Student Number : 9202936M - PhD thesis - School of Geoscience - Faculty of Science / Kannemeyeria simocephalus is probably the best known Middle Triassic dicynodont from South Africa and has been the standard against which other Triassic dicynodonts are compared. In the past studies have concentrated on the cranial morphology of K. simocephalus and how this affected Triassic dicynodont taxonomy and phylogeny. There has been little work on the postcranial anatomy of K. simocephalus, which remains poorly understood. This current study undertook a detailed descriptive analysis of the postcranial anatomy of K. simocephalus that lead to the identification of diagnostic characters of the postcranial skeleton. During the course of the analysis of the postcranial anatomy of K. simocephalus it was noted that material previously assigned to this taxon was significantly different from that recognised as K. simocephalus. Unfortunately, this material consists only of postcranial material and it is therefore referred to as Morphotype B rather than a new species of Kannemeyeria or as a new taxon from the Cynognathus Assemblage Zone (subzone B). A phylogenetic analysis was performed which included K. simocephalus and Morphotype B, and used cranial and postcranial characters. The preliminary phylogenetic results show that there are possibly two taxa of medium to large dicynodonts in the Cynognathus Assemblage Zone (subzone B); one a kannemeyeriid and the second a stahleckeriid. It has also evident that more attention needs to be paid to the study of the postcranial anatomy of Triassic dicynodonts, especially those from Africa and Asia.

Mosasauria is a clade of essentially Late Cretaceous marine reptiles. Although well known by several nicely preserved specimens, phylogenetic relationships of mosasaurians within Squamata are still a matter of intense debate. Most of the works discussing the relationships of mosasaurians in global contexts of squamates were based mainly on more derived taxa, including only few basal forms. Here the anatomy, phylogeny, ontogeny and taxonomy of the basalmost mosasaurian radiation, the commonly known \"dolichosaurs\", is reviewed, mostly on the light of new and exquisitely preserved coniasaur remains from Texas. New remains described here encompass dozens of specimens, including a new species represented by a gravid female and several embryos. A revision of the genus Coniasaurus suggest it as encompassing four species: C. crassidens, C. longicollis (former Dolichosaurus longicollis), C. gracilodens and the new taxon described here. Contrary to what is observed in more derived forms, the patterns of tooth attachment in coniasaurs are very similar to those of varanoids, suggesting similarities between tooth attachment and implantation in snakes and derived mosasaurs to be the result of homoplasies. The evolution of the dolichosaurian postcranial anatomy is assessed, finding new diagnostic characters for several distinct lineages. A phylogenetic analysis of Mosasauria in a global matrix of squamates, including the largest sample of basal forms ever tested, consistently found the group to be closely related to Varanoidea, rejecting the hypotheses of the group being closely related either to snakes or lying in a more basal position among squamates. Results gathered by this thesis are expected to greatly contribute to the knowledge of this astonishing group / Mosasauria é um clado formado essencialmente por répteis marinhos do Cretáceo Superior. Embora bem conhecido por diversos espécimes, as relações filogenéticas do grupo dentro de Squamata formam um tópico de intenso debate. A maior parte dos trabalhos discutindo o tema em análises globais de Squamata foram baseadas em táxons mais derivados, incluindo apenas poucas formas basais. Aqui, a anatomia, filogenia, ontogenia e taxonomia da irradiação mais basal do grupo, os \"dolicossauros\", foi revista, principalmente à luz de novos restos fósseis de coniassauros do Texas. Os novos fósseis descritos aqui englobam dezenas de espécimes, incluindo uma nova espécie representada por uma fêmea gravida e diversos embriões. Uma revisão do gênero Coniasaurus sugere que o mesmo engloba quatro espécies: C. crassidens, C. longicollis (antes Dolichosaurus longicollis), C. gracilodens e o novo táxon descrito aqui. Ao contrário do observado em formas mais derivadas, os padrões de fixação dentária nos coniassauros é muito similar àqueles dos varanóides, sugerindo que as similaridades observadas nestes padrões entre serpentes e mosassauros derivados resulta da ocorrência de homoplasias. A evolução do esqueleto pós-craniano dos dolicossauros foi avaliada, encontrando novos caracteres diagnósticos para diferentes linhagens. Uma análise filogenética de Mosasauria em uma matriz global de Squamata, incluindo a maior amostragem de formas basais já testada, consistentemente encontrou o grupo como proximamente relacionado ao clado Varanoidea, rejeitando hipóteses de proximidade com serpentes ou numa posição mais basal dentro de Squamata. Espera-se que os resultados provenientes desta tese contribuam consideravelmente para o conhecimento deste incrível grupo