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A new close mammal relative and the origin and evolution of the mammalian central nervous system
Mammals are distinguished by the presences of the cerebral neocortex, and dentary-squamosal jaw joint, among other traits. These traits likely evolved outside of Mammalia, in Mammaliaformes. Recent fossil discoveries from South America elucidate the evolution of the brain in taxa outside of Mammaliaformes. A new skull of a close mammal relative, Pseudotherium argentinus, from the Late Triassic Ischigualasto Formation in Argentina was scanned at The University of Texas High-Resolution X-ray Computed Tomography (CT) Facility. CT data reveal a unique combination of ancestral and derived characters. Phylogenetic analysis supports a sister-taxon relationship between Pseudotherium and the derived Tritylodontidae. An endocast reconstruction further supports a derived phylogenetic position among cynodonts. A comparison of the Pseudotherium endocast with other cynodont endocasts suggests that the cerebral hemispheres enlarged in probainognathian cynodonts, while the total endocranial volume remained relatively constant until the origin of Mammaliaformes. This expansion is also present in the foramen magnum. Encephalization volume and skull length were compared with foramen magnum size in extinct and extant cynodonts, birds, and lizards. Endocranial volume and foramen magnum size, and foramen magnum size and skull length, are correlated following a 3/2 power law. Therefore, foramen magnum size can be used to predict endocranial volume for fossils. Regression analyses show foramen magnum size is significantly increased in Mammaliaformes. This change reflects an increase in medulla oblongata size and supports a concerted model of brain evolution outside of Mammalia. Because the increase in medullary size coincides with the origin of the neocortex, I hypothesize that the mammalian pyramidal tract originated in Mammaliaformes. The hypotheses from this dissertation are testable given recent fossil discoveries. However, morphological data of those specimens are not readily available. Morphological descriptions in this dissertation are accompanied by detailed figures, and the data will be digitally archived and made publically available on DigiMorph.org. The intent is to model a communication and data-sharing standard to be implemented in all future fossil discoveries.Geological Science
A qualitative study of physical activity drivers in autistic individuals using COM-B:Autistic and non-autistic perspectives
BackgroundDespite evidence of the health benefits of physical activity in non-autistic populations and the additional benefits for autistic populations, physical activity levels remain stubbornly low in autistic individuals. Understanding the determinants of physical activity is essential in order to support intervention development.MethodsThe current research applied the Theoretical Domains Framework (TDF) and Capability Opportunity Motivation, Behaviour (COM-B) model of behaviour to identify determinants of physical activity behaviour, mechanisms of action, and potentially efficacious behaviour change techniques. Fifteen semi-structured interviews were conducted with autistic adults (N = 4) and children (N = 2), parents of autistic children (N = 4), and stakeholders in autism care and support (N = 5). A deductive approach was taken to map themes onto TDF and COM-B.ResultsParticipants identified three overarching themes: Discordance between autistic and non-autistic perspectives; physically active environments; and autonomy and choice. Eight subthemes were identified and mapped onto COM-B and TDF. Recommendations for intervention development are made and potential behaviour change techniques are identified.ConclusionsGiven the important role of care providers, future research should focus on the attitudes and behaviours of individuals who care for and support autistic individuals to identify barriers and drivers of physical activity promotion, particularly for individuals with high support needs. An argument is made for co-design in future intervention development
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