bluuebunny/crossref_metadata_2025_split huggingface dataset:
Devonian rhizodontids and tristichopterids (Sarcopterygii; Tetrapodomorpha) from East Gondwana
Authors: Johanson Zerina , Ahlberg Per E. 
Published: July 2007

ABSTRACTDevonian rhizodontid fishes from East Gondwana include Gooloogongia loomesi Johanson & Ahlberg 1998 from near Canowindra, New South Wales (NSW), Australia and Aztecia mahalae gen. nov., sp. nov. from southern Victoria Land, Antarctica. Gooloogongia loomesi is known from well-preserved cranial and postcranial material, and as such represents the most complete rhizodont known. Newly discovered elements (braincase, pelvic girdle) are described for the first time. Aztecia mahalae gen. nov., sp. nov. is based on shoulder girdle material formerly assigned to Notorhizodon Young et al. 1992, which, based on skull and lower jaw morphology, is a member of the Tristichopteridae. The presence of several plesiomorphic characters suggests that Gooloogongia occupies a basal phylogenetic position within the Rhizodontida, while Aztecia n. gen. possesses a more derived shoulder girdle. We argue that the Rhizodontida evolved on the Gondwanan landmass. Notorhizodon occupies a relatively derived position within the Tristichopteridae, but is contemporary with the earliest and phylogenetically most basal Laurussian members of the group. This shows that the tristichopterids achieved a worldwide distribution considerably earlier than previously thought.
The tetrapod Caerorhachis bairdi Holmes and Carroll from the Lower Carboniferous of Scotland
Authors: Ruta Marcello , Milner Andrew R. , Coates Michael I. 
Published: July 2007

ABSTRACTThe tetrapod Caerorhachis bairdi, probably from the Pendleian Limestone Coal Group in the Scottish Midland Valley, is rediagnosed and redescribed, and its affinities are discussed. Caerorachis was originally interpreted as a temnospondyl amphibian, based on characters that are now regarded as primitive for tetrapods, or of uncertain polarity. Several features of Caerorhachis (e.g. gastrocentrous vertebrae, curved trunk ribs, reduced dorsal iliac blade, L-shaped tarsal intermedium) are observed in certain primitive amniotes. In particular, Caerorhachis resembles ‘anthracosaurs’, generally considered to be among the most primitive of stem-group amniotes.The phylogenetic position of Caerorhachis is considered in the light of recently published cladistic analyses of Palaeozoic tetrapods. Most analyses place Caerorhachis at the base of, or within, ‘anthracosaurs’. When multiple, equally parsimonious solutions are found, its ‘anthracosaur’ affinities are shown in at least some trees, and are supported by several informative and, generally, highly consistent characters. Alternative phylogenetic placements (e.g. sister taxon to temnospondyls) are usually less well corroborated.If the fundamental evolutionary split of most early tetrapods into stem-group lissamphibians (e.g. temnospondyls) and stem-group amniotes (e.g. ‘anthracosaurs’) is accepted, then the revised interpretation of Caerprhachis sheds light on near-ancestral conditions for Amniota.
The age of the Middle Cambrian ‘Paradoxides forchhammeri Grit’ of the Wrekin district, Shropshire, England
Authors: Rushton A. W. A. , Berg-Madsen V. 
Published: July 2007

ABSTRACTThe fossiliferous bed in the Upper Comley Sandstone, described by Cobbold & Pocock (in 1934) as the ‘Paradoxides forchhammeri Grit’ and correlated by them with the Andrarum Limestone of the late Middle Cambrian (P. forchhammeri Stage) in Scandinavia, is shown to be a shallow-water development of the older punctuosus Zone (medial Middle Cambrian, P. paradoxissimus Stage). It is here re-named the ‘Rushton Brook Bed’. The trilobite fauna, formerly considered comparable with that of the Andrarum Limestone, is reviewed and found taxonomically distinct, the supposed similarities being attributable to facial and preservational factors.
A monograph of the Bradoriid arthropods from the Lower Cambrian of SW China
Authors: Xian-guang Hou , Siveter David J. , Williams Mark , Xiang-hong Feng 
Published: July 2007

