Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references (leaves 533-552). Also available in an electronic version. Also available from UMI.

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A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2013 / A thorough description and cladistic analysis of the Antetonitrus ingenipes type material sheds further light on the stepwise acquisition of sauropodan traits just prior to the Triassic/Jurassic boundary. Although the forelimb of Antetonitrus and other closely related sauropododomorph taxa retains the plesiomorphic morphology typical of a mobile grasping structure, the changes in the weight-bearing dynamics of both the musculature and the architecture of the hindlimb document the progressive shift towards a sauropodan form of graviportal locomotion. Nonetheless, the presence of hypertrophied muscle attachment sites in Antetonitrus suggests the retention of an intermediary form of facultative bipedality. The term Sauropodiformes is adopted here and given a novel definition intended to capture those transitional sauropodomorph taxa occupying a contiguous position on the pectinate line towards Sauropoda. The early record of sauropod diversification and evolution is re-examined in light of the paraphyletic consensus that has emerged regarding the ‘Prosauropoda’ in recent years.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016. / The Palaeontological record of South Africa is remarkable in that it preserves the two major temporal transitions of the Mesozoic: The Triassic–Jurassic boundary (the Elliot Formation) and the earliest depositional stages of the Cretaceous (the Kirkwood Formation). Work within the Elliot Formation has reiterated the importance of this horizon for our understanding of the early evolution and subsequent radiation/diversification of basal sauropodomorph dinosaurs. Moreover, inextricably contained within this radiation is the early evolution of the columnar-limbed, long necked sauropods, the largest terrestrial animals to have ever evolved. The Elliot Formation therefore imparts vital information on the genesis of the group that would become the dominant dinosaurian herbivores throughout most of the Mesozoic. However, several outstanding issues obscure a full understanding of this important radiation. Of primary concern is the complicated taxonomy of the sauropodomorphs of the Upper Triassic lower Elliot Formation and a lack of current consensus as to what precisely constitutes a true sauropod. The latter issue is further complicated by a lack of well-preserved sauropod material prior to the Toarcian. The discovery of new, associated material from both the lower and upper Elliot Formation has direct relevance to both of these concerns. Specifically, although the genus Eucnemesaurus is supported in the current analysis, the bauplan diversity of lower Elliot Sauropodomorpha remains relatively conservative save for the stocky pedal architecture of Blikanasaurus and the autapomorphically robust morphology of a newly rediscovered ilium that is potentially referable to it. Within the upper Elliot Formation, a recently discovered highly apomorphic bone-bed is diagnosed as a new species of sauropod that, in addition to placing the earliest unequivocal sauropods within the basal rocks of the Jurassic, suggests the underlying ecological factors driving the divergence of the derived sauropodan bauplan. In addition to new information provided by the Elliot Formation, two decades’ worth of collecting from the Early Cretaceous Kirkwood Formation affords a long overdue insight into the sauropod fauna occupying southern Gondwana at the outset of the Cretaceous. The surprising diversity of forms recognized from the Kirkwood suggests that the taxonomic decline of Sauropoda previously inferred for the earliest Cretaceous is a product of sampling bias compounded by a generally poor fossil record. However, a lack of absolute dates for the Kirkwood Formation means that the plethora of “Jurassic-type” specimens is potentially explicable via their being contemporaneous with similar Late Jurassic faunas of eastern Africa and North America. / LG2017

