The Avalon Assemblage (Ediacaran, late Neoproterozoic) provides some of the oldest evidence of diverse macroscopic life and underpins current understanding of the early evolution of epibenthic communities. However, its overall diversity and provincial variability are poorly constrained and are based largely on biotas preserved in Newfoundland, Canada. We report coeval high-diversity biotas from Charnwood Forest, UK, which share at least 60% of their genera in common with ones in Newfoundland. This indicates that substantial taxonomic exchange took place between different regions of Avalonia, probably facilitated by ocean currents, and suggests that a diverse deepwater biota may already have been widespread at the time. Contrasts in the relative abundance of prostrate versus erect taxa likely record differential sensitivity to physical environmental parameters (hydrodynamic regime, substrate) and highlight their significance in controlling community structure.

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Interpretation of the stratigraphy and structure of the Lower Palaeozoic Manx Group has been strongly influenced by the assumed equivalence of distinct sandstone sequences, the Niarbyl and Lonan Flags, exposed along the west and east coasts of the Isle of Man, respectively. However, new palaeontological evidence confirms an Arenig age for the Lonan Flags and indicates a mid-Silurian age for the Niarbyl Flags, thereby necessitating a complete revision of previous interpretations. The Niarbyl Flags are formally defined here as the Niarbyl Formation and are assigned to a new group, the Dalby Group. A previously unrecognized lithofacies in the formation, laminated hemipelagite, is also distinguished and described and this indicator of anoxic deposition is compared and contrasted with the Manx Group and other Lower Palaeozoic sequences. Combined turbidite facies, palaeocurrent and petrofacies analysis of the turbidite suite further serves to reinforce the distinction with the Manx Group, in particular palaeocurrent and petrofacies data that indicates provenance from a magmatic-arc source to the west-northwest. The turbidite sequence is interpreted as a mid-lower fan, slope-apron sequence of interlobe and sandy lobe packets. Finally, the regional correlation and significance of the formation in its Iapetus Ocean setting, as well as the significance of the Niarbyl Shear Zone that defines its lower contact with the Manx Group, is considered and compared.

The discovery of a mid-late Wenlock (Silurian) graptolite and orthoconic nautiloid fauna at Traie Dullish Quarry, Peel Hill, in the Niarbyl Formation (Dalby Group) of the Isle of Man, disproves all earlier correlations between the Niarbyl and Lonan Flags on the west and east coasts of the island, respectively. All previous structural hypotheses require re-examination. The graptolites comprise Cyrtograptus cf. lundgreni, Monograptus flemingii cf. warreni and Monograptus ex gr. flemingii . They suggest, but do not prove, a lundgreni Biozone age, thus indicating a possible correlation between the Niarbyl Formation and the Birk Riggs Formation of the English Lake District, and the Denhamstown Formation of the Balbriggan Inlier, Southern Ireland.

-Graptolites are common fossils in Early Palaeozoic strata, but little is known of their softpart anatomy. However, we report a long-overlooked specimen of Dicranograptus aff. ramosus from Late Ordovician strata of southern Scotland that preserves a strongly polymorphic, recalcitrant, organicwalled network hitherto unseen in graptoloid graptolites. This network displays three morphologies: proximally, a strap-like pattern, likely of flattened tubes; these transform distally into isolated, hourglass-shaped structures; then, yet more distally, revert to a (simpler) strap-like pattern. The network most likely represents a stolon-like system, hitherto unknown in graptoloids, that connected individual zooids. Its alternative interpretation, as colonial xenobionts that infested a graptoloid colony and mimicked its architecture, is considered less likely on taphonomic and palaeobiological grounds. Such polymorphism is not known in non-graptolite pterobranchs, which are less diverse and morphologically more conservative: a division of labour between graptoloid zooids for such functions as feeding, breeding and rhabdosome construction may have been the key to their remarkable evolutionary success.