The Rhaetian Vertebrates of Chipping Sodbury, South Gloucestershire, UK, a Comparative Study

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Lakin, R. J., Duffin, C. J., Hildebrandt, C., & Benton, M. J. (2016). The Rhaetian vertebrates of Chipping Sodbury, South Gloucestershire, UK, a comparative study. Proceedings of the Geologists' Association, 127(1), 40-52. https://doi.org/10.1016/j.pgeola.2016.02.010

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The Rhaetian vertebrates of Chipping Sodbury, South Gloucestershire, UK, 1 2 3 a comparative study 4 5 6 7 8 Rebecca J. Lakina, Christopher J. Duffinaa,b,c, Claudia Hildebrandta, Michael J. Bentona 9 10 a 11 School of Earth Sciences, University of Bristol, BS8 1RJ, UK 12 13 b146 Church Hill Road, Sutton, Surrey, SM3 8NF, UK. 14 15 c 16 Earth Sciences Department, The Natural History Museum, Cromwell Road, London, SW7 17 18 5BD, UK. 19 20 21 22 23 ABSTRACT 24 25 Microvertebrates are common in the basal bone bed of the Westbury Formation of England, 26 27 28 documenting a fauna dominated by fishes that existed at the time of the Rhaetian 29 30 Transgression, some 206 Myr ago. Two sites near Chipping Sodbury, south Gloucestershire, 31 32 33 Barnhill Quarry and Chipping Sodbury railway cutting, show differing faunas. Top predators 34 35 are the large bony fish Severnichthys and the shark Hybodus cloacinus, which preyed on 36 37 38 smaller sharks such as Lissodus and Rhomphaiodon. These fishes in turn may have fed on a 39 40 mixed diet of other fishes and invertebrates, and Lissodus was a shell crusher. Comparisons of 41 42 these faunas with others described recently from the Bristol region, and from Devon, indicate 43 44 45 remarkable faunal similarities in the Rhaetian basal Westbury Formation bone bed over a 46 47 wide area, based on a variety of ecological statistics that document species diversities and 48 49 50 relative abundances. Only the fauna from the Chipping Sodbury railway cutting differs 51 52 significantly. 53 54 55 56 57 Keywords: Late Triassic; Systematics; Chondrichthyes; Actinopterygii; Bristol; Rhaetian; 58 59 Rhaetian bone bed; Westbury Formation. 60 61 62 63 64 65 2

1. Introduction 1 2 The Rhaetian was a significant stage of the Triassic, during which there were profound 3 4 5 changes in the Earth’s climate and topography, and biosphere. During this short span of time 6 7 (205.7–201.3 Myr ago; Maron et al., 2015), Pangaea began to break up (de Lamotte et al., 8 9 10 2015), and this presumably greatly influenced the global climate system by driving cyclical 11 12 extremes of climate (Trotter et al., 2015). The Rhaetian was terminated by the end-Triassic 13 14 mass extinction, which saw the rapid, global extinction of ~50% of marine and terrestrial 15 16 17 genera (Deenen et al., 2010), including the conodonts and many marine reptiles and 18 19 invertebrates, as well as many archosaurs, some therapsids, and most temnospondyl 20 21 22 amphibians. 23 24 Rhaetian outcrops in the UK, assigned to the Penarth Group, extend from Teesside in 25 26 27 the north-east of England to Dorset on the south coast, and on both sides of the Severn 28 29 Estuary, in South Wales and around Bristol (Swift and Martill, 1999). The stratigraphy of the 30 31 Rhaetian follows a common pattern throughout the UK, but differs in continental European 32 33 34 locations. However, one constant throughout all occurrences is that there is generally a basal 35 36 bone bed that yields abundant bones and microfossils of bony fishes, sharks, and reptiles. A 37 38 39 number of British Rhaetian bone bed sites have been described (Swift and Martill, 1999; 40 41 Allard et al., 2015; Korneisel et al., 2015; Nordén et al., 2015) and many of them share the 42 43 44 key elements of their faunas in common; however, there has never been a numerical 45 46 comparison of the faunal lists, key taxa and relative abundances between different sites. Are 47 48 49 they constant, representing unbiased preservation of a common fauna, or are there differences 50 51 in diversity and relative abundance, perhaps reflecting palaeoenvironmental or taphonomic 52 53 differences? 54 55 56 The aim of this paper is to explore variations in the composition of the vertebrate faunas 57 58 from the Rhaetian bone beds of southern England. Here, we examine two sites, Barnhill and 59 60 61 62 63 64 65 3

Chipping Sodbury railway cutting, chosen because they are located geographically adjacent to 1 2 each other. Further, we analyse census data from these sites, and others, to assess the variation 3 4 5 in faunal assemblages and relative abundances of taxa among a number of Rhaetian bone bed 6 7 sites 8 9 10 11 12 2. History and geological setting 13 14 2.1. Historical setting 15 16 17 The two sites, Barnhill Quarry (National Grid Reference [NGR] ST 72604 82620) and 18 19 Chipping Sodbury railway cutting (NGR ST 71484 80904 to ST 75242 81473) are 20 21 22 approximately 1.1 km apart, both being located towards the eastern end of Chipping Sodbury 23 24 (Fig. 1). Barnhill Quarry, sometimes called Arnold’s Quarry (Murray and Wright, 1971), was 25 26 27 first mentioned on a tithe map printed in 1839, when the quarry was much smaller and 28 29 shallower than it is today, and quarrying operations were small-scale. From 1844, however, 30 31 the quarry was presumably a much larger undertaking, and was recruiting workers from the 32 33 34 Sodbury Union Workhouse. In 1859, records show a specialist limestone quarry, as well as a 35 36 limekiln on the site (Ridge Wood, 2015). At this time, the quarry covered 11 acres, 2 rods and 37 38 2 39 7 perches (approx. 46,719 m ). From the 1860s, there is evidence of a railway siding leading 40 41 into the quarry (Ridge Wood, 2015), built and run by the Midland Railway Company. It is 42 43 44 likely that packhorses and mules were used to carry cut stone from the quarry to the railway 45 46 line. After the First World War, quarrying became the principal source of employment in the 47 48 49 area, as the demand for limestone increased with the growing network of roads being laid at 50 51 the time. 52 53 In 1928, several small-scale West Country quarries were grouped together to form the 54 55 56 British Quarrying Company (Hopkins, 1979), which later became the Amalgamated 57 58 Roadstone Corporation (ARC); Barnhill Quarry was used as the headquarters for what was at 59 60 61 62 63 64 65 4

the time the largest stone company in the world. Eventually, however, the limestone yield of 1 2 the quarry began to decline, and by 1955, the quarry had been abandoned. The site was 3 4 5 declared an SSSI for its two-fold stratigraphic significance; in representing the Lower 6 7 Cromhall Sandstone of the Carboniferous, which is noted for the demonstration of 8 9 10 sedimentary structures, and in demonstrating an excellent Rhaetian section sitting directly on 11 12 Carboniferous Limestone. However, there is much ongoing debate about the future of the site. 13 14 Houses and a supermarket were built (2014-2016) in the southern part of the quarry, and the 15 16 17 remainder could become a household waste landfill site. Today, the site covers just 7.7 acres 18 19 (31,160.8 m2), but the geological sections forming the east, north and west faces of the quarry 20 21 22 are still intact. 23 24 Chipping Sodbury railway cutting was excavated by the former Great Western Railway 25 26 27 Company, which had been the primary railway company in the west since its establishment in 28 29 1835 (Roden, 2010). Following successful completion of the Severn Railway Tunnel in 1887 30 31 (Walker, 1888), the construction of a new railway line between Swindon and the tunnel began 32 33 34 in November, 1897 (Robertson and Abbott, 1989). This would allow South Wales coal traffic 35 36 bound for London to bypass Bristol. In order to lay a track bed across such an uneven 37 38 39 landscape, great volumes of rock and earth were excavated to build tunnels and cuttings, and 40 41 a large number of embankments and viaducts also had to be erected (Husband, 1902). 42 43 44 Chipping Sodbury railway cutting leads into Chipping Sodbury tunnel, which is the 45 46 second longest railway tunnel in the Great Western region (4,433 m), exceeded in length only 47 48 49 by the Severn tunnel (7,008 m). Construction of the former was made possible by 'shaft 50 51 excavation', and at one point the tunnel had up to 40 gangs of navvies tunnelling ventilation 52 53 shafts directly down into the hill, then tunnelling horizontally at the correct depth to link up 54 55 56 with other shafts (Husband, 1902). Work on the line was completed in 1903, and by this time, 57 58 59 60 61 62 63 64 65 5

