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Bivalves from the Changhsingian (upper Permian) Bellerophon Formation of the Dolomites (Italy): ancestors of Lower Triassic post‐extinction benthic communities
No full textDiverse shallow marine fossil assemblages from the Changhsingian Bellerophon Formation (Dolomites) record late Palaeozoic marine life immediately before the end-Permian mass extinction. We classified c. 6500 bivalves from western Dolomites localities, identifying 26 species including one new family (Ladinomyidae), three new genera (Ladinomya, Lovaralucina, Gardenapecten) and 10 new species: Acharax frenademezi, Bakevellia (Bakevellia) preromangica, Edmondia hautmanni, Etheripecten stuflesseri, Ladinomya fosteri, Lovaralucina covidi, Palaeolima badiotica, Promytilus merlai, Tambanella? stetteneckensis and Volsellina carinata. The occurrence of three Eumorphotis species with different stratigraphic distributions, leads us to propose an upper Permian ‘Lower Eumorphotis Zone’, divided into E. praecurrens, E. striatocostata and E. lorigae subzones, and distinct from the existing Lower Triassic Eumorphotis Zone (here renamed ‘Upper Eumorphotis Zone’). Palaeoecological analysis produced six biofacies and four ecofacies, based on richness, dominance and ecological lifestyle. The bivalves inhabited lagoonal to nearshore environments affected by stressed conditions: high temperatures, high salinity, shallow water depths, low oxygen and high terrigenous input. The upper Bellerophon Fm is characterized by increasingly fully marine conditions, although eurytopic taxa still suggest stressed conditions. Bivalve richness of the upper Permian Bellerophon and Lower Triassic Werfen formations was compared to estimate the genus-level extinction rate. The disappearance of almost half (47%) of Bellerophon Fm genera is remarkably low compared with other, coeval bivalve faunas. Pre-extinction bivalve faunas were dominated by stress-adapted taxa (Unionites, Eumorphotis, Bakevellia, Towapteria) able to thrive in extreme environmental conditions, survive the end-Permian mass extinction, and become the dominant biotic component of Lower Triassic benthic communities globally
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
I bivalvi della Formazione a Bellerophon (Permiano superiore) delle Dolomiti nord-occidentali nel contesto dell’estinzione di massa di fine Permiano
Full text linkThe Bellerophon Formation (upper Permian) in the Western Dolomites (Badia and Gardena valleys) is mainly constituted by solfatic evaporites (gypsum and anhydrite) and dolomites in the lower part, and by marls, dolomites and micritic to biocalcarenitic limestones, in the upper part.
During the 19th and 20th centuries several palaeontologists described many new bivalve species from this formation, but the material on which these studies were based is often badly preserved, and lack of stratigraphic setting.
The Bellerophon Formation records the last stage of the Palaeozoic marine life, just before the greatest mass extinction in the history of life that marks the transition between the Permian and Triassic periods.
The present study aims to investigate the variation in the diversity of the bivalve communities through systematic and biostratigraphic analyses in order to define the extinction and survival rates, and to contribute in the investigation on the dynamics of the end Permian extinction, when 90 % of marine species and 70% of terrestrial vertebrate species disappeared. The peak of the extinction has been recently dated to 252,28 ± 0.08 million years ago; it seems to have been caused by a global warming linked to a strong and protracted volcanic activity of the Siberian traps and methane emission.
The bivalves object of the present study have been collected from extensive outcrops of the Bellerophon Formation located in the Badia and Gardena valleys. The stratigraphic distribution of the bivalves has been reconstructed through a detailed bed-by-bed sampling of the more complete successions from the two above mentioned Ladinian valleys. Most of the sections, although known since the XIX century, have been described and sampled for the first time in the present thesis.
The sections analysed in the Gardena valley are: Bulla (Ortisei, 30 m thick), Balest (Ortisei, 130 m thick), Pic (S. Cristina, 46 m thick); the sections analysed in the Badia valleys are Preroman (San Martino in Val Badia, 52 m thick), Seres (Longiarù valley, 37 m thick, which is the only one the be already described in detail).
