57 resultados para ARTICULATED POLYPLACOPHORAN
How subtle are the biases that shape the fidelity of the fossil record? A test using marine molluscs
Resumo:
Biases in preservation shape the fossil record, and therefore impact on our reconstructions of past environments and biodiversity. Given the intensive recent research in the general fields of taphonomy and exceptional preservation, surprisingly, fundamental questions remain unanswered about species-level variation in skeletal preservation potential at low taxonomic levels (e.g. between genera from the same family, or between taxa from related families) across myriad groups with multi-element skeletons. Polyplacophoran molluscs (chitons sensu lato) are known from the late Cambrian to Recent, and possess a distinctive articulated scleritome consisting of eight overlapping calcareous valves. The apparent uniformity of living chitons presents an ideal model to test the potential for taphonomic biases at the alpha-taxon level. The vast majority of fossil chitons are preserved as single valves; few exhibit body preservation or even an articulated shell series. An experimental taphonomic programme was conducted using the Recent polyplacophorans Lepidochitona cinerea and Tonicella marmorea (suborder Chitonina) and Acanthochitona crinita (Acanthochitonina). Experiments in a rock tumbler on disarticulated valves found differential resistance to abrasion between taxa; in one experiment 53.8-61.5% of Lepidochitona valves were recovered but 92% of those from Tonicella and 100% of elements from Acanthochitona. Chiton valves and even partly decayed carcasses are more resistant to transportation than their limited fossil record implies. Different species of living chitons have distinctly different preservation potential. This, problematically, does not correlate with obvious differences in gross valve morphology; some, but not all, of the differences correlate with phylogeny. Decay alone is sufficient to exacerbate differences in preservation potential of multi-element skeletons; some, but not all, of the variation that results is due to specimen size and the fidelity of the fossil record will thus vary intra-specifically (e.g. between ontogenetic stages) as well as inter-specifically.
Resumo:
Three species of fossil polyplacophoran molluscs are known from Ireland. Two species were originally described in the nineteenth century: Helminthochiton griffithi Salter in M‘Coy, 1846 and Pterochiton thomondiensis (Baily, 1859), and an articulated specimen representing a third indeterminate species, described here for the first time. Previous work on the evolutionary context of these species has relied on published illustrations and descriptions without examination of the type material. as chitons are considered rare in the fossil record, these specimens represent an interesting and important aspect of Irish palaeobiology.
Resumo:
The palaeoloricate ‘polyplacophorans’ are an extinct paraphyletic group of basal chiton-like organisms known primarily from their fossilized valves. Their phylo- genetic placement remains contentious, but they are likely to include both stem-group Polyplacophora and stem- group Aplacophora. Candidates for the latter position include ‘Helminthochiton’ thraivensis from the Ordovician of Scotland, which we redescribe here through a combined optical and micro-CT (XMT) restudy of the type material. The 11 specimens in the type series are all articulated, presenting partial or complete valve series as well as moul- dic preservation of the girdle armature; they demonstrate a vermiform body plan. The valves are typically palaeolori- cate in aspect, but differ in detail from all existing palaeol- oricate genera; we hence erect Phthipodochiton gen. nov. to contain the species. The most notable feature of the fossils is the spicular girdle; this is impersistently preserved, but demonstrably wraps entirely around the ventral surface of the animal, implying that a ‘true’ (i.e. polyplacophoran like) foot was absent, although we do not exclude the pos- sibility of a narrow solenogastre-like median pedal groove having been present. Phthipodochiton thraivensis presents an apparent mosaic of aplacophoran and polyplacophoran features and as such will inform our understanding of the relationship between these groups of extant molluscs. An inference may also be drawn that at least some other pal- aeoloricates possessed an ‘armoured aplacophoran’ body plan, in contrast to the ‘limpet-like’ body plan of extant Polyplacophora.
Resumo:
We address the problem of non-linearity in 2D Shape modelling of a particular articulated object: the human body. This issue is partially resolved by applying a different Point Distribution Model (PDM) depending on the viewpoint. The remaining non-linearity is solved by using Gaussian Mixture Models (GMM). A dynamic-based clustering is proposed and carried out in the Pose Eigenspace. A fundamental question when clustering is to determine the optimal number of clusters. From our point of view, the main aspect to be evaluated is the mean gaussianity. This partitioning is then used to fit a GMM to each one of the view-based PDM, derived from a database of Silhouettes and Skeletons. Dynamic correspondences are then obtained between gaussian models of the 4 mixtures. Finally, we compare this approach with other two methods we previously developed to cope with non-linearity: Nearest Neighbor (NN) Classifier and Independent Component Analysis (ICA).
