19. Most widely accepted hypothesis for extncions at end of Ordovician: A. glaciaion and associated effects...
19. Most widely accepted hypothesis for extncions at end of Ordovician: A. glaciaion and associated effects on sea level and climate B. meterorite impact in Laurentia C. excessive predaton by cephalopods D. massive methane explosion on seafloor E. overharvesting by Marians for seafood restaurants 20. Type of plant (includes conifers) occurring for first time in Late Devonian A. Angiosperms B. Gymnosperms C. Pteridophytes D. Stromatolites