Os depósitos triássicos continentais do sul do Brasil abrigam uma grande diversidade de tetrápodes terrestres, incluindo terápsidos, rincossauros, rincocefálios e arcossauros, como pseudosúquios e dinossauromorfos. Inserida neste contexto, a Formação Santa Maria, de porção superior datada do Carniano superior, tem papel fundamental no entendimento da origem e irradiação inicial dos dinossauromorfos, pois abriga alguns dos mais antigos registros do grupo em todo mundo, incluindo vários fósseis de dinossauros. Atualmente, a fauna de dinossauromorfos desta unidade é representada por Ixalerpeton polesinensis, Teyuwasu barberenai, Staurikosaurus pricei, Saturnalia tupiniquim, Pampadromaeus barberenai, Buriolestes schultzi e Bagualosaurus agudoensis, enquanto para o Noriano da Formação Caturrita são conhecidos Guaibasaurus candelariensis, Unaysaurus tolentinoi e Sacisaurus agudoensis. Visando o melhor entendimento da diversidade de dinossauromorfos oriundos destes depósitos, foram descritos, no contexto dessa tese, diversos novos fósseis do grupo: ULBRA-PVT059, 280, LPRP/USP 0651, MCN PV 10007-8, 10026, 10027 e 10049. Adicionalmente, foi considerado o recente histórico de pesquisas sobre a origens dos dinossauros para examinar o impacto de novas descobertas e das diferentes hipóteses filogenéticas no entendimento dos padrões biogeográficos da irradiação dos dinossauros. ULBRA-PVT059 e 280 representam os holótipos de duas espécies de dinossauromorfos: Ixalerpeton polesinensis e Buriolestes schultzi. I. polesinensis é o primeiro lagerpetídeo descrito para o Brasil e o único no mundo que preserva elementos do crânio e do membro escapular. O material revela que algumas características antes inferidas como sinapomórficas para Dinosauria já estavam presentes em outros dinossauromorfos. B. schultzi é um sauropodomorfo, provável grupo-irmão dos demais representantes do grupo. Além disso, sua anatomia dentária e relações filogenéticas sugerem que os primeiros dinossauros, incluindo os sauropodomorfos, eram adaptados a faunivoria. LPRP/USP 0651 é o holótipo de uma nova espécie de dinossauro, Nhandumirim waldsangae, da Formação Santa Maria. Apesar de incompleto, as partes preservadas mostram que este se tratava de um indivíduo juvenil, mas que difere em vários aspectos dos demais dinossauros do Carniano, em especial daqueles provenientes dos mesmos níveis estratigráficos. As relações filogenéticas de N. waldsangae indicam que o novo táxon se trata de um dinossauro saurísquio não-sauropodomorfo, possivelmente afim aos terópodos. MCN PV 10007-8, 10026, 10027 e 10049 se tratam de materiais de dinossauros provenientes da localidade tipo de Sacisaurus agudoensis. Estes representam um sauropodomorfo morfologicamente mais semelhante a membros mais recentes do grupo do que aqueles do Carniano. Assim, correlações bioestratigráficas sugeridas pela presença destes sauropodomorfos indicam uma idade mais nova para a localidade tipo de S. agudoensis do que a das biozonas carnianas. As análises biogeográficas consistentemente otimizaram a porção sul do Gondwana como a área ancestral de Dinosauria, o mesmo se dando para clados mais inclusivos. Estes resultados mostram que a hipótese em questão é robusta mesmo com maior amostragem taxonômica e geográfica, e independentemente das hipóteses filogenéticas. Desta forma, é demonstrado que não há suporte para a hipótese da Laurásia representar a área ancestral dos dinossauros. / The Triassic deposits of southern Brazil harbor a great diversity of terrestrial tetrapods, including therapsids, rhynchocephalians, rhynchosaurs, and archosaurs like pseudosuchians and dinosauromorphs. In this context, the Carnian Santa Maria Formation is important for the understanding of the origins and early diversifications of Dinosauromorpha, as it bears one of the oldest records for the group worldwide, including some of the oldest dinosaurs. Its dinosauromorph fauna is currently represented by Ixalerpeton polesinensis, Staurikosaurus pricei, Saturnalia tupiniquim, Pampadromaeus barberenai, Buriolestes schultzi, Bagualosaurus agudoensis, and Teyuwasu barberenai. In comparison, the Norian Caturrita Formation have yielded Guaibasaurus candelariensis, Unaysaurus tolentinoi, and Sacisaurus agudoensis. In order to better understand the dinosauromorph diversity from these deposits, several new fossil remains were described as parts of this thesis: ULBRA-PVT 059, 280, LPRP/USP 0651, MCN PV 10007-8, 10026, 10027, and 10049. In addition, the last 20 years of research efforts on the origins of dinosaurs were compiled to investigate the impact of new discoveries and conflicting phylogenetic hypotheses on the biogeographic history of early dinosauromorphs. ULBRA-PVT 059 and 280 represent the holotypes of a lagerpetid dinosauromorph, Ixalerpeton polesinensis, and a sauropodomorph dinosaur, Buriolestes schultzi. I. polesinensis is the first lagerpetid described