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Borings of microscopic organisms (euendoliths) are described from the Henson Gletscher Formation (middle Cambrian, Miaolingian Series, Wuliuan Stage) of Peary Land, North Greenland (Laurentia). Partially phosphatised sclerites of Chancelloria and valves of the brachiopod Nisusia reveal abundant casts of borings following dissolution of skeletal calcium carbonate in weak acetic acid. Threads referred to Scolecia dominate, occurring together with coccoids (Planobola) and the branching Fascichnus, in a suite comparable to a lower Cambrian assemblage from the Maidiping Formation of Sichuan, China.

The periostracum, a non-calcified organic layer that envelops the mineralized shell layer ('ostracum') of molluscs, acts as an initial framework for the calcified 'ostracum.' Despite its significance in biomineralization in molluscs, fossil examples of the periostracum are limited in the geological record, especially from the Palaeozoic era, due to its susceptibility to post-mortem decay. In this study, we describe radial threads found on the outer surface of Cambrian molluscs, including helcionelloids and rostroconchs, which we interpret as fossilized periostracal structures. These radial threads are observed in 13 species from five valid genera, exhibiting a widespread palaeogeographical distribution encompassing Gondwana (Australia), Siberia, western Laurentia (Utah), and eastern Laurentia (Greenland), and spanning Cambrian Stage 4-Drumian deposits. These radial threads always cover the outermost surface of shells, dividing it into regular intervals, and develop through incremental growth. They originate from the apical area of helcionelloids or the umbo of rostroconchs. Detailed examination has revealed that the radial threads initiate at the apical region, but may be absent from the protoconch (embryonic shell). The radial threads are most likely preserved by mineral encrustation on the periostracum. Similar, but not homologous, radial threads are found in other fossil and modern molluscan taxa, such as the adhesive radial lines of anomalodesmatan bivalves or the periostracal ridges of viviparid gastropods.

The upper Henson Gletscher Formation (Cambrian, Miaolingian Series, Wuliuan Stage) of southern Lauge Koch Land and Londal, south-western Peary Land, North Greenland (Laurentia) yields diverse assemblages of phosphatised Small Shelly Fossils after treatment with weak acetic acid. The occurrence merits description as a fossil Lagerstatte on account of the exceptional preservation of soft parts in some specimens, although the phosphatisation itself is generally rather coarse. Bradoriid and phosphatocopid arthropods are common and display substantial variation in their preservational history. Some specimens retain traces of internal morphology, although details are generally obscured by indifferent preservation. Rare specimens extend the range of stem-group pentastomid arthropods back by more than 10 million years. A unique hatching larva demonstrates the same early developmental stage of a stem-group priapulan worm to that described in some present-day priapulans. The preservation of an in place operculum has demonstrated that the widespread, sup-posed mollusc Protowenella is actually an unusual, strongly coiled hyolith. Abundant coprolites and cololites provide additional evidence of early phosphatisation. In terms of morphology, Cambrocoryne lagenamorpha gen. et sp. nov. superficially resembles wiwaxiid and some annelid sclerites, thelodont scales and the foraminiferan Lagena, but its true identity is obscure.

Multiple, small (diameter <20 μm) swellings on the apex of internal moulds of the laterally compressed helcionelloids Eotebenna viviannae and the new species Eotebenna danica from the middle Cambrian (Miaolingian) of Bornholm, Denmark, are interpreted as a muscle attachment scars. The scar pattern is unique amongst currently known helcionelloids both in the abundance of attachment sites and in crossing the median plane of symmetry on the supra-apical (dorsal) surface. Sites of typically two pairs of dorsal muscle scars in other helcionelloids are distributed symmetrically on the dorso-lateral areas. The recognition of four groups of muscle scar patterns in helcionelloids suggests a degree of anatomical diversity within the group that is obscured by the morphological simplicity of the enclosing cap-shaped shells, although evolutionary links to mollusc crown groups are unresolved. In addition to the muscle scars, traces of shell micro-structure are described.

