Abstract
Tuberculate fragments referred to Nikolarites spasskyi are compared with a complete carapace and other material of Spinospitella from Cambrian Series 2, Stage 4 in North Greenland. The descriptions expand earlier brief records from Laurentia of the two bradoriids, originally described from Siberia and Australia, respectively. The mutually exclusive occurrences of the two taxa indicate ecological control of their distribution in North Greenland. Robust fragments of Nikolarites spasskyi occur in reworked higher energy deposits of the Aftenstjernesø Formation, while thin-walled carapaces of Spinospitella characterise deeper water mudstones within the Buen and Aftenstjernesø formations.
Highlights
Trilobites, with their heavily mineralised exoskeletons, are the most conspicuous arthropods in the Cambrian, localities with exceptional preservation, such as the lagerstätten of Chengjiang, Sirius Passet and the Burgess Shale (Briggs et al 1994; Ineson and Peel 2011; Peel and Ineson 2011; Hou et al 2017), with a wealth of lightly sclerotised forms, present a more accurate picture of arthropodan diversity
Rozanov (1986: 89) suggested that a new family Mongolitubulidae might be erected within hyolithelminths to include Mongolitubulus, at that time considered to be tubular rather than spinose, but it was later discussed as a “conodontomorph” by Rozanov and Zhuravlev (1992)
Skovsted et al (2006) described Spinospitella from the Mernmerna Formation (Cambrian Stage 3–4) of South Australia based on collections containing a juvenile valve and partially broken bradoriid shields showing exquisite details of the ornamentation
Summary
Trilobites, with their heavily mineralised exoskeletons, are the most conspicuous arthropods in the Cambrian, localities with exceptional preservation, such as the lagerstätten of Chengjiang, Sirius Passet and the Burgess Shale (Briggs et al 1994; Ineson and Peel 2011; Peel and Ineson 2011; Hou et al 2017), with a wealth of lightly sclerotised forms, present a more accurate picture of arthropodan diversity. The Aftenstjernesø Formation represents the first of these carbonate progradation events, overlying the siliciclastic shelf sediments of the Buen Formation (Ineson and Peel 1997; Peel and Willman 2018), and it can be traced north almost to the outer margin of the shelf It is dominated by cliff-forming dolostone grainstones that attain a thickness of about 62 m (Ineson and Peel 1997) in its type area at the head of J.P. Koch Fjord (Fig. 1a, locality TS) but this value is reduced to only 18 m at the Navarana Fjord locality (Fig. 1a, locality NF). Koch Fjord, and in outcrops eastward to Løndal and across southern Peary Land, beyond
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