Nanomechanical variability in the early evolution of vertebrate dentition.

Conodonts are an extinct group of primitive jawless vertebrates whose elements represent the earliest examples of a mineralized feeding apparatus in vertebrates. Their relative relationship within vertebrates remains unresolved. As teeth, conodont elements are not homologous with the dentition of vertebrates, but they exhibit similarities in mineralization, growth patterns, and function.

Atlanticalymene, a new genus of Middle Ordovician (Darriwilian) calymenine trilobites, and revision of the calymenoidean genus Protocalymene Ross.

Middle Ordovician (Darriwilian) species representing early Laurentian occurrences of the Subfamily Calymeninae Milne Edwards, 1840 (=Flexicalymeninae Siveter, 1977) are assigned to Atlanticalymene n. gen. (type species: A.

Ontogenetic variability in crystallography and mosaicity of conodont apatite: implications for microstructure, palaeothermometry and geochemistry.

X-ray diffraction data from Silurian conodonts belonging to various developmental stages of the species demonstrate changes in crystallography and degree of nanocrystallite ordering (mosaicity) in both lamellar crown tissue and white matter. The exclusive use of a single species in this study, combined with systematic testing of each element type at multiple locations, provided insight into microstructural and crystallographic differentiation between element type ( , , ) as well as between juveniles and adults. A relative increase in the unit cell dimensions / ratio of nanocrystallites during growth was apparent in areas demonstrating single-crystal behaviour, but no such relationship was seen in dominantly polycrystalline areas.

The pliomerid trilobite Ibexaspis and related new genera, with species from the Early Ordovician (Floian; Tulean, Blackhillsian) of the Great Basin, western USA.

Field-based revision and phylogenetic analysis demonstrate that the pliomerid trilobite taxon Ibexaspis Přibyl and Vaněk (in Přibyl et al., 1985), previously known from a single formally named species (I. brevis [Young, 1973]), belongs to a complex of 14 mostly newly discovered, related species from the Early Ordovician (Floian; Tulean and Blackhillsian) of the northern Laurentian margin.