Phytosaurs are the most basal group of crurotarsan archosaurs. Superficially resembling crocodiles in habit and probably also in their ecological requirements, they form an important component of terrestrial vertebrate communities in the Late Triassic. The phytosaurs from the Stubensandstein deposits (Norian) of southwestern Germany are among the first representatives to become known of the group. However, our poor knowledge of European Norian phytosaurs is well exemplified by many morphological details of the cranium that in the course of this study were found to be hitherto unknown, or to be at variance with the literature. Virtually all phytosaur specimens from these deposits were examined to established their taxonomic status. The specimens comprise four valid species, which are referred to the genera Nicrosaurus FRAAS, 1866 and Mystriosuchus FRAAS, 1896. Both genera and all species are redefined on the basis of shared derived characters. The aim of this thesis is to redescribe the cranial anatomy of each taxon, a prerequisite to determine the variability and to test the validity of cranial characters that have been utilised to establish phylogenetic relationships among phytosaurs. A comprehensive skull osteology and a study of the variation in cranial characters of Nicrosaurus kapffi (MEYER, 1860) forms the main part of the thesis. The complete upper dentition is described in order to determine the positional variation of dental characters. Nicrosaurus kapffi is characterised by two features of its prenarial crest. Two morphs are recognised among the specimens based mainly on different skull width. The distinction is congruent with the distribution of other dimorphic features of the postorbital part of the skull and details of the crested rostrum, many of which are currently employed in phytosaur taxonomy. The intraspecific variation is interpreted as sexual dimorphism. The study demonstrates also that other characters are actually variable at species level and can provide only limited taxonomic and phylogenetic information. These include, most importantly, a reduction of the suborbital opening, a partly persisting parietal foramen, and, varying individually, the configuration of a number of dermal skull bones. The slender-snouted and gracile specimens previously referred to Belodon plieningeri MEYER, 1844 actually represent a species of Nicrosaurus, here referred to as Nicrosaurus species B. A hitherto undescribed skull provides important missing information on the temporal region in this taxon. Nicrosaurus species B is more derived than Nicrosaurus kapf in having, among more uncertain characters, a more elongated squamosal with a pointed squamosal tip and a narrower supratemporal fenestra. Nicrosaurus species B shows the same two intraspecific morphotypes regarding skull width, but, additionally, a significant variation of the shorter prenarial crest can be observed. Additional cranial data is provided to characterise the highly derived Mystriosuchus planirostris (MEYER, 1863), the type species of the genus. Previous suggestions that a particular skull represents a different species of Mystriosuchus are confirmed. The occipital aspect of this skull is redescribed, and a new reconstruction of the braincase is presented. The hitherto unnamed species is distinguished by numerous cranial characters, including details of the temporal region, an orbitosphenoid, a supernumerary bone in the occipital region, and possibly a premaxillary crest. A phylogenetic analysis of 22 phytosaur taxa based on 49 characters using PAUP was conducted. As a preliminary result, the Paleorhininae were found not to be monophyletic as previously suggested, but to represent the paraphyletic stem-group of all other phytosaurs (Phytosauridae). Secondly, Mystriosuchus is not closely related to any non-phytosaurid phytosaur, but the most derived Phytosauridae forming a Glade with Pseudopalatus pristinus and Arribasuchus buceros

<p> An attempt is made to determine compositional and textural trends in the direction of sediment transport in middle Triassic cross-bedded sandstone samples collected from northeastern British Columbia. Petrographic measurements of textural and compositional properties were made and a multiple regression analysis was performed on 27 samples collected from a particular lithological unit. The general petrographic aspects of middle Triassic sandstones were investigated and are discussed.</p> / Thesis / Master of Science (MSc)

Macroevolutionary patterns of adaptation are a product of natural selection acting on genetic and developmental variation within populations, the basis of microevolution. In microevolution, an adaptive landscape is used to visualize the relationship between phenotype and fitness, through a series of peaks and valleys. The adaptive landscape, as a concept suggests that there is some phenotypic optimum, or a combination of phenotypes, that result in a maximum fitness. This peak is not stable but is a reflection of interactions between the environment and the flora and fauna within. To expand the adaptive landscape to macroevolutionary scales is to assume that there is some optimum that a species or population is adapted to, and that numerous species can be compared to one another on the same landscape. The world of phylogenetic comparative methods uses the theory of the adaptive landscape in investigating the trajectory of trait change but is often limited to extant organisms. The fossil record often represents a major gap in the use of adaptive landscape theory, due in part to the incomplete nature of specimens or difficulties in untangling evolutionary relationships. Within this gap, the Triassic Period (252.2 – 201.5 MA) is sparsely represented, due to the often highly incomplete nature of Triassic fossils and our constantly evolving understanding of their phylogenetic relationships. However, the Triassic Period is bookended by mass extinctions, and is thus a useful case study to explore the utility of adaptive landscape theory for organisms in a time of rapid environmental change. My