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

The Gray Fossil Site, Washington County, Tennessee, has produced a remarkable Mio-Pliocene fauna and flora with no known correlative in the Appalachian region. After its discovery in 2000, a series of auger holes were drilled by the Tennessee Department of Transportation (TDOT) to determine the areal extent of the site. Drilling indicated that the fossils occurred in fill material within a paleokarst basin, but the distribution of boreholes does not permit details of sinkhole topography, and therefore its formation and fill history, to be adequately resolved. To better image the sinkhole basin, a high-resolution gravity survey, which included 1104 gravity measurement stations, was conducted. These data were used to create complete Bouguer and residual gravity anomaly maps and a 3D density model via inversionmethods. The residual gravity anomaly map compares favorably with 29 TDOT auger holes drilled to basement, but contains significantly more detail. The residual gravity anomaly map reveals the presence of seven separate sinkholes. However, 3D inverse modeling constrained by drill-hole depths and density data indicates that there are 11 separate sinkholes formed within the Knox Group carbonates. These sinkholes, which range between 20 and 44 m in depth, are aligned along northwest and northeast trending linear features that correlate to structural features formed during the Appalachian orogenies. It is possible that the overall sinkhole basin formed as the result of partial coalescence of multiple sinkhole structures controlled by a joint system and that the sinkholes then acted as a natural trap for the Gray Fossil Site fauna and flora.

No description available.

This work is mainly based on the collection of Neogene (Miocene-Pliocene) odontocetes (toothed whales) from the area of Antwerp (northern Belgium, southern margin of the North Sea Basin) preserved at the Institut royal des Sciences naturelles de Belgique (IRSNB). The systematic revision of members of the long-snouted dolphin family Eurhinodelphinidae leads to the description/re-description of five species in the genera Eurhinodelphis (E. cocheteuxi and E. longirostris), Schizodelphis (S. morckhoviensis), and Xiphiacetus n. gen. (X. cristatus and X. bossi). Furthermore, the systematic status of several eurhinodelphinid species from other localities in the world is revised. A cladistic analysis with the parsimony criterion is undertaken to highlight the phylogenetic relationships of several eurhinodelphinid taxa with other fossil and extant odontocetes. Eurhinodelphinids are more closely related to the beaked whales; the latter are distinctly separated from the sperm whales. A second analysis, with a likelihood criterion, reaches nearly identical results. Then a separate parsimony analysis investigates the relationships within the family Eurhinodelphinidae; the results suggest sister-group relationships between Schizodelphis + Xiphiacetus and Ziphiodelphis + (Mycteriacetus + Argyrocetus) and a more stemward position for Eurhinodelphis. After that, anatomical, palaeogeographic, and phylogenetic data allow several suggestions about the ecological features of the eurhinodelphinids. The extinction of this family, before the end of the Miocene, is commented, related to the changes in the biodiversity of other odontocete groups and to a contemporary major sea level drop. Members of the family Platanistidae, subfamily Pomatodelphininae, are recorded for the first time in the Miocene of the North Sea, on the basis of several long-snouted specimens. The review of the large collection of Neogene beaked whales (Ziphiidae) from the IRSNB diagnoses eleven species in seven genera: Aporotus recurvirostris, A. dicyrtus, Beneziphius brevirostris n. gen. n. sp., Cetorhynchus atavus, Choneziphius planirostris, C. macrops, Mesoplodon longirostris, Ziphirostrum marginatum, Z. turniense, Z. recurvus, and Archaeoziphius microglenoideus n. gen. n. sp. The latter is dated with dinoflagellates from the Middle Miocene; it constitutes the oldest beaked whale known by diagnostic cranial material. A parsimony analysis indicates sister-group relationships between Ziphirostrum + Beneziphius and Choneziphius + (Tusciziphius + Ziphius). A functional anatomy chapter deals with the pachy-osteosclerotic structure of the rostrum in several beaked whale species from Antwerp; several functional hypotheses (including deep diving and intraspecific fights) are confronted to data on extant taxa and to the evolutionary history of the family. Finally, the review of the Miocene short-snouted dolphin species Protophocaena minima leads to the first European record of members of the family Pontoporiidae.