Resumo:
This paper uses Ridley Scott’s 2001 film blockbuster Black Hawk Down to examine the claim that popular film is the ‘newest component of sovereignty’. While the topic of the film – the 1993 UN/US intervention in Somalia – lends itself to straightforward politicisation, this paper is equally interested in the film’s production history and its reception by global audiences. While initial reactions to the film focused on its ideological commitments (e.g. racism, collusion between Hollywood and the Pentagon, post-11 September patriotism), these readings continually posed an imagined ‘America’ against ‘the world’. This paper argues that Black Hawk Down is not about sovereignty as traditionally conceived, that is, about national interest shaping global affairs. Rather, Black Hawk Down articulates, and is articulated by, a new and emerging global order that operates through inclusion, management and flexibility. Drawing on recent theoretical debates over this new logic of rule, this paper illustrates how Black Hawk Down invoked much more diffuse, complex and deterritorialized categories than national sovereignty. In effect, Scott’s film goes beyond traditional notions of sovereignty altogether: its production, signification and reception deconstruct simple notions of ‘America’ and ‘the world’ in favour of what Hardt and Negri call ‘Empire’, what Zizek calls ‘post-politics’, and what we refer to as ‘meta-sovereignty’.
Resumo:
This article examines the role of contemporary art in a post-9/11 context through The American Effect exhibition at the Whitney Museum of American Art in New York in 2003. This exhibition displayed a range of artworks from around the world that specifically engaged with, commented upon and interrogated the USA's pre-eminent position as a global superpower. In the politically charged climate after 9/11, the exhibition offered itself as a critical voice amid the more obvious patriotic clamour: it was one of the places where Americans could ask (and answer) the question, `Why do they hate us so much?' Although The American Effect claimed to be a space of dissent, it ultimately failed to question, let alone challenge, US global hegemony. Instead, the exhibition articulated a benevolent patriotism that forced artwork from other nations into supplicating and abject positions, and it obscured the complex discursive networks that connect artists, curators, critics, audiences and art museums.
Resumo:
This article argues that Irish “traditional” music is modern in its form and history, and explores the ramifications of this thesis for understanding of the peculiarities of Irish modernity and identity. The article exhaustively surveys the historiography of Irish traditional music and uniquely interprets this literature in relation to competing conceptions of identity and modernity articulated by Taylor, Appiah and Žižek. It also interprets Irish traditional music in relation to conceptions of Irish modernity articulated in a wide range of disciplines within Irish studies. Reflecting on the author’s lifelong engagement with traditional music performance, the article argues that the resilience of traditional music within the broader culture is connected to the peculiar character of Irish modernity, and that it suffers from problems of aesthetic exhaustion shared by much modern art in the contemporary conjuncture.
Resumo:
In Northern Ireland of the mid-1990s, many were caught off-guard by the comet-like arrival of a previously unarticulated Ulster Scots identity, replete with its own folk traditions. The article exploits the author’s position as Traditional Arts Officer of the Arts Council of Northern Ireland from 1998 until 2003 to offer an auto-ethnographic reflection on the literature on cultural politics in Northern Ireland since the outbreak of the Troubles, informed by extensive fieldwork with arts administrators and with contemporary Ulster Scots musicians. The article gives a close reading and historical contextualisation of the Ulster-Scots musical revue On Eagle's Wing, which was developed during this period. The article uses the concept of "suture" articulated by Lacan and developed by Laclau, Mouffe, and Žižek to explain both the potential for Ulster Scots culture to enter political discourse out of a seeming vacuum and its subsequent difficulties, offering an original interpretation of the role of culture in the contemporary trajectory of Northern Ireland politics.
Resumo:
Recent years have seen the emergence of a markedly more critical discourse in the Netherlands as regards European integration. Concerns over both the size of the net national contribution to the European Union budget and the implications for the country of EU enlargement have given rise to high-profile public debates. An explicitly articulated discourse of national interest, centred on but not limited to the Liberal VVD, has become a staple of political debate. At the same time, movements with clearly Eurosceptic agendas (the Pim Fortuyn List and the Socialist Party) have enjoyed unparalleled levels of electoral success. Although not of significant electoral salience, 'Europe' has nevertheless emerged as an issue in Dutch politics. The present article examines these stirrings of dissent in an EU member state which had long been regarded as one of the most enthusiastic supporters of further integration.
Resumo:
Purpose
– Information science has been conceptualized as a partly unreflexive response to developments in information and computer technology, and, most powerfully, as part of the gestalt of the computer. The computer was viewed as an historical accident in the original formulation of the gestalt. An alternative, and timely, approach to understanding, and then dissolving, the gestalt would be to address the motivating technology directly, fully recognizing it as a radical human construction. This paper aims to address the issues.