dissertation explores convergence and growth through an adaptive landscape framework, to reconstruct how species were evolving, or populations adapting, to a changing environment. The first chapter of my dissertation explores the evolution of a long snout in reptiles, with exploration of convergent evolution for both extant and extinct reptiles across the tree of life. The second chapter of my dissertation explores a statistical method to incorporate variation due to fossilization in estimating and quantifying growth curves. This second chapter was necessary to explore the third chapter of my dissertation, the ontogeny of a large-bodied mammal relative, Exaeretodon argentinus. With my third chapter, I quantify growth curves, compare them across other proto mammals closely related to Exaeretodon, and explore how diet may have changed over the lifetime of a single individual. These chapters focus on the adaptive landscape over different scales (population vs clade), and serve as a basis for future work in estimating dietary evolution. / Doctor of Philosophy / Evolutionary studies are often divided into macroevolution and microevolution. Microevolution can be thought of as the primary process of evolution, such as evolution by natural selection. Macroevolution, however, relates to patterns in evolution, such as the repeated evolution of flight in insects, birds, bats, and many extinct reptiles known only from fossils. Surprisingly, we lack any convincing models that can accurately relate evolution by natural selection with macroevolutionary patterns. One idea to bridge this gap is the adaptive landscape, an 80-year-old concept that relates a trait to the fitness of a population or a species. The adaptive landscape provides a visual representation of evolution through a series of peaks and valleys. Peaks embody high fitness, reflecting a population that is well adapted to their environment. Valleys on the other hand represent extinction traps, where populations are maladapted to their environment, and are in decline and at a higher risk of extinction. The adaptive landscape essentially quantifies how different traits of a population relate to their environment. My dissertation seeks to explore evolution through the lens of the adaptive landscape, to better reconstruct hypotheses about how animals interact with their environments, particularly in extinct animals known from fossils. I view the adaptive landscape with a macroevolutionary lens by redescribing a fossil reptile and investigating the repeated evolution of a long snout in reptiles. I then attempt to look at the adaptive landscape at a microevolutionary scale, by investigating patterns of growth in a 230-million-year-old mammal relative. My dissertation views evolution across scales and sets the stage for future work to better connect those scales.

Student Number : 9902718G - MSc dissertation - School of Geosciences - Faculty of Science / The Late Permian (251.0 ± 0.4 Ma) mass extinction is universally acknowledged as the most consequential of the five major Phanerozoic mass extinctions. More than 90% of marine species, ~70% of terrestrial vertebrates, and ~90% of plant life were lost in a very short interval. The nature of the Permian-Triassic (P-Tr) boundary and the cause of the mass extinction associated with it have been the subject of extensive international debate. Possible causes for the P-Tr extinction include asteroid/comet impact, oceanic anoxia, volcanism, methane clathrate dissociation, or combinations of these causes. Geochemical studies of the P-Tr boundary have traditionally been focused on the marine realm, as the boundary in continental sections is typically difficult to pinpoint. One continental setting of the P-Tr boundary that has, however, received much attention is that in the main Karoo Basin, South Africa. The Karoo Basin is a large retro-arc foreland basin which accumulated sediment from the Carboniferous (300 Ma) through to the Early Jurassic (180 Ma) in southwestern Gondwana. Mineralogical and geochemical investigations across two palaeontologically well-constrained continental P-Tr boundary sections at Commando Drift Dam and Wapadsberg in the southern Karoo Basin of South Africa have been undertaken in order to aid in our understanding of this extinction event. The Commando Drift Dam section is also constrained palaeomagnetically. There is a change in paleosol colour across the P-Tr boundary from green-grey to red-brown, which is believed to reflect a change of oxidizing conditions at the P-Tr boundary. Quartz grains were examined for possibly impact-produced microdeformation features, but these were not found. Iridium concentrations are below the detection limit (by instrumental neutron activation analysis) and the sections could not be evaluated as to whether any significant enrichment has taken place at the P-Tr boundary. Major element chemical profiles are dominated by the signatures of carbonate nodular horizons in both sequences. Iron contents (and accompanying siderophile element abundances) increase across the palaeontologically-defined P-Tr boundary, followed by a decrease thereafter. The major element concentrations, together with the effects of weathering, largely control trace element distribution. Carbon isotopic results from the Commando Drift Dam section show a gradual decrease in values before the P-Tr boundary, with a larger negative excursion at the P-Tr boundary. Above the boundary, gradual recovery to initial ratios is observed, followed by another gradual decrease in values to the palaeomagnetically defined boundary. No evidence supporting an extraterrestrial impact extinction mechanism has been found. Rather, the carbon isotope data from this study support two gradual palaeoclimatic changes separated by a sudden change in the carbon isotopic content of the atmosphere. The size and nature of these excursions support the addition of large amounts of anoxic material into the atmosphere. This is proposed to have been caused by the multiple influx of carbon dioxide, methane and other greenhouse gases at various times and by different mechanisms. Such a release of carbon dioxide, methane and other greenhouse gases could have been caused by the coincident volcanic event (the formation of the Siberian Traps) and the episodic release of methane clathrates.