The Kilmaluag Formation on the Isle of Skye, Scotland, provides one of the richest Mesozoic vertebrate fossil assemblages in the UK, and is among the richest globally for Middle Jurassic tetrapods. Since its discovery in 1971, this assemblage has predominantly yielded small-bodied tetrapods, including salamanders, choristoderes, lepidosaurs, turtles, crocodylomorphs, pterosaurs, dinosaurs, non-mammalian cynodonts and mammals, alongside abundant fish and invertebrates. It is protected as a Site of Special Scientific Interest and by Nature Conservancy Order. Unlike contemporaneous localities from England, this assemblage yields associated partial skeletons, providing unprecedented new data. We present a comprehensive updated overview of the Kilmaluag Formation, including its geology and the fossil collections made to date, with evidence of several species occurrences presented here for the first time. We place the vertebrate faunal assemblage in an international context through comparisons with relevant contemporaneous localities from the UK, Europe, Africa, Asia and the US. This wealth of material reveals the Kilmaluag Formation as a vertebrate fossil assemblage of global significance, both in terms of understanding Middle Jurassic faunal composition and the completeness of specimens, with implications for the early evolutionary histories of mammals, squamates and amphibians.

Dinosaur body fossil material is rare in Scotland, previously known almost exclusively from the Great Estuarine Group on the Isle of Skye. We report the first unequivocal dinosaur fossil from the Isle of Eigg, belonging to a Bathonian (Middle Jurassic) taxon of uncertain affinity. The limb bone NMS G.2020.10.1 is incomplete, but through a combination of anatomical comparison and osteohistology, we determine it most likely represents a stegosaur fibula. The overall proportions and cross-sectional geometry are similar to the fibulae of thyreophorans. Examination of the bone microstructure reveals a high degree of remodelling and randomly distributed longitudinal canals in the remaining primary cortical bone. This contrasts with the histological signal expected of theropod or sauropod limb bones, but is consistent with previous studies of thyreophorans, specifically stegosaurs. Previous dinosaur material from Skye and broadly contemporaneous sites in England belongs to this group, including Loricatosaurus and Sarcolestes and a number of indeterminate stegosaur specimens. Theropods such as Megalosaurus and sauropods such as Cetiosaurus are also known from these localities. Although we find strong evidence for a stegosaur affinity, diagnostic features are not observed on NMS G.2020.10.1, preventing us from referring it to any known genera. The presence of this large-bodied stegosaur on Eigg adds a significant new datapoint for dinosaur distribution in the Middle Jurassic of Scotland.

The late Viséan anthracosauroid Eldeceeon rolfei from the East Kirkton Limestone of Scotland is re-described. Information from two originally described and two newly identified specimens broadens our knowledge of this tetrapod. A detailed account of individual skull bones and a revision of key axial and appendicular features are provided, alongside the first complete reconstructions of the skull and lower jaw and a revised reconstruction of the postcranial skeleton. In comparison to Silvanerpeton, the only other anthracosauroid from East Kirkton, Eldeceeon is characterised by a proportionally wider semi-elliptical skull, comparatively smaller nostrils set farther apart, smaller and more rounded orbits, a shorter skull table with gently convex lateral margins, and a deeper suspensorium with a straight posterior margin and a small dorsal embayment. The remarkably large hind feet and elongate toes of Eldeceeon presumably represent an adaptation for attaining high locomotory speed through increased stride length and reduced stride frequency. This would necessitate great muscle force but few muscle contractions. At the beginning of a new stride cycle, repositioning the pes anteriorly and lifting the toes off the ground would require a strong and large muscle to pull the femur upward and rotate it inward and forward. It is hypothesised that such muscle might correspond to the puboischiofemoralis internus 2, which would extend along the posterior half of the vertebral column, consistent with the occurrence of long, curved ribs in the anterior half of the trunk. Using maximum parsimony and Bayesian inference, cladistic analyses of all major groups of stem amniotes retrieve a sister group relationship between Eldeceeon and Silvanerpeton, either as the most plesiomorphic stem amniote clade or as a clade immediately crownward of anthracosauroids.

Foraminifers, calcareous algae and incertae sedis Algospongia of late Asbian to late Brigantian age in limestones from East Fife, East Lothian and Northumberland, enable the base of the late Brigantian to be recognised in all these areas. Preservation of the late Asbian and early Brigantian limestones in cyclothemic successions is generally poor. The St Monans White Limestone (St Monans, Fife), First Abden Limestone (Kirkcaldy, Fife), Middle Longcraig Limestone (East Lothian) and Lower Bath-House Wood/Middle Bath-House Wood (Northumberland) were confidently correlated by their foraminiferal assemblages. These limestones are all assigned to the top of the Assemblage 6 in northern England (Single Post Limestone). The St Monans Brecciated/St Monans Little/Charlestown Main limestones (St Monans, Fife) and the Second Abden/Seafield Tower limestones (Kirkcaldy, Fife), Upper Longcraig/Lower Skateraw limestones (East Lothian), Upper Bath-House Wood/Shotto Wood limestones and Eelwell Limestone (Northumberland) are assigned to the Assemblage 7 in northern England (Scar Limestone and Five Yard Limestone). The paired Middle/Upper Skateraw limestones (East Lothian) and the Acre Limestone (Northumberland) contain representatives of the Assemblage 8 from northern England (Three Yard Limestone). Higher up in the succession, in Northumberland, the foraminiferal assemblage in the Sandbanks Limestone can be compared with Assemblage 9 in northern England (Four Fathom Limestone). Above the Great Limestone and Little Limestone, with their characteristic Pendleian assemblages, the Sugar Sands Limestone and Corbridge Limestone contain Arnsbergian foraminiferal assemblages, typical of the Lower Felltop Limestone in northern England. The Lower Foxton Limestone is correlated with the Upper Felltop Limestone, whereas the Thornbrough Limestone in Northumberland lacks diagnostic Arnsbergian taxa.