Nuevo registro de Cuspidaria patagonica Smith, 1885 (Bivalvia: Cuspidariidae) en el norte de Chile

sin resume

Constructional morphology of the shell/ligament system in opisthogyrate rostrate bivalves

The bivalve ligament provides the thrust for shell opening, acting as the resistance in a lever system against which adductor muscle effort is applied. Usually, its outer lamellar layer is subjected to tensile stress, while the inner fibrous layer is compressed, with the pivotal axis located between them. However, opisthogyrate rostrate bivalves display a concave dorsal margin, and both the umbo and the postero-dorsal angle of the shell project dorsally to the ligament, which then fails to act as pivotal axis. Three opisthogyrate rostrate genera of unrelated lineages show somewhat different solutions to this morpho-functional challenge. In Cuspidaria (Anomalodesmata), the ligament is internal, subjected only to compression and ventral to the pivotal axis, a thickened periostracum develops, forcing the dorsal margins of the valves to act as pivotal axis, and the posterior parts of the shell’s dorsal margins gape dorsally. In Nuculana (Palaeotaxodonta), the inner layer of the ligament is internal, the outer layer is external but reduced, and some species develop a dorsal ridge parallel to the commissural plane, on a level with the rostrum and acting as pivotal axis. In Pterotrigonia (Palaeoheterodonta) and other rostrate trigoniides, the ligament is external opisthodetic, but is allometrically reduced. Trigoniides may also develop a dorsal ridge.Facultad de Ciencias Naturales y Muse

Bivalves from a Middle Jurassic submarine high (Bajocian, Som Hill, Bakony Mts, Hungary)

Marine bivalves from a fissure filling of Upper Bajocian (Middle Jurassic) age are briefly described and figured. Palaeoecological analysis of the Som Hill assemblageas well as the similarity of its taxonomic composition to those of other, coeval faunas preserved in fissure-fillings suggest that a distinct bivalve assemblage populated fissures of some Mediterranean seamounts during the Middle Jurassic. Both in diversity and density, bivalves are subordinate to gastropods in the Som Hill fauna. The bivalve fauna is dominated by the epibyssal forms and consists of representatives of extinct genera except Limopsis and Cuspidaria s. 1., which latter two are frequent in Recent deep-sea bivalve assemblages

Benthic communities in Pen Duick escarpment (Gulf of Cadiz)