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015. / Thrinaxodon liorhinus, a cynodont that has been of captivating importance in the evolution of therapsids, is one of the best known transitional fossil taxa from non-mammaliaform cynodonts to mammals. The species is abundant in the South African Karoo Basin and is one of the best represented taxa immediately after the Permian-Triassic mass extinction. One of the key adaptive characteristics that may have aided in their survival was fossorialism. Numerous fossils of Thrinaxodon have been found in burrows or in a curled-up position, which has provided important circumstantial evidence for the formalization of the hypothesis of Thrinaxodon as a burrower. However, finding a fossil inside a burrow or even in a curled-up position only provides firm evidence for burrow use, not for burrow creation. Direct evidence for burrowing capability can come from the understanding of the functional morphology of Thrinaxodon limbs. The present study investigates internal and external structure of the Thrinaxodon forelimb, a variety of reptiles characterized by different behavioural patterns, and other cynodonts in order to advance present knowledge about the functional morphology of the transitional phase cynodont. The study uses Geometric Morphometric analyses, forelimb metric indices, torsion and cortical thickness of humeri in order to determine the extent to which, the Thrinaxodon forelimb functionally and structurally resembles that of a fossorial mammal versus a digging reptile. Results of the study tease apart the extent to which the Thrinaxodon forelimb illustrates modifications due to gait (e.g., sprawling versus semi-sprawling) versus a fossorial lifestyle. This would indicate that Thrinaxodon retained the reptilian skeletal configuration and adapted a posture that had begun to resemble parasagittal more than sprawling or semi-sprawling gait. Nonetheless, Thrinaxodon exhibits forelimb structural similarities to digging species, whether mammals or reptiles.

The genus Kannemeyeria is one of the most important and distinctive taxa of the Triassic dicynodonts. It became the first Triassic dicynodont known to science, and thus forms the benchmark for the comparison of the evolution and morphology of other Triassic dicynodonts. An understanding of this genus forms an integral part of the biozonation of the Beaufort Group, and is pivotal in influencing the interpretation of the evolution, physiology and phylogenetic relationships of the Triassic dicynodonts. This study focuses on the detailed cranial morphology and relationships of the Kannemeyeria, and uses a rigorous morphological investigation as the basis for a meaningful elucidation of the functional and thus physiological aspects of this dicynodont. The descriptions demonstrate that variations related to the skull size, distortion or naturally occurring variation within the genus allow for the synonymy of the formerly recognised species K. latifrons Broom (1898; 1913), K. erithrea Haughton (1915) and K. wilsoni Broom (1937). This conclusion is further supported by the allometric analysis which cannot distinguish the variation observed in the holotypes with that occurring naturally within a growth series. Apart from the large specimen, the other smaller individuals are accommodated in the genus as different ontogenetic stages of the growth series represented by K. simocephalus Weithofer (1888). Several allometric variables show unusual patterns of development, indicating that Kannemeyeria can be subdivided into ontological classes, as juvenile and adult forms, separated from each other by a particular level of development. An age-related threshold level is suggested, and considered to represent an animal reaching sexual maturity. It is consequently proposed that the Kannemeyeria population was, at an age-related level, subdivided into sexually mature and immature groups but remained ecologically homogeneous. Both the descriptions and the allometric analysis of the species K. cristarhynchus Keyser & Cruickshank (1979) clearly indicate that it does not conform to the growth series of K. simocephalus and thus the differences observed between these two taxa are not constrained to size increases. Consequently, the recognition of the species K. cristarhynchus is considered valid. From the observations of the cranial morphology, tested using an allometric analysis, generic and specific diagnoses are constructed for Kannemeyeria and its two African species. Several features of Kannemeyeria are discussed in a functional context. A corrugated hom-covered snout and large caniniform processes are considered to be associated with defence and posturing behaviour. Several features of the braincase also suggest herding behaviour. Kannemeyeria also has a slightly different occipital musculature arrangement than that proposed for many other dicynodonts. Most Kannemeyeria cranial features are related to its masticatory function. From the analysis of masticatory cycle it is clear that the jaw action is described via a single pivot-point, which in Kannemeyeria approached the original, primitive position of the jaw hinge. The vertical orientation of the articulation and this pivot-point ensured that the muscle action during second phase of mastication produced an upward crushing and grinding action instead of the typical fore-and-aft motion of many other dicynodonts. It also meant that the muscle force was at their maximum, and little or no energy was lost to translation of the moment arm at the jaw articulation. Consequently, the Kannemeyeria masticatory cycle was both highly effective and extremely efficient. The morphology, and resultant physiology, of Kannemeyeria skull is considered to represent the innovative foundation for much of the success of many of the later Triassic dicynodonts.

