Taphonomy and ontogeny of a multibranched Ediacaran fossil: Bradgatia from the Avalon Peninsula of Newfoundland

2008 ◽  
Vol 45 (10) ◽  
pp. 1095-1109 ◽  
Author(s):  
Lija I. Flude ◽  
Guy M. Narbonne

Rangeomorphs, an extinct group of Ediacaran organisms with a fractal architecture and modular construction, occur abundantly in the Mistaken Point assemblage (575–560 Ma) of the Avalon Peninsula of Newfoundland. Bradgatia is represented by hundreds of specimens, collectively permitting analysis of its morphology, growth mode, and life habits. Bradgatia is a petalage that consists of a radial array of up to eight petals, each exhibiting up to four visible orders of rangeomorph branching. The taphonomy and ontogeny of Bradgatia are tightly linked by a change in preserved morphology, from juvenile I- to V-shaped specimens to larger U-shaped specimens, to the largest and ontogenetically oldest O-shaped specimens. Bradgatia probably maintained a constant number of petals that gradually spread out with age. The number of frondlets per petal does not correlate with length, suggesting either fractal or inflationary growth. Presence of a structure from which petals branch, abundance of contour-parallel specimens, differential preservation within specimens, and specimens overlying spindles and discs all imply that Bradgatia had an attached, epifaunal, suspension-feeding lifestyle. Bradgatia's multiple thin petals would have helped to filter water more efficiently, while its lack of a stem would have allowed for suspension feeding along the entire length of each petal.

2020 ◽  
Vol 6 (49) ◽  
pp. eabc6721
Author(s):  
John R. Paterson ◽  
Gregory D. Edgecombe ◽  
Diego C. García-Bellido

Radiodonts are nektonic stem-group euarthropods that played various trophic roles in Paleozoic marine ecosystems, but information on their vision is limited. Optical details exist only in one species from the Cambrian Emu Bay Shale of Australia, here assigned to Anomalocaris aff. canadensis. We identify another type of radiodont compound eye from this deposit, belonging to ‘Anomalocaris’ briggsi. This ≤4-cm sessile eye has >13,000 lenses and a dorsally oriented acute zone. In both taxa, lenses were added marginally and increased in size and number throughout development, as in many crown-group euarthropods. Both species’ eyes conform to their inferred lifestyles: The macrophagous predator A. aff. canadensis has acute stalked eyes (>24,000 lenses each) adapted for hunting in well-lit waters, whereas the suspension-feeding ‘A.’ briggsi could detect plankton in dim down-welling light. Radiodont eyes further demonstrate the group’s anatomical and ecological diversity and reinforce the crucial role of vision in early animal ecosystems.


Paleobiology ◽  
2018 ◽  
Vol 44 (2) ◽  
pp. 273-289 ◽  
Author(s):  
Sonny A. Walton ◽  
Dieter Korn

AbstractThe fossil conchs of ammonoids provide valuable information about the life habits of this extinct group. A new conch measurement, the apertural surface area (ASarea), is introduced here along with modeled sizes of the buccal mass and the hyponome, based on ratios of these organs in comparison with the aperture height from the RecentNautilus pompilius. A principal components analysis was performed using the three main characters: (1) apertural surface area index (i.e., the ratio of the apertural surface and the conch diameter), (2) buccal mass area index (i.e., the ratio between the buccal mass area and the ASarea), and (3) coiling rate of the conch. It revealed an ecomorphospace where life history traits can be tentatively assigned to species of the Ammonoidea. In this morphospace, RecentNautilushas a marginal position, being one of the ectocochleate cephalopods with best properties for active life (capacity for handling large food items, rather good mobility). In contrast, most ammonoids possessed, at comparable conch sizes, much smaller buccal apparatuses and hyponomes, suggesting a more passive life history with reduced mobility potential and reduced capacities for larger prey items.