from Brazil and only worldwide that preserves skull and scapular limb remains, showing that some previously inferred dinosaur synapomorphies were already present in other early diverging dinosauromorphs. B. schultzi is found as the sister-group to all other sauropodomorphs. In addition, its tooth anatomy and phylogenetic position suggest that early dinosaurs, including sauropodomorphs, were adapted to faunivory. LPRP/USP 0651 is the holotype of a new dinosaur, Nhandumirim waldsangae, from the Santa Maria Formation. Although incomplete, the preserved parts show that it was a juvenile individual, but differing in several respects from other Carnian dinosaurs, especially those from the same stratigraphic levels. The phylogenetic relations of N. waldsangae suggest that the new taxon is a nonsauropodomorph saurischian dinosaur, possibly related to theropods. Dinosaur materials from the type-locality of Sacisaurus agudoensis (MCN PV 10007-8, 10026, 10027, and 10049) represent a sauropodomorph, more similar morphologically to later members of the group than to those of Carnian age. Hence, biostratigraphic correlations suggested by these sauropodomorphs indicate an age for the type-site of S. agudoensis younger than that of the Carnian biozones. Biogeographic analyzes consistently optimize southern Gondwana as the ancestral area for Dinosauria, and this is also the case for more inclusive clades. The results show that the South Gondwanan hypothesis for the origin of dinosaurs is robust even with increased taxonomic and geographic sampling, and independent of phylogenetic uncertainties. It is, therefore, demonstrated that there is no support for Laurassia as the ancestral area of dinosaurs.

L’évolution des dinosaures sauropodomorphes et la radiation des grands sauropodes sont encore loin d'être comprises, ni même datées avec précision. Si les premiers sauropodes semblent apparaître à la fin du Trias, ils ne se diversifient qu'à partir du Jurassique moyen. L’incertitude entourant la définition à donner au clade Sauropoda est une des principales causes de l'absence de consensus quant à la transition prosauropodes – sauropodes. C’est ce problème du « stem-group » des sauropodes qui est abordé dans cette thèse. Certains prosauropodes sont ainsi aujourd’hui considérés comme des sauropodes à part entière par certains auteurs. Ces taxons basaux diffèrent cependant beaucoup selon les auteurs. La multiplication des analyses cladistiques n’a rien résolu puisque celles-ci n’ont jamais été comparées entre elles.La découverte en 2008, par une équipe du MNHN, dans le Jurassique inférieur du Lesotho, d'un squelette de prosauropode articulé sert ici de base à une étude anatomique et systématique des sauropodomorphes basaux. De nombreux autres restes de dinosaures inédits du Lesotho appartenant aux collections du MNHN viennent compléter le matériel d’étude. Parmi ceux-ci, du matériel rapporté au prosauropode de Maphutseng et des fossiles attribués au genre Meroktenos sont entièrement décrits en détail pour la première fois.Une comparaison critique et détaillée des analyses phylogénétiques antérieures a été réalisée en utilisant la méthode de cladistique comparée telle qu’elle a été formalisée par Sereno en 2009. Elle a permis de démontrer l’impact très important du choix des caractères et de leur codage sur la topologie des arbres. Suite à cela, un premier retour sur une liste compilée de 449 caractères a été effectué. Il a nécessité la vérification d’une matrice de 15 000 à 20 000 cellules, et plus de 1300 mesures. Ce retour aux caractères ont entraîné la suppression de plus d’une centaine de caractères, et la création d’une matrice inédite de 49 unités taxonomiques et 308 caractères. Les résultats de l’analyse phylogénétique de cette matrice, bien que préliminaires, soulèvent plusieurs points intéressants. Plusieurs clades, généralement retrouvés dans les analyses les plus récentes publiées par d’autres auteurs, n’apparaissent pas. En revanche, des clades qui n’avaient jusque-là jamais été retrouvés font leur apparition. Les différentes analyses pointent également du doigt le problème de l’origine des Sauropodomorpha, et relancent le débat sur l’origine du clade Sauropoda. / The evolution of sauropodomorph dinosaurs and the radiation of the large sauropods are still far from being understood and well-dated. If the first sauropods seem to appear at the end of the Triassic, they don’t start to diversify before the Middle Jurassic. The uncertainty surrounding the definition of the clade Sauropoda