Mestrado em Biologia MarinhaEste trabalho foi realizado no Golfo de Cádis, na Escarpa de Pen Duick. Esta escarpa, com cerca de 4,5 Km de comprimento e 100 m de altura, ocorre a 525 m de profundidade na margem continental marroquina (NE Atlântico). É caracterizada pela presença de crostas carbonatadas e recifes de corais pétreos maioritariamente em declínio. Os objectivos principais deste trabalho são: i) a caracterização da composição taxonómica e estrutura das comunidades de macroinvertebrados bentónicos da escarpa de Pen Duick e ii) investigar os padrões de distribuição de acordo com o gradiente de profundidade, o tipo de substrato e a presença de substrato duro (corais pétreos e crostas carbonatadas). A comunidade bentónica estudada é constituída maioritariamente por espécies de crustáceos, anelídeos e hidrozoários. Numa análise não quantitativa, encontram-se diferenças significativas nas comunidades em diferentes sub-habitats (presença de coral à superfície, coral coberto por sedimento e ausência de coral) e na cor do sedimento (que pode ser relacionada com as condições biogeoquímicas do sedimento). A riqueza específica é maior nos locais onde se encontram corais do que em locais de sedimento fino. Hidrozoários e poliquetas caracterizam os sub-habitats com corais e os bivalves caracterizam os locais de sedimento fino. Os crustáceos encontram-se distribuídos por todos os sub-habitats. Numa análise quantitativa, encontram-se diferenças ao longo do gradiente profundidade. A maior diversidade e equitabilidade nas comunidades bentónicas é encontrada a profundidades superiores a 480 m na parte superior e na base da escarpa de Pen Duick. A profundidades inferiores a 480 m as comunidades bentónicas apresentam maior densidade e maior dominância, características estas que podem ser relacionadas com a presença de ambientes sedimentares particulares - as crateras de vulcões de lama. O elevado número de espécies em comunidades com elevada equitabilidade encontradas na escarpa de Pen Duick, reforçam a hipótese de que os recifes de coral de água fria mesmo em declínio são zonas que contribuem para uma maior heterogeneidade ambiental e proporcionam condições favoráveis à ocorrência de uma elevada diversidade biológica. ABSTRACT: This work was carried out in the Pen Duick Escarpment, Gulf of Cadiz. This scarp occurs at 525 m depth, and has about 4.5 km in length and 100 m in height. It is characterized by the presence of carbonated crusts and stony coral reefs predominantly in decline. The main objectives of this study are: i) to characterise the composition and structure of the benthic macroinvertebrate assemblages associated with the Pen Duick Escarpment and ii) to identify patterns of distribution according to the depth gradient, sediment type and presence of hard substrate (stony corals and carbonate concretions). The studied benthic assemblages are composed mainly by crustaceans, annelids and hydrozoans. The non quantitative analysis showed significant differences in the assemblages from different subhabitats (presence of coral at surface, coral in the sediment and absence of coral) and sediment colour (which can be related to the biogeochemical conditions of the sediments). The number of species is higher in samples with coral than in samples with fine sediment. Hydroids and polychaetes characterized the subhabitats with corals and molluscs characterized the subhabitats of fine sediment. Crustaceans occurred in both subhabitats. The quantitative analysis showed differences along the depth gradient with great diversity and evenness at depths greater than 480 m at the top and base of the escarpment. At depths shallower than 480 m, the benthic assemblages showed higher densities and dominance that can be related to the particular sediment environment - the crater of mud volcanoes. The high number of species in low dominance assemblages found in the Pen Duick Escarpment reinforce the hypothesis that cold-water coral reefs even declining are areas that enhance habitat heterogeneity and provide environmental that favour high biological diversity

