—Fern identification usually requires the use of mature sporophytes, since attempts to identify juveniles using morphological traits often provides unsatisfactory results. Here we examined young sporophytes found among boulders in a river basin of a xeric valley in central Peru. Attempts to identify these sporophytes first pointed to four different genera, two in Pteridaceae (Anogramma and Pity...

Investigations of breeding ecology of interior least tern (Sternula antillarum athalassos) and piping plover (Charadrius melodus) in the Platte River basin in Nebraska, USA, have embraced the idea that these species are physiologically adapted to begin nesting concurrent with the cessation of spring floods. Low use and productivity on contemporary Platte River sandbars have been attributed to a...

Peak-ring basins represent an impact-crater morphology that is transitional between complex craters with central peaks and large multi-ring basins. Therefore, they can provide insight into the scale dependence of the impact process. Here the transition with increasing crater diameter from complex craters to peak-ring basins on Mercury is assessed through a detailed analysis of Eminescu, a geolo...

Hypsometry (frequency distribution of elevations) is often used to characterize landscape morphology, traditionally in the context of the degree of fluvial dissection. Recently, the hypsometry of glaciated regions has been used to infer how rates of glacial erosion compare with tectonic uplift rates. However, many factors other than tectonics can also exert a major influence on the hypsometry o...

Body morphology of juvenile Chinook salmon Oncorhynchus tshawytscha in the upper Willamette River, Oregon, U.S.A., was analysed to determine if variation in body shape is correlated with migratory life-history tactics followed by juveniles. Body shape was compared between migrating juveniles that expressed different life-history tactics, i.e. autumn migrants and yearling smolts, and among parr ...

Introduction: Building on Bridges et al. [2003], we are currently studying the general geologic history and evolution of the Isidis basin based on topographic and imaging data obtained by orbiting spacecraft such as Mars Global Surveyor (MGS) and Mars Odyssey. This study complements our recently completed analyses on Syrtis Major to the west [Hiesinger and Head, 2003] and the transition between...

Argyre, located in the southern highlands southeast of Tharsis, is one of the largest impact basins on Mars and formed in Early Noachian time. We use Mars Global Surveyor (MGS) data to characterize the basin and its geologic features and units. It has been proposed that meltback of a south polar ice cap during the Noachian completely 6lled the basin with water, that the out7ow channel in the no...