Neil D. L. Clark

Dinosaur footprints from the Duntulm Formation (Bathonian, Jurassic) of the Isle of Skye

Synopsis The first in situ dinosaur tracks from Scotland were discovered at the top of the Duntulm Formation (Bathonian, Jurassic) near to Staffin in northeastern Skye. Fifteen individual tridactyl footprints were recorded of which two pairs appear to have been part of the same trackway. The footprints are preserved as natural moulds on a mud-cracked sandstone surface. The individual track sizes range from about 30 cm to over 50 cm in length with narrow to broad digits suggestive of having been made by a medium to large bipedal dinosaur.

Dinosaur Tracks from the Kilmaluag Formation (Bathonian, Middle Jurassic) of Score Bay, Isle of Skye, Scotland, UK

Tracks of a juvenile theropod dinosaur with footprint lengths of between 2 and 9 cm as well as adults of the same ichnospecies with footprints of about 15–25 cm in length were found in the Bathonian (Middle Jurassic) Kilmaluag Formation of Score Bay, northwestern Trotternish Peninsula, Isle of Skye, Scotland, UK. Two footprint sizes occur together on the same bedding plane in the central portion of Score Bay, both in situ and on loose blocks. Another horizon containing footprints above this was also identified. The footprints from the lowest horizon were produced in a desiccated silty mud that was covered with sand. A close association of both adults and juveniles with similar travel direction indicated by the footprints may suggest post-hatching care in theropod dinosaurs. Other footprints, produced on a rippled sandy substrate, have been found on the slightly higher bedding plane at this locality. Loose blocks found 130 m to the northeast in the central part of Score Bay have not been correlated with any in situ sediments, but were preserved in a similar manner to those from the higher bedding plane. These tracks represent the youngest dinosaur remains yet found in Scotland.

A thyreophoran dinosaur from the Early Bajocian (Middle Jurassic) of the Isle of Skye, Scotland

Synopsis The proximal parts of the right ulna and radius of a thyreophoran dinosaur from Bearreraig Bay, Isle of Skye, represent the first occurrence of this type of dinosaur from the Middle Jurassic rocks of Scotland. The incompleteness of the bones and the lack of more diagnostic features does not allow a precise identification although the ulna has more features in common with that of a eurypodan (stegosaurs and ankylosaurs) than a basal thyreophoran. The earliest identifiable stegosaur from Europe that has similar proximal expansion of the ulna is the middle Callovian (Middle Jurassic) Lexovisaurus of England and France. The ulna of the ankylosaur Mymoorapelta from the Upper Jurassic of Western Colorado, also shows close morphological similarity to the Scottish bone. Other ankylosaur fragments have been recorded from as early as the late Bajocian (Middle Jurassic) of England. The stratigraphic horizon from which the new bones come from is the Bearreraig Sandstone Formation (Early Bajocian, Middle Jurassic).

Chirotherium barthii Kaup 1835 from the Triassic of the Isle of Arran, Scotland

Synopsis The mould of a track from SE Arran, and several in situ trackways and individual tracks, as well as a partial trackway on a loose block of Triassic sandstone, from western Arran, represent the first verifiable fossil tracks of Chirotherium from the Triassic of Scotland and support a Scythian (Lower Triassic) age for the base of the Auchenhew Beds. The grouping of the I-IV toes with toe V behind and lateral to the group is characteristic of Chirotherium-like tracks. A comparison with European and American Triassic trackways suggests that the tracks belong to the species Chirotherium barthii Kaup, 1835, first described from Hildburghausen, Germany.

The first definitive Middle Jurassic atoposaurid (Crocodylomorpha, Neosuchia), and a discussion on the genus Theriosuchus

Atoposaurids were a clade of semiaquatic crocodyliforms known from the Late Jurassic to the latest Cretaceous. Tentative remains from Europe, Morocco, and Madagascar may extend their range into the Middle Jurassic. Here we report the first unambiguous Middle Jurassic (late Bajocian–Bathonian) atoposaurid: an anterior dentary from the Isle of Skye, Scotland, UK. A comprehensive review of atoposaurid specimens demonstrates that this dentary can be referred to T heriosuchus based on several derived characters, and differs from the five previously recognized species within this genus. Despite several diagnostic features, we conservatively refer it to T heriosuchus sp., pending the discovery of more complete material. As the oldest known definitively diagnostic atoposaurid, this discovery indicates that the oldest members of this group were small‐bodied, had heterodont dentition, and were most likely widespread components of European faunas. Our review of mandibular and dental features in atoposaurids not only allows us to present a revised diagnosis of T heriosuchus, but also reveals a great amount of variability within this genus, and indicates that there are currently five valid species that can be differentiated by unique combinations of dental characteristics. This variability can be included in future broad‐scale cladistics analyses of atoposaurids and closely related crocodyliforms, which promise to help untangle the complicated taxonomy and evolutionary history of Atoposauridae. 