Unravelling the diversity of Anomalodesmata (Mollusca: Bivalvia) : a morphological and phylogenetic approach

Orientador: Flávio Dias PassosTese (doutorado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: Considerado um grupo monofilético, os Anomalodesmata Dall, 1889 possuem atualmente mais de 800 espécies, abrigando alguns dos bivalves marinhos mais raros, bizarros e especializados. Essa raridade aliada a uma carência de informações anatômicas detalhadas sobre suas espécies sempre foram obstáculos para a compreensão de suas relações internas, consequentemente, resultando também em uma baixa representatividade de táxons em reconstruções filogenéticas. Com o intuito de preencher algumas das principais lacunas no conhecimento dos Anomalodesmata, a presente Tese propôs três objetivos específicos, buscando, através de diferentes ferramentas, ampliar, atualizar e apresentar novas idéias ao conhecimento evolutivo, morfológico e taxonômico desse importante grupo de bivalves. O primeiro objetivo se deu por meio de coletas realizadas na Baía do Araçá, litoral Norte do Estado de São Paulo, onde foi possível observar e descrever em detalhes a morfologia funcional e o comportamento de Cardiomya cleryana, trazendo novos insights sobre os bivalves carnívoros como um todo. O segundo objetivo foi realizado por meio do acesso à coleção malacológica do Museum of Comparative Zoology - Harvard University, onde grande parte dos lotes depositados nessa instituição foram revisados, gerando novos dados conquiliológicos e anatômicos para a elaboração de uma análise morfológica, gerando uma nova filogenia para os Anomalodesmata. Por fim, o terceiro objetivo versou sobre o uso de microtomógrafos de raios-x para ampliar o conhecimento anatômico dos anomalodesmados, culminando nos primeiros protocolos de contraste para bivalves marinhos, comparações entre diferentes técnicas invasivas, além das primeiras descrições anatômicas de bivalves baseadas exclusivamente em imagens tomográficas e reconstruções 3DAbstract: Considered a monophyletic group, the Anomalodesmata Dall, 1889 currently have more than 800 species, bearing some of the rarest, bizarre and specialized marine bivalves. This rarity combined with the scarcity of detailed anatomical information about their species has always been obstacles to the understanding of their internal relationships, consequently, also resulting in a low representativeness of taxa in phylogenetic reconstructions. In order to fill some of the main gaps in the knowledge of Anomalodesmata, the present thesis proposed three specific objectives, by using different tools, to expand, update and present new insights about the evolutionary, morphological and taxonomic knowledge of this important group of bivalves. The first objective took place through field collections in the Araçá Bay, north coast of the State of São Paulo, where it was possible to observe and to describe in detail the functional morphology and behaviour of Cardiomya cleryana, bringing new ideas about the carnivorous bivalves as a whole. The second goal was through the access to the malacological collection of the Museum of Comparative Zoology - Harvard University, where most of the lots deposited in this institution were reviewed, generating new conchological and anatomical data for the elaboration of a morphological analysis, generating a new phylogeny for the Anomalodesmata. Finally, the third objective was to increase the anatomical knowledge of anomalodesmatans by using X-ray microtomography, culminating in the first contrast protocols for marine bivalves, comparisons between different invasive techniques, and the first anatomical descriptions of bivalves based exclusively on tomographic images and 3D reconstructionsDoutoradoBiodiversidade AnimalDoutor em Biologia AnimalCAPE

