Sponge spicules from the Holm Dal Formation (Cambrian Series 3, Guzhangian) of North Greenland (Laurentia)

Disarticulated sponge spicules are described in two diverse assemblages from the Holm Dal Formation of North Greenland (Cambrian Series 3, Guzhangian Stage, Lejopyge laevigata Biozone). They compare most closely with contemporaneous spicules described from the Mindyallan Stage of Queensland, Australia. Although originating on separate palaeocontinents, the Laurentian and Gondwanan spicule assemblages accumulated in equatorial latitudes, demonstrating the potential stratigraphic and palaeogeographic utility of disarticulated spicules in the Cambrian. Samples from Gustav Holm Dal are dominated by robust acanthose pentactins with widely spaced spines also present in the solariform Seqineqia bottingi n. gen. n. sp. Australispongia sinensis Dong & Knoll, 1996, Silicunculus australiensis Bengtson, 1986 and Silicunculus saaqqutit Peel, 2017 also occur but are not common. Samples from Navarana Fjord are dominated by tetractins and pentactins. Speciosuspongia cf. wangcunensis Chen & Dong, 2008 may be common. Tetractins of Tallitaniqa petalliformis n. gen. n. sp., Kuonamia fusiformis (Fedorov in Fedorov & Pereladov, 1987) and Sisamatispongia erecta n. gen. n. sp. are only recorded from Navarana Fjord.