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The Kremmling Paleontological Resource Area (KPRA) contains one of the most fossiliferous units within the Late Cretaceous Western Interior Seaway of North America. It was deposited during the late Campanian Baculites compressus/cuneatus ammonite biozones ((\approx) 72.5 Ma) and records slightly less than one million years of depositional history. Examination of the fauna, its dominant preservational mode and taphonomy as well as the lithologic evidence from measured stratigraphic sections strongly suggests that the depositional environment of the KPRA was a shallow, relatively nearshore environment. A detailed taxonomic examination of the molluscan fauna was undertaken in order to re-evaluate past work as well as to more thoroughly document the fauna. Samples were collected from 79 locations within the (\approx) 1 km² study area. The molluscan fauna from the KPRA consists of 47 bivalve, 22 gastropod, and 13 cephalopod species; ten of these species are new. In addition, two inarticulate brachiopods and one serpulid are described. This highly diverse assemblage points to an increase in nearshore diversity as compared to faunas described from earlier intervals with similar environmental settings. The timing of this increase in species richness remains elusive, but may have initiated in the late Campanian and continued into the early Maastrichtian.

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

The Campanian Iles Formation of the Mesaverde Group in northwestern Colorado contains a stacked series of some 11 shoreline sequences that form clastic wedges extending east and southeastwards from the Sevier orogenic belt to the Western Interior Seaway. Iles Formation shorelines and their alluvial and coastal plain equivalents (Neslen Formation, Trail and Rusty members of the Ericson Formation) are well exposed from Utah and from southern Wyoming into northwestern Colorado. The Iles Clastic Wedge was examined in the subsurface Piceance Basin and at outcrops in Meeker and south of Rangely, NW Colorado. The clastic wedge contains low-accommodation regressive-transgressive sequences (8-39 m thick) of Loyd Sandstones, Sego Sandstone, Corcoran Member, and Cozzette Member and their updip-equivalent Neslen Formation strata. Facies associations of the sandstone succession indicate storm-wave dominated coasts that transition seaward into offshore/prodelta mudstones with thin-bedded sandstones and extend landward into tidal/fluvial channels and coal-bearing strata; facies associations also indicate interdeltaic coastal embayments with moderate tidal influence. 14, 75-km-long Piceance Basin transects (dip and strike oriented) makes it possible to evaluate coastline variability, and the progressive southeasterly pinchout of the 11 coastline tongues within the larger Iles Clastic Wedge. The thickness and great updip-downdip extent of the Iles stratigraphic sequences (compared to the underlying Blackhawk or overlying Rollins sequences) support previous observations of a low accommodation setting during this time. It has been suggested that this low accommodation was caused by combined effects of embryonic Laramide uplifts and Sevier subsidence across the region. Uplift or greatly reduced subsidence across the Western Interior Seaway would have caused an increase in coastal embayments as well as generally accelerated coastal regressions and transgressions in this 3.3 My interval. / text

No description available.

No description available.