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Summary of Late Triassic and Early Jurassic stratigraphy in England (after Swift, 1999; Trueman and Benton, 1997).
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One of the most dramatic environmental changes in the Mesozoic history of Europe was the switch from terrestrial to marine deposition marked by the Rhaetian Transgression, 205 Ma. Beginning with this event, the Mendip Hills, composed primarily of uplifted and folded Lower Carboniferous limestones, were flooded in a stepwise manner from the Late Tri...
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... Late Triassic was a time of major environmental change. The Rhaetian transgression marks the switch from primarily terrestrial to marine conditions about 205.5 Ma, and it has been noted across much of Europe. The event is marked in the UK by the switch from the Mercia Mudstone Group to the Penarth Group ( Fig. 1), starting with the famous Westbury Formation basal bone bed, which is made up of a rich accumulation of disarticulated vertebrate fossils (Storrs, 1994). The change is evident at many localities, especially those such as Aust Cliff ( Cross et al., 2018) where the Mercia Mudstone Group largely comprises red beds and is conformably ...
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... Finally, McMurtrie (1885, pp. 103-106) repeated some of Moore's comments, but especially highlighted how the Carboniferous limestone along the banks of the Mells River was overlaid successively by Rhaetian, Lias and Middle Jurassic rocks, corresponding to an inferred steeply rising palaeotopography of the eroded top of the Carboniferous limestone (Fig. 1B). Woodward (1890) gave a generalised overview of Mendip geology, and provided (p. 489, Fig. 2) a rather poorly redrawn version of the unconformity illustrated by De la Beche (1846, p. ...
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... a diversity of building stones (Stokes, 1999). Quarrying in Vallis Vale began in 1893 with the formation of the Somerset Quarry Company (Foundations of the Mendips, 2017) to work quarries in the valley of the Mells River beside Hapsford Mill, on the Vallis Road (A362). The company worked four quarry faces along the south bank of Vallis Vale ( Fig. 2A, localities 1-3), and the 41-man team produced over 100 tons of rock a day of which 10 % was burnt for lime in two quarry kilns and the rest was crushed for road building (Thornes, 2015, p. 75). The limestone was transported in wagons called 'tubs' and drawn by horses along narrowgauge rail lines to Hapsford Mill. There, the full tubs of stone were ...
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... work focuses on the Rhaetian bone beds at the Hapsford Bridge roadside locality (ST 76057 49507) which runs parallel to the Mells River ( Fig. 2A, locality 1). Other quarries in the Vallis area were also examined ( Fig. 2A) and these include two further disused quarries (ST 760494, ST 760493; location 2), the site of the De la Beche unconformity (ST 7557 4918; location 3), and Egford Quarry (ST 7575 4871; location ...
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... of the palaeontological study is based on samples of the basal Rhaetian bone bed collected in October 2018 (Fig. 4). Samples were taken from the measured beds ( Fig. 4C), with some 1 kg each of potential bone beds sampled from Beds 2, 3 4, 5, 6 and 8 and small blocks from beds 4, 6 and 8 collected for slab-cutting (Fig. ...
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... surface of the root is roughened, and it bears some large, circular pores. Some of the Hapsford specimens are complete (Fig. 7A, B), but others are broken (Fig. 7C-F), as commonly seen in previously described examples from Vallis Vale (Duffin, 1982), Manor Farm Quarry (Allard et al., 2015, Fig. 4B), Hampstead Farm Quarry (Mears et al., 2016, Fig. 6k), and Belgium ( Duffin et al., 1983). The affinities of Vallisia coppi have been debated, with Cuny and Benton (1999) confirming that the ultrastructure of the enameloid is not neoselachian. ...
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... 'Birgeria'-type teeth (Fig. 8M-O) are < 1 mm in height and the translucent tip occupies more of the tooth length. All Severnichthys teeth lack distinct ridges, which probably reflects their somewhat abraded state: Cross et al. (2018 , Fig. 10b, c) shows unabraded examples with distinct longitudinal wrinkles and ridges in the Saurichthys-type teeth. ...
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... found 45 barnacle pieces, all of them phosphatic, black on the outer surface, likely to be from Eolepas, but they are all broken (Fig. 10A-D). One example shows the classic pattern of horizontal, parallel growth lines, intersecting a vertical pattern of fine ridges on the outer face (Fig. 10A), but with a smooth inner face (Fig. 10B). Another specimen shows the same external sculpture (Fig. 10C) and a platform and concave shape internally (Fig. 10D). All of the fragments ...