ABSTRACTThis paper evaluates the taxonomy, biostratigraphy, and palaeogeographical significance of the Cambrian bradoriid arthropods of China, the majority of which occur in the lower Cambrian of SW China. Of bradoriid faunas world-wide, Chinese occurrences yield the greatest number of specimens and a comparatively high diversity at all taxonomic levels. Nevertheless, taxonomic diversity is much less than previously supposed. Some 80 bradoriid genera and nearly 300 species have been proposed on the basis of Chinese material. By contrast, in our study, which encompasses all of the important Chinese bradoriid faunas, we recognise only 16 genera and 21 species, including those treated under open nomenclature. Interpretation of deformed specimens as discrete species and lack of application of the rules of the International Code of Zoological Nomenclature resulted in taxonomic splitting and a proliferation of names. There are an additional 12 poorly known monotypic genera of uncertain systematic status that are listed but not treated further herein. One phosphatocopid species, a group originally thought closely related to the Bradoriida, is also described.Most Chinese bradoriid material is known from Yunnan Province; the group also occurs in Guizhou, Henan, Hubei, Hunan, Liaoning, Qinghai, Shaanxi, Sichuan, Xinjiang and Zhejiang provinces. The first bradoriids occur just below the Abadiella trilobite Biozone. They are most prolific and diverse in the Qiongzhusian Stage, constituting the most abundant animal group; the succeeding Canglangpuian Stage contains fewer individuals and species. A previously proposed bradoriid biozonal scheme lacks rigour and is of little practical value: of the five supposed biozones, two correspond to trilobite zones and three are based on taxa that herein are considered to belong to a single species.Palaeogeographically the bradoriids occur in the Middle and especially the Western subprovinces of the Cambrian of the SW China (Yangtze) Platform. Almost all of the bradoriid genera and species are endemic to that region. The palaeogeographical links with other bradoriid faunas are mostly within the Redlichiid trilobite Realm, with areas such as N China, Australia and parts of central Asia.
Stratigraphy and geochemistry of volcanic mass flows in the Stac Fada Member of the Stoer Group, Torridonian, NW Scotland
Authors: Young Grant M. 
Published: July 2007

ABSTRACTThe Stac Fada Member, which forms part of the Stoer Group, contains the only definitive evidence of volcanic activity within the thick Torridonian succession. At the type area in the Bay of Stoer, four volcanic-rich sandy mudstone units are recognised in the Stac Fada. An irregular erosional contact at the base of the main Stac Fada unit truncates two thinner layers of similar volcanic-rich material that were formerly interpreted as intrusions. Directional sedimentary structures associated with the Stac Fada mass flows, and the distribution and thickness of an accretionary or armoured lapilli tuff, support the existence of at least two volcanic sources. Geochemical evidence suggests that the thick Stac Fada unit at the Bay of Stoer and comparable units to the SW were derived from the same volcanic centre. The chemical composititon of volcanic fragments in the main Stac Fada unit indicates that their potassic nature is not a primary feature but is due to alteration and subsequent metasomatism.
Shark fauna and depositional environment of the earliest Cretaceous Vitabäck Clays at Eriksdal, southern Sweden
Authors: Rees Jan 
Published: July 2007

ABSTRACTA section of the Vitabäck Clays at Eriksdal in southern Sweden was sampled for vertebrate fossils. Large bulk samples were collected from three horizons, including two coquina beds, VC3 and VC11, and a silty clay bed, VC7. Shark teeth are very common and constitute the main portion of the vertebrate material discussed herein. The selachian tooth faunas are almost exclusively represented by hybodonts, although a single tooth from a neoselachian shark, Squatinidae indet., was recorded from one horizon (VC3). Hybodont species identified from the Vitabäck Clay samples include Egertonodus basanus, Hybodus parvidens and Parvodus rugianus. Hybodont remains, other than teeth, include five morphotypes of placoid scales, incomplete cephalic spines and fragmentary fin spines.Other fossil groups represented in the sieved residues from the bulk samples include bivalves, gastropods and bony fish. Together with the selachians, they indicate fluctuating palaeosalinities in the area. The lower coquina bed, VC3, includes taxa indicating mesohaline conditions while the composition of the fauna in the other coquina bed, VC11, suggests oligohaline settings. In bed VC7, the presence of amphibian remains and the rarity of selachian fossils indicate an even lower salinity. Palynomorphs from the basal part of the section, immediately below bed VC3, indicate an earliest Cretaceous (Berriasian) age.
Tylosaurus ivoensis: a giant mosasaur from the early Campanian of Sweden
Authors: Lindgren Johan , Siverson Mikael 
Published: July 2007