Biodiversidade da macrofauna associada a habitats batiais na margem marroquina (Golfo de Cádis, NE Atlântico)

Mestrado em Biologia MarinhaThe Gulf of Cadiz is an extensive seepage area between the south Iberian and north Moroccan margins, west of the Strait of Gibraltar (NE Atlantic). It encompasses numerous carbonate mounds characterised by accumulations of mostly fossil deepwater corals, isolated coral patches and coral rubble, and over 40 submarine mud volcanoes at depths ranging 200 to 4,000m. This tectonically active area has a long geologic history and a central biogeographic location. The complex circulation of water masses ensures oceanographic connectivity with the Mediterranean Sea, Equatorial and North Atlantic regions. At the Gulf of Cadiz, the Pen Duick Escarpment, a feature with 4 km length and 100 m height, is located at ca. 500 m depth, on the south-eastern branch of the Renard Ridge, westwards of the El Arraiche mud volcano field. Cold-water corals, vulnerable, slow-growing metazoans that inhabit cold dark waters in the deep-sea, have been receiving increased attention in recent years. Under the framework of the research programs MiCROSYSTEMS and Moundforce (European Science Foundation), selected sites along the Moroccan margin were investigated, aiming to describe the composition, abundance and community structure of the benthic macrofaunal assemblages living in association with fossil cold-water coral reef habitats present in the vicinity of mud volcanoes and carbonate mounds. Sampling was undertaken during the cruises M2005 (64PE237), M2006 (64PE253) and M2007 (64PE268), onboard the RV Pelagia. From the 120 box-core subsamples collected at depths ranging 220 to 900 m, 426 macroinvertebrate taxa were identified. The macrofaunal assemblages were highly heterogeneous in composition and community structure and were mainly represented by arthropods, annelids and molluscs. Multivariate analyses supported significant differences between distinct geological features and between distinct substrate types. High diversity, abundance and evenness were common in mound, coral and mud volcano assemblages, whilst off mound sediments and areas without hard substrates were represented by less diverse and less abundant assemblages. The assemblages are dominated by a relatively low percentage of the most common taxa and include mainly polychaetes, sipunculids and tanaidaceans. Analysis in relation to depth also revealed differences in taxa richness and abundance. The results obtained are discussed in relation to previous knowledge on carbonate mounds, fossil coral reefs, El Arraiche mud volcanoes and surrounding area, reinforcing the hypothesis that the presence of carbonate mounds and fossil cold-water coral reefs increases deep-sea habitat heterogeneity and support a highly diverse assemblage of benthic invertebrates.O Golfo de Cádis, localizado entre a margem sul Ibérica e a margem norte Marroquina, a oeste do Estreito de Gibraltar (NE Atlântico), engloba inúmeros montes carbonatados caracterizados pela acumulação de corais de profundidade fósseis e, mais de 40 vulcões de lama submarinos, a profundidades entre os 200 e 4000 m. Esta área localizada na interface de várias regiões biogeográficas, é tectonicamente ativa e caracterizada por uma longa história geológica; a complexa circulação de massas de água assegura a conectividade oceânica entre o Mar Mediterrâneo e as regiões Equatorial e Norte do Atlântico. No Golfo de Cádis, a Escarpa de Pen Duick, com 4 km de comprimento e 100 m de altura, está situada a cerca de 500 m de profundidade no ramo sudeste do "Renard Ridge", na parte ocidental do campo de vulcões do El Arraiche. Os corais de água fria, organismos vulneráveis e de crescimento lento que vivem em águas frias e escuras no oceano profundo, têm vindo a receber atenção acrescida nos últimos anos. No contexto dos programas de investigação MiCROSYSTEMS e Moundforce (Fundação Europeia para a Ciência), locais selecionados ao longo da margem Marroquina do Golfo de Cádis foram investigados, com o objetivo de descrever a composição, abundância e estrutura das comunidades de macrofauna bentónicas que vivem em associação com habitats de recifes de corais de água fria predominantemente fósseis presentes nas proximidades de vulcões de lama e montes carbonatados. A amostragem decorreu durante as campanhas M2005 (64PE237), M2006 (64PE253) e M2007 (64PE268), a bordo do NO Pelagia. Foram analisadas 120 subamostras de box-core recolhidas a profundidades entre os 220 e 900 m, nas quais foram identificados 426 taxa de macroinvertebrados. As comunidades de macrofauna revelaram ser altamente heterogéneas a nível de composição e estutura, sendo maioritariamente representadas por artrópodes, anelídeos e moluscos. As análises multivariadas revelaram diferenças significativas entre estruturas geológicas distintas e entre diferentes tipos de substratos. Elevada biodiversidade, abundância e equitibilidade são comuns entre as comunidades de montes carbonatados, áreas coralinas e vulcões de lama, enquanto que nas zonas de referência ("off mound") e áreas sem presença de coral as comunidades de macroinvertebrados demonstraram ser caracterizadas por menor diversidade e abundância. No geral, estas comunidades são dominadas por uma percentagem relativamente baixa dos taxa mais comuns, incluindo principalmente poliquetas, sipúnculos e tanaidáceos. A análise em relação à profundidade também revelou diferenças a nível da riqueza de taxa e abundância. Os resultados obtidos são discutidos em relação ao conhecimento prévio acerca da Escarpa de Pen Duick, montes carbonatados, recifes de coral fóssil, vulcões de lama da região de El Arraiche e área circundante, reforçando a hipótese de que a presença de montes carbonatados e recifes de coral de água fria fósseis aumentam a heterogeneidade de habitats no mar profundo e suportam uma comunidade de invertebrados bentónicos altamente diversa

Comprehensive database on Induan (Lower Triassic) to Sinemurian (Lower Jurassic) marine bivalve genera and their paleobiogeographic record

Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits worldwide are reviewed in terms of their validity, stratigraphic range, paleogeographic distribution, paleoautecology, and shell mineralogy. Data were originally compiled at species level and are arranged systematically. A brief discussion for each genus includes synonymy, taxonomic status, and included subgenera, as well as current uncertainties about their validity and range. The distribution of each genus is also shown on paleogeographic maps. Type species and first and last appearances of each genus are also mentioned. We recognize as valid 281 genera and their included subgenera, and we further discuss 148 genera (arranged alphabetically) that were mentioned for the study interval but are not included for different reasons. The purpose of this paper is to provide an updated critical assessment of all available basic information for each genus, in order to obtain a sound database to study the generic paleodiversity of marine bivalves in the time interval from the Induan (Early Triassic) to the Sinemurian (Early Jurassic). This was a critical time for bivalve evolution and diversification, which began with the recovery from the Permian¿Triassic extinction and ended with the recovery from the Triassic¿Jurassic extinction

Latest Cretaceous to earliest Paleogene molluscan faunas of New Zealand : changes in composition as a consequence of the break-up of Gondwana and extinction