excavation of the cuttings had required the work of 4,000 navvies, 44 steam locomotives, 17 1 2 steam shovels, 11 steam cranes and 1,800 wagons (Robertson and Abbott, 1989). 3 4 5 6 7 2.2. Geology of Chipping Sodbury railway cutting 8 9 10 Chipping Sodbury is located on low-lying Upper Triassic and Lower Jurassic 11 12 sediments (Fig. 1), and the succession youngs eastwards, passing up through Lower and 13 14 Middle Jurassic sediments, with outcrops all trending roughly north to south at this point. 15 16 17 About 1 km east of the eastern limit of Chipping Sodbury, the landscape rises as a ridge 18 19 formed from the Dyrham Formation and Bridport Sand Formation (both Lower Jurassic; 20 21 22 Pliensbachian and Toarcian respectively), and the Inferior Oolite Group (Aalenian to 23 24 Bathonian) and overlying Middle Jurassic units. This Lower–Middle Jurassic ridge is 25 26 27 penetrated by the Chipping Sodbury tunnel. East of the tunnel is a 3.5-km-long cutting 28 29 through a succession of formations, from west to east, descending through the Charmouth 30 31 Mudstone Formation (Sinemurian–Pliensbachian) and the Rugby Limestone Member 32 33 34 (Hettangian–Sinemurian) east of the former Chipping Sodbury station, the Saltford Shale 35 36 Member (Rhaetian–Hettangian) from Chipping Sodbury station to Lilliput Bridge, the 37 38 39 Wilmcote Limestone Member (Rhaetian–Hettangian) west of Kingrove Bridge, and then the 40 41 Cotham Member and Westbury Formation (Rhaetian), Blue Anchor Formation (Norian– 42 43 44 Rhaetian), and older red beds of the Mercia Mudstone Group (Early Triassic - Rhaetian) 45 46 further west. The Chipping Sodbury quarries, including Barnhill Quarry, cut down through 47 48 49 the Triassic and Jurassic sediments to reach various limestone formations of the Lower 50 51 Carboniferous. The railway cutting also exposes these Carboniferous units in small patches at 52 53 track level, from west to east (Avon Group mudstone, Black Rock Group limestone, Friars 54 55 56 Point Limestone Formation, Gully Oolite Formation, Cromhall Sandstone Formation, Oxwich 57 58 Head Limestone Formation; Courceyan to Brigantian). Reynolds and Vaughan (1904) 59 60 61 62 63 64 65 6

described the geology of the railway cutting, based on their field work as it was being 1 2 excavated. Their descriptions provide a remarkable longitudinal sketch of rocks exposed 3 4 5 along the section when it was clean (it is now entirely overgrown), as well as summary 6 7 sedimentary logs taken at several points along the track (Fig. 2) 8 9 10 Reynolds and Vaughan (1904) note that the outcrop of Rhaetian bone bed they 11 12 uncovered was very clear, and extended from a point ‘east of the Lilliput Bridge’ as far as ‘the 13 14 Old-Red-Sandstone outcrop lying west of Chipping Sodbury railway-station’ (Fig. 2). The 15 16 17 railway station no longer exists, but it was located at ST 742816, and the BGS map shows a 18 19 small exposure of Old Red Sandstone, the Tintern Sandstone Formation, dated as Late 20 21 22 Devonian to Early Mississippian, located in the track bed of the railway cutting at ST 732817, 23 24 and underlying the Black Rock Limestone Subgroup, dated from the Tournaisian 25 26 27 (Courceyan–Chadian substages), immediately to the west in the railway cutting. Along the 28 29 cutting, Reynolds and Vaughan (1904, p. 197) note that the Rhaetian ‘varies a great deal in 30 31 thickness, being thickest where the Palaeozoic rocks have been much denuded. At two points 32 33 34 where large rounded hummocks of the Palaeozoic project into the Rhaetic, the Black Shale is 35 36 deposited on them in an arched manner, forming an anticline of bedding.’ Thus, the picture is 37 38 39 of Rhaetian sediments overstepping underlying Palaeozoic rocks unconformably from the 40 41 west, with the basal parts of the Triassic sequence draped over discontinuities in the eroded 42 43 44 surface. 45 46 The basal bone bed occurred sporadically (Fig. 2): as Reynolds and Vaughan (1904, pp. 47 48 49 197–198) note, ‘[i]t is first met with as one passes east from Lilliput Bridge at a point about 50 51 150 yards from the bridge : it extends for a distance of about 130 yards, and then again 52 53 disappears, reappearing after some 200 yards, and extending continuously to the end of the 54 55 56 Palaeozoic outcrop’. They describe it as a ‘Hard Bone-Bed, containing quartz-pebbles and 57 58 crowded with vertebrates; Plicatula cloacina is not infrequent’, being 3 inches [7.5 cm] thick, 59 60 61 62 63 64 65 7

and immediately overlaid by a thin unit of ‘Soft black clay, crowded with vertebrates’. They 1 2 do not note any other bone-bearing horizons in the section, despite their being aware of such 3 4 5 multiple bone beds at other sites. 6 7 8 9 2.3. Geology of Barnhill Quarry 10 11 Barnhill Quarry excavates the Clifton Down Limestone and the Lower Cromhall 12 13 14 Sandstone formations (Visean: Arundian to Brigantian). The Clifton Down Limestone 15 16 sequence, which include coral beds and stromatolite horizons, has received detailed study and 17 18 19 environmental interpretation (e.g. Murray and Wright, 1971). It shows a cycle of 20 21 sedimentation passing from intertidal algal mats, through lagoons, barrier and open shelf 22 23 24 deposits and back through the same sequence to intertidal algal mats. 25 26 The Penarth Group is exposed around the edges of Barnhill Quarry, especially in the 27 28 29 south-east corner, where a 6-m section shows Westbury Formation, Cotham Member, and 30 31 some overlying Lias Group (Figs. 3, 4). The Westbury Formation, and the basal bone bed, sit 32 33 directly on the eroded and karstified Carboniferous Limestone (‘A’, Fig. 3A; Fig. 4B). The 34 35 36 exposed upper surface of the Carboniferous Limestone forms four platforms (‘A’–‘D’, Fig. 37 38 3), two of which display well-developed clints and grykes, karstic solution channels produced 39 40 41 by subaerial weathering (Reynolds, 1938). The other top surfaces of the Carboniferous 42 43 Limestone are smooth, perhaps eroded by the Rhaetian transgression. 44 45 46 The Rhaetian sediments are typical of the area, starting with 3.8 m of Westbury 47 48 Formation, largely dark grey and black fissile shales and thin interbedded limestones and 49 50 sandstones, and overlain by 1.7 m of the Cotham Member of the Lilstock Formation, 51 52 53 comprising typical pale buff-coloured shales and thinly bedded limestones (Fig. 3B). 54 55 Reynolds (1938) characterized two lithologies of the basal bone bed, the first being a dark- 56 57 58 coloured crystalline limestone containing phosphatic nodules, coprolites, and bone fragments, 59 60 and the second characterized by large (up to 1.2 m long) rounded blocks, some of them 61 62 63 64 65 8