ABSTRACTThe nominal species Mosasaurus ivoensis from the latest early Campanian of the Kristianstad Basin in southern Sweden, is redescribed and assigned to the tylosaurine genus Tylosaurus on the basis of its dental and vertebral morphology. A partial skeleton (KUVP 1024) from the late Coniacian to earliest Campanian Smoky Hill Chalk Member of the Niobrara Formation in western Kansas, USA, was previously referred to “M”. ivoensis. Nevertheless, its marginal teeth are markedly different, both in size and morphology, from those of topotypic T. ivoensis.Examination of type specimens and topotypic material of the nominal tylosaurines Hainosaurus pembinensis from the late early Campanian of Manitoba, Canada, H. gaudryi from the late Santonian or early Campanian of northwestern France, and H. lonzeensis from the Coniacian or Santonian of Belgium, indicates that all three may be Tylosaurus.The utility of isolated tooth-crowns in mosasaur taxonomy has been hampered by the often poor quality of the published illustrations of these fossils in combination with poor stratigraphic control. All Swedish remains of T. ivoensis, including 172 marginal teeth, 6 pterygoid teeth, several jawbone fragments and 12 vertebrae, were collected from a narrow stratigraphic interval corresponding to the highest biozone in the German eight-fold division of the early Campanian, providing the first good insight into the intraspecific dental variation in a tylosaurine mosasaur.
A revised reconstruction of the dermal skull roof of Acanthostega gunnari, an early tetrapod from the Late Devonian
Authors: Clack J. A. 
Published: July 2007

ABSTRACTA revised reconstruction of the dermal skull roof of Acanthostega gunnari from the Upper Devonian of East Greenland is provided, incorporating modifications consequent upon further study of the specimens and in the light of new information from the Upper Devonian genus Ventastega from Latvia. The new reconstruction features a midline gap between the frontal and nasal bones and median rostrals. A revised profile for the skull and a rendition of the dermal ornament is also provided.
Revision of the Xenacanthida (Chondrichthyes: Elasmobranchii) from the Carboniferous of the British Isles
Authors: Hampe Oliver 
Published: July 2007

ABSTRACTXenacanthids were a very successful group of elasmobranchs that ranged from the Lower Carboniferous to the Upper Triassic. The history of discovery of the xenacanthids, which is closely connected with the history of coal prospecting in England, began with the finding of the type specimen of Xenacanthus laevissimus in the Westphalian B of the West Midlands. In this first review of British Carboniferous xenacanthids, the number of taxa, mainly erected during Victorian times, is reduced to 14 species distributed among six genera. Determinable remains are recorded from at least 96 localities in the British Isles. Unique characteristics of the Dinantian Diplodoselache suggest that the lineage to which this taxon belongs marks a dead end in xenacanthid evolution. This investigation also shows that the Pendleian Dicentrodus, formerly described as Cladodus, belongs to the xenacanthids. The occurrence of Orthacanthus cf. kounoviensis in the Pennines, also known from the German Saar-Nahe basin, the Saale depression and from Bohemia, indicates a faunal exchange between these intramontainous basins during the Carboniferous. The genus Triodus is identified from British deposits for the first time. A cladistic analysis of the xenacanthids suggests that they evolved from phoebodontid elasmobranchs. This analysis also confirms separation of the Middle Devonian Antarctilamna from a relationship with xenacanthid sharks.
Magmatism of the Kenya Rift Valley: a review
Authors: Macdonald Ray 
Published: July 2007

