The oldest pelmatozoan encrusted hardground and holdfasts from Laurentia (Cambrian Series 2–3)

Disarticulated discoidal holdfasts and holomeric columnals from the Henson Gletscher Formation (Cambrian Series 2, Stage 4) of North Greenland represent the oldest evidence in Laurentia of colonization of hard grounds by pelmatozoans. Additional occurrences are also reported from the uppermost Henson Gletscher Formation (Cambrian Series 3, Stage 5) and from the Fimbuldal Formation (Cambrian Series 3, Drumian Stage), while hardgrounds encrusted with abundant pelmatozoan holdfasts are described from the Holm Dal Formation (Cambrian Series 3, Guzhangian Stage). The North Greenland occurrence in Stage 4 (Ovatoryctocara granulata assemblage) correlates precisely with finds of similar holdfasts in the Brèche à Micmacca Member (Marocconus notabilis Biozone) in Morocco, suggesting the simultaneous appearance of encrusting pelmatozoans in Laurentia and western Gondwana.