partially coated with pyrite. In many cases, these blocks are isolated, but when they occur in 1 2 groups, bone-bearing and quartz pebble-rich sediment often infills the spaces, producing a 3 4 5 very coarse-grained conglomerate. This coarse conglomerate occurs only sporadically. 6 7 In attempting to understand the Rhaetian of Barnhill Quarry, a field drawing by 8 9 10 Reynolds (1938, showing the quarry when it was still working, in the late 1930s, is very 11 12 helpful (Fig. 3). The small building at the top left appears on Ordnance Survey maps until the 13 14 1960s, at which point it was presumably pulled down. It, as well as the road marked by fence 15 16 17 posts, and the orientation of the illustration, confirm that this drawing was made from the 18 19 west side of Barnhill Quarry, facing east, with the telegraph poles (and a person) marching 20 21 22 along the side of the Wickwar Road (B4060). The boundary between the large, steeply 23 24 dipping beds of the Carboniferous Limestone and the overlying thinly bedded, dark-coloured 25 26 27 Westbury Formation is clear, as it is today, although much overgrown (Fig. 4). An annotated, 28 29 detailed 25-inch-to-the mile (1:2500) Ordnance Survey map of Barnhill Quarry in the Curtis 30 31 archive at BRSUG shows exactly where he collected his fossiliferous samples, and that is 32 33 34 from the base of the Westbury Formation at the extreme right of the diagram, below the arrow 35 36 pointing to the ‘Penarth Group’ (Fig. 3), namely at NGR ST 72606 82675. 37 38 39 Bench ‘A’ in Figure 3 is the location of the fossil collections made by Mike Curtis in 40 41 1976 from the basal Westbury Formation bone bed. On revisiting the site in August 2015, 42 43 44 bench ‘A’ was located, close to a fence beside a footpath that runs behind some new houses 45 46 and close to the boundary fence of the quarry site. The Carboniferous-Triassic contact is clear 47 48 49 (Fig. 4B), and samples of the basal Westbury Formation bone bed were collected. 50 51 52 53 3. Materials and methods 54 55 56 The microvertebrate fossils described here were collected from 1975–1977 by Mike 57 58 Curtis (1951-2009), an amateur geologist from Gloucestershire. Throughout his life, Curtis 59 60 61 62 63 64 65 9

collected vast quantities of fossil material from Bristol and the surrounding area, and is hailed 1 2 as a highly reliable source of information owing to his methodical collecting, identification 3 4 5 and labelling (Nordén et al., 2015). Curtis kept meticulous records of his collecting, and wrote 6 7 detailed summaries of his observations. When these collections were made, Curtis was Quarry 8 9 10 Manager of the Chipping Sodbury Quarries. 11 12 Curtis’ field notebooks and annotated maps of the region, although helpful in describing 13 14 the geology of the localities, unusually yield no information about the horizons at Barnhill 15 16 17 Quarry or in Chipping Sodbury railway cutting from which the material was gathered or the 18 19 original volume of unprocessed material gathered, and no lab books have been found which 20 21 22 describe the preparation of this material. However, we assume that he followed his usual 23 24 meticulous procedures, as outlined by Korneisel et al. (2015). 25 26 27 Initial identifications of the microvertebrates were by Curtis, and these have all been 28 29 thoroughly checked and revised here. As much as half of the unidentified material in his 30 31 collection has now been identified, based on published works (Swift and Martill, 1999; Allard 32 33 34 et al., 2015; Nordén et al., 2015), as well as comparisons with collections from other sites. 35 36 The materials described here represent a tiny proportion (< 5%) of the tens of thousands of 37 38 39 identified Rhaetian-age microvertebrates that Curtis collected during his lifetime, and which 40 41 are now lodged in the collections of Bristol City Museum (BRSMG) and the University of 42 43 44 Bristol (BRSUG). 45 46 47 48 49 4. Systematic palaeontology 50 51 Specimen numbers from both sites are small (Table 1). The fossils from both localities 52 53 are generally of good quality, some with signs of abrasion. No morphotypes have been 54 55 56 allocated, since the majority of the unidentified material is heavily eroded, fragmented and 57 58 59 60 61 62 63 64 65 10

difficult to group. We describe materials from both sites together, but clarify the sources 1 2 throughout. 3 4 5 6 7 4.1. Chondrichthyans 8 9 10 In total, the remains of three taxa of sharks, as well as some partially identifiable shark 11 12 and holocephalan remains, were recovered from the two locations, all of which are previously 13 14 known from the Rhaetian. Most of the chondrichthyan remains come from members of the 15 16 17 Hybodontiformes. 18 19 20 21 22 4.1.1. Lissodus minimus (Agassiz, 1839) 23 24 By far the most common species from the railway cutting, the teeth of Lissodus minimus 25 26 27 are distinctive (Allard et al., 2015), being broadly triangular and carrying strong ridges. The 28 29 teeth exhibit clear monognathic heterodonty, and several different morphs may be found (Fig. 30 31 5); some possess tricuspid crowns (Fig. 5A), whereas others show a more pronounced single, 32 33 34 central cusp (Fig. 5B–E). In occlusal view (Fig. 5D), the teeth possess narrow, flattened 35 36 crowns that taper mesially and distally from the centre, with rounded tips. In labial view (Fig. 37 38 39 5E), the characteristic labial peg is located low on the crown, at the base of the very low 40 41 central cusp, which is flanked by even lower pairs of lateral cusplets. In some specimens, the 42 43 44 occlusal crest, a ridge running from end to end of the occlusal surface of the crown and 45 46 passing through all of the cusp apices, appears almost crenulated. Vertical ridges descend 47 48 49 both labial and lingual faces of the crown from the occlusal crest, usually terminating at the 50 51 crown shoulder, which is commonly marked by a horizontal ridge. Specimens vary from 1.5– 52 53 3 mm in maximum dimension, and 0.5–1 mm in height. The flattened shape of these teeth 54 55 56 suggests durophagous feeding. Many specimens are incomplete. 57 58 59 60 61 62 63 64 65 11

4.1.2. Hybodus cloacinus (Quenstedt, 1858) 1 2 This large species is reasonably common at Barnhill, representing up to 10% of 3 4 5 specimens, but represented by only a single tooth at the railway cutting. The specimens found 6 7 at Barnhill are remarkably well preserved, and several virtually complete pentacuspid crowns 8 9 10 have been found (Fig. 6A, B). The principal cusp, over twice the height of the adjacent lateral 11 12 cusplets, is situated slightly off-centre, and possesses a distinctive and characteristic labial 13 14 node at its base. Relatively coarse vertical ridges descend the crown, especially labially, often 15 16 17 bifurcating basally and occasionally swollen toward their base to form nodes. Up to three 18 19 pairs of lateral cusplets are present. The principal cusp is inclined distally in anterolateral 20 21 22 teeth, which are also asymmetrical in labial view. The complete teeth represent the largest 23 24 specimens recovered from either site, with the largest measuring 7.9 mm x 4.5 mm. 25 26 27 Accompanying these specimens are many examples of worn and broken teeth. 28 29 The material from Barnhill and Chipping Sodbury railway cutting agrees well with the 30 31 morphological variation shown by this species from other Rhaetian localities (see 32 33 34 Discussion), and an articulated dentition from the Lower Lias (Lower Jurassic) of Lyme Regis 35 36 (Duffin 1993b, 2010, pl. 59, fig. 2). 37 38 39 40 41 4.1.3. Rhomphaiodon minor (Agassiz, 1837) 42 43 44 This species is abundant at Barnhill quarry, but scarcer at the railway cutting. Several 45 46 tooth morphs are present at Barnhill, as well as fin spines recovered from the railway cutting. 47 48 49 A complete specimen of one morph is shown in Figures 7A, B. The central cusp in teeth of R. 50 51 minor is symmetrical, unlike those of H. cloacinus. The teeth commonly possess five cusps; 52 53 the central cusp is flanked by two pairs of low lateral cusplets. The central cusp is over twice 54 55 56 the height of the smaller lateral cusplets. All cusps are triangular in shape, have an elliptical 57 58 cross-section and are inclined lingually (Fig. 7B). There are broad, shallow, non-branching 59 60 61 62 63 64 65 12