All the studied sections are located on a southwest-northeast oriented transect, along which an increasing of the marine conditions, ranging from coastal and restricted to open, occurred. Nevertheless, even during the transgressive phase peaks, the beds originated always in euphotic and eurytopic conditions, with variations of some environmental limiting factors, such as oxygen and nutrients. The Bellerophon Formation succession shows a transgressive trend, punctuated by some regressive episodes that allowed to recognize third order depositional sequences, which were used to correlate the bioevents between the analysed sections.
The systematic analysis performed on the collected material and the historical collections of the bivalves from the Bellerophon Formation studied by STACHE, CANEVA, GORTANI and MERLA, allowed to classify 17 genera and 25 species, with 2 new species and one new genus, which will be formally named and described in a future work. The species described in the present study can be subdivided on the basis of their mode of life as follows:
• Infaunal suspension feeders: Permophorus tenuistriatus NAKAZAWA & NEWELL, 1968; Permophorus cfr. tenuistriatus NAKAZAWA & NEWELL, 1968; Permophorus cfr. octocostatus (WELLER, 1916); Pleurophorella jacobi (STACHE, 1878); Pleurophorella sp.; Schizodus obscurus (SOWERBY, 1821); Edmondia cf. rudis MC COY, 1853;
• Semi-infaunal endobyssate suspension feeders: Modiolus n. sp.; Volsellina aurioides (YIN & GON, 1978); Bakevellia ceratophaga (SCHLOTHEIM, 1816); Towapteria sp.; Marmaronia peracuta (STACHE, 1878);
• Epifaunal suspension feeders, epibyssate and/or free swimmers in adult stage: Aguilerella n. sp.; Palaeolima sp. 1; Palaeolima sp. 2; Parallelodon cf. multicostatus GIRTY, 1908; ”Pecten” trinkeri (STACHE, 1878); Eumorphotis praecurrens MERLA, 1930; Eumorphotis striatocostata (STACHE, 1878); Eumorphotis lorigae POSENATO, 2005; Pernopecten tirolensis (STACHE, 1878); Pernopecten symmetricus NEWELL, 1940; ?Scythentolium sp.;
• infaunal facultatively mobile deposit feeders : Janeia typa (WAAGEN, 1881); Janeia cfr. cheni LI & LI, 1997
Stenotipic organisms well adapted to undisturbed and predictable in the abiotic modifications open see environments, such as brachiopods, shows very high extinction rates, while euritopic organisms, such as the bivalves, well adapted to coastal disturbed and unpredictable environments, show higher survival rates, becoming the dominant benthic taxonomic group during the Early Triassic.
In the Bellerophon Formation, 6 bivalve associations have been recognized. They record the different phases of a marine regression, ranging from the open marine environment, almost undisturbed and predictable in the abiotic modifications, where stenotopic organisms such as brachiopods were adapted, to lagoon environments with oxygen depletion, high temperature and high levels of salinity, inhabited by low diversified benthic communities dominated by opportunistic species.
Association A has the highest levels of richness. This association is related to the maximum flooding surfaces, when the most open marine conditions occurred and the abiotic parameters were affected by weak fluctuations. The high levels of oxygen allowed the presence of a benthic fauna rich in bivalves such as Eumorphotis, Schizodus, Palaeolima, Edmondia, Janeia, Bakevellia, Permophorus, Pernopecten, Modiolus, Parallelodon. This association contains both infaunal and epifaunal bivalves. Few specimens of Aviculopecitinidae gen. nov., Marmaronia and Pleurophorella and abundant individuals of nautiloids, bellerophontids, and Comelicania characterize the assemblage.
Association B. It is linked to an environment with high values of salinity and temperatures. The benthic communities still show high richness: Aviculopecitinidae gen. nov., Pleurophorella jacobi, Modiolus, Volsellina, Schizodus and few individuals of Eumorphotis striatocostata. However, it differs from the Association A for the lacking of species typical of more open and stable marine environment such as Pernopecten, Paleolima and Paralledon. Nautolioids and bellerophontids are rare, while the brachiopod Comelicania is missing.