Shell microstructure and exquisite details of muscle attachment scars are preserved on the surface of internal moulds in the bivalve Fordilla troyensis from the Aftenstjerneso Formation (Cambrian Series 2, Stage 4) of North Greenland (Laurentia). Subsidiary muscles developed in commarginal series that extend laterally from the anterior and posterior adductor muscles probably controlled the centrally emergent foot. Their position close to the ventral margin indicates that only slight withdrawal and limited manipulation of the foot was possible, confirming that Fordilla was not a burrower. The pattern suggests derivation of Fordilla from a clamping mollusc with shell muscles distributed around the shell margin. No such pattern of serially repeated muscles close to the shell margin is currently known in the few available records of helcionelloid muscle scars, but Postacanthella has a commarginal U-shaped muscle scar reflecting its limpet-shaped shell form. Shell microstructure in Fordilla troyensis is closely similar to Pojetaia, with central areas of the valves dominated by a laterally continuous imbricate lamellar structure with a width of 10-20 mu m between successive crests. Imbricate lamellae with about half this spacing form a marginal zone with crests lying perpendicular to the valve edge. The hinge line lacks teeth, although a single tooth is present in each valve of the related Fordilla sibirica and Fordilla germanica. The site of the simple ligament is coarsely striated. Comparative material of Fordilla troyensis is illustrated from New York State, North-East Greenland and Denmark.

A single phosphatised specimen from the middle Cambrian Henson Gletscher Formation (Miaolingian Series, Wuliuan Stage) of North Greenland is interpreted as the hatching larva of a total-group priapulid worm. A plated lorica is not present but probably was developed at a later larval stage, by comparison with the described development of extant Priapulus caudatus and Halicryptus spinulosus. A characteristic priapulid introvert with scalids is not seen but it was likely withdrawn in the available specimen. The new find is consistent with a similar ontogeny in Cambrian priapulid cycloneuralians to that seen in their present day relatives. New taxon: Inuitiphlaskus kouchinskyi gen. et sp. nov.

Records of diagenetically mineralized, filamentous, cavity-dwelling microorganisms extend back to strata from the early Paleoproterozoic (2400 Ma). In North Greenland (Laurentia), they are first known from the Ediacaran (Neoproterozoic; ca. 600 Ma) Portfjeld Formation of southern Peary Land, in association with a biota similar to that of the Doushantuo Formation of China. The Portfjeld Formation cavity dwellers are compared with more widespread occurrences in Cambrian (Series 2, Stage 4, Miaolingian Series) strata from the same region in which assemblages in postmortal shelter structures within articulated acrotretoid brachiopods and other invertebrates are common. All specimens were recovered by digestion of carbonate samples in weak acids. The described fossils are preserved as mineral encrusted threads but this diagenetic phosphatization unfortunately obscures their biological identity.

The hyolith fauna of the middle Bystraya Formation (Cambrian Series 2) of eastern Transbaikalia (Zabaykalsky Krai), Siberia, includes at least 17 described taxa distributed between the orders Hyolithida and Orthothecida. Species of Microcornus, Parkula, Conotheca, Neogloborilus and Cupitheca are widely reported from Cambrian strata elsewhere. Triplicatella uslonica sp. nov. is known only from Transbaikalia. Dauritheca is proposed as a replacement generic name for the junior homonym Pachytheca, originally described from Xinjiang, China, and its range is extended to Transbaikalia. A conch with prominent comarginal ribs is referred to Salanytheca daurica sp. nov., a genus otherwise known from the early Cambrian of Mongolia and northern Siberia.

Diverse assemblages of helcionelloid molluscs and mollusc-like microfossils are described from the upper Henson Gletscher Formation (Cambrian, Miaolingian Se-ries, Wuliuan Stage) of Lauge Koch Land and western Peary Land, North Greenland (Laurentia). The fauna compares closely to an assemblage of similar age from the Coonigan Formation of Australia, although the latter is preserved as silica replicas while the North Greenland fossils are dominantly preserved as phosphatized internal moulds. These internal moulds often retain a detailed impression of the inner surface of the shell, with a fine pitted texture typically present. Prominent deep grooves on the sub-apical surface in the erect helcionellids Dorispira and Erugoconus, correspond-ing to ridges on the shell interior, seem to be associated with control of water flow through the mantle cavity. Well-developed shell pores, preserved as tubercles on the internal mould, are common in species of the laterally compressed Mellopegma. New taxa: Dorispira avannga sp. nov., Dorispira septentrionalis sp. nov., Dorispira tavsenensis sp. nov., Dorispira tippik sp. nov., Erugoconus acuminatus gen. et sp. nov., Scenella? siku sp. nov., Sermeqiconus gen. nov., Tavseniconus erectus gen. et sp. nov., Vendrascospira troelseni gen. et sp. nov., Vendrascospira frykmani gen. et sp. nov.