vertical ridges running down both labial and lingual faces of the cusps, but these are less well 1 2 defined in the smaller cusplets. The root is very broad, with the distance between the most 3 4 5 proximal and most distal parts of the root being over 70% of the height of the entire tooth. 6 7 The entire tooth is small, measuring 1.25 mm H x 1.94 mm W x 0.95 mm D. 8 9 10 Another tooth type (Fig. 7C, D) is tricuspid and laterally flattened. The root is bulbous, 11 12 and pitted with vascular foramina, and the crown is broadly ridged and triangular. It could be 13 14 argued that this tooth morphotype should be allocated to the morphologically slightly similar 15 16 17 synechodontiform shark Parascylloides turnerae recently described from the Rhaetian of 18 19 Barnstone, Nottinghamshire and several localities in Germany (Thies et al., 2014). The teeth 20 21 22 described by Thies et al (2014) are more laterally compressed than the specimens described 23 24 and figured here, their lateral cusplets are much lower in comparison to the height of the 25 26 27 central cusp, and the ornamentation of the crown is also different, especially on the lingual 28 29 face of the central cusp. The tooth type in Figures 7C, D clearly belongs to R. minor. 30 31 32 33 34 4.1.4. Holocephali 35 36 A single dermal denticle of an unidentified holocephalan chondrichthyan was 37 38 39 recovered (Fig. 7E, F) at Barnhill Quarry. It comprises a small crown sitting on top of a more 40 41 massive root that expands to twice the diameter of the crown. The enamel on the rounded 42 43 44 crown is black and smooth. The larger root of the denticle tapers from the base upwards, and 45 46 bears irregular longitudinal ridges. This identification is based on close similarity to 47 48 49 specimens identified as Group C morphotype by Sykes (1974, p. 59) from Barnstone in 50 51 Nottinghamshire, suggested to come from a chimaeriform by him, and a very similar example 52 53 is given by Korneisel et al. (2015, fig. 6A, B). 54 55 56 57 58 4.1.5. Nemacanthus sp. 59 60 61 62 63 64 65 13

A single portion of a fin-spine (Fig. 8A, B) from an unidentified species of 1 2 Nemacanthus was recovered from Chipping Sodbury railway cutting. The fragment consists 3 4 5 of an irregularly dimpled golden brown shaft with a furrow running longitudinally along the 6 7 posterior edge, to accommodate the anterior margin of the dorsal fin. On the anterior edge of 8 9 10 the spine is a black enamel ridge, presumably to give the fin stability and to act as a prow to 11 12 streamline the fin and aid in ‘cutting’ through the water. Complete specimens of Nemacanthus 13 14 fin spines from localities such as Aust Cliff show that the enamelled anterior ridge extended 15 16 17 the full length of the exserted portion of the fin spine (Storrs, 1994, p. 225; Duffin, 1999, p. 18 19 204). 20 21 22 23 24 4.1.6. Hybodontiform dorsal fin spines 25 26 27 Some dorsal fin spine fragments are incomplete, and lack both a tip and base. They are, 28 29 however, recognisable by the deep, regular longitudinal ridges (costae) and furrows on the 30 31 lateral walls of the exserted portion of the spine (Fig. 8C), and by the series of small 32 33 34 downturned denticles along the posterior margin of the spine. These two aspects of the spine 35 36 ornament are diagnostic of hybodontiforms, and differ from fin spines of neoselachians, 37 38 39 which have smooth enamelled lateral walls, and those of ctenacanthiforms, which usually 40 41 possess a tuberculated ornament on the lateral walls. The spines supported the leading edge of 42 43 44 the dorsal fins during life, acting both defensively and as a cutwater. It is impossible to assign 45 46 the dorsal fin spine fragments to a particular species of hybodontiform shark. 47 48 49 50 51 4.1.7. Hybodontiform dermal denticles (scales) 52 53 A small number of hybodontiform dermal denticles were recovered from the railway 54 55 56 cutting, but not from Barnhill Quarry. These denticles could not be characterised to species 57 58 level, although many are of extremely good quality. One example (Fig. 9A, B) is of a type 59 60 61 62 63 64 65 14

described by Sykes (1974) as simply a ‘Rhaetian hybodont denticle’, and measures 1 2 approximately 700 µm in length. Although the base is flared and subquadrate in shape, there 3 4 5 is a distinct ‘waist’ forming a narrow pedicel below the expanded crown, which is flattened 6 7 along the lateral axis. Nine vertical ridges ascend the pedicel and the outer (= anterior) face of 8 9 10 the crown, which is produced into a series of denticles along the posterior margin. The 11 12 anterior and posterior facets are irregularly ridged and furrowed. 13 14 15 16 17 4.2. Osteichthyans 18 19 Four osteichthyan taxa were recovered from both sites, all of which are known to occur 20 21 22 in the Rhaetian (Duffin, 1982). Three of these are actinopterygians, and one a sarcopterygian. 23 24 25 26 27 4.2.1. Gyrolepis albertii (Agassiz, 1835) 28 29 This species makes up a large proportion of fossil material recovered from the railway 30 31 cutting, where teeth and scales are abundant. This species was identified from Swift & Martill 32 33 34 (1999), and of the six known species of Gyrolepis, only G. albertii is found in the Penarth 35 36 Group (Davis, 1871). The scales (Fig. 10A, B), as in many Rhaetian beds, are ubiquitous 37 38 39 (Allard et al., 2015), and are laterally flattened, with a thick base, which varies in colour from 40 41 honey gold to chestnut, topped with a thinner, jet-black patterned enamel covering with a 42 43 44 diagonal rippled pattern of enamel ridges running in the cranial-caudal direction. The teeth are 45 46 slender, long and tapered, with a distinctive, gentle hook-like curve (Fig. 10C, D), finely 47 48 49 ridged at the base and smooth at the offset, clear-coloured tip. 50 51 52 53 4.2.2. Severnichthys acuminatus (Agassiz, 1844) 54 55 56 The teeth of S. acuminatus are very common in these deposits, and were described from 57 58 the Chipping Sodbury railway cutting by Reynolds (1904), although he did not differentiate 59 60 61 62 63 64 65 15

between the different tooth types of this species. Here, we report two heterodont morphs from 1 2 both deposits, the ‘Birgeria acuminata’ tooth type and the ‘Saurichthys longidens’ tooth type. 3 4 5 These were previously considered to be separate species, but were synonymized by Storrs 6 7 (1994) when a single jaw containing both tooth types was identified. 8 9 10 At Barnhill Quarry, the ‘Birgeria acuminata’-type teeth dominate. These are 11 12 particularly well preserved, but otherwise unexceptional. In some specimens, the complete, 13 14 enamel-tipped tooth has been preserved with the root, and even the pulp cavity is readily 15 16 17 distinguishable (Fig. 11A, B). The teeth are deeply but sparsely ridged in the lower 50%, and 18 19 the root is both ridged and pitted. The tooth cap is smooth as a result of post mortem abrasion. 20 21 22 In the ‘Saurichthys longidens’ tooth type (Fig. 11C, D), there is no mark to distinguish 23 24 the root from the crown, other than the distal cessation of shallow grooves that run 25 26 27 longitudinally along the surface. This tooth type is represented in our samples by incomplete 28 29 teeth, all of which are missing the root. Some specimens retain the translucent, pearl-coloured 30 31 enamelled tip, and all are ridged along the length of the crown. 32 33 34 Superficially, the ‘Birgeria acuminata’-type teeth of this species are difficult to 35 36 distinguish from the teeth of Gyrolepis albertii, but they differ in shape, with those of G. 37 38 39 albertii being more steeply curved and hook-shaped, with the cap forming a much smaller 40 41 percentage of the total tooth height. Both types of S. acuminatus teeth are slender and needle- 42 43 44 shaped, with deep grooves on the sides of the root, and the transition from root to crown takes 45 46 place three-quarters of the way along the tooth from the base. The crown of the tooth finishes 47 48 49 in an enamelled tip that is smooth. In the ‘Birgeria acuminata’ tooth type, there is a shallow 50 51 but pronounced groove that distinguishes the ridged root from the smooth crown. 52 53 54 55 56 4.2.3. Sargodon tomicus (Plieninger, 1847) 57 58 59 60 61 62 63 64 65 16

