Early periods in Earth's history have seen a progressive increase in complexity of the ecosystems, but also dramatic crises decimating the biosphere. Such patterns are usually considered as large-scale changes among supra-specific groups, including morphological novelties, radiation, and extinctions. Nevertheless, in the same time, each species evolved by the way of micro-evolutionary processes...

The evolution of body size in tetrapods is assessed using a database that includes 107 early stegocephalian species ranging in time from the Frasnian (Upper Devonian) to the Tatarian (Upper Permian). All analyses use methods that incorporate phylogenetic information (topology and branch lengths). In all tests, the impact of alternative topologies and branch lengths are assessed. Previous report...

Late Devonian (Frasnian) abiotic marine calcite has been microsampled and analyzed for R’Sr/*6Sr ratios, 6’*0 and d13C values, and minor element concentrations. Portions of marine cement crystals from the Alberta and Canning Basins have escaped diagenetic alteration and preserve original marine S180 values f-4.8%0 + 0.5, PDB), Si3C values (+2.0 to +3.0b, PDB), *‘Sr/*6Sr ratios (0.70805 + 3), an...