Theropod dinosaurs from the Middle Jurassic (Bajocian–Bathonian) of Skye, Scotland

The Isle of Skye, Scotland, has yielded a diverse Middle Jurassic terrestrial vertebrate fauna, but little is known about the predatory dinosaurs (theropods) occupying the top and secondary carnivore roles in these ecosystems, as their fossils have been limited to rare footprints of small- to mid-sized taxa. We describe two isolated theropod body fossils, a tooth and a middle-posterior caudal vertebra, from the late Bajocian–Bathonian Valtos Sandstone Formation of northeastern Skye, and use a variety of quantitative techniques to determine their taxonomic affinities. We conservatively refer both specimens to Theropoda indet., but suggest that the tooth most likely belonged to a megalosaurid, basal tyrannosauroid, or dromaeosaurid, and that the vertebra belonged to a small-bodied basal coelurosaur of approximately the same size as Coelurus (c. 2 m long, c. 30 kg mass). Although fragmentary, these fossils and the footprints demonstrate that both small and mid to large theropods were present in the Middle Jurassic of Scotland, and that these may have included some of the oldest coelurosaurs, and potentially some of the earliest-diverging tyrannosauroids and dromaeosaurids. Supplementary material Skye Theropod Tooth: Data and Analyses are available at www.geolsoc.org.uk/SUP18866

Ichthyosaurs from the Jurassic of Skye, Scotland

Fossils of Mesozoic vertebrates are rare in Scotland, particularly specimens of marine reptiles such as plesiosaurs and ichthyosaurs. We describe a suite of ichthyosaur fossils from the Early to Middle Jurassic of Skye, which to our knowledge are the first ichthyosaurs from Scotland to be described and figured in detail. These fossils span approximately 30 million years, from the Sinemurian to the Bathonian, and indicate that ichthyosaurs were a major component of Scottish marine faunas during this time. The specimens include isolated teeth that could represent the most northerly known occurrences of the widespread Sinemurian species Ichthyosaurus communis, a characteristic component of the famous Lyme Regis faunas of England, suggesting that such faunas were also present in Scotland during the Early Jurassic. An associated humerus and vertebrae from Toarcian–Bajocian-aged deposits are named as a new genus and species of basal neoichthyosaurian, Dearcmhara shawcrossi. The taxonomic affinities of this taxon, which comes from a critical but poorly sampled interval in the fossil record, suggest that non-ophthalmosaurid neoichthyosaurians dominated European assemblages around the Early–Middle Jurassic boundary, and were later replaced by ophthalmosaurids, whose radiation likely took place outside Europe. Many of these specimens were collected by amateurs and donated to museum collections, a co-operative relationship essential to the preservation of Scotland’s fossil heritage.

A comparison between dinosaur footprints from the Middle Jurassic of the Isle of Skye, Scotland, UK, and Shell, Wyoming, USA

Synopsis Measurements of Middle Jurassic tridactyl dinosaur tracks from the Bathonian, Lealt Shale, Valtos Sandstone, Duntulm and Kilmaluag formations of the Isle of Skye, UK, are compared to the same measurements taken for dinosaur footprints from the Bajocian, Gypsum Spring and the Bathonian, Sundance Formation of the Bighorn Basin, Wyoming, USA. Principal component analysis of the data suggests that the smaller footprints from the Valtos Sandstone and Kilmaluag formations are indistinguishable from the footprints of the Sundance Formation. The single footprint from the Lealt Shale Formation is similar to the larger footprints from the Valtos Sandstone Formation. The footprints from the Duntulm and Gypsum Springs formations form distinct groupings from all other footprints. Four different groupings of dinosaur footprints can be recognized from the principal component analysis that may represent at least four different types of dinosaur.

Carboniferous coprolitic bacteria from the Ardross Shrimp Bed, Fife

The Ardross Shrimp Bed of eastern Fife is well known as the type locality for the eumalacostracan crustacean, Crangopsis socialis (Salter 1861) (Schram 1979). Associated with this crustacean is a rather poorly preserved, although diverse, fish fauna, along with plants, brachiopods, bivalves and a few other arthropods (Peach 1902, White 1937), but hitherto, no conodonts. The fauna is typical of the low-energy restricted marine to brackish water deposits which are preserved intermittently throughout the Carboniferous in Scotland (Schram 1981, Schram 1983; Wood 1982; Briggs and Clarkson 1983, 1985a, b; Clarkson 1985a, b). Conodonts, while rare in these restricted environments, are not unknown, occasional complete conodont animals having been found at Muirhouse, near Edinburgh (Briggs et al. 1983; Aldridge et al. 1986; Aldridge 1987; Aldridge et al. 1988). As the environment of deposition is similar to that of other crustacean-bearing shales, it was likely that conodonts would eventually be found at the Ardross locality. However, if their discovery is not unexpected, their state of preservation is; the conodonts being present in what appears to be a bacteria-rich coprolite of a conodontophagous animal. This represents the first record of bacterial structures in a coprolite of a conodontophagous animal and the first conodonts recorded from the Ardross Shrimp Bed. Material The coprolite specimen (HM Y77a–c), which is held in the Hunterian Museum of Glasgow, is associated with two specimens of Crangopsis socialis on the same fragment of shale. A small fragment (HM Y77c) was prepared for scanning electron microscopy. Description The strand of . . .

New discoveries of Isochirotherium herculis (Egerton 1838) and a reassessment of chirotheriid footprints from the Triassic of the Isle of Arran, Scotland

Synopsis Several in situ trackways and individual chirotheriid footprints have been found at a number of locations along the southern coast of the Isle of Arran. A locality on the coast near Sliddery has five trackways with three of over 17 footprints and one locality west of Kildonan also has a trackway with over 10 footprints. They are all from the Triassic Auchenhew Beds, but may belong to several levels within these beds. The state of preservation of the footprints is variable, but a combination of morphological characters and landmark polygons suggests that they belong to Isochirotherium herculis (Egerton) 1838. Previously described footprints from Arran, originally described as Chirotherium barthii (Clark et al. 2002), are reidentified as I. herculis.