Gnathostomes, or jawed vertebrates, make up the overwhelming majority of modern vertebrate diversity. Among living vertebrates, they comprise the chondrichthyans (“cartilaginous fishes” such as sharks, skates, rays, chimaeras) and the osteichthyans (“bony fishes” or bony vertebrates, inclusive of tetrapods). Gnathostomes appear to have originated in the early Palaeozoic Era, but their early fossil record is fairly scant. The best fossils appear first in the Late Silurian and Devonian periods. Much of gnathostome diversity owes to unique adaptations in the internal skeleton of their head (the endocranium). The endocranium is composed of the braincase, jaws, hyoid arch, and branchial arches, which sometimes fossilise when they are composed of bone or calcified cartilage. The purpose of this thesis is to describe and compare the fossilised cranial endoskeletons of a variety of different Palaeozoic gnathostomes. The objective is to test current conceptions of gnathostome interrelationships (i.e. phylogeny) and infer aspects of key morphological transformations that took place during the evolution of Palaeozoic members of this group. Two key areas are examined: the morphology and interrelationships of Palaeozoic gnathostomes and the morphology of the visceral arches in sarcopterygian fishes. New data on the visceral arches are described from the stem tetrapods Panderichthys and rhizodontids. These provide insight into the sequence of character acquisition leading to the tetrapod middle ear. Panderichthys shows key features of the tetrapod middle ear chamber were established prior to the origin fo digited limbs. New morphological data are described from the “acanthodian” fish Ptomacanthus. Ptomacanthus provides only the second example of a well-preserved braincase from any member of this group. It shows dramatic differences from that of its counterpart, Acanthodes, providing new evidence for acanthodian paraphyly. New interpretations of basal gnathostome and osteichthyan phylogeny are presented, challenging or enriching existing views of these problems.

Approximately 600 to 500 million years ago, a major evolutionary radiation called the “Cambrian Explosion” gave rise to nearly all of the major animal phyla known today. This radiation is recorded by various fossil lagerstätten, such as the Burgess Shale in Canada, where soft-bodied animals are preserved in exquisite detail. Many Cambrian fossils are enigmatic forms that are morphologically dissimilar to their modern descendants, but which still provide valuable information when interpreted as stem-group taxa because they record the actual progression of evolution and give insight into the order of character acquisitions and homologies between living taxa. One such group of fossils is the anomalocaridids, large presumed predators that have had a complicated history of description. Their body has a trunk with a series of lateral lobes and associated gills, and a cephalic region with a pair of large frontal appendages, a circular mouth apparatus, stalked eyes and a cephalic carapace. Originally, two taxa were described from the Burgess Shale, Anomalocaris and Laggania, however data presented herein suggests that the diversity of the anomalocaridids was much higher. Newly collected fossil material revealed that a third Burgess Shale anomalocaridid, Hurdia, is known from whole-body specimens and study of its morphology has helped to clarify the morphology and systematics of the whole group. Hurdia is distinguished by having mouthparts with extra rows of teeth, a unique frontal appendage, and a large frontal carapace. Two species, Hurdia victoria and Hurdia triangulata were distinguished based on morphometric shape analysis of the frontal carapace. A phylogenetic analysis placed the anomalocaridids in the stem lineage to the euarthropods, and examination of Hurdia’s well-preserved gills confirm the homology of this structure with the outer branches of limbs in upper stem-group arthropods. This homology supports the theory that the Cambrian biramous limb formed by the fusion of a uniramous walking limb with a lateral lobe structure bearing gill blades. In this context, new evidence is present on the closely allied taxon Opabinia, suggesting that it had lobopod walking limbs and a lateral lobe structure with attached Hurdia-like gills. The diversity of the anomalocaridids at the Burgess Shale is further increased by two additional taxa known from isolated frontal appendages. Amplectobelua stephenensis is the first occurrence of this genus outside of the Chengjiang fauna in China, but Caryosyntrips serratus is an appendage unique to the Burgess Shale. To gain a better understanding of global distribution, a possible anomalocaridid is also described from the Sirius Passet biota in North Greenland. Tamisiocaris borealis is known from a single appendage, which is similar to Anomalocaris but unsegmented, suggesting this taxon belongs to the arthropod stem-lineage, perhaps in the anomalocaridid clade. Thus, the anomalocaridids are a widely distributed and highly diverse group of large Cambrian presumed predators, which provide important information relevant to the evolution of the arthropods.

