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

Figures & data

Figure 1. Geological map. A. Map of Sweden with the study area indicated. B. Simplified geological map of the Torneträsk area with the fossil locality of Luobákte indicated. Brown colour represents outcrop areas of the autochthonous Cambrian strata along the margin of the Caledonian thrust sheets. C. Field photo of the Luobákte locality, taken from a low ridge north of Mt. Luovarri. The extent of the main stratigraphic units and approximate boundaries are indicated

Figure 2. Lithostratigraphic section through the Grammajukku Formation, Torneträsk Formation, Luobákte, Lapland, including ranges of fossil taxa. Biostratigraphic ranges of taxa in light grey have been taken from Axheimer et al. (2007), all other taxa (in regular black text) are documented from this study. Abbreviations: Brachs-Brachiopods, Hy.-Hyoliths, Prot.-Protoconodonts and Mol.-Molluscs

Figure 3. Fossils from the lower part of Grammajukku Formation, Torneträsk Formation, Luobákte, Lapland. A–D. Ellipsocephaus cf. gripi. A. NRM Ar72661, cephalon in dorsal view. B. NRM Ar72662, cephalon in dorsal view. C. NRM 72663, cephalon in dorsal view. D. NRM Ar72664, cephalon in dorsal view. E. Holmia? sp. NRM, Ar72665, possible genal spine with prominent terrace lines. F. Ind. Orthothecid hyolith NRM Mo193048. G, J. Eoobolus cf. priscus (Poulsen 1932); G. NRM Br151128, ventral valve interior. J. NRM Br151129, dorsal valve exterior. H, I. Botsfordia cf. caelata (Hall 1847), NRM Br151130. H. Partly disarticulated complete shell showing dorsal valve exterior (lower right) and partial ventral valve interior (upper left). I. Dorsal valve exterior showing pustulose external shell ornament

Figure 4. Botsfordia cf. caelata (Hall, 1847) from the bioclastic limestone, top of the Grammajukku Formation, Luobákte, Lapland. A, B. NRM Br151131. A. Posterior part of broken ventral valve exterior. B. Detail of posterior margin in oblique view showing outline of brephic shell and open pedicle groove. C, D. NRM Br151132. C. External view of broken ventral valve. D. Detail of shell ornament showing postulose ornament and superimposed radial costellae. E, F. NRM Br151133. E. Ventral valve interior. F. Oblique view showing imprints of muscle scars, pedicle nerves and vascular system. G. NRM Br151134, ventral valve interior showing muscle scars and imprints of pedicle nerves. H. NRM Br151135, Dorsal valve interior showing imprints of muscle scars and short median septum. I, J. NRM Br151136. I. Dorsal valve interior in oblique lateral view showing muscle scars and median septum. J. Oblique posterior view showing profile of brephic shell with two pustules. K, L. NRM Br151137. K. External view of shell fragment. L. Detail of shell surface showing pustulose ornament. Scale bars equal 200 µm in A–C, E–K; 100 µm in D, L

Figure 5. Eoobolus cf. priscus (Poulsen 1932) from the bioclastic limestone, top of Grammajukku Formation, Torneträsk Formation, Luobákte, Lapland. A, B. NRM Br151138. A. Fragmentary ventral valve in plan view. B. Oblique view of apex showing outline of brephic shell and pedicle notch. C. NRM Br151139, internal view of fragmentary ventral valve. D. NRM Br1515140, ventral valve interior showing pseudointerarea and median tongue. E. NRM Br151141, ventral valve interior showing pseudointerarea. F, G. NRM Br151142. F. Dorsal valve exterior. G. Detail of pustulose surface sculpture, oblique view. H, I. NRM Br151143. H. Dorsal valve interior showing pseudointerarea and visceral area. I. Oblique view of visceral area showing bisected median tongue and reticulate ornament (indicated by arrows). J. NRM Br 151144, complete dorsal valve in exterior view. K, L. NRM Br151145. K. External view of fragmentary dorsal valve. L. Oblique view of broken shell margin showing columnar shell structure. Scale bars equal 200 µm in A–F, H, J, K; 100 µm in G, I; 20 µm in L

Figure 6. Lapworthella shodackensis (Lochman 1956) from the bioclastic limestone, top of Grammajukku Formation, Luobákte, Lapland. A, K. NRM X10299. A. View of concave lateral side of conical sclerite with circular cross-section. K. Detail of shell ornament in oblique apertural view showing denticles on rib crests and growth lines on adapertural slope of ribs. B. NRM X10300, lateral view of spine-shaped sclerite. C. NRM X10301, lateral view of spine-shaped sclerite. D. NRM X10302, lateral view of narrow conical sclerite. E. NRM X10303, sub-symmetrical sclerite with rectangular cross-section viewed from convex surface. F. NRM X10304, asymmetrical sclerite with rectangular cross-section viewed from concave side. G, H. NRM X10305. G. Asymmetrical conical sclerite in apical view. H. Lateral view. I, J. NRM X10306. I. Fragment of sclerite with rectangular cross-section. J. Detail of shell surface in oblique view showing rectangular ornament on adapical slope of ribs. Scale bars equal 50 µm in A–I; 20 µm in J, K

Figure 7. Bradoriid arthropods from the bioclastic limestone, top of Grammajukku Formation, Luobákte, Lapland. A–F. Bradoria sp. A, B. NRM Ar72666. A. Plan view of broken valve fragment. B. Oblique lateral view. C–F. NRM Ar72667. C. Broken valve fragment in oblique view from ventral margin. D. Detail of shell ornament. E. Detail of D showing two types of shell perforations. F. Detail of E with enlargement of open perforation with internal spikes. G–J. Mongolitubulus spinosus (Hinz 1987). G. NRM Ar72668, spine tip in lateral view. H. NRM Ar72669, spine with flaring base in lateral view. I, J. NRM Ar72670. I. Spine fragment in lateral view. J. Detail of reticulate ornament with serrated edges. K. NRM Ar72671, valve fragment of bradoriid with spinose margins in lateral view. Scale bars equal 500 µm in A–C; 100 µm in G–I, K; 40 µm in D, J; 10 µm in E; 4 µm in F

Figure 8. Fossils from the bioclastic limestone, top of Grammajukku Formation, Luobákte, Lapland. A, B. Fragments of ellipsocephalid trilobites. A. NRM Ar72672, cranidium in dorsal view. B. NRM Ar72673, free cheek with small spine. C, D. Laterally compressed helcionelloid mollusc NRM Mo193049. C. Shell in dorsal view. D. Oblique lateral view showing overhanging apex. E, F. Broken protoconodont element NRM X10307. E. Plan view. F. Oblique lateral view. Scale bars equal 1 mm in A; 200 µm in B–F

Axheimer, N., Ahlberg, P., & Cederstrom, P., 2007: A new lower Cambrian eodiscoid trilobite fauna from Swedish Lapland and its implications for intercontinental correlation. Geological Magazine 144, 953–961. doi:https://doi.org/10.1017/S0016756807003597.

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