ABSTRACTTertiary–Recent magmatism in the Kenya Rift Valley was initiated c. 35 Ma, in the northern part of Kenya. Initiation of magmatism then migrated southwards, reaching northern Tanzania by 5–8 Ma. This progression was accompanied by a change in the nature of the lithosphere, from rocks of the Panafrican Mozambique mobile belt through reworked craton margin to rigid, Archaean craton. Magma volumes and the geochemistry of mafic volcanic rocks indicate that magmatism has resulted from the interaction with the lithosphere of melts and/or fluids from one or more mantle plumes. Whilst the plume(s) may have been characterised by an ocean island basalt-type component, the chemical signature of this component has everywhere been heavily overprinted by heterogeneous lithospheric mantle. Primary mafic melts have fractionated over a wide range of crustal pressures to generate suites resulting in trachytic (silica-saturated and-undersaturated) and phonolitic residua. Various Neogene trachytic and phonolitic flood sequences may alternatively have resulted from volatile-induced partial melting of underplated mafic rocks. High-level partial melting has generated peralkaline rhyolites in the south–central rift. Kenyan magmatism may, at some future stage, show an increasing plume signature, perhaps associated ultimately with continental break-up.
Holocene relative sea levels and coastal changes in the lower Cree valley and estuary, SW Scotland, U.K.
Authors: Smith D. E. , Wells J. M. , Mighall T. M. , Cullingford R. A. , Holloway L. K. , Dawson S. , Brooks C. L. 
Published: July 2007

ABSTRACTChanges in Holocene (Flandrian) relative sea levels and coastal geomorphology in the lower Cree valley and estuary, SW Scotland, are inferred from detailed morphological and stratigraphical investigations. A graph of relative sea level changes is proposed for the area. Rising relative sea levels during the early Holocene were interrupted at c. 8300–8600 14C years B.P.(c. 9400–9900 calibrated years B.P.), when an extensive estuarine surface was reached at c. −1 m O.D., after which a fluctuating rise culminated at c. 6100–6500 14C B.P. (c. 7000–7500 calibrated years B.P.) in a prominent shoreline and associated estuarine surface measured at 7·7–10·3 m O.D. A subsequent fall in relative sea level was followed by a rise to a shoreline at 7·8–10·1 m O.D., exceeding or reoccupying the earlier shoreline over much of the area after c. 5000 14C B.P. (c. 5,800 calibrated years B.P.), before relative sea level fell to a later shoreline, reached after c. 2900 14C B.P. (c. 3100 calibrated years B.P.) at 5·5–8·0 m O.D., following which relative sea levels fell, ultimately reaching present levels. During these changes, a particular feature of the coastline was the development of a number of barrier systems. The relative sea level changes identified are compared with changes elsewhere in SW Scotland and their wider context is briefly considered.
The seymouriamorph tetrapod Utegenia shpinari from the ?Upper Carboniferous–Lower Permian of Kazakhstan. Part II: Postcranial anatomy and relationships
Authors: Klembara Jozef , Ruta Marcello 
Published: July 2007

ABSTRACTThe postcranial skeleton of the seymouriamorph Utegenia shpinari (?Upper Carboniferous–Lower Permian, Kurgalin Formation, Kazakhstan) is redescribed. Features that distinguish it from other Lower Permian seymouriamorphs (Discosauriscus, Ariekanerpeton, Seymouria) are: broad anterior portion of the interclavicle stem, merging indistinctly into the interclavicle plate; absence of a bulge in the anterior half of such a stem; presence of at least 28 presacral vertebrae; gastralia. The poorly ossified limbs of the largest Utegenia specimens are similar in degree of development to those of larval Discosauriscus, but the almost cylindrical, anterior trunk pleurocentra recall the condition of early juvenile Discosauriscus. A phylogeny of the best known seymouriamorphs, using a small but diverse exemplar from other early tetrapod groups, places Utegenia within seymouriamorphs as sister taxon to discosauriscids (Ariekanerpeton plus Discosauriscus). This conclusion affects origin and dispersal scenarios for seymouriamorphs, and supports the hypothesis of a widespread geographical record of Lower Permian taxa spanning across western Euramerica and eastern Asia.
The status of Conohyus giganteus (Nyanzachoerini, Tetraconodontinae, Suidae) – Reply to Pickford (2001)
Authors: van der Made J. 
Published: July 2007

