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dc.contributor.advisorBotha-Brink, J.
dc.contributor.advisorButler, H. J. B.
dc.contributor.authorDu Plessis, Dewald
dc.date.accessioned2018-01-19T07:09:04Z
dc.date.available2018-01-19T07:09:04Z
dc.date.issued2010-09
dc.identifier.urihttp://hdl.handle.net/11660/7631
dc.description.abstractEnglish: The palaeoneurology (study of the nervous system of extinct animals) of nonmammalian cynodonts, which were the ancestors of mammals, is poorly understood. It is thought that the relative brain size of cynodonts increased with time, and that this change significantly affected their physiology and behaviour. Forty-four cynodont skulls belonging to eleven genera from Permian, Triassic and Jurassic strata were scanned and analysed using neutron computerized tomography (NCT), at the SAFARI-1 Nuclear Research Reactor of the Nuclear Energy Corporation of South Africa (Necsa). Data concerning the endocranial casts was hereby obtained in a non-destructive manner. Four specimens, namely Galesaurus, Platycraniellus, Langbergia and Tritylodon produced successful scans and were used for further study. Measurements of the cranial material were used to calculate the size of the brain endocasts and the approximate body masses were determined from an equation using skull length. The encephalization quotient (EO), a measure of brain size relative to body size, was determined for each specimen using brain volume and body mass. Changes in the position of the brain inside the skull, and an overall increase in size of the brain in the more derived cynodonts indicate some development towards the mammalian condition. Taxonomic variation regarding the shape and size of the olfactory bulbs and other parts of the brain endocasts is discussed and related to differences in ecology or behaviour. The relatively deep and large olfactory bulbs in some cynodonts may be an adaptation to either nocturnal behaviour, dietary or habitat preferences. Relatively large cranial endocasts in Galesaurus, Platycraniellus, Massetognathus, Tritylodon, Chiniquodon and the tritheledonts may be related to habitat preference or social behaviour. The basal epicynodonts Galesaurus and Platycraniellus have the largest cranial endocasts of all the cynodonts studied. Their large cranial endocasts may be related to behavioural or ecological preferences, but the results require confirmation from a larger sample size. The present study provides an important foundation from which further cranial endocast studies on cynodonts can be developed.en_ZA
dc.description.abstractAfrikaans: Min is bekend oor die palaeoneurologie (studie van die senuweestelsel van uitgestorwe diere) van nie-soogdieragtige Cynodontia, wat die voorouers van soogdiere is. Daar word vermoed dat die relatiewe breingrootte van Cynodontia oor tyd toegeneem het, en dat hierdie verandering hulle fisiologie en gedrag aansienlik beïnvloed het. Vier-en-veertig Cynodontia-skedels, wat tot elf genera behoort en uit Permiese, Triassiese en Jurassiese aardlae afkomstig is, is met behulp van neutron gerekenariseerde tomografie (NCT), by die SAFARI-1 Kernnavorsingsreaktor van die Suid-Afrikaanse Kernkragkorperasie (Necsa) geskandeer en ontleed. Inligting rakende die binneskedelvormafdrukke is hierdeur op 'n nie-vernietigende wyse bekom. Vier eksemplare, naamlik Galesaurus, Platycraniellus, Langbergia en Tritylodon, het suksesvolle skanderings geproduseer en is vir verdere studie gebruik. Afmetings van die skedelmateriaal is gebruik om die grootte van die breinafgietsels te bereken en die benaderde liggaamsmassa is bepaal uit 'n vergelyking wat van skedellengte gebruik maak. Die ensefalisasiekwosiënt (EK), 'n maatstaf van breingrootte relatief tot liggaamsgrootte, vir elke eksemplaar is bepaal deur breinvolume en liggaamsmassa te gebruik. Veranderinge in die ligging van die brein binne die skedel, en 'n algehele toename in grootte van die brein in die meer gevorderde Cynodontia dui op 'n neiging van ontwikkeling in die rigting van 'n meer soogdieragtige toestand. Taksonomiese variasie rakende die olfaktoriese lobbe en ander dele van die breinafgietsels is bespreek en verbind met verskille in ekologie of gedrag. Die relatief diep en groot olfaktoriese lobbe by sommige Cynodontia is dalk 'n aanpassing vir naglewende gedrag, dieet- of habitatsvoorkeure. Relatiewe groot breinafgietsels in Galesaurus, Platycraniellus, Massetognathus, Tritylodon, Chiniquodon en die Tritheledonta word toegeskryf aan habitatvoorkeur of sosiale gedrag. Die basale Epicynodontia Galesaurus en Platycraniellus het die grootste breinafgietsels van al die Cynodontia wat bestudeer is. Hulle groot breinafgietsels hou dalk verband met gedrags- of ekologiese voorkeure, maar die resultate benodig bevestiging van 'n groter monstergrootte. 'n Belangrike fondering word deur hierdie studie gebied, waaruit verdere breinafgietselstudies by Cynodontia ontwikkel kan word.af
dc.description.sponsorshipNational Research Foundation (NRF)en_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectComputerised tomographyen_ZA
dc.subjectCynodontiaen_ZA
dc.subjectEncephalizationen_ZA
dc.subjectPalaeoneurologyen_ZA
dc.subjectPaleontology, Triassicen_ZA
dc.subjectReptiles, Fossilen_ZA
dc.subjectTherapsidaen_ZA
dc.subjectFossils -- Morphologyen_ZA
dc.subjectTomographyen_ZA
dc.subjectDissertation (M.Sc. (Zoology and Entomology))--University of the Free State, 2010en_ZA
dc.titleAn examination of non-mammalian cynodont cranial endocastsen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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