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... found 45 barnacle pieces, all of them phosphatic, black on the outer surface, likely to be from Eolepas, but they are all broken (Fig. 10A-D). One example shows the classic pattern of horizontal, parallel growth lines, intersecting a vertical pattern of fine ridges on the outer face (Fig. 10A), but with a smooth inner face (Fig. 10B). Another specimen shows the same external sculpture (Fig. 10C) and a platform and concave shape internally (Fig. 10D). All of the fragments seem to be partial scutum and carina ...
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... found 45 barnacle pieces, all of them phosphatic, black on the outer surface, likely to be from Eolepas, but they are all broken (Fig. 10A-D). One example shows the classic pattern of horizontal, parallel growth lines, intersecting a vertical pattern of fine ridges on the outer face (Fig. 10A), but with a smooth inner face (Fig. 10B). Another specimen shows the same external sculpture (Fig. 10C) and a platform and concave shape internally (Fig. 10D). All of the fragments seem to be partial scutum and carina ...
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... black on the outer surface, likely to be from Eolepas, but they are all broken (Fig. 10A-D). One example shows the classic pattern of horizontal, parallel growth lines, intersecting a vertical pattern of fine ridges on the outer face (Fig. 10A), but with a smooth inner face (Fig. 10B). Another specimen shows the same external sculpture (Fig. 10C) and a platform and concave shape internally (Fig. 10D). All of the fragments seem to be partial scutum and carina ...
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... Eolepas, but they are all broken (Fig. 10A-D). One example shows the classic pattern of horizontal, parallel growth lines, intersecting a vertical pattern of fine ridges on the outer face (Fig. 10A), but with a smooth inner face (Fig. 10B). Another specimen shows the same external sculpture (Fig. 10C) and a platform and concave shape internally (Fig. 10D). All of the fragments seem to be partial scutum and carina ...
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... examples of bivalves were identified. Some are broken portions of large oysters with heavy zig-zag commissure line, like Lopha haidingeriana (cf. Ivimey-Cook et al., 1999, pl. 13, Fig. 8). Two (Fig. 10E-F) show the general shape, irregular layering, and radiating pattern of fine ridges seen in Atreta intusstriata (cf. Ivimey-Cook, et al., 1999, pl. 13, Figs. 3, 4). Both are 5-6 mm in size, and represent incomplete fragments from near the hinge line, showing irregular folds in the shell, and radiating ...
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... rare in the Westbury Formation, occurring more commonly in the Lilstock Formation. It is a dimyoid oyster (Order Ostreoida), typically small (maximum height 12 mm, and width 9 mm) and the right valve was cemented to the rock, presumably close to shore. We identified it also as one of the encrusting bivalves on the uprooted Carboniferous pebbles (Fig. ...
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... identified 14 echinoid spines, possibly those of cidaroids, all of which are elongate and cylindrical, and range in size from 2 mm to over 9 mm in length, and 1-2 mm in diameter. They are all preserved differently, one ( Fig. 10G) being grey-coloured and mottled, 8 mm long, another (Fig. 10H) orange, and 6 mm long, and showing some tapering, and a further one (Fig. 10I) grey and tapering, 8 mm ...
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... identified 14 echinoid spines, possibly those of cidaroids, all of which are elongate and cylindrical, and range in size from 2 mm to over 9 mm in length, and 1-2 mm in diameter. They are all preserved differently, one ( Fig. 10G) being grey-coloured and mottled, 8 mm long, another (Fig. 10H) orange, and 6 mm long, and showing some tapering, and a further one (Fig. 10I) grey and tapering, 8 mm ...
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... echinoid spines, possibly those of cidaroids, all of which are elongate and cylindrical, and range in size from 2 mm to over 9 mm in length, and 1-2 mm in diameter. They are all preserved differently, one ( Fig. 10G) being grey-coloured and mottled, 8 mm long, another (Fig. 10H) orange, and 6 mm long, and showing some tapering, and a further one (Fig. 10I) grey and tapering, 8 mm ...
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... spines are frequently reported in sieved residues of the Rhaetian bone beds (Swift, 1999). Our examples are rather featureless when compared to those reported from Hampstead Farm Quarry ( Mears et al., 2016, Fig. 17h), which show the basal boss or acetabulum by which they attach to the echinoid test and short pines on longitudinal ridges along the length of the ...
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... specimen, originally identified as a cidaroid spine (Fig.10J), is composed of crystalline calcite which shows a radiating pattern on the broken end. It is hard to identify definitively as either cidaroid or belemnite because of considerable abrasion of the outer surface. ...