A single good-quality tooth of this species was found at Barnhill Quarry (Fig. 11E, F). 1 2 The specimen is approximately 57 mm in length, and has a smooth, dark coffee-coloured tip, 3 4 5 separated from the rest of the tooth by a small circular ridge and groove. The crown has a 6 7 smooth, marbled pattern, and the inferior face is concave (Fig. 11E). The root is missing. 8 9 10 11 12 4.2.4. Ceratodus sp. 13 14 Two very worn sarcopterygian teeth belonging to an unknown species of Ceratodus 15 16 17 were identified from the Barnhill collection. The occlusal surfaces of these teeth (Fig. 12A– 18 19 D) are composed of pleromic hard tissue (tubular dentine) containing pillars of 20 21 22 hypermineralised dentine. Although heavily worn, shown by their high polish, and 23 24 fragmentary nature, there is some evidence of the transverse ridges, characteristic of more 25 26 27 complete specimens of Ceratodus tooth plates from localities such as Aust Cliff, which gave a 28 29 sectorial component to the process of occlusion. 30 31 32 33 34 4.3. Miscellaneous vertebrate material 35 36 From both sites, there was an abundance of unidentifiable vertebrate material, none of 37 38 39 which could be further characterised, and so is not presented here. 40 41 42 43 44 5. Diversity and relative abundance 45 46 Comparison of the two sites shows that Barnhill Quarry has a more species-rich fauna 47 48 49 (nine identifiable taxa) than the railway cutting (seven identifiable taxa), with six species 50 51 shared, and ten taxa identified in total. Sample sizes were different, with 1100 identifiable 52 53 specimens from the railway cutting and 316 from Barnhill Quarry. The relative proportions of 54 55 56 taxa differ quite substantially (Table 1), with Lissodus minimus and Severnichthys acuminata 57 58 equally abundant at Barnhill (Fig. 13A), but Lissodus minimus overwhelmingly abundant in 59 60 61 62 63 64 65 17

the railway cutting, and Severnichthys acuminata much less frequent in the railway cutting 1 2 (Fig. 13B). Oddly, Gyrolepis albertii is equally abundant at both sites, and other taxa are quite 3 4 5 rare in the railway cutting due to the overwhelming abundance of Lissodus minimus there 6 7 (Fig. 13A, B). 8 9 10 The higher species diversity at Barnhill is exaggerated when the relative proportions of 11 12 specimens per species are considered. The Shannon-Wiener Index of Biodiversity (H′) is 13 14 higher at Barnhill (1.524) than at Chipping Sodbury (0.938), as is the Species Evenness (J′) 15 16 17 (0.69 and 0.48, respectively). This shows that the Barnhill Quarry fauna is considered to be 18 19 more diverse because the relative proportions of specimens among species are more unequal 20 21 22 (Tuomisto, 2010). This is confirmed by Simpson’s Index of Diversity (D), which is 0.529 for 23 24 the railway cutting and 0.254 for Barnhill. This index reflects the probability that two species 25 26 27 sampled from each site will be of the same species (Simpson, 1949), and therefore the lower 28 29 figure for Barnhill suggests higher overall diversity. 30 31 When the two species samples are compared, they turn out to be similar, based on a 32 33 34 reasonably high Sørenson-Dice Coefficient (0.75). 35 36 There is a wider question of how typical such values might be, and how the faunas of 37 38 39 geologically comparable Rhaetian bone beds might differ or resemble each other. The current 40 41 data set was compared with other recently studied samples, from Manor Farm Quarry (NGR 42 43 44 ST 574896), near Aust Cliff, South Gloucestershire (Allard et al., 2015), Charton Bay (NGR 45 46 SY 281893), on the south Devonshire coast (Korneisel et al. 2015), and Marston Road Quarry 47 48 49 (NGR ST 73114485), near the village of Nunney in Somerset (Nordén et al., 2015). 50 51 The comparisons (Table 2) show that most localities have statistically indistinguishable 52 53 index values, except for the values of H’ and D from Chipping Sodbury railway cutting. 54 55 56 These outliers were determined using the Interquartile Range, and these confirm that the 57 58 overall ecological diversity at the railway cutting, based on species richness and on individual 59 60 61 62 63 64 65 18

species frequencies, is smaller than that found at any other sampled locality. This difference 1 2 emerges despite the fact that there is no statistically significant difference between the species 3 4 5 evenness (J’) of any of the localities. 6 7 These comparisons confirm the general similarity in Rhaetian bone bed samples among 8 9 10 localities that are geographically widespread, from Gloucestershire to the south Devon coast, 11 12 a distance of about 150 km. The stratigraphic evidence is that the Rhaetian basal bone beds at 13 14 all these locations are likely of exactly the same age, representing an event that took place 15 16 17 geologically instantaneously, namely the termination of the Triassic red beds of the Mercia 18 19 Mudstone Group by the Rhaetian transgression, and the exactly coeval basal Westbury 20 21 22 Formation bone bed that has been proved to have been deposited at the same time as marine 23 24 shrimps were excavating burrows on the top of the eroded Blue Anchor Formation (Korneisel 25 26 27 et al., 2015). 28 29 Therefore, in trying to understand the difference between the majority of the sites and 30 31 the Chipping Sodbury railway cutting microfauna, four hypotheses should be considered, 32 33 34 namely that the differences could result from differences in stratigraphic age, geographic 35 36 differences, facies and environmental differences, or sampling. The first three can probably be 37 38 39 rejected based on the evidence of generally close matching between samples – the bone beds 40 41 are all the same age, there is no evidence for geographic variation, and the facies are 42 43 44 seemingly similar from site to site – indeed the Rhaetian succession is highly predictable 45 46 (Swift and Martill, 1999). One slight caveat is that we do not have primary evidence of the 47 48 49 exact horizon from which Mike Curtis excavated his Chipping Sodbury railway cutting 50 51 Rhaetian bone bed samples, and it could have been from a bone bed higher in the Westbury 52 53 Formation for example. However, the Westbury Formation basal bone bed was clearly present 54 55 56 in the railway cutting (Reynolds and Vaughan, 1904), and these authors mention no other 57 58 occurrences of bones from their first-hand observations of the freshly cut sections, so it is 59 60 61 62 63 64 65 19

most likely that Curtis sampled from the basal bone bed. The railway cutting sample yielded 1 2 1100 identifiable specimens, compared to 316 from the Barnhill Quarry sample, so the 3 4 5 difference cannot simply be explained by sampling, but in the end, sampling bias of some 6 7 kind would seem to be the most likely explanation of the fact that the Chipping Sodbury 8 9 10 railway cutting sample shows such different proportions of taxa from the other Rhaetian basal 11 12 bone beds. 13 14 The Sørenson-Dice Coefficient (CC) for all five sites together was calculated to be 0.63. 15 16 17 This statistic is a measure of similarity between communities (Dice, 1945; Sørenson, 1948), 18 19 and ranges from 0–1, 0 indicating entirely independent and separate communities, and 1 20 21 22 indicating identical communities. The relatively low value suggests that the similarity 23 24 between the five localities is reasonable, perhaps indicating they are essentially from the same 25 26 27 age and environment. Table 3 outlines the individual CC values for each pair of sites. 28 29 30 31 32 6. Discussion 33 34 6.1. The Chipping Sodbury railway cutting fauna 35 36 Lissodus minimus dominates this ecosystem, making up 70% of identifiable material 37 38 39 from this site, as noted earlier (Reynolds & Vaughan, 1904), and as is the case at other 40 41 Rhaetian sites (Duffin, 1999; Korneisel et al., 2015). The teeth of this species suggest that it 42 43 44 was a shell crusher (Korneisel et al., 2015), feeding opportunistically on molluscs and 45 46 arthropods, which are known to be numerous in the Westbury Formation and Cotham 47 48 49 Member (Reynolds and Vaughan, 1904; Mander and Twitchett, 2008; Marquez-Aliaga et al., 50 51 2010). 52 53 The second most common species, comprising 15% of the sample, is the palaeoniscid 54 55 56 chondrostean Gyrolepis albertii, which had previously been reported from the railway cutting 57 58 (Reynolds and Vaughan, 1904). G. albertii was a large, predatory fish; a specimen from 59 60 61 62 63 64 65 20