ABSTRACTThe recently published model of evolution and biogeography and the resulting classification of the Tetraconodontinae (Van der Made 1999) were criticised by Pickford (2001) on eight points. It was claimed that Conohyus giganteus is a suine, and that this ‘radically modifies tetraconodont systematics’. However, Pickford failed to demonstrate that the type specimen is a suine, and even if it were a suine, this would affect only one of over twenty species names; not a radical change of the proposed evolutionary model.
Does the fossil record of spiders track that of their principal prey, the insects?
Authors: Penney David 
Published: July 2007

ABSTRACTThe currently accepted cladogram of spider phylogeny and palaeontological data are used to evaluate spider family richness through geological time. A significantly more diverse spider fossil record is predicted than observed. The predicted rate of spider family diversification is considered more accurate because of its close similarity at 0 Ma to the number of extant families. Predicted spider family palaeodiversity is compared with insect family palaeodiversity to investigate whether spiders track insects through geological time. At the family level, the insects, and observed and predicted spider fossil records show an exponential increase over time, the pattern typical of a radiating group. No significant differences are observed in the rates of change in the slopes, and hence rate of diversification of spiders and insects over time. This suggests that spiders probably co-radiated alongside the insects, with the major radiations of both groups occurring at least 100 Ma before the origin of angiosperms.
History of research on the geology and palaeontology of the Rhynie area, Aberdeenshire, Scotland
Authors: Trewin Nigel H. 
Published: July 2007

ABSTRACTGeological and palaeontological research in the Rhynie area, Aberdeenshire, Scotland, has progressed in several stages. Following early surveys in the nineteenth century, Dr William Mackie mapped the western margin of the basin in 1910–1913, and discovered the plant-bearing chert. Following trenching of the chert in 1913, Kidston & Lang described the plant fossils between 1917 and 1921 and Scourfield, Hirst and Maulik the arthropods in the 1920s. Following a ‘dark age’ of some 30 years, Geoffrey Lyon awakened interest in the late 1950s. Trenching in 1963–1971 provided Lyon and his co-workers with new material, and resulted in finds of new plants and reinterpretations of earlier work. The next phase was initiated by Winfried Remy's discovery of gametophytes in material given to him by Lyon. Since 1980, the Münster school has continued to make exciting discoveries. Aberdeen University involvement began in 1987 with geochemical work confirming a hot spring origin for the chert. Drill cores taken in 1988 and 1997, and further trenching have allowed structural, sedimentological and stratigraphic reappraisals, and resulted in the discovery of a new biota in the Windyfield chert. Long-term collaborative international research continues to advance interpretation of this unique Early Devonian hot spring system, and the remarkably diverse freshwater and terrestrial biota of the cherts.
A new univalve crustacean from the Early Devonian Rhynie chert hot-spring complex
Authors: Anderson Lyall I. , Crighton William R. B. , Hass Hagen 
Published: July 2007

ABSTRACTA new aquatic crustacean is described from the Early Devonian Rhynie chert. The small, broadly oviform carapace consists of a univalve symmetrical about its longitudinal axis, formed by a continuous cuticle with no fold or hinge. In transverse cross-section, the ventral surface exhibits a broadly ‘W’-shaped outline. Areas of fine, setose objects are preserved, positioned antero-ventrally on either side of the mid-line axis. In transverse sections, a ring-shaped internal structure is also visible. In longitudinal cross-section, this structure is resolved into an axially positioned, internally subdivided tube occupying the mid- and posterior part of the carapace. A small, anteriorly positioned rostrum has a deep pit on each side, perhaps indicative of the socket of an antennal appendage. The arthropods are commonly found clustered together around plant axes, comprising groups of up to 25 or more similarly sized individuals. The chert texture enclosing many individual specimens indicates a sub-aqueous preservational environment. The same organism has recently been discovered in preparations from the nearby and equivalently aged Windyfield hot spring deposit. The morphology of this new arthropod suggests affinity with Branchiopoda and it is tentatively placed within the Diplostraca (an order which contains both ‘conchostracans’ and ‘cladocerans’, or water fleas). The presence of a univalve test suggests a cladoceran affinity, but the lack of diagnostic appendages in the present material does not allow us to take the classification any further. This is potentially the earliest known occurrence of the group and would extend their fossil record back from the Early Cretaceous. The remarkable similarity between these arthropods and their present-day representatives strongly indicates morphological stasis within the group from early on in their evolutionary history