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... identified only four coprolites in our collection ( Fig. 10K-N). They measure 1-2 mm in diameter and 3-7 mm long, but all are broken and incomplete. All coprolites are light brown/grey in colour and show the usual spiral structure. None of them show identifiable remains of plants or fish scales on the ...
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... generally <10 specimens each. Therefore, comparing the relative proportions of the different categories between the five fossiliferous horizons was less useful than we had expected, unlike in the case of the Hampstead Farm Rhaetian where substantial differences were found in faunal composition up through the section ( Mears et al., 2016). Here (Fig. 11), we can say that Gyrolepis teeth are generally the most common fossils at all levels, then with main occurrences of Synechodus and Duffinselache in bed 5, Synechodus and Lissodus in bed 8, and Severnichthys in beds ...
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... the sharks, the absence of Rhomphaiodon is surprising, as it is usually the most common shark tooth in other British Rhaetian bone beds ( Allard et al., 2015;Norden et al., 2015;Cross et al., 2018). Further differences are the occurrence of the shark Vallisia coppi and the barnacle Eolepas rhaetica at Hapsford Bridge, taxa that occur only rarely elsewhere; Vallisia was reported from Hampstead Farm Quarry ( Mears et al. 2016, p. 487) and Manor Farm (Allard et al., 2015, p. 768). Finally, unlike most other Rhaetian bone bed sites, we do not find teeth of the durophagous actinopterygians Sargodon and Lepidotes. ...
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... actinopterygians Gyrolepis and Severnichthys were also predatory, feeding on small to medium-sized prey respectively. As in previous Rhaetian bone bed food web reconstructions (e.g., Cross et al. 2018, Fig.15), Gyrolepis is in the middle of the food chain, probably preying on invertebrates and smaller fishes, and preyed upon by Severnichthys and the sharks. ...
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... Vallis Vale Rhaetian is also a source of bored and encrusted pebbles of Carboniferous limestone, which occur in the basal mudstones and in the bone bed. Richardson (1911) noted these at several locations, and Copp (1980, pp. 327-340) reported several examples from Vallis Vale. One specimen (Fig.12A, B) shows numerous borings of two size classes, 0.8-0.9 mm and 3-4 mm in diameter, and both up to 10 mm long. Two or three shallow borings, 4-6 mm in diameter and 6-10 mm deep, have a flask-like shape, broader at the rounded base and with a narrower neck (the 'clavate' shape). Note that the borings occur on one side only of the flat ...
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... of the pebbles (e.g., Fig. 12C, D) are also encrusted with examples of two bivalves, Atreta intusstriata and the oyster Liostrea, both typical of the Rhaetian (Swift, 1999). This confirms that uplift and tumbling of the pebbles happened in the Rhaetian, when they became encrusted as they lay on the sea floor and before ...
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... pebbles confirm that the Carboniferous limestone top surface formed a hardground under the advancing Rhaetian sea, and here and there the energy of the Rhaetian waters tore up chunks of that hardground, retaining the borings, but tumbling and abrading the pebbles before they were redeposited (Fig. 11E, F). Then, some of them became encrusted by oysters in the shallow Inferred history, as encrusting worms and bivalves make Trypanites and Gastrochaenolites borings, respectively, presumably in earliest Rhaetian times (E), and then some surface layers of the Carboniferous pavement is stripped off, and the fragments tumbled and abraded, ...
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... identified putative storm bed sediments at three levels in the Westbury Formation (Fig. 5C), in the muddy limestone containing the 'basal' bone bed (Fig. 13A, B), in the calcareous mudstone 60 cm above (Fig. 13C, D), and in the muddy limestone a further 43 cm above (Fig. 13E, F). When cut vertically, these muddy limestone blocks show suspended conglomerates. The first example (Fig. 13A, B) shows a limited intraformational conglomeratic layer comprising some mudstone clasts, and abundant shelly ...
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... identified putative storm bed sediments at three levels in the Westbury Formation (Fig. 5C), in the muddy limestone containing the 'basal' bone bed (Fig. 13A, B), in the calcareous mudstone 60 cm above (Fig. 13C, D), and in the muddy limestone a further 43 cm above (Fig. 13E, F). When cut vertically, these muddy limestone blocks show suspended conglomerates. The first example (Fig. 13A, B) shows a limited intraformational conglomeratic layer comprising some mudstone clasts, and abundant shelly debris in an otherwise fine-grained limestone. The ...
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... identified putative storm bed sediments at three levels in the Westbury Formation (Fig. 5C), in the muddy limestone containing the 'basal' bone bed (Fig. 13A, B), in the calcareous mudstone 60 cm above (Fig. 13C, D), and in the muddy limestone a further 43 cm above (Fig. 13E, F). When cut vertically, these muddy limestone blocks show suspended conglomerates. The first example (Fig. 13A, B) shows a limited intraformational conglomeratic layer comprising some mudstone clasts, and abundant shelly debris in an otherwise fine-grained limestone. The second and third examples (Fig. 13C-F) show some large (up to 10 cm ...