The end-Permian extinction at 252 Ma is widely regarded as the most severe of the Phanerozoic mass-extinctions and enabled the evolution of the modern carbon cycle and ecosystem structure. The cause of the extinction is still debated but the synergistic pressures of global climate change, such as anoxia and ocean acidification, were clearly important. The extinction occurred in two phases and is marked by a uniquely protracted recovery period of ~ 5 Myrs where diversity fails to reach pre-extinction levels until the Middle Triassic. This period is characterized by an unstable global carbon cycle, secondary extinctions, reef, chert and coal gaps, and changes in the carbonate factory from reef to microbial and abiotic dominated deposition. This thesis focuses on using geochemical data from the Arabian Margin to investigate the carbon cycle record and the links between kill mechanisms and carbon cycle dynamics. A new record of carbon cycling is presented for the Tethys in the form of a carbon isotope record for the entire Early Triassic from the Musandam Peninsula, United Arab Emirates (UAE). The Musandam carbon isotope record can be broadly correlated with global isotopic events but also resolves additional secondary excursions. These new short-lived events are probably related to the occurrence of the more widely recognized Early Triassic excursions, and may represent fluctuations in the driving mechanisms superimposed on the continued instability of the global carbon cycle in the aftermath of the end-Permian extinction. To unravel palaeo-depositional redox conditions this work utilizes geochemical proxies based on Fe systematics (Fe-speciation). To date, however, these proxies have only been calibrated in relation to modern and ancient siliciclastic marine sediments. This clearly limits the use of the Fe-speciation proxy, particularly in relation to carbonate-rich sediments and rocks. This thesis explores the use of Fe-speciation in carbonates using compiled literature and new data from modern oxic and anoxic settings. This new assessment expands the utility of Fe-based redox proxies to also incorporate carbonate-rich rocks that contain significant total Fe (>0.5 wt%), providing care is taken to assess possible impacts of diagenetic processes such as dolomitization. Based on this calibration work Fe-speciation is used to reconstruct the redox structure for the Arabian Margin mixed carbonate and clastic sediments, from the late Permian to the Middle Triassic. Fe-S-C systematics are utilized to identify the spatial and temporal dynamics of anoxia for a Neo-Tethyan shelf-to-basin transect. The unique spatial resolution afforded by this transect allows a direct link to be drawn between biodiversity, carbon cycling and anoxic events. For the first time we can directly observe a switch from deep-ocean dominated anoxia to a dynamic anoxic wedge at the end-Permian extinction. Additionally the data suggest that ferruginous conditions (anoxic non-sulphidic) were dominant in the Tethyan Ocean throughout the Early Triassic, proposing that euxinia was restricted regionally with potential implications for nutrient recycling, carbon cycle models and driving mechanisms. Redox dynamics may have had important implications for the wider carbonate cycle. These two themes are particularly inter-related with regards to oceanic alkalinity and pH. This thesis presents the first shallow water boron isotope record for the Permian Triasssic Boundary, used as a proxy for pH. The record demonstrates some unexpected results; firstly a sudden increase in pH is observed, prior to the first phase of the extinction and interpreted to reflect alkalinity supply from the development of slope anoxia. Secondly there is no evidence for an acidification event at the first phase of the extinction where pH remains stable. A rapid acidification event is, however, seen in the earliest Triassic, contemporary to the second phase of the mass extinction, but delayed compared to the main negative carbon isotope excursion that indicates the main phase of Siberian Trap volcanism. These events may be explained by dramatic changes in ocean the ocean’s buffering capacity linked to changes in alkalinity supply and the carbonate factory.

