1,721,009 research outputs found
Dataset for: Quantifying intracortical bone microstructure: a critical appraisal of 2D and 3D approaches for assessing vascular canals and osteocyte lacunae
No full textData to support article "Quantifying intracortical bone microstructure: a critical appraisal of 2D and 3D approaches for assessing vascular canals and osteocyte lacunae". Journal of Anatomy. Oct 2020. doi: 10.1111/joa.13325</span
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Protochordate Zic genes define primitive somite compartments and highlight molecular changes underlying neural crest evolution
No full textThe vertebrate Zic gene family encodes C2H2 zinc finger transcription factors closely related to the Gli proteins. Zic genes are expressed in multiple areas of developing vertebrate embryos, including the dorsal neural tube where they act as potent neural crest inducers. Here we describe the characterization of a Zic ortholog from the amphioxus Branchiostoma floridae and further describe the expression of a Zic ortholog from the ascidian Ciona intestinalis. Molecular phylogenetic analysis and sequence comparisons suggest the gene duplications that formed the vertebrate Zic family were specific to the vertebrate lineage. In Ciona maternal CiZic/Ci-macho1 transcripts are localized during cleavage stages by asymmetric cell division, whereas zygotic expression by neural plate cells commences during neurulation. The amphioxus Zic ortholog AmphiZic is expressed in dorsal mesoderm and ectoderm during gastrulation, before being eliminated first from midline cells and then from all neurectoderm during neurulation. After neurulation, expression is reactivated in the dorsal neural tube and dorsolateral somite. Comparison of CiZic and AmphiZic expression with vertebrate Zic expression leads to two main conclusions. First, Zic expression allows us to define homologous compartments between vertebrate and amphioxus somites, showing primitive subdivision of vertebrate segmented mesoderm. Second, we show that neural Zic expression is a chordate synapomorphy, whereas the precise pattern of neural expression has evolved differently on the different chordate lineages. Based on these observations we suggest that a change in Zic regulation, specifically the evolution of a dorsal neural expression domain in vertebrate neurulae, was an important step in the evolution of the neural crest
Isolated tooth reveals hidden spinosaurid dinosaur diversity in the British Wealden Supergroup (Lower Cretaceous)
Full text linkIsolated spinosaurid teeth are relatively well represented in the Lower Cretaceous Wealden Supergroup of southern England, UK. Until recently it was assumed that these teeth were referable to Baryonyx, the type species (B. walkeri) and specimen of which is from the Barremian Upper Weald Clay Formation of Surrey. British spinosaurid teeth are known from formations that span much of the c. 25 Ma depositional history of the Wealden Supergroup, and recent works suggest that British spinosaurids were more taxonomically diverse than previously thought. On the basis of both arguments, it is appropriate to doubt the hypothesis that isolated teeth from outside the Upper Weald Clay Formation are referable to Baryonyx. Here, we use phylogenetic, discriminant and cluster analyses to test whether an isolated spinosaurid tooth (HASMG G369a, consisting of a crown and part of the root) from a non-Weald Clay Formation unit can be referred to Baryonyx. HASMG G369a was recovered from an uncertain Lower Cretaceous locality in East Sussex but is probably from a Valanginian exposure of the Hastings Group and among the oldest spinosaurid material known from the UK. Spinosaurid affinities are both quantitatively and qualitatively supported, and HASMG G369a does not associate with Baryonyx in any analysis. This supports recent reinterpretations of the diversity of spinosaurid in the Early Cretaceous of Britain, which appears to have been populated by multiple spinosaurid lineages in a manner comparable to coeval Iberian deposits. This work also reviews the British and global records of early spinosaurids (known mainly from dental specimens), and revisits evidence for post-Cenomanian spinosaurid persistence
An enigmatic large mawsoniid coelacanth (Sarcopterygii, Actinistia) from the Upper Jurassic Kimmeridge Clay Formation of England
No full textA large mawsoniid coelacanth from the lower part of the marine Kimmeridge Clay Formation of England (Kimmeridgian, Upper Jurassic) is studied here. The material is constituted by a group of bones from the head and shoulder girdle of a considerably large individual (estimated length ca. 1.5 m), including the left angular, left dentary, left prearticular, left palatoquadrate complex, both ceratohyals and right cleithrum. Characters such as the coarse external ornamentation of the angular, and the robustness of the quadrate and the cleithrum allow classification of the individual as a member of the Mawsoniidae; whereas the configuration of external bones of the lower jaw (ornamentation of the angular constituted mainly by longitudinal ridges, the presence of a lateral swelling in the dentary) indicates