Uppermost Cretaceous (Campanian?-Maastrichtian) to lowermost Paleogene (Paleocene) rocks of New Zealand contain an exceptional record of Bivalvia, Gastropoda and Scaphopoda. The composition of these faunas is closely linked with the separation of New Zealand from the East Antarctic-Australian sector of Gondwana, development of open oceanic conditions by Early Campanian time (c. 80-85 Ma), and Cretaceous-Tertiary boundary extinctions. This work aims to: 1) document the changes in paleobiogeographic elements (endemic, paleoaustral, Indo-Pacific/Tethyan, and cosmopolitan) of molluscs across the K-T interval; 2) provide a quantitative analysis of the Weddellian Biotic Province hypothesis of Zinsmeister (1979), which has resulted in a refined biogeographic model for the Gondwana Realm; and 3) examine the extent and effect of the terminal Cretaceous extinction event on the Mollusca of New Zealand. This study recognises 329 species of latest Cretaceous to earliest Paleogene molluscs from New Zealand. Of these, 118 new species are described in the systematic catalogue together with comments on their inferred feeding habits. Previously established species are refigured and where justified, redescribed and taxonomically updated. Of 329 species, 159 are of latest Cretaceous age (Piripauan to Haumurian stages) and 170 are Paleocene ("Wangaloan" or Teurian). A total of 79 bivalve, 47 gastropod and 2 scaphopod genera/subgenera are recognised in the Late Cretaceous record, with 35 bivalve, 76 gastropod and 3 scaphopod comparable taxa from the Paleocene. New genera/subgenera proposed in the systematics section are Brookula (Paleobrookula n. subgen.) (Skeneidae), Kaiparomphalus n. gen. (Trochidae), Saulopsis n. gen. (Tudiclidae), Wangaluta n. gen. (Volutidae), Wangacteon n. gen. (Acteonidae), and Kaurueon n. gen. (Acteonidae). Thirty-four new combinations are proposed. Zelandiella Finlay, 1926, is synonymised with Austrocominella von Ihering, 1907. Conchothyra marshalli (Trechmann, 1917) is considered as distinct from C. parasitica Hutton, 1877. The following species-group synonymies are proposed: Bittiscala communis Finlay and Marwick, 1937, with~- simplex (Marshall, 1917); Conchothyra expedita Finlay and Marwick, 1937, with C. australis (Marshall, 1916); Euspira lateaperta (Marwick, 1924) with Euspira fyfei (Marwick, 1924); and Campylacrum debile Finlay and Marwick, 1937,with C. sanum Finlay and Marwick, 1937. Though the biostratigraphic resolution of uppermost Cretaceous and Paleocene New Zealand rocks has improved recently, problems still exist in correlating some macrofossil localities because of rarity of index microfossils, facies faunas, and incomplete knowledge of stratigraphic ranges of some taxa. Thus, Piripauan (Campanian? Maastrichtian?) and Haumurian (Maastrichtian) stages are virtually inseparable in the field and laboratory. At Wangaloa, southeastern Otago, a K-T boundary section appears to be present c.10 m below the shell beds. Reintroduction of the abandoned Wangaloan Stage may be appropriate, pending further microfossil work, as the relationship of this stage to the very long (c. 8 m. y.) Teurian Stage could be established. Molluscan faunas at Wangaloa and elsewhere in South Island can be correlated to the lower part of the dinoflagellate Palaeocystodinium qolzowense Zone, indicating a late Early Paleocene age. A macrofossil zone, Zeacolpus (Leptocolpus) semiconcavus Assemblage-zone, is proposed for widespread molluscan-rich Paleocene faunas of South Island. Compared to other Austral sequences, New Zealand has an excellent record of latest Cretaceous to earliest Paleogene molluscs. Dramatic compositional changes across this interval ultimately reflect the break-up of Gondwana and environmental perturbations on shallow shelf faunas. Endemism in New Zealand latest Cretaceous molluscs was weak (c. 8% of genera/subgenera), but increased substantially (c. 32%) by Paleocene time, partially reflecting the geographic and genetic isolation of "greater New Zealand" at this time. The paleoaustral component, including endemics herein, was also relatively weak (c. 21%) during the Cretaceous but marked (c. 60%) by the Paleocene. The IndoPacific/ Tethyan and cosmopolitan components decreased from c. 48% to c. 26% and c. 26% to c. 12% across the interval, respectively. Few