Aetosaurians are a clade of pseudosuchian archosaurs that were globally dispersed during the Late Triassic Epoch. Aetosaurians are characterized by a suite of osteoderms that covered much of the body. These osteoderms are commonly recovered as fossils and possess characteristic surface ornamentation that can be diagnostic for taxa. The abundance of these osteoderms and the ease of identification have made aetosaurians ideal index taxa for Late Triassic biostratigraphy. Of special interest are specimens from South and North America and Europe that have been assigned to the genus Stagonolepis, which have been utilized for correlation of continental sedimentary units and to approximately date the timing of important biotic events. New finds have called the synonymy of these Stagonolepis-like specimens into question, jeopardizing their ability to serve as biochronological markers. Detailed examination of all of the specimens assigned to Stagonolepis robertsoni demonstrates that all of these specimens do not represent the same species. The South American material is assigned to the genera Aetosauroides, Aetobarbakinoides, and Polesinesuchus; the European material to Stagonolepis; and the North American material to Calyptosuchus, Adamanasuchus, and a newly recognized taxon, Scutarx deltatylus. Scutarx deltatylus can be differentiated from other aetosaurians by the presence of a strongly raised, triangular boss, on the posteromedial corner of the paramedian osteoderms. Scutarx deltatylus also preserves the first good skull material from a Stagonolepis-like aetosaur from North America. A dorsoventrally thickened skull roof and an anteroposteriorly short parabasisphenoid further demonstrate the distinctness of this material from that of South America and Europe. A detailed phylogenetic analysis of all known aetosaurians further demonstrates the distinctness of these taxa. This new expanded analysis of 28 taxa and 83 characters recovers Aetosauroides scagliai as the sister taxon to all other aetosaurians. Stagonolepis robertsoni from Scotland does not clade with Stagonolepis olenkae from Poland. Calyptosuchus wellesi is the sister taxon to a clade consisting of Scutarx deltatylus and Adamanasuchus eisenhardtae. However, distribution of autapomorphies across these taxa precludes them from being synonymized. As a result the Stagonolepis-like aetosaurs cannot be used for global scale correlations of Upper Triassic strata, but do appear to be of utility for regional correlations, in particular those between the Chinle Formation and Dockum Group in the American Southwest. / text

No description available.

Triassic igneous rocks in southeast Queensland show a number of subduction related geochemical characteristics. Extensive calc-alkalic granitoids chains characterise the region and define the ancient arc setting. Despite good evidence that an arc was present, Triassic volcanic rocks are relatively sparse in southeast Queensland. The Mt Marcella Volcanics, of the northern Esk Trough are a previously poorly understood piece of the Middle Triassic convergent margin of southeast Queensland. A three stage model is proposed for the eruptive development of the Middle Triassic (245- 230Ma) volcanic succession that involves; 1) The Middle Triassic basalt, comprising coalesced lava flows covering as much as 500km2 with an estimated eruptive volume in the order of 50km3. 2) The Penwhaupell Volcanic Centre, a concentration of inter-bedded lavas and pyroclastic rocks dominated by dacite that forms a volcanic pile exceeding 2km stratigraphic thickness and representing an eruptive volume of approximately 48km3. 3) The Ettiewyn Caldera, representing the catastrophic culmination of the Mt Marcella Volcanics event, with a sequence of caldera out-flow and in-fill andesite ignimbrites and post-caldera lavas with a total eruptive volume in the order of 130km3. The “Penwhaupell Volcanic Centre” and the “Ettiewyn Caldera” are two new sub-divisions and the proposed names, for the lower and upper sequences of the previously undifferentiated Mt Marcella Volcanics. The Mt Marcella Volcanics magma compositions show cogenetic characteristics that define three evolutionary pathways; 1) a mildly alkali series, from basaltic-andesite to trachy-dacite related through fractionation dominated by plagioclase and clinopyroxene 2) an amphibole series, basaltic-andesite to hornblende dacite through fractionation dominated by plagioclase and hornblende under hydrous conditions, and 3) a pyroxene series, from basaltic-andesite to pyroxene andesite through fractionation dominated by plagioclase and pyroxene. Quantitative petrogenetic models generally support the proposed fractional crystallisation pathway, however weaknesses are acknowledged, with good results for the major elements and REE off-set by generally poor results for the LILE. Despite the inconclusive trace element results for the modelled fractionation, strong geochemical similarities and cogenetic relationships have been established. A typical arc-like geochemical signature including a pronounced Nb depletion characterises the Mt Marcella Volcanics. However, the geochemical character within the Middle Triassic volcanic succession reveals an unusual transition from an OIB character of the Middle Triassic basalts, to the Andean arc character of later Mt Marcella Volcanics. The implications of this could have profound impact on our understanding of how southeast Queensland’s Triassic tectonic setting operated by providing support for hotspot activity rather than subduction-driven activity.