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... sediments at three levels in the Westbury Formation (Fig. 5C), in the muddy limestone containing the 'basal' bone bed (Fig. 13A, B), in the calcareous mudstone 60 cm above (Fig. 13C, D), and in the muddy limestone a further 43 cm above (Fig. 13E, F). When cut vertically, these muddy limestone blocks show suspended conglomerates. The first example (Fig. 13A, B) shows a limited intraformational conglomeratic layer comprising some mudstone clasts, and abundant shelly debris in an otherwise fine-grained limestone. The second and third examples (Fig. 13C-F) show some large (up to 10 cm diameter), well-rounded clasts of grey brown and yellow-coloured mudstone, all of which match bedded sediments ...
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... muddy limestone a further 43 cm above (Fig. 13E, F). When cut vertically, these muddy limestone blocks show suspended conglomerates. The first example (Fig. 13A, B) shows a limited intraformational conglomeratic layer comprising some mudstone clasts, and abundant shelly debris in an otherwise fine-grained limestone. The second and third examples (Fig. 13C-F) show some large (up to 10 cm diameter), well-rounded clasts of grey brown and yellow-coloured mudstone, all of which match bedded sediments in the Westbury Formation succession. Around these larger clasts, there is a finer mush of 1-3 cm rounded pebbles and debris of < 10 mm diameter. The sediment above and below is fine-to ...
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... are two kinds of conglomerates at Hapsford Bridge, both indicating storm bed deposition. First, the flat pebbles (Fig. 12) presumably formed part of a flat-pebble conglomerate, a kind of deposit long interpreted as direct evidence of storm wave activity (Bourgeois and Leithold, 1984;Myrow et al., 2004), indicating high energy, churning currents that ripped up pebbles from the seabed and dumped them, often chaotically in basal storm deposits. Second, the ...
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... conglomerate, a kind of deposit long interpreted as direct evidence of storm wave activity (Bourgeois and Leithold, 1984;Myrow et al., 2004), indicating high energy, churning currents that ripped up pebbles from the seabed and dumped them, often chaotically in basal storm deposits. Second, the intraformational suspended conglomerate layers (Fig. 13) also indicate storm activity. Conglomerates usually show grading, as water currents diminish or increase in energy, but here, otherwise fine-grained sediments are suddenly visited by a pulse of large clasts from local sources. These are analogous to suspended coquinas, shell beds that unexpectedly occur in the midst of otherwise ...
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... Hapsford Bridge Penarth Group succession shows the usual marine characteristics as widely seen in the Rhaetian. The lower portions of the Westbury Formation were deposited presumably close to shore, and our evidence (Fig. 13) suggests that storm activity was frequent. Suan et al. (2012) noted five cycles of climate change throughout the time of deposition of the Westbury Formation, each marked by a pulse of organic carbon enrichment. At times of water deepening, abundant phosphate was generated, corresponding to successions of black, anoxic mudstones and ...
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... In the Triassic Rhaetian Epoch (208.5−201.3 Ma), continued rifting in the Arctic-North Atlantic led to opening of the Viking Corridor, resulting in a southward transgression ( Figure 4e) and the development of shallow marine and transitional sandstones in the northern part of the basin (Steel and Ryseth, 1990;Lindström and Erlström, 2006;Ronan et al., 2020). (Marzoli et al., 1999), leading to a marine transgression in the North Sea Basin and the passage of the North Atlantic Warm Current through it. ...
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... Here, we describe chondrichthyan and actinopterygian remains sampled in 2018. They are compared with the material from the subrosion pipe (Diependaal & Reumer, 2021) and with the abundantly preserved Rhaetian fish material from the British Penarth Group (Korneisel et al., 2015;Nordén et al., 2015;Lakin et al., 2016;Slater et al., 2016;Cavicchini et al., 2018;Cross et al., 2018;Ronan et al., 2020;Moreau et al., 2021;Williams et al., 2022). The material here described concerns the first in situ Rhaetian from the Netherlands, and it considerably increases our knowledge of the Dutch Triassic. ...
