A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes
- Coates, Michael I, Gess, Robert W, Finarelli, John A, Surname, Name - one for each creator, Criswell, Katharine E, Tietjen, Kristen
- Authors: Coates, Michael I , Gess, Robert W , Finarelli, John A , Surname, Name - one for each creator , Criswell, Katharine E , Tietjen, Kristen
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/72246 , vital:30021 , https://doi.org/10.1038/nature20806
- Description: Chimaeroid fishes (Holocephali) are one of the four principal divisions of modern gnathostomes (jawed vertebrates). Despite only 47 described living species1, chimaeroids are the focus of resurgent interest as potential archives of genomic data2 and for the unique perspective they provide on chondrichthyan and gnathostome ancestral conditions. Chimaeroids are also noteworthy for their highly derived body plan1,3,4. However, like other living groups with distinctive anatomies5, fossils have been of limited use in unravelling their evolutionary origin, as the earliest recognized examples already exhibit many of the specializations present in modern forms6,7. Here we report the results of a computed tomography analysis of Dwykaselachus, an enigmatic chondrichthyan braincase from the ~280 million year old Karoo sediments of South Africa8. Externally, the braincase is that of a symmoriid shark9,10,11,12,13and is by far the most complete uncrushed example yet discovered. Internally, the morphology exhibits otherwise characteristically chimaeroid specializations, including the otic labyrinth arrangement and the brain space configuration relative to exceptionally large orbits. These results have important implications for our view of modern chondrichthyan origins, add robust structure to the phylogeny of early crown group gnathostomes, reveal preconditions that suggest an initial morpho-functional basis for the derived chimaeroid cranium, and shed new light on the chondrichthyan response to the extinction at the end of the Devonian period.
- Full Text:
- Date Issued: 2017
- Authors: Coates, Michael I , Gess, Robert W , Finarelli, John A , Surname, Name - one for each creator , Criswell, Katharine E , Tietjen, Kristen
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/72246 , vital:30021 , https://doi.org/10.1038/nature20806
- Description: Chimaeroid fishes (Holocephali) are one of the four principal divisions of modern gnathostomes (jawed vertebrates). Despite only 47 described living species1, chimaeroids are the focus of resurgent interest as potential archives of genomic data2 and for the unique perspective they provide on chondrichthyan and gnathostome ancestral conditions. Chimaeroids are also noteworthy for their highly derived body plan1,3,4. However, like other living groups with distinctive anatomies5, fossils have been of limited use in unravelling their evolutionary origin, as the earliest recognized examples already exhibit many of the specializations present in modern forms6,7. Here we report the results of a computed tomography analysis of Dwykaselachus, an enigmatic chondrichthyan braincase from the ~280 million year old Karoo sediments of South Africa8. Externally, the braincase is that of a symmoriid shark9,10,11,12,13and is by far the most complete uncrushed example yet discovered. Internally, the morphology exhibits otherwise characteristically chimaeroid specializations, including the otic labyrinth arrangement and the brain space configuration relative to exceptionally large orbits. These results have important implications for our view of modern chondrichthyan origins, add robust structure to the phylogeny of early crown group gnathostomes, reveal preconditions that suggest an initial morpho-functional basis for the derived chimaeroid cranium, and shed new light on the chondrichthyan response to the extinction at the end of the Devonian period.
- Full Text:
- Date Issued: 2017
Colonised minds?: post-development theory and the desirability of development in Africa
- Authors: Matthews, Sally
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142213 , vital:38059 , DOI: 10.1080/01436597.2017.1279540
- Description: While post-development theory is very concerned with the ways in which development has impacted upon the countries of the Global South, there has been relatively little written on post-development theory from an African perspective. This paper identifies some of the ways in which post-development theory fails to adequately understand the African experience of development. In particular, I explore the difficulty that post-development theory confronts when faced with the continued desire on the part of many people in Africa for development.
- Full Text:
- Date Issued: 2017
- Authors: Matthews, Sally
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142213 , vital:38059 , DOI: 10.1080/01436597.2017.1279540
- Description: While post-development theory is very concerned with the ways in which development has impacted upon the countries of the Global South, there has been relatively little written on post-development theory from an African perspective. This paper identifies some of the ways in which post-development theory fails to adequately understand the African experience of development. In particular, I explore the difficulty that post-development theory confronts when faced with the continued desire on the part of many people in Africa for development.
- Full Text:
- Date Issued: 2017
Customary management as TURFs: social challenges and opportunities
- Authors: Aswani, Shankar
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145403 , vital:38435 , DOI: 10.5343/bms.2015.1084
- Description: There is a growing interest in working with customary management (CM) systems to effectively manage benthic resources and small-scale fisheries. The underlying notion is that CM institution as territorial use rights in fisheries (TURFs) can be sufficiently adaptive and dynamic to create the local incentives that are necessary for promoting sustainable fishing practices and marine conservation more generally in a given region. This paper reviews the social opportunities and challenges of working with CM systems as a form of TURF, particularly in Oceania. A key conclusion is that policy makers and managers not only need to recognize natural interconnectivity in any one marine space, but also consider the social interconnectivity of stakeholders that covers customary TURFs. Only by recognizing and working with the existing social networks that overlay any given marine territory can the operational principles of CM (as reviewed in this paper) be effectively deployed for achieving some kind of bioeconomic efficiency and creating an equitable rights-based fisheries management system.
