Growth rates and skeletal secretion of siculae in Early Ordovician (Arenig) graptolites from western Newfoundland; implications for development and paleoecology of graptolites

Didymograptina Didymograptus Eastern Canada Cow Head Group Central Europe Cenozoic Canada Germany Graptoloidea Hemichordata Isograptus Monograptus Newfoundland Graptolithina Europe Lower Ordovician Monograptina Silurian Upper Silurian paleoecology Quaternary Pleistocene North German Plain Ordovician Paleozoic