Paleobiology ◽  
1976 ◽  
Vol 2 (3) ◽  
pp. 183-190 ◽  
Author(s):  
Michael J. S. Tevesz ◽  
Peter L. McCall

The typical pelecypod form, long thought to be primitively adaptive to burrowing, is likely to have been originally adaptive to a suspension feeding, epifaunal, possibly crawling mode of life. At small body size (< 1 cm), pelecypods possessing typical burrowing features can function as epifaunal crawlers. Pelecypods arose at small body sizes and are part of a molluscan evolutionary sequence in which relative size of the mantle cavity increased to accommodate a few large gills specialized for suspension feeding.Acquisition of a bivalved shell by ancestral epifaunal suspension feeders may have offered protection from sediment clogging on soft bottoms, additional control over the direction, volume, and rate of water flow through the mantle cavity, more effective protection from predators, and better short-term control of the internal environment. Consideration of invertebrate groups analogous to the pelecypods (Branchiopoda, Cladocera, Ostracoda, Phyllocarida) support the view that the bivalve condition is primarily an adaptation for suspension feeding and predator avoidance in benthic environments.The earliest known pelecypod, Fordilla troyensis Barrande, was not necessarily infaunal just because it had features similar to much larger, Recent burrowers. The size, shell morphology and environment of preservation of F. troyensis all suggest that it is reasonable to envision Cambrian pelecypods as epifaunal suspension feeders, possibly crawling on sedimentary bottoms. Moreover, the sudden Ordovician expansion of pelecypods and increase in individual size may be explained as a result of invasion of the infaunal adaptive zone.


2018 ◽  
Vol 19 (2) ◽  
pp. 68
Author(s):  
Raden Sudarwo ◽  
Yusuf Yusuf ◽  
Anfas Anfas

This study aims to determine the influence of learning facilities and student learning motivation towards the independence of student learning. The result of the research shows that there is positive and significant influence of learning tool (X1) on learning independence (Y). It is obtained by tvalue (2,159) with p = 0,034 <0,05 and ttable at 5% significant level with df = 78 equal to 1,991. There is a positive and significant influence of learning motivation (X2) on learning independence (Y). It is obtained tvalue (7,858) with p = 0,000 <0,05 and ttable at 5% significant level with df = 78 equal to 1,991. There is a positive and significant influence of learning facilities (X1) and learning motivation (X2) simultaneously to the independence of learning (Y). This shows the coefficient of double correlation RY (1,2) = 0,746 and R² = 0,557 and price Fvalue equal to 48,980 with p = 0,000 <0,05 and Ftable = 3,11 at 5% significant level. Coefficient value X1 = 0,186 and X2 = 0,647, constant number equal to 8,650 so that can be made regression equation Y = 8,650 + 0,186X1 + 0,647X2. The higher the learning means (X1) and the learning motivation (X2), the higher the learning independence (Y). Coefficient of Determination is R² of 0,557. Means 55,7% learning independence is explained by learning tools and learning motivation. Meanwhile, 44,3% is explained by other factors not discussed in this study. The study concludes that partially, learning facilities and student learning motivation has a positive and significant effect on student independence (self-sufficiency) in learning.  In addition, both learning facility and motivation have a positive and significant effect on student learning independence or sense of self-sufficiency. Penelitian ini bertujuan untuk mengetahui pengaruh fasilitas belajar dan motivasi belajar siswa terhadap kemandirian belajar siswa. Hasil penelitian menunjukkan bahwa ada pengaruh yang positif dan signifikan sanara belajar (X1) terhadap kemandirian belajar (Y). Hal ini diperoleh dengan nilai thitung (2,159) dengan p = 0,034 <0,05 dan ttabel pada 5% tingkat signifikan dengan df = 78 sama dengan 1,991. Ada pengaruh positif dan signifikan motivasi belajar (X2) pada kemandirian belajar (Y). Diperoleh nilai thitung (7,858) dengan p = 0,000 <0,05 dan ttabel pada taraf signifikan 5% dengan df = 78 sebesar 1,991. Ada pengaruh yang positif dan signifikan dari fasilitas belajar (X1) dan motivasi belajar (X2) secara bersamaan terhadap kemandirian belajar (Y). Hal ini menunjukkan koefisien korelasi ganda RY (1,2) = 0,746 dan R² = 0,557 dan harga Fhitung sebesar 48,980 dengan p = 0,000 <0,05 dan Ftabel = 3,11 pada taraf signifikan 5%. Nilai koefisien X1 = 0,186 dan X2 = 0,647, bilangan konstan sebesar 8,650 sehingga dapat dibuat persamaan regresi Y = 8,650 + 0,186X1 + 0,647X2. Semakin tinggi nilai sarana belajar (X1) dan motivasi belajar (X2), semakin tinggi kemandirian belajar (Y). Koefisien Determinasi adalah R² 0,557. Berarti 55,7% kemandirian belajar dijelaskan oleh alat belajar dan motivasi belajar. Sementara itu, 44,3% dijelaskan oleh faktor-faktor lain yang tidak dibahas dalam penelitian ini. Penelitian ini menyimpulkan bahwa secara parsial, baik ketersediaan sarana prasaran belajar dan motivasi berpengaruh positif dan signifikan pada kemandirian mahasiswa, dari dari kedua variable tersebut motivasi mempunyai pengaruh lebih besar. Secara simultan ketersediaan sarana prasarana dalam belajar dan pembelajaran, serta motivasi berpengaruh positif terhadap kemandirian belajar.