- Full Text:
- Date Issued: 2017
- Authors: Aswani, Shankar
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145403 , vital:38435 , DOI: 10.5343/bms.2015.1084
- Description: There is a growing interest in working with customary management (CM) systems to effectively manage benthic resources and small-scale fisheries. The underlying notion is that CM institution as territorial use rights in fisheries (TURFs) can be sufficiently adaptive and dynamic to create the local incentives that are necessary for promoting sustainable fishing practices and marine conservation more generally in a given region. This paper reviews the social opportunities and challenges of working with CM systems as a form of TURF, particularly in Oceania. A key conclusion is that policy makers and managers not only need to recognize natural interconnectivity in any one marine space, but also consider the social interconnectivity of stakeholders that covers customary TURFs. Only by recognizing and working with the existing social networks that overlay any given marine territory can the operational principles of CM (as reviewed in this paper) be effectively deployed for achieving some kind of bioeconomic efficiency and creating an equitable rights-based fisheries management system.
- Full Text:
- Date Issued: 2017
Interrogating citizen journalism practices: a case study of Rhodes University’s Lindaba Ziyafika Project
- Nyathi, Sihle, Garman, Anthea
- Authors: Nyathi, Sihle , Garman, Anthea
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158915 , vital:40240 , https://doi.org/10.1080/23743670.2016.1259740
- Description: Several scholars have noted that citizen journalism in the West is essentially an online phenomenon, driven by the affordability of Internet technologies. In Africa, projects such as Ushahidi in Kenya have been enabled by platforms such as cell phones and social networks. Voices of Africa, based in southern Africa, publishes on the web only. Publishing on the Internet presumes a citizenry which is relatively well educated; has familiarity with, and access to, new media as a form of social communication; and is confident in their right to participate in newly developed public spheres – particularly those online.
- Full Text:
- Date Issued: 2017
- Authors: Nyathi, Sihle , Garman, Anthea
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/158915 , vital:40240 , https://doi.org/10.1080/23743670.2016.1259740
- Description: Several scholars have noted that citizen journalism in the West is essentially an online phenomenon, driven by the affordability of Internet technologies. In Africa, projects such as Ushahidi in Kenya have been enabled by platforms such as cell phones and social networks. Voices of Africa, based in southern Africa, publishes on the web only. Publishing on the Internet presumes a citizenry which is relatively well educated; has familiarity with, and access to, new media as a form of social communication; and is confident in their right to participate in newly developed public spheres – particularly those online.
- Full Text:
- Date Issued: 2017
Thermoluminescence of the main peak in SrAl2O4: Eu2+, Dy3+: spectral and kinetics features of secondary emission detected in the ultra-violet region
- Authors: Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124197 , vital:35575 , https://doi.org/10.1016/j.radmeas.2016.12.001
- Description: We report the thermoluminescence of SrAl2O4:Eu2+,Dy3+ measured in the ultra-violet region of the spectrum between 300 and 400 nm. Complementary measurements of X-ray excited optical luminescence confirm emission bands of stimulated luminescence in this region. As a further test, optically stimulated luminescence was also measured in this region. The glow curve measured at 1 °C s−1 following irradiation to various doses appears simple and single but is in reality a collection of several components. This was shown by results from the Tm-Tstop method on both ends of the peak, application of thermal cleaning beyond the peak maximum as well as the dependence of the peak on fading. The latter shows that new peaks appear as preceding ones fade. Kinetic analysis of some of the main peaks was carried out giving an activation energy of 0.6 eV. The implication of the results on measurement of phosphorescence, interpretation of dose response and fading is discussed.
- Full Text: false
- Date Issued: 2017
- Authors: Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124197 , vital:35575 , https://doi.org/10.1016/j.radmeas.2016.12.001
- Description: We report the thermoluminescence of SrAl2O4:Eu2+,Dy3+ measured in the ultra-violet region of the spectrum between 300 and 400 nm. Complementary measurements of X-ray excited optical luminescence confirm emission bands of stimulated luminescence in this region. As a further test, optically stimulated luminescence was also measured in this region. The glow curve measured at 1 °C s−1 following irradiation to various doses appears simple and single but is in reality a collection of several components. This was shown by results from the Tm-Tstop method on both ends of the peak, application of thermal cleaning beyond the peak maximum as well as the dependence of the peak on fading. The latter shows that new peaks appear as preceding ones fade. Kinetic analysis of some of the main peaks was carried out giving an activation energy of 0.6 eV. The implication of the results on measurement of phosphorescence, interpretation of dose response and fading is discussed.
- Full Text: false
- Date Issued: 2017
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