First discovery of Small Shelly Fossils and new occurrences of brachiopods and trilobites from the early Cambrian (Stage 4) of the Swedish Caledonides, Lapland

Abstract

New fossil discoveries are reported from the Grammajukku Formation at Luobákte south of Lake Torneträsk in northern Swedish Lapland, including a fauna of Small Shelly Fossils (SSF) from a limestone bed in the uppermost part of the formation and new occurrences of brachiopods and trilobites in siltstones of the lower part of the formation. The moderately diverse SSF fauna is the first of its kind reported from the Swedish Caledonides and includes the first record of the tommotiid Lapworthella schodackensis and the bradoriid spine Mongolitubulus spinosus from Baltica, together with fragmentary specimens of Bradoria sp. and remains of one additional bradoriid arthropod, a protoconodont and a helcionelloid mollusc. In addition, the limestone bed yields abundant specimens of the brachiopods Botsfordia cf. caelata and Eoobolus cf. priscus and an unidentified ellipsocephalid trilobite. Lower down in the Grammajukku Formation, specimens of both brachiopod taxa, orthothecid hyoliths, the trilobite Ellipsocephalus cf. gripi and an unidentified holmiid trilobite were found at several levels in a siltstone, previously regarded as unfossiliferous. These discoveries markedly increase the known diversity of the palaeobiota from the Grammajukku Formation in northern Lapland and provide new insights into the biostratigraphy and palaeoenvironment of the lower Cambrian in Scandinavia and the palaeobiogeography of Cambrian faunas in general.

The Skyberg Lagerstätte from the Mjøsa area, Norway: a rare window into the late early Cambrian biodiversityof Scandinavia

“…reported from the uppermost early Cambrian strata in Skåne, Sweden (Bergström & Ahlberg 1981). Skovsted et al (2021) reported Eoobolus cf. priscus (Poulsen, 1932), from Swedish Lapland and suggested that several earlier reported lingulid specimens of similar age from Sweden were presumably conspecific.…”

“…It is of large size, comparable to the Mjøsa specimens, and showing a highly raised and coneshaped ventral valve, reminiscent of the more flattened valves preserved in mudstone from the Skyberg Member. Skovsted et al (2021) reported Botsfordia cf. caelata from northern Swedish Lapland, approximately age-equivalent with the Skyberg Member, and suggested that the two taxa may be synonymized.…”

“…Hence, this new record of the weakly mineralized bradoriid carapaces adds considerably to the number of this group from Norway. Some rare early Cambrian taxa are previously reported from Sweden (Wiman 1903;Thorslund & Westergård 1938;Kautsky 1945;Bergström & Ahlberg 1981;Ahlberg 1989;Álvarez et al 2008;Streng et al 2008;Skovsted et al 2021), presumably belonging to the genera Indiana Matthew, 1902b, Bradoria Matthew, 1899, Beyrichona Matthew, 1902b, Mongolitubulus, and Walcottella? Ulrich & Bassler, 1931(see Streng et al 2008Streng & Geyer 2019 for details), comprising very few complete specimens and valves.…”

“…Only isolated organophosphatic shells showing distinct morphotypes are known, and the assignment to both phylum and class is uncertain. Three species of the tommotiid genus Lapworthella Cobbold, 1921, are recorded from Baltica (Skovsted et al 2021) and only three samples from the Skyberg Member contain sclerites of Lapworthella sp. (Fig.…”