Gigantism is widespread among Palaeozoic arthropods, yet causal mechanisms, particularly the role of (abiotic) environmental factors versus (biotic) competition, remain unknown. The eurypterids (Arthropoda: Chelicerata) include the largest arthropods; gigantic predatory pterygotids (Eurypterina) during the Siluro-Devonian and bizarre sweep-feeding hibbertopterids (Stylonurina) from the Carbonif...

The history of the appearance and evolution of the suture, one of the major structural elements of the shells of ammonoids (a subclass of Cephalopoda), is briefly discussed. Its morphology is considered in the Devonian Anarcestida, the first members of which are very similar to the ancestral Bactritoidea, in the Late Devonian Clymeniida, the Devonian–Permian Tornoceratida, the Carboniferous–Per...

Coelacanths are well-known sarcopterygian (lobe-finned) fishes, which together with lungfishes are the closest extant relatives of land vertebrates (tetrapods). Coelacanths have both living representatives and a rich fossil record, but lack fossils older than the late Middle Devonian (385-390 Myr ago), conflicting with current phylogenies implying coelacanths diverged from other sarcopterygians...

Mass extinctions have altered the trajectory of evolution a number of times over the Phanerozoic. During these periods of biotic upheaval a different selective regime appears to operate, although it is still unclear whether consistent survivorship rules apply across different extinction events. We compare variations in diversity and disparity across the evolutionary history of a major Paleozoic...

■ Abstract The Cordilleran orogen of western North America is a segment of the Circum-Pacific orogenic belt where subduction of oceanic lithosphere has been underway along a great circle of the globe since breakup of the supercontinent Pangea began in Triassic time. Early stages of Cordilleran evolution involved Neoproterozoic rifting of the supercontinent Rodinia to trigger miogeoclinal sedime...

The Late Devonian to Early Mississippian is an important metallogenic epoch within the Canadian cordillera resulting in the production of significant sediment exhalative massive sulphide (SEDEX) and volcanogenic massive sulphide (VMS) mineral occurrences within rocks of cratonic or pericratonic affinity. Major belts include the Late Devonian Earn-hosted SEDEX deposits of the Selwyn and Gataga d...

Seed plants underwent first major evolutionary radiation in the Late Devonian (Famennian), as evidenced by the numerous ovules described to date. However, the early pollen organs are underrepresented, so that their structure and evolution remain poorly known. Here we report a new taxon of pollen organ Placotheca minuta from the Late Devonian. The synangium consists of many basally and more or l...

The Late Devonian (Frasnian-Famennian) interval includes one of the most dramatic intervals of biotic turnover in the Phanerozoic. Statistical evaluation of diversity change reveals that the primary cause of biodiversity decline was reduced speciation during the crisis interval, not elevated extinction rates. Although various hypotheses have been proposed to explain extinction increase during t...

Abundance and multilateral extension of prominent genus and species of Brachiopoda in the majority of sedimentation series of the Late Devonian have been observed in all parts of Iran. The variability and rapid change in this respect has made it possible to delineate different lines of orthogenetism, biozonation and present biostratigraphical models at the sub-stage level. These characteristics...