The Proterozoic period saw some of the most fundamental revolutions in the biological and geological world. During this period, life diversified and set the stage for the radiation of multicellular life, altering the face of the planet in the process. The fossil record of this time is not yet fully understood, and a revisitation of a historically reported fossil deposit in the 1 Ga Torridon rocks of northwest Scotland shows that they host the fossils of the earliest non-marine eukaryotes, as well as a full and diverse fossil assemblage preserved in sedimentary phosphates and shales. Fine scale sedimentology of the fluvio-lacustrine rocks of the Torridon Group reveals them to be laid down in a laterally variable basin with distinctly different palaeoenvironments. The resident biota is seen to be similarly variable between lithofacies. New criteria for classifying taphonomic effects are presented, and used to characterise assemblages from different palaeoenvironments, with broader applications beyond this study. The Torridon rocks are also host to macrostructures on the surfaces and soles of beds, and these are interpreted as of likely biological origin, with their variability mapped between different lithofacies. High-resolution studies of both the preserved biota and the mineralogy of the preserving medium reveal in detail not only the fine scale structure of the fossil organisms, but also the reasons for their exceptional preservation. Phosphate is analysed in detail to explain its enigmatic occurrence in Proterozoic lakes. To place the Torridon deposits in context, both older and younger rocks were examined in comparison, from the 2 Ga Gunflint Formation of Ontario, Canada, and the Precambrian-Cambrian successions of eastern Newfoundland respectively. New finds of phosphate in these rocks help to reveal biochemical interactions and evolution on the early Earth, with implications for further understanding life on our own planet and elsewhere.

No description available.

The Deadhorse Coulee Member of the Milk River Formation of southern Alberta preserves one of the oldest well-documented non-marine vertebrate assemblages in Canada. In this study, the taxonomic diversity of this member is updated, and vertebrate localities are placed in geographic and stratigraphic context. The stratigraphic provenance of specimens indicates all vertebrate material from this member is latest Santonian (83.5 Ma). A new species of turtle is described. Analyses of the rank and relative abundances of taxa support interpretations of this member as a prograding clastic wedge with localities approximately 40 km from the palaeoshoreline at time of deposition. Results support high local abundances of vertebrates in western North America, with faunal provincialism regulated by distance to the palaeoshoreline and mean annual temperatures. Morphologic changes in small theropod taxa through the latest Cretaceous of western North America act as a case study for evaluating species turnover of vertebrate microfossil material. / Systematics and Evolution

There are over 18,500 living species of acanthomorph (spiny-rayed fishes), and they represent half of all living fish species and a third of extant vertebrates. They inhabit countless ecological niches, they are incredibly diverse, and they have developed a number of specialised morphological innovations. The earliest acanthomorphs are known from the Cenomanian, but they were neither diverse not abundant during the Cretaceous period. Following the end-Cretaceous extinction event, the acanthomorphs radiated, and by the Eocene they were anatomically modern. However, our understanding of the relationships between most fossil and living acanthomorphs, and the macroevolutionary processes behind their rise to dominance in the Recent, are poorly known. In this thesis, I aimed to develop our understanding of the evolution of the acanthomorphs by combining palaeontological and neontological data. I undertook three separate projects to accomplish this. First, I studied the anatomy two fossil representatives (†Aipichthys pretiosus and †'Aipichthys' nuchalis) of a primitive acanthomorph lineage, the lampridomorphs. I then placed these taxa in a phylogenetic analysis to reveal the pattern of character evolution leading to the crown-group. Second, I aimed to understand the morpho- logical condition at the base of the acanthomorph tree by studying the relationships between two extinct groups (†Ctenothrissiformes and †Pattersonichthyiformes) that may have branched from the acanthomorph stem. Phylogenetic analyses utilising morphological and molecular data support a stem ctenosquamate placement for these taxa. Third, using a timescaled supertree, I studied the evolution of one of the major acanthomorph innovations, the protrusile upper jaw. The combination of palaeontological and neontological data provided deep insight into the evolution of the acanthomorphs, and allowed for the identification of patterns and processes that could not be identified from studying extant taxa in isolation.