Pfersdorf, in the Schweinfurt district of Germany measured 31 cm in length (Steinkern, 2012), 1 2 and the long, needle-like hooked teeth suggest that it was a piscivore (Tintori, 1998; Korneisel 3 4 5 et al., 2015). It is possible that G. albertii preyed on the abundant, and smaller Lissodus. 6 7 minimus. 8 9 10 Of the remaining ~15% of identifiable fossil material, the most common species is 11 12 Severnichthys acuminata, which was described by Reynolds and Vaughan (1904) as 13 14 dominating this locality along with L. minimus, but in this collection it occurs at a frequency 15 16 17 of just 9%. In other regions of the Westbury Formation, Severnichthys represents the top 18 19 predator (Storrs, 1994), and is similar to G. albertii, in as much as it is a large predatory 20 21 22 species, and probably fed on small chondrichthyans and osteichthyans. 23 24 Some 3% of the total material is made up of the remains of Rhomphaiodon minor. This 25 26 27 small shark is found throughout the Westbury Formation, and only a single specimen has 28 29 previously been noted from Chipping Sodbury cutting. Reynolds and Vaughan (1904) 30 31 describe finding ‘one small tooth…probably to be referred to this species [Rhomphaiodon 32 33 34 minor]’. Elsewhere in the Westbury Formation, the heterodont teeth and fin spines of this 35 36 species are common (Duffin, 1999). R. minor likely represents a small, opportunistic predator, 37 38 39 or possibly even a scavenger (Tintori, 1998), but would also likely have been prey to 40 41 Gyrolepis and Severnichthys. 42 43 44 The small number of specimens assigned to Hybodus cloacinus was slightly 45 46 unexpected, especially as Reynolds and Vaughan (1904) also recorded H. cloacinus from this 47 48 49 site. 50 51 52 53 6.2. The Barnhill Quarry fauna 54 55 56 The ecology of the Rhaetian fishes from Barnhill Quarry is more diverse, with relatively 57 58 even proportions of species frequencies compared to the railway cutting. Here, the ‘Birgeria 59 60 61 62 63 64 65 21

acuminata’ type teeth of Severnichthys acuminatus dominate the ecosystem, at a species 1 2 frequency of 33%. Also common here is Gyrolepis albertii, found here at a species frequency 3 4 5 of 17%, opposite proportions to those of the railway cutting. 6 7 As well as these two large actinopterygians, other predators are found at Barnhill. The 8 9 10 largest specimens are the teeth of the hybodontiform shark Hybodus cloacinus, which occur at 11 12 a frequency of 9.4% at Barnhill, and are classified as clutching type teeth (Cuny and Benton, 13 14 1999), adapted to grasping and tearing flesh from large prey, as opposed to a habit of pursuing 15 16 17 smaller species. Lissodus minimus also occurs here, but at a relatively low frequency 18 19 compared to the railway cutting (32%). 20 21 22 Some of the best-preserved teeth in the Curtis collection are those of Rhomphaiodon 23 24 minor, a small synechodontiform shark that occurs at a frequency of 10% in the Barnhill 25 26 27 collection. This species is known from Triassic deposits in many European countries 28 29 including Belgium (Duffin and Delsate, 1993; Duffin et al., 1983), France (Cuny et al., 2000) 30 31 and Luxembourg (Godefroit et al., 1998) as well as the UK (Norden et al., 2015). Due to the 32 33 34 curved, knife-shaped structure of the teeth, it is reasonable to suggest that R. minor may have 35 36 fed on smaller osteichthyans and invertebrates known to have been found in the Rhaetian 37 38 39 (Smith et al., 2014). 40 41 A single tooth of Sargodon tomicus was also found in the Barnhill collection. This 42 43 44 species is relatively rare in the Westbury Formation, and is entirely absent from the Cotham 45 46 Member (Allard et al., 2015). 47 48 49 50 51 6.3. Wider comparison 52 53 The fish species found at the two sites are typical of the Westbury Formation (Duffin, 54 55 56 1999), and the majority are also the most common in shallow-sea biomes (Storrs, 1994). 57 58 Associated fossils, such as bivalves and other marine invertebrates have been noted in 59 60 61 62 63 64 65 22

association with similar vertebrate faunas from other localities nearby (Reynolds and 1 2 Vaughan, 1904; Nordén et al., 2015; Allard et al., 2015) and from other parts of the region 3 4 5 (Richardson, 1906; Korneisel et al., 2015). However, because the fossiliferous sediment was 6 7 treated with acetic acid, invertebrate remains were likely to have been damaged or destroyed, 8 9 10 and so were not reported here. 11 12 In our comparison of faunas, we established two points, namely (1) that most of the 13 14 basal bone bed samples showed essentially identical faunal compositions, and (2) the railway 15 16 17 cutting assemblage showed most differences from the others. We have over 1000 identified 18 19 specimens from this latter assemblage, so it is not likely to be simply a question of sample 20 21 22 size. However, we cannot rule out that other sampling biases might have come into play, such 23 24 as some selectivity in preservation of remains, or in the collection and processing procedures 25 26 27 used by Mike Curtis. Perhaps, however, the human aspect was minimal because Curtis, so far 28 29 as we know, applied the same methods in all his field and laboratory work, and so would not 30 31 have used some different means of excavation or different methods of chemical treatment or 32 33 34 sample sieving, but we cannot prove that. So, perhaps there was some taphonomic sorting of 35 36 fossil remains before deposition, and the sporadic wedging in and out of the basal bone bed 37 38 39 along the railway cutting, reported by Reynolds and Vaughan (1904) might be slight evidence 40 41 in support of such a tentative conclusion. 42 43 44 How typical are these British faunas when compared with those from elsewhere in 45 46 Europe? We compare the composition of the Barnhill Quarry and Chipping Sodbury railway 47 48 49 cutting ichthyofaunas with those sampled from other Rhaetian sequences in the West 50 51 Country, the East Midlands and further afield in continental Europe (Table 4). Only those 52 53 faunas which have been directly examined by us, or which have been the subject of good 54 55 56 quality illustration have been included so as to avoid any significant variation in taxon 57 58 identification. It is clear that some species are extremely rare in the Rhaetian as a whole, 59 60 61 62 63 64 65 23

being recorded at very few localities and in small numbers (e.g. the sharks Palaeobates 1 2 reticulatus, Parascylloides turnerae, Vallisia coppi, the holocephalans Agkistracanthus 3 4 5 mitgelensis and Myriacanthus paradoxus, and coelacanths and dipnoans). Some species are 6 7 based on occasional records outside their standard time range; Lissodus lepagei was originally 8 9 10 described from the Norian of Medernach in Luxembourg (Duffin 1993a) but has since been 11 12 recorded at Syren, Lorraine-Luxembourg by Godefroit et al (1998). 13 14 Hybodus cloacinus, which ranges into the Lower Jurassic (Hettangian to Sinemurian of 15 16 17 Lyme Regis; Duffin 1993b), is widely distributed but, having rather large teeth that are 18 19 subject to taphonomic filtering, is usually a minor component of Rhaetian vertebrate faunas. 20 21 22 The teeth of Lissodus minimus and Rhomphaiodon minor may vary in frequency but are 23 24 ubiquitous components of the Rhaetian fish fauna. The teeth of Pseudodalatias barnstonensis, 25 26 27 Duffinselache holwellensis, Pseudocetorhinus pickfordi and Synechodus rhaeticus, although 28 29 not so widespread or common as the former two species, are nevertheless sufficiently well 30 31 represented across a range of localities to be counted amongst the shark species which are 32 33 34 useful indicators of deposits of Rhaetian age. 35 36 37 38 39 7. Conclusion 40 41 The geographic proximity of the sites from which these collections were gathered, 42 43 44 located about 1 km apart, was an important driver of this study and, unexpectedly, the relative 45 46 proportions of taxa differ substantially. Not only do these faunas differ statistically from each 47 48 49 other according to several standard ecological indices, but the Chipping Sodbury railway 50 51 cutting fauna was found to be substantially different from a number of other Rhaetian basal 52 53 bone bed faunas reported from Devon to Gloucestershire, a distance of 150 km, whereas these 54 55 56 faunas all show considerable resemblances to each other. This anomaly cannot immediately 57 58 be investigated as the site is now densely overgrown and, being within a deep cutting of an 59 60 61 62 63 64 65 24