cosmopolitan Late Cretaceous species and endemic genera/subgenera of this age have been recorded. Most Late Cretaceous taxa are endemic species of cosmopolitan or wide-ranging genera/subgenera (c. 92%). The Paleocene fauna is entirely endemic at species-level, apart from possible records of Cucullaea (Cucullona) inarata Finlay and Marwick, 1937, from the Paleocene of southeastern Australia and Taieria allani Finlay and Marwick, 1937, from the Paleocene of Chatham Islands. High similarity coefficient values (≤ 0.76; Simple, Dice and Simple Matching) of latest Cretaceous and Paleocene molluscan genera/subgenera from New Zealand, Chatham Islands, Australia, New Caledonia, Antarctic Peninsula and southern South America, indicate strong faunal links between these areas during the latest Cretaceous. Such links corroborate the Weddellian Province hypothesis. The marked homogeneity of these widespread faunas probably reflects large shelf area, a low sea-surface temperature gradient, and favourable oceanic circulation including perhaps a trans-Antarctic seaway during the latest Cretaceous. Sea-surface temperatures across the K-T boundary were probably subtropical to at least warm temperate in New Zealand. The New Zealand Subprovince of the Austral Province (Kauffman, 1973) should be abandoned because of the low endemic component of New Zealand molluscs during the Late Cretaceous. For the Paleocene only New Zealand and southeastern Australia have significantly similar faunas (Simpson similarity indices: 0.36- bivalves, 0.91-gastropods). In the Paleocene, the Weddellian Province probably was reduced to the New Zealand-southeastern Australia and possibly Chatham Islands region along the newly opened Tasman Sea. New Zealand data are consistent with the idea that gradual environmental changes resulting from the final fragmentation of Gondwana, coupled with a probable bolide impact(s) in lower latitudes, caused mass extinction and suppressed biomass productivity, but was followed by faunal rebound during the Early Paleocene. In this study the latest Maastrichtian – earliest Danian time interval could not be resolved enough to identify any low diversity "disaster fauna" above the K-T boundary. The magnitude, however, of the extinction can be gauged along with the extent of the inferred initial radiation phase. In total, about 39% and 36% of bivalve genera/subgenera and gastropods became extinct at the end of the Cretaceous in New Zealand. All New Zealand species recorded in uppermost Cretaceous rocks became extinct sometime during the late Maastrichtian and earliest Danian. The extinction at genus-level was not as severe as in other areas including North Africa, Atlantic Coastal Plain, and northern Europe. The extinction particularly affected infaunal and epifaunal suspension feeders (c. 89%), fewer epifaunal herbivores and browsers (c. 65%), and negligible carnivores and deposit feeders. Data support the idea that the K-T event was selective against suspension feeders and that there was diminished productivity of phytoplankton at the base of the food chain. About 50% of latest Cretaceous molluscs, including Lazarus taxa, crossed the K-T boundary. Most survivors were seemingly eurybathyal with recorded species in a spectrum of shelf settings. Approximately half of Paleocene survivors were infaunal suspension feeders, but few were epifaunal. Most gastropod survivors were carnivores and deposit feeders. Significantly, Paleocene survivors and presumed new taxa became extinct during the Paleocene (c. 27%). Gamma (total) species diversity changed little across the K-T boundary indicating that diversity quickly recovered in the first few million years after the extinction. Bivalve diversity decreased substantially over the K-T interval, whereas gastropod diversity climbed. This “flip-flop” in diversity indicates that gastropods outpaced bivalves during the early Tertiary and could help explain the veritable burst of radiation in inferred "bloom" families (e. g. N.e.ticidae, Turridae, Acteonidae). The "Wangaloan" fauna probably characterises rapid evolution in isolation and an initial phase of radiation reflecting high speciation in which many new groups filled the ecological vacuum left by the extinction, followed by a further less severe extinction pulse in late Danian time