Design/methodology/approach
– The paper adopts a social epistemological perspective and is concerned with collective, rather than primarily individual, ways of knowing.
Findings
– Information technology tends to be received as objectively given, autonomously developing, and causing but not itself caused, by the language of discussions in information science. It has also been characterized as artificial, in the sense of unnatural, and sometimes as threatening. Attitudes to technology are implied, rather than explicit, and can appear weak when articulated, corresponding to collective repression.
Research limitations/implications
– Receiving technology as objectively given has an analogy with the Platonist view of mathematical propositions as discovered, in its exclusion of human activity, opening up the possibility of a comparable critique which insists on human agency.
Originality/value
– Apprehensions of information technology have been raised to consciousness, exposing their limitations.
Resumo:
This essay uses the concepts of ‘distance’ and ‘proximity’ to investigate and assess perceptions of community, nation and empire in inter-war New Zealand and Ulster (as well as Ireland and Northern Ireland) within a British imperial context, and explores the extent to which service of the empire (for example in the First World War) promoted both notions of imperial unity and local autonomy. It focuses on how these perceptions were articulated in the inter-war years during visits to Northern Ireland by three New Zealand premiers – Massey, Forbes and Coates – and to New Zealand by the Prime Minister of Northern Ireland, Lord Craigavon. It discusses the significant ways in which distance from their ‘home base’ and proximity to expatriate communities (in Craigavon's case) and Irish unionists and nationalists (in the case of the New Zealand premiers) inflected public statements during their visits. By examining these inter-war visits and investigating the rhetoric used and the cultural demonstrations associated with them, the factors of both distance and proximity can be used to evaluate similarities and difference across two parts of the empire. Thus, we can throw some light on the nature and dynamics of British imperial identity in the early twentieth century.
Resumo:
This paper is concerned with the production and reproduction of segregation in Northern Ireland and how territoriality has impacted on the Protestant community in Derry/Londonderry. The city was pivotal in the development of the most recent conflict, has a majority Catholic population, sits on a contested border and has attempted to respond to expressions of alienation that have emerged from the Protestant community. The research used multiple methods to understand the nature of alienation and exclusion using secondary data, a quantitative household survey, in-depth interviews and focus
groups. This empirical commitment was important in identifying and unpacking the claims of various stakeholders with an interest in the use and development of the area. It is argued here that a version of Collaborative Planning provides a loosely articulated conceptual and methodological framework for drawing Protestant communities into the wider planning framework for the city. The data, however, suggest that the nature of stakeholders is complex and contradictory, and discursive practice that seeks consensus has limits, especially in validating or legitimating the assertions of self-acclaimed stakeholders. The research shows that the Protestant community had declined and residualised but had little experience of direct conflict with the majority community. Moreover, the Protestant community is now more likely to use the city centre (a predominantly Catholic space) for consumption and work, and its demographic decline has stopped. These findings are important as policy responses and community relations programmes have failed to distinguish between measurable socioeconomic needs and claims concerning ethnic alienation based on emotion and manipulation. Such alienation has tended to bolster single identity communities who have little or no prospect and/or knowledge of the collaborative efforts required to deliver meaningful regeneration. More realistic strategies based on agonism focus attention on power relations and the authenticity of positions adopted by competing interests in land use management and change. The paper concludes by highlighting the need to acknowledge and value contestation but to challenge sectarian discourses represented as legitimate claims about community needs and priorities.
Reterritorialising Canada: Arctic ice’s liquid modernity and the imagining of a Canadian archipelago
Resumo:
Studying mobile actor networks of moving people, objects, images, and discourses, in conjunction with changing time-spaces, offers a unique opportunity to understand important, and yet relatively neglected, “relational material” dynamics of mobility. A key example of this phenomenon is the recontinentalization of Canada amidst dramatically changing articulations of the meanings and boundaries of the Canadian land-ice- ocean mass. A notable reason why Canada is being re-articulated in current times is the extensiveness of Arctic thawing. The reconfiguration of space and “motility” options in the Arctic constitutes an example of how “materiality and sociality produce themselves together.” In this paper we examine the possibilities and risks connected to this recontinentalization of Canada’s North. In exploring the past, present, and immediate future of this setting, we advance the paradigmatic view that Canada’s changing Arctic is the key element in a process of transformation of Canada into a peninsular body encompassed within a larger archipelagic entity: a place more intimately attuned to its immense (and growing) coastal and insular routes.