Thesis (Ph.D.)--University of Puerto Rico, Mayaguez Campus, 2005. / Includes bibliographical references.

No description available.

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

presented. Several new proposals are made for the measurement and classification of fossil footprints. Field studies by the author have revealed many new vertebrate footprint discoveries in the British Triassic, including one at Hilbre, Wirral which is one of the most complete footprint assemblages found in recent years. Field case studies are presented for three localities: The Bendricks in S, Wales, Hilbre Island, Wirral, and Hollington, Staffordshire. New discoveries at Hollington confirm that the site has a typical Mid Triassic assemblage of footprints of medium-sized archosaurs (Chirotherium sp.) and small diapsids (Rhynchosauroides sp.). The Hollington footprint assemblage is comparable to better-known assemblages from Storeton and Runcorn in Cheshire dated as Lower Anisian. The sedimentary nature and organisation of the lithofacies suggests a fluvial environment which was initially of low sinuosity but became more sinuous later. A major review of the ichnofamily Chirotheriidae in the British Triassic shows that there are at least three valid ichnospecies of Chirotherium, one of Synaptichnium, and one of Isochirotherium. The presence of a fourth related ichnogenus. Brachychirotherium. is unclear and cannot yet be confirmed in Britain. A comparison of the lithostratigraphy of footprint localities shows that Chirotherium. Synaptichnium and Isochirotherium can only be confirmed in British Middle Triassic rocks of Lower - Middle Anisian age. These results are almost certainly not a true reflection of the stratigraphic distribution of these ichnogenera, but probably highlight the facies dependant nature of footprint preservation. Probable Chirotheriidae footprint forms occur throughout the British Triassic in rocks of Lower Scythian to possibly Upper Norian age. Unfortunately, the quality of Lower and Upper Triassic specimens obtained to date is relatively poor; hence identification of these footprints to ichnogenus level is difficult. A taxonomic review of the morpho-family Rhynchosauriidae in the British Triassic was undertaken. There is evidence to suggest that the "Rhynchosaurus" footprints found by Ward at Grinshill, Shropshire, in 1838, which later gave rise to the establishment of the ichnogenus Rhynchosauroides. should be reassigned to the ichnogenus Rotodactylus Peabody 1948. This study confirms the occurence of Rotodactyl us in the British Triassic. Twenty British Triassic footprint forms that have been previously, or are presently, assigned to the ichnogenus Rhynchosauroides, together with five other related forms have been restudied. Two are considered to be Rotodactylus sp.; one is reassigned to the chirotheroid ichnogenus Synaptichnium sp.; five are considered poorly preserved examples of either Rotodactylus or Rhynchosauroides and have been reassigned to ichnogenus indet; one is considered to be an inorganic sedimentary structure and is referred to ichnotaxa indet; and only six are considered to be forms of Rhynchosauroides. Rhynchosauroides is recorded and confirmed from at least twelve British localities, and Rotodactylus from seven.The lithostratigraphic range of Rotodactylus is ?Middle Scythian - Middle Anisian, Lower - Middle Triassic. The lithostratigraphic range of Rhynchosauroides is ?Middle Scythian -Upper Carnian (possibly Norian), Lower - Upper Triassic. The oldest skeletons of dinosaurs date from the Late Triassic (Carnian) but supposed dinosaur footprints have been reported from Early and Mid Triassic ;rocks dated up to 20 Myr: ~earlier. A restudy of several.museum specimens was undertaken; supposed Lower Triassic dinosaur footprints from Britain are reinterpreted as ripple marks, mud rip-up clasts, and possible limulid prints. The Middle Triassic material is reinterpreted as partial specimens of Chirotherium , presumably produced by rauisuchians and one indeterminate specimen, possibly also of chirotheroid affininites. The oldest dinosaur footprints from Britain come from the marginal Triassic (Non an, Upper Triassic) in South Wales. Elsewhere 10 the world, the oldest dinosaur footprints appear to be Carnian corresponding in age to the oldest skeletal remains