active railway line, is not readily accessible. If equal samples of Rhaetian sediment could be 1 2 obtained from each of the five sites investigated here, and possibly from other well-known 3 4 5 sites, then this hypothesis of sampling bias could be tested. 6 7 8 9 10 Acknowledgements 11 12 We thank curators Debbie Hutchinson and Isla Gladstone for access to BRSMG 13 14 materials. We thank the late Mike Curtis for his care and enthusiasm in making his collections 15 16 17 of Rhaetian microvertebrates. We thank Simon Curtis of Bloor Homes for his assistance in 18 19 our accessing the Rhaetian outcrop at Barnhill Quarry, and Tom Davies for assistance with 20 21 22 microphotography. We thank Elaine Arthurs, of the STEAM Museum of the Great Western 23 24 Railway, for allowing us access to the museum’s archives. This paper arises from an 25 26 27 undergraduate summer internship by R.L. in the Bristol Palaeobiology Laboratories, which 28 29 would not have been possible without the help and support of Lucy Tallis, and Peter and 30 31 Gwenyth Lakin. 32 33 34 35 36 References 37 38 39 Allard, H., Carpenter, S., Duffin, C.J., Benton, M.J., 2015. Microvertebrates from the classic 40 41 basal Rhaetian bone bed of Manor Farm Quarry, near Aust (Bristol, UK). Proceedings of 42 43 44 the Geologists’ Association, online ahead of print (doi: 10.1016/j.pgeola.2015.09.002). 45 46 Benton, M.J., Cook, E., Turner, P., 2002. Permian and Triassic Red Beds and the Penarth 47 48 49 Group of Great Britain. Geological Conservation Review Series, No. 24. Joint Nature 50 51 Conservation Committee, Peterborough, 337 pp. 52 53 Cuny, G.. Benton, M.J., 1999. Early radiation of the neoselachian sharks in western Europe. 54 55 56 Geobios 32, 193–204. 57 58 59 60 61 62 63 64 65 25

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Sørenson, T., 1948. A method of establishing groups of equal amplitude in plant sociology 1 2 based on similarity of species and its application to analyses of the vegetation on Danish 3 4 5 commons. Kongelige Danske Videnskabernes Selskab, Biologiske Skrifter 5, 1–34. 6 7 Steinkern, 2012. Middle Triassic; Gyrolepis alberti, [Online] Available from 8 9 10 http://www.steinkern.de/steinkern-de-galerie/mainfranken/gyrolepis-alberti.html 11 12 [Accessed 27/07/15]. 13 14 Storrs, G.W., 1994. Fossil vertebrate faunas of the British Rhaetian (latest Triassic), 15 16 17 Zoological Journal of the Linnaean Society 112, 217–259. 18 19 Suan, G., Föllmi, K.B., Adatte, T., Bomou, B., Spangenberg, J.E.,Van De Schootbrugge, B., 20 21 22 2012. Major environmental change and bonebed genesis prior to the Triassic–Jurassic 23 24 mass extinction. Journal of the Geological Society 169, 191–200. 25 26 27 Swift, A., Martill, D.M., 1999. Fossils of the Rhaetian Penarth Group, UK. The 28 29 Palaeontological Association, London. 30 31 Sykes, J.H., 1974. On elasmobranch dermal denticles from the Rhaetic Bone Bed at 32 33 34 Barnstone, Nottinghamshire. Mercian Geologist 5, 49–64. 35 36 Sykes, J.H., Cargill, J.S., Fryer, H.G., 1970. The stratigraphy and palaeontology of the 37 38 39 Rhaetian beds (Rhaetian: Upper Triassic) of Barnstone, Nottinghamshire. Mercian 40 41 Geologist 3, 233–264. 42 43 44 Thies, D., Vespermann, J., Solcher, J., 2014. Two new neoselachian sharks (Elasmobranchii, 45 46 Neoselachii, Synechodontiformes) from the Rhaetian (Late Triassic) of Europe. 47 48 49 Palaeontographica, Abteilung A 303, 137–167. 50 51 Tintori, A., 1998. Fish biodiversity in the marine Norian (Late Triassic) of northern Italy: the 52 53 first neopterygian radiation. Italian Journal of Zoology 65, 193–198. 54 55 56 57 58 59 60 61 62 63 64 65 29

Trotter, J.A., Williams, I.S., Nicora, A., Mazza, M., Rigo, M., 2015. Long-term cycles of 1 2 Triassic climate change: a new δ18O record from conodont apatite. Earth and Planetary 3 4 5 Science Letters 415, 165–174. 6 7 Tuomisto, H., 2010. A diversity of beta diversities: straightening up a concept gone awry. Part 8 9 10 1. Defining beta diversity as a function of alpha and gamma diversity, Ecography, 33, 2– 11 12 22. 13 14 Walker, T.A., 1888. The Severn Tunnel: Its Construction and Difficulties 1872-1887, 1st ed. 15 16 17 Richard Bentley and Son, London. 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 30

Fig. 1. Geological map of the Chipping Sodbury area, with Barnhill Quarry and the Chipping 1 2 Sodbury railway cutting marked (yellow stars). Key geological formations are indicated, 3 4 5 separated into four key Carboniferous units (bottom of column) and the key Triassic–Jurassic 6 7 units above. © Crown Copyright and Database Right 2015. Ordnance Survey (Digimap 8 9 10 Licence). 11 12 13 Fig. 2. Cross-section of the section of railway line where the bone bed is exposed (NGR ST 14 15 728816), with three stratigraphic columns through the Rhaetian succession, as documented by 16 17 18 Reynolds and Vaughan (1904). The longitudinal section is from Reynolds and Vaughan 19 20 (1904). Metric scales are added. 21 22 23 Fig. 3. Illustration of Barnhill Quarry taken from Reynolds (1938) to show the position of the 24 25 26 Penarth Group within the quarry, with buildings and figures for scale. The four quarried 27 28 platforms, marking the top of the Carboniferous Limestone are labelled ‘A’–‘D’, and the 29 30 overlying Penarth Group is labelled at top right. T(a), T9B), and T(c) are three overthrusts, 31 32 33 structural features noted by Reynolds (1938). 34 35 36 Fig. 4. The Carboniferous-Triassic unconformity at Barnhill Quarry. (A) Dipping 37 38 Carboniferous Limestone beds overlain with Rhaetian at the level of the vegetation. (B) 39 40 41 Close-up of the contact between Carboniferous and Rhaetian sections, with the bone bed just 42 43 above the blocky, orange-stained limestone. 44 45 46 Teeth of the shark from Barnhill Quarry and the Chipping Sodbury 47 Fig. 5. Lissodus minimus 48 49 railway cutting. (A) BRSMG Cf14012; (B) BRSMG Cf14013; (C) BRSMG Cf14014; (D and 50 51 E) BRSMG Cf14015, in occlusal (D) and lateral (E) views. 52 53 54 Anterolateral teeth of the shark from Barnhill Quarry. (A) BRSMG 55 Fig. 6. Hybodus cloacinus 56 57 Cf14204 in labial view; (B) BRSMG Cf14205 in occlusal view. 58 59 60 61 62 63 64 65 31