is one of the main causes of the lack of consensus regarding the prosauropod – sauropod transition. It is this issue of the “stem-group” of sauropods that is dealt with in this thesis. Some prosauropods are now considered to be sauropods by some authors. These basal taxa differ a lot depending on the authors. The multiplication of the cladistic analyses didn’t solve the problem as they never were compared.The discovery in 2008, by a MNHN team, in the Early Jurassic of Lesotho, of a prosauropod articulated skeleton is used herein as the basis for anatomical and systematic study of basal sauropodomorphs. Many other new dinosaur remains from Lesotho, housed in the MNHN collections, complement the study material. Among these, material referred to the Maphutseng prosauropod and fossils referred to the genus Meroktenos are described in details for the first time.A critical and detailed comparison of previous phylogenetic analyses is performed, using the comparative cladistics method as formalized by Sereno in 2009. This work allowed to highlight the significant impact of the choice of characters and their scoring on the topology of the trees. After that, a first reappraisal of a list of 449 compiled characters was carried out. It required the reexamination of a matrix consisting in 15 000 to 20 000 cells, and more than 1300 measures. This work led to remove more than one hundred morphological characters, and the building of a new matrix including 49 taxonomic units and 308 characters. The results of the phylogenetic analysis, although preliminary, raise some interesting points. Several clades, often recovered in the most recent analyses published by other authors, are not recognized here. However, clades that had, until then, never been found, are recovered. The different analyses also point out the hurdle of the origin of Sauropodomorpha, and reopen the debate on the origin of Sauropoda.

For 130 years dinosaurs have been divided into two distinct clades – Ornithischia and Saurischia. This dissertation looks at the earliest evolution of the clade Dinosauria by focusing upon the interrelationships of the major subsidiary clades within it. It does this following examination, comparison and description of early dinosaur material, and by utilising modern phylogenetic analysis techniques, to rigorously and objectively test the fundamental groupings within the clade Dinosauria using a newly compiled dataset of early dinosaurs and other dinosauromorphs (= close dinosaur relatives). The current consensus on how the principal clades within Dinosauria (Theropoda, Sauropodomorpha and Ornithischia) are related to one another is challenged by the results of these analyses. This study finds, for the first time, a sister-group relationship between Ornithischia and Theropoda, here termed Ornithoscelida. Consequently, a new definition for Dinosauria is presented, as the historic definition would exclude all members of Sauropodomorpha from the clade. As well as this, I propose revisions to the definitions of each of the principal dinosaurian sub-divisions and propose a new timeframe and geographic setting for the origin of Dinosauria. These new hypotheses force re-evaluations of early dinosaur cladogenesis and character evolution, suggest the independent acquisition of hypercarnivory in multiple dinosaur groups and offers an explanation for many of the anatomical features previously regarded as striking convergences between theropods and early ornithischians. As well as presenting new anatomical data on many early dinosaurs and dinosauromorphs, including a comprehensive re-description of the postcranial anatomy of Lesothosaurus diagnosticus (Chapter 2), and a new anatomical dataset of early dinosaurs (the largest ever compiled), this thesis goes on to implement the new dataset to investigate a number of important outstanding questions about early dinosaur evolution and provides new lines of enquiry for future workers to pursue. The results of this thesis reveal the oldest known members of the dinosaurian clades Theropoda and Sauropodomorpha (Chapter 6), as well as a new clade within Ornithischia; a taxon previously thought to represent a derived theropod has been recovered as a potential ‘missing link’ between theropods and ornithischians using the new dataset. This work now provides a unique tool for the assessment of the phylogenetic affinities of early dinosaurs and dinosauromorphs and, once published, will hopefully become the benchmark dataset for palaeontologists working in this area.