and distribution in the Tethyan and Atlantic regions, and persist today in tropical to warm‐temperate zones of the Atlantic and Mediterranean Sea. Investigation of poorly studied, low‐ to mid‐latitude regions are likely to yield more new species of Herentia and Therenia.

Reinterpretation of the Cambrian ‘Bryozoan' Pywackia as an Octocoral

Abstract 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.

A parautochthonous shallow marine fauna from the Late Burdigalian (early Ottnangian) of Gurlarn (Lower Bavaria, SE Germany): Macrofaunal inventory and paleoecology

This paper describes and illustrates a diverse parautochthonous macrofauna from a single Upper Burdigalian (lower Ottnangian) horizon at Gurlarn in Lower Bavaria (SE Germany). In total, 80 different taxa are recorded in specific or open nomenclature; some 50 % of these taxa are bryozoans, followed by bivalves (16 taxa), cirripedes (7 taxa), echinoderms, corals (5 taxa each), brachiopods, fish (4 taxa each), serpulids, and gastropods (3 taxa each). The presence of additional organisms was documented by actualistic comparison based on indirect evidence such as drillholes, bite marks, and specialized growth forms of bryozoan colonies. Analysis of autand synecological indicators suggests that the fauna thrived in a near-shore shallow marine setting at a water depth of 5-20 m. Based on particular faunal elements and overall faunal composition we hypothesize that the environment is characterized by three distinct but interfingering habitats, i.e. (1) rocky slopes and boulders, (2) seagrass meadows, and (3) bryozoan meadows. Because similar, albeit less wellpreserved, faunas occur at several localities along the northern coast of the early Ottnangian Molasse Sea, the parautochthonous assemblage from Gurlarn provides an excellent example for the structure of these typical biota.

Atlantic Origin of the Arctic Biota? Evidence from Phylogenetic and Biogeographical Analysis of the Cheilostome Bryozoan Genus Pseudoflustra

The intricate geological evolution of the Arctic Ocean is paralleled by complexities in the biogeographical and phylogenetical histories of the Arctic biota, including bryozoans. Here we present revised taxonomic descriptions for all known species of the bryozoan genus Pseudoflustra, and use the present-day distributions and phylogenetic relationships between these species to infer the historical biogeography of the genus. Nine species belonging to the genus Pseudoflustra are recognized in the Arctic and North Atlantic. One new species, previously identified as Ichthyaria aviculata, is described as Pseudoflustra radeki sp. nov. Another species, previously assigned to Smittoidea as S. perrieri, is transferred to Pseudoflustra. Biogeographical analysis of Pseudoflustra reveals that species distributions mostly match current patterns pertaining in the North Atlantic and Arctic Ocean. Distributions were probably shaped by recent geological history as present-day current directions in the Arctic Ocean are believed to have been similar for at least the last 120 000 years. Phylogenetic analysis of Pseudoflustra places the five Arctic-North Atlantic species in a clade crownward of a paraphyletic grouping of North Atlantic species. Given that the Arctic Ocean was fully glaciated until 18 000 years, the most likely explanation for this phylogeographical pattern is that species of Pseudoflustra colonized the Arctic relatively recently from North Atlantic sources. However, a fuller understanding of the origin of Pseudoflustra in the Arctic will require molecular and fossil data, neither of which are currently available.

FEEDING TRACES OF RECENT RAY FISH AND OCCURRENCES OF THE TRACE FOSSIL PISCICHNUS WAITEMATA FROM THE PLIOCENE OF SANTA MARIA ISLAND, AZORES (NORTHEAST ATLANTIC)

Abstract The bowl-shaped trace fossil Piscichnus waitemata Gregory 1991 appears in Pliocene sandstones from Santa Maria Island (Azores Archipelago), extensively excavated during a stage of island evolution when the volcanic edifice was a guyot (flat-topped seamount) isolated in the NE Atlantic. The host sediments were deposited at depths from the intertidal zone to fair-weather wave base in a tropical climate under the influence of periodic storms and hurricanes. The traces were produced by ray fishes hunting for polychaetes, crustaceans and bivalves living in the sediment, similar to present-day nearshore, warm waters in the Azores, Baja California Sur (Mexico), and New Zealand, from which examples of feeding depressions are drawn (incipient Piscichnus). While P. waitemata is abundantly present in planar sediments on top of the guyot, far fewer trace fossils occur in sandstone deposited on the guyots margins. Presumably, the different densities of ray holes in the two sedimentary bodies were a response to lesser availability of prey, lower seawater temperatures (due to greater depths), and a more dynamic environment in which life conditions were less favorable. Moreover, the potential preservation of bowl-shaped depressions was lower in this setting, given the steepness of the seafloor, stronger currents, and constant sediment mobility. The top of the guyot was a more favorable habitat, refuge and/or nursery ground for many ray fishes. Measurement of the diameters of the ray holes indicate three distinct size classes, which may suggest that several species were responsible for their formation.

Systematics and diversity of deep-water Cheilostomata (Bryozoa) from Galicia Bank (NE Atlantic)

Galicia Bank is a large seamount situated c. 200 km off NW Iberia with a minimum depth of 600 m. It was recently included in Natura 2000, an EU-wide network of nature protection areas. We here present the first taxonomic descriptions of cheilostome bryozoans from this bank. The specimens were collected through the Spanish project INDEMARES (during BANGAL 0811 cruise conducted in 2011) and during two previous campaigns, the French Seamount 1 in 1987 and the German Victor Hensen in 1997). Twenty-five species were found, including 12 that are new to science, while five species remain in open nomenclature. Three new cheilostome genera (Breoganipora, Galiciapora and Placidoporella) are described. A lectotype is designated for Setosella vulnerata (Busk), and Palmicellaria tenuis Calvet is transferred to the genus Porella [as Porella tenuis (Calvet) n. comb.]. Additionally, our study shows that 48-60% of the bryozoan species are endemic to Galicia Bank. The degree of endemism of the Cheilostomata is thus the highest among all orders present on this seamount.