Fig. 7. Teeth of the shark Rhomphaiodon minor from Barnhill Quarry and the Chipping 1 2 Sodbury railway cutting. (A and B) Complete pentacuspid tooth (BRSMG Cc6321) in 3 4 5 occlusal (A) and labial (B) views. (C and D) Complete tricuspid tooth (BRSMG Cc6322) in 6 7 occlusal (C) and labial (D) views. (E and F) Unidentified holocephalan dermal denticle 8 9 10 (BRSMG Cc6323) in lateral (E) and dorsal (F) views. 11 12 13 Fig. 8. Shark fin spines from Chipping Sodbury railway cutting. (A and B) Nemacanthus sp. 14 15 fin spine (BRSMG Cc6324), in two views (A, B). (C) Unidentified hybodontiform fine spine 16 17 18 fragment (BRSMG Cf14082.52). 19 20 21 Fig. 9. Hybodont dermal denticle (BRSMG Cc6325), from Chipping Sodbury railway cutting, 22 23 in anterior (A) and lateral (B) views. 24 25 26 Fig. 10. Remains of the osteichthyan Gyrolepis albertii from Barnhill Quarry and the 27 28 29 Chipping Sodbury railway cutting. (A and B) Dermal scale (BRSMG Cc6326) in external (A) 30 31 and internal (B) views. (C and D) Tooth (BRSMG Cf14266) in lateral distal (C) and proximal 32 33 34 (D) views. 35 36 37 Fig. 11. Teeth of bony fishes from Barnhill Quarry and the Chipping Sodbury railway cutting. 38 39 (A and B) Birgeria acuminata-type tooth (BRSMG Cf14308) of Severnichthys acuminatus, 40 41 42 (C and D) Saurichthys longidens-type tooth (BRSMG Cf14322) of Severnichthys acuminatus. 43 44 (E and F) A tooth of Sargodon tomicus (BRSMG Cf14379). 45 46 47 Fig. 12. Teeth of Ceratodus sp. from Barnhill Quarry. (A and B) Partial tooth BRSMG 48 49 50 Cf14250, in occlusal (A) and ventral (B) views. (C and D) Partial tooth BRSMG Cf14251, in 51 52 occlusal (C) and lingual (D) views. 53 54 55 Fig. 13. Pie charts illustrating relative species frequencies, among identifiable material from 56 57 58 Barnhill Quarry (A) and the Chipping Sodbury railway cutting (B). Species are named in the 59 60 key; Misc., Miscellaneous. 61 62 63 64 65 32

Table 1. Abundance table of taxa from Barnhill Quarry and Chipping Sodbury Railway 1 2 Cutting, showing raw numbers of specimens 3 4 5 ______6 7 8 9 Taxon Barnhill Quarry Chipping Sodbury Railway Cutting 10 11 12 ______13 14 15 Lissodus minimus 102 774 16 17 18 Hybodus cloacinus 17 3 19 20 21 Rhomphaiodon minor 33 33 22 23 24 Holocephali 1 0 25 26 27 Nemacanthus 0 1 28 29 30 31 Misc. Hybodontiforms 2 12 32 33 34 Gyrolepis albertii 53 173 35 36 37 Severnichthys acuminatus 105 104 38 39 40 Sargodon tomicus 1 0 41 42 43 Ceratodus sp. 2 0 44 45 46 TOTAL 316 1100 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 33

Table 2. Comparison of five Rhaetian bone beds, according to some standard ecological 1 2 statistical measures, the Shannon-Wiener Biodiversity Index (H’), Species Evenness (J’), and 3 4 5 Simpson’s Index of Biodiversity (D). 6 7 8 9 10 Locality H' J' D 11 12 13 14 15 Barnhill Quarry 1.524 0.69 0.254 16 17 18 19 20 Chipping Sodbury Railway Cutting 0.938 0.48 0.529 21 22 23 24 Manor Farm Quarry 1.539 0.62 0.274 25 26 27 28 29 Charton Bay 1.729 0.79 0.223 30 31 32 33 34 Marston Road Quarry 1.735 0.72 0.237 35 36 37 38 39 Interquartile range 0.205 0.10 0.037 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 34

Table 3. Comparison of five Rhaetian bone beds using the standard statistical measure of the 1 2 Sørenson-Dice Coefficient. 3 4 5 6 Bhl Rly MF Ch MR 7 8 9 10 11 12 Bhl X X X X X 13 14 15 Rly 0.75 X X X X 16 17 18 19 MF 0.67 0.63 X X X 20 21 22 23 Ch 0.67 0.63 0.76 X X 24 25 26 27 MR 0.70 0.67 0.87 0.80 X 28 29 30 31 32 Key: 33 34 Bhl - Barnhill Quarry 35 36 Rly - Chipping Sodbury Railway Cutting 37 38 MF - Manor Farm Quarry 39 40 Ch - Charton Bay 41 42 MR - Marston Road Quarry 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 1 2 3 35 4 5 6 Table 4. Wider comparison of Rhaetian fish faunas based upon personal observations and Allard et al. (2015), Duffin (1980a, 1980b), Duffin & 7 Delsate (1993), Duffin et al. (1983), Godefroit et al. (1998), Korneisel et al. (2015), Nordén et al. (2015), Sykes et al. (1970). GB = Great Britain, 8 B = Belgium, L = Luxembourg. 9 10 Group Taxon 11 12 13 14

15 16

19 20 21 Vieille (B) Vieille

22 - Bay (GB) (GB) Bay

23 -

24 25 Barnhill Quarry (GB) Barnhill Quarry Cutting Chipping Sodbury Railway (GB) Quarry Farm Manor Road (GB) Marston (GB) Quarry Holwell Chilcompton (GB) Charton (GB) Barnstone Habay (B) Attert (L) Syren

26 (GB) 27 Hybodontiformes Lissodus minimus X X X X X X X X X X X 28 Lissodus lepagei X 29 30 Hybodus cloacinus X X X X X X X X X 31 Palaeobates reticulatus X 32 Neoselachii Rhomphaiodon minor X X X X X X X X X X X 33 34 Duffinselache holwellensis X X X X X X 35 Synechodus rhaeticus X X X X 36 Nemacanthus fin spines X X X X X X 37 Vallisia coppi X X X 38 39 Pseudodalatias barnstonensis X X X X X 40 Pseudocetorhinus pickfordi X X X X X X X 41 Parascylloides turnerae X 42 43 Holocephali Agkistracanthus mitgelensis X 44 Holocephalan scales X X X X X X X 45 46 47 48 49 1 2 3 36 4 5 6 Osteichthyes Gyrolepis albertii X X X X X X X X X X X 7 Severnichthys acuminatus X X X X X X X X X X X 8 Sargodon tomicus X X X X X X X X X 9 10 Lepidotes sp. X X X 11 Dapedium sp. X ? 12 cf. Colobodus X X X X 13 Indet. coelacanth (quadrates) X X 14 15 Ceratodus latissimus ? ? 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 Figure

Alluvium Scale 1:10000 0 100 200 300 400 500 600 700 800 900 1000 m TRIASSIC–JURASSIC Charmouth Mudstone Formation

Wilmcote Limestone Member

Saltford Shale Member

Langport Member and Wilmcote Limestone Member

Penarth Group

Blue Anchor Formation

CARBONIFEROUS Black Rock Limestone Formation

Gully Oolite Formation

Clifton Down Limestone Formation

0.11 m Black, clayey soil Grey shale (Molluscs) 0.06 m Hard grey limestone Brown shale 0.09 m Black paper shales Argillaceous 0.06 m Compact grey limestone limestone 0.06 m Black paper shales Brown/grey shale Brown/grey (Mollusca) shale Upper Rhaetic Hard grey crystalline Black shale 0.61m Pale limestone 0.40 m with calcerous 0.13m limestone bands 0.91m

Upper Grey shale Rhaetic Black shale 0.18m 0.08m Argillaceous limestone with sandy Dark crystalline layers (Mollusca) Limestone(molluscs) Black shale 3.66m Black (few teeth/ limestone vertebrae) 0.30 m Grey black shales Soft black clay Lower Rhaetic (rich in Lower Rhaetic vertebrates) Bone-bed (molluscs & vertebrates) 8.5 m to track

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A B Lissodus minimus Hybodus cloacinus Rhomphaiodon minor Holocephali Misc Hybodontidae Gyrolepis albertii Severnichthys acuminata Sargodon tomicus Ceratodus sp. e-component Click here to download e-component: Lakin-SI-rev.xlsx