2008 ◽  
Vol 62 (6) ◽  
pp. 700-703
Author(s):  
Makoto Matsushita ◽  
Yoshiharu Numata

Author(s):  
Tochukwu Moses ◽  
David Heesom ◽  
David Oloke ◽  
Martin Crouch

The UK Construction Industry through its Government Construction Strategy has recently been mandated to implement Level 2 Building Information Modelling (BIM) on public sector projects. This move, along with other initiatives is key to driving a requirement for 25% cost reduction (establishing the most cost-effective means) on. Other key deliverables within the strategy include reduction in overall project time, early contractor involvement, improved sustainability and enhanced product quality. Collaboration and integrated project delivery is central to the level 2 implementation strategy yet the key protocols or standards relative to cost within BIM processes is not well defined. As offsite construction becomes more prolific within the UK construction sector, this construction approach coupled with BIM, particularly 5D automated quantification process, and early contractor involvement provides significant opportunities for the sector to meet government targets. Early contractor involvement is supported by both the industry and the successive Governments as a credible means to avoid and manage project risks, encourage innovation and value add, making cost and project time predictable, and improving outcomes. The contractor is seen as an expert in construction and could be counter intuitive to exclude such valuable expertise from the pre-construction phase especially with the BIM intent of äóÖbuild it twiceäó», once virtually and once physically. In particular when offsite construction is used, the contractoräó»s construction expertise should be leveraged for the virtual build in BIM-designed projects to ensure a fully streamlined process. Building in a layer of automated costing through 5D BIM will bring about a more robust method of quantification and can help to deliver the 25% reduction in overall cost of a project. Using a literature review and a case study, this paper will look into the benefits of Early Contractor Involvement (ECI) and the impact of 5D BIM on the offsite construction process.


1995 ◽  
Vol 32 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Donald Ian Phillips

On-site stormwater detention is widely used in Australia as a means of controlling the increased storm discharges from urban consolidation projects. However, unless the maximum permissible site discharge is correctly determined, the local piped drainage system may be overloaded. This paper presents a generic methodology that integrates detention storage behaviour with drainage design theory in such a manner as to protect the entire length of the downstream drainage system. Its generic nature facilitates its universal application to all systems, protecting these valuable community assets throughout their service lives.


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