42 research outputs found
Enantioselective Narasaka-Heck Cyclizations:Synthesis of Tetrasubstituted Nitrogen-Bearing Stereocenters
A SPINOL-derived P,N-ligand system enables Pd-catalyzed 5-exo cyclization of oxime esters with trisubstituted alkenes to generate dihydropyrroles in up to 86% yield and 95 : 5 e.r.</p
Newly discovered reproductive isolation reveals sympatric populations of Esox Indus in the Baltic
Flexible modes of anadromy in Baltic sea trout: making the most of marginal spawning streams
Ophiuroids Discovered in the Middle Triassic Hypersaline Environment
Echinoderms have long been considered to be one of the animal phyla that is strictly marine. However, there is growing evidence that some recent species may live in either brackish or hypersaline environments. Surprisingly, discoveries of fossil echinoderms in non-(open)marine paleoenvironments are lacking. In Wojkowice Quarry (Southern Poland), sediments of lowermost part of the Middle Triassic are exposed. In limestone layer with cellular structures and pseudomorphs after gypsum, two dense accumulations of articulated ophiuroids (Aspiduriella similis (Eck)) were documented. The sediments with ophiuroids were formed in environment of increased salinity waters as suggested by paleontological, sedimentological, petrographical and geochemical data. Discovery of Triassic hypersaline ophiuroids invalidates the paleontological assumption that fossil echinoderms are indicators of fully marine conditions. Thus caution needs to be taken when using fossil echinoderms in paleoenvironmental reconstructions