Jawed vertebrates (gnathostomes) consist of two clades with living representatives, the chondricthyans (cartilaginous fish including sharks, rays, and chimaeras) and the osteichthyans (bony fish and tetrapods), and two fossil groups, the "placoderms" and "acanthodians". These extinct forms were thought to be monophyletic, but are now considered to be paraphyletic partly due to the discovery of early chondrichthyans and osteichthyans with characters that had been previously used to define them. Among these are fin spines, large dermal structures that, when present, sit anterior to both median and/or paired fins in many extant and fossil jawed vertebrates. Making comparisons among early gnathostomes is difficult since the early chondrichthyans and "acanthodians", which have less mineralized skeleton, do not have large dermal bones on their skulls. As a result, fossil fin spines are potential sources for phylogenetic characters that could help in the study of the gnathostome evolutionary history. This thesis examines the development and internal structure of fin spines in jawed vertebrates using two-dimensional (2D) thin sections and three-dimensional (3D) synchrotron datasets. The development of the dorsal fin spine of the holocephalan, Callorhinchus milii, was described from embryos and compared to that of the neoselachian, Squalus acanthias, whose spine has been the model for studying fossil shark spines. It was found that the development of the C. milii fin presents differences from S. acanthias that suggest it might be a better candidate for studying "acanthodian" fin spines. The 3D histology of fossil fin spines was studied in Romundina stellina, a "placoderm"; Lophosteus superbus, a probable stem-osteichthyan; and sever­­al "acanthodians". The 3D vascularization reconstructed from synchrotron radiation microtomographic data reveal that "acanthodian" and Lophosteus spines grew similarly to what is observed in chondrichthyans, which differs slightly from the growth of the Romundina spine. Chondrichthyans and "acanthodians" also share similarities in their internal organization. Overall, Lophosteus and Romundina spines are more similar in terms of morphology and histology compared to chondrichthyans and "acanthodians". These results support the current hypothesis of gnathostome phylogeny, which places "acanthodians" on the chondrichthyan stem. They also emphasize the need for further study of vertebrate fin spines using 3D approaches.

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.

No description available.

Within animal societies, individuals often differ greatly in their level of investment in cooperative activities. Individuals are predicted to show high cooperative investment if high levels of relatedness lead to large indirect fitness benefits, or if differences in individual characteristics such as age, sex, rank, or body condition increase the direct fitness benefits of helping. However, individual differences often persist after these differences are controlled for; a residual variation that remains unexplained. Understanding the proximate mechanisms underlying variation in behaviour can give novel insights into the selection pressures shaping behavioural differences. This suggests that a research focus onto the proximate mechanisms underpinning cooperative behaviours is needed to further our understanding of why individuals behave differently within social groups. In this thesis, I address this shortfall in understanding by investigating hormonal variation alongside individual differences in cooperative investment in the banded mongoose (Mungos mungo). Banded mongooses are a highly social carnivore with two highly conspicuous forms of cooperative offspring care that are easily measurable and show large inter-individual variation. In chapter 3, I demonstrate a negative carry-over effect of investment in offspring care in consecutive breeding attempts. I show that this carry-over effect is mediated by variation in glucocorticoid concentrations, which may be attributable to the energetic costs of helping. Glucocorticoids predict investment in offspring care, suggesting that this mechanism may drive inter-individual variation in cooperative investment. In chapter 4, I find evidence for a testosterone mediated trade-off between offspring care and mating effort, which suggests that inter-individual differences may also be driven by variation in the costs of helping attributable to missed mating opportunities. In chapter 5, I use simulated territorial intrusions to show that there is unlikely to be a trade-off between offspring care and territory defence in banded mongoose societies. However, carers and non-carers show a differential physiological response to territorial intrusion, suggesting that there may be a more subtle behavioural trade-off that occurs post-intrusion. In chapter 6, I find evidence for consistent individual differences in both cooperative and competitive behaviours, which suggests that individual differences in adult behaviour may be determined by early-life effects. Individual differences in cooperative investment are positively correlated, suggesting that individuals are not specialised to different cooperative activities, but are consistently either helpful or selfish. Together, these results give insights into the selection pressures shaping individual differences and highlight endocrine research as a valuable tool in understanding the evolution of cooperative societies.

No description available.

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