Association C shows a moderate richness in bivalves. It is characterized by the abundance of Pleurophorella jacobi and "Pecten" trinkeri, by few Eumorphotis striatocostata and small-sized individuals of Marmaronia peracuta, Modiolus and ?Bakevellia. This association can be related to low levels of oxygen, as suggested by the dominance of Aviculopectinidae, which are considered as marker of disaerobic environments.
Association D is essentially composed by the two species Pleurophorella jacobi and “Pecten” tinkeri suggesting an environment of oxygenated muddy substrate, allowing the settlement of infaunal species such as P. jacobi.
Association E is a monospecific association with Pleurophorella jacobi suggesting euryhaline conditions.
Association F is a monospecific association with “Pecten” trinkeri, which suggests disoxic bottom conditions.
The differences in biodiversity of bivalve assemblages are related both to palaeogeographic and stratigraphic setting, with the highest diversity occurring in the Val Gardena area and in the Bulla Member, which represent the top of the formation. In this unit the presence of a rich benthic association, dominated by brachiopods and a few individuals of Eumorphotis striatocostata, "Pecten" trinkeri, ?Scythentolium sp. and Bakevellia sp. should be interpreted as the early effects of the palaeoenvironmental variations prior the extinction event.
During the sedimentation of the Bellerophon Formation there is no evidence of extinctions in the community of bivalves, but only regional disappearance connected to the establishment of adverse environmental conditions, such as the disappearance of some nautiloids and bivalves of the Association A (e.g., Palaeolima, Edmondia, Janeia, Pernopecten and Parallelodon) occurring above the Nautiloid Horizon B in the Balest, Pic and Preroman sections and in the lowermost part of the sequence Lo 5 in the Preroman section. This event seems to be connected to the disappearance of suitable niches for the settlement of the above quoted genera. This habitat lost was probably caused by the fast transgression which characterizes the base of the Bulla Member, where articulate brachiopods appear already since the basal decimetres.
In the Bellerophon Formation 25 species of bivalves have been classified. Between them, 16% survived to the peak of end Permian extinction (Eumorphotis striatocostata, Marmaronia peracuta, Bakevellia ceratophaga and ?Scythentolium sp.). It is not clear if the mentioned taxa occurs in bed younger than the Tesero Member of Werfen Formation. On the basis of this analysis 84% of the bivalve species found in the Bellerophon Formation extinguished at end of the Permian.
In the Bellerophon Formation 17 genera have been described. The extinction rate at generic level reached 41%, corresponding to the following 7 genera: Edmondia, Schizodus, Volsellina, Pleurophorella, Janeia, Towapteria /Marmaronia and Aviculopectinidae gen. nov., while 10 (59%) survived the extinction. Five genera (Permophorus, Towapteria or Marmaronia, ?Scythentolium, Bakevellia and Eumorphotis) can be found in the Werfen Formation. They all died out during the Early Triassic, while Permophorus and Bakevellia disappeared during the Jurassic. When looking at the Lazarus taxa two of them (Palaeolima and Pernopecten) re-emerges and then dies out before the end of the Upper Triassic, Aguilerella re-appears during the Jurassic, Parallelodon during the Triassic and survives until the Cretaceous and Modiolus is still alive.
The end-Permian extinction seems to have had a remarkable impact on the bivalve associations of the Bellerophon Formation. This extinction mostly affected the infaunal suspension feeding and deposit feeding bivalves while the semi-infaunal and epifaunal ones show higher percentages of surviving. The high rate of extinction at species level is likely taphonomically biased, because many Lower Triassic species have been classified with different names from the Permian ones, because their poor preservation.
From a generic point of view, the bivalves show an extinction rate decidedly lower than other benthic invertebrate groups, with a survival rate of 65%. This allowed to these molluscs to proliferate in the strongly stressed Lower Triassic environments, when they occupied the most part of ecological niches previously occupied by the articulate brachiopods. This replacement represents the third and last evolutionary stage of the marine fauna (Modern Marine Fauna, SEPKOSKI, 1984)
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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