stronger Gondwanan affinities than previously expected (i.e., with the genus Mawsonia, up to now only recorded in South America by the end of the Jurassic). Considering the above, two alternative evolutionary, paleobiogeographic, and taxonomic scenarios are discussed: (1) the new individual can be referred to the European mawsoniid genus Trachymetopon (Lower–Middle Jurassic), in which case it should be assumed this genus reached the Upper Jurassic, and with a morphological variability higher than previously suspected (including some characters previously assumed as diagnostic for Mawsonia). Or (2) an unknown Mawsonia-like form was present in the Upper Jurassic of Europe. The last scenario puts the identification of isolated elements of European Jurassic giant mawsoniids in a new complex taxonomic and paleobiogeographic context, which will deserve further research
Ontogenetic changes in cortical bone vascular microstructure in the domestic duck (Anas platyrhynchos) and ring-necked pheasant (Phasianus colchicus)
No full textAge-related changes in bone microstructure can inform our understanding the biology of both extant and fossil birds, but to date, histological work in birds, and particularly work using high-resolution 3D imaging, has largely been restricted to limited growth stages. We used minimally destructive synchrotron radiation-based X-ray computed tomography to visualise and measure key morphological and histological traits in 3D across development in the domestic duck and ring-necked pheasant. We use these measurements to build on the database of key reference material for interpreting bone histology. We found that growth patterns differed between the two species, with the ducks showing rapid growth in their lower limbs and early lower limb maturation, while pheasants grew more slowly, reflecting their later age at maturity. In the pheasant, both walking and flight occur early and their upper and lower limbs grew at similar rates. In the duck, flight and wing development are delayed until the bird is almost at full body mass. Through juvenile development, the second moment of area for the duck wing was low but increased rapidly towards the age of flight, at which point it became significantly greater than that of the lower limb, or the pheasant. On a microstructural level, both cortical porosity and canal diameter were related to cortical bone deposition rate. In terms of orientation, vascular canals in the bone cortex were more laminar in the humerus and femur compared with the tibiotarsus, and laminarity increased through juvenile development in the humerus, but not the tibiotarsus, possibly reflecting torsional vs compressive loading. These age-related changes in cortical bone vascular microstructure of the domestic duck and pheasant will help understanding the biology of both extant and fossil birds, including age estimation, growth rate and growth patterns, and limb function.</p
Dataset for: Reptile-like physiology in Early Jurassic stem mammals
Full text linkDataset supports: Newham, E. et al. (2020). Reptile-like physiology in Early Jurassic stem-mammals. Nature Communications.
Virtual thin sections through tooth roots of Jurassic mammals, showing cementum increments.</span
Dataset for: A robust, semi-automated approach for counting cementum increments imaged with X-ray computed tomography
No full textData of manuscript A robust, semi-automated approach for counting cementum increments imaged with X-ray computed tomography in PloS One.</span
Data from: A highly pneumatic ‘mid Cretaceous’ theropod from the British Lower Greensand
No full textThis character matrix, based upon the work of Cau (2018), includes 133 operational taxonomic units (OTUs) scored for 1781 characters.,A series of axial elements from the Aptian Ferruginous Sandstone Formation of the Lower Greensand Group, discovered on the foreshore near Knock Cliff on the Isle of Wight, United Kingdom (UK) are – bar some isolated teeth – the youngest non-avian theropod remains reported from the British Mesozoic. These specimens have the potential to shed light on a poorly known section of the European dinosaur record. A consistency in size, appearance and adhering matrix indicate that the vertebrae belong to the same individual. This was a mid-sized tetanuran, the presence of several diagnostic characters indicating that it should be recognised as a new taxon, herein namedVectaerovenator inopinatus. The cervical and dorsal vertebrae are camerate and highly pneumatic. Tetanuran affinities include opisthocoelous cervicals and pneumatic foramina located within fossae, however assigning this specimen to a specific clade is problematic. Within Tetanurae, Vectaerovenatorpossesses axial structures and homoplastic features seen in megalosauroids, carcharodontosaurians and certain coelurosaurs. Not only is Vectaerovenatorone of the UK’s youngest non-bird dinosaurs, and one of few valid British Greensand taxa, it is also the first diagnosable theropod taxon to be named from Aptian deposits of Europe.</span
Synchrotron radiation-based X-ray tomography reveals life history in primate cementum incrementation
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