... This species has also been mentioned from the UK (Duffin, 1985(Duffin, , 1998aCuny & Risnes, 2005;Foffa et al., 2014;Allard et al., 2015;Nordén et al., 2015;Korneisel et al., 2015;Slater et al., 2016;Whiteside et al., 2016;Lakin et al., 2016;Whiteside & Duffin, 2017;Landon et al., 2017;Cavicchini et al., 2018;Cross et al., 2018;Ronan et al., 2020;Moreau et al., 2021;Williams et al., 2022), Eastern Europe (Chrząstek, 2008;Michalík et al., 2013;Ősi et al., 2013;Posmoşanu, 2015;Botfalvai et al., 2019;Szabó et al., 2019) and Western Europe (Duffin, 1993;Duffin & Delsate, 1993;Cuny, 1995;Godefroit et al., 1998;Henz & Hertel, 2011;Cuny et al., 2013;Sander et al., 2016;Diependaal & Reumer, 2021). ...
... The height of these scales is about 1 mm. This type of scale is mentioned from many localities of the British Penarth Group (e.g., Duffin, 1998a;Landon et al., 2017;Cavicchini et al., 2018;Ronan et al., 2020;Moreau et al., 2021;Williams et al., 2022) and also from Poland (Duffin & Gaździcki, 1977) and Luxemburg (Delsate & Duffin, 1999). ...
Chondrichthyan and actinopterygian fish remains from Rhaetian (c. 208.05-201.36 Ma) or perhaps Late Norian deposits in the Winterswijk quarry are described. The most abundant taxon is the actinopterygian Gyrolepis albertii, followed by the chondrichthyan Lissodus minimus. Furthermore, the palaeopterygian actinopterygians Saurichthys longidens and Birgeria acuminata, and some teeth of neopterygians Sargodon tomicus, 'Lepidotes' sp. and indeterminate pycnodontiforms are recorded in addition to the chondrichthyans Rhomphaiodon minor, Parascylloides turnerae and some 'Hybodus' cf. cuspidatus (senior synonym of H. cloacinus). Chondrichthyan dermal denticles, actinopterygian scales and gill rakers, tooth plates, and some fish bones were also found. There is considerable faunal resemblance to the various localities from the Rhaetian of the British Penarth Group, although it depends on the location as to whether chondrichthyans or actinopterygians prevail in the samples. On average, there are more chondrichthyan teeth present in the British samples than actinopterygian teeth, which is opposite to the situation in Winterswijk. That might be explained by different ecological circumstances, such as lower oxygen levels in bottom waters in Winterswijk and freshwater input and/or changes in salinity in the UK.
... Recent studies by members of the Palaeobiology Research Group at Bristol University have concentrated on the Rhaetian microvertebrate faunas from a wide range of localities in the West of England, and the coprolite components of the various faunas have been noted (e.g. Korneisel et al., 2015;Nordén et al., 2015;Allard et al., 2015;Lakin et al., 2016;Slater et al., 2016;Mears et al., 2016;Landon et al., 2017;Cavicchini et al., 2018;Cross et al., 2018;Ronan et al., 2020). One locality, Hampstead Farm Quarry, near Chipping Sodbury in Gloucestershire, has yielded a numerically abundant coprofauna. ...
Coprolites from the Rhaetian bone beds in southwest England can be assigned to crustaceans and fishes. Here, we report crustacean microcoprolites, including Canalispalliatum and Favreina, the first records from the British Rhaetian, from Hampstead Farm Quarry near Bristol, evidence for diverse lobsters and their relatives not otherwise represented by body fossils. Further, we identify five fish coprolite morphotypes that differ in shape (cylindrical, flattened) and in presence or absence of a spiral internal structure. Many coprolites show bony inclusions on the surface, often relatively large in proportion to the coprolite; these show little or no evidence for acid damage, suggesting that the predators did not have the physiological adaptations of many modern predatory fishes and reptiles to dissolve bones. CT scanning has revealed the nature, packing and identity of inclusions within the coprolites, mainly fish scales, and some coprolites can contain more than twenty. An extraordinary discovery in one coprolite comprises a single sculptured skull element of the large bony fish Severnichthys together with two caudal vertebrae of the marine reptile Pachystropheus: did the coprolite producer, likely a fish, scavenge some flesh from the head of Severnichthys and then bite off the tail of the reptile? Assigning coprolites to producers is difficult, but it seems that Gyrolepis was preyed on by nearly every predator. The faunas and trophic relations revealed by the coprolites show that this was a modern-style marine ecosystem, with abundant crustaceans and several species of durophagous fishes, evidence for an early stage in the Mesozoic Marine Revolution.
The cliff and foreshore sections at Blue Anchor Bay, north Somerset, provide a detailed picture of the transitional Triassic–Jurassic succession. The site has been recorded as a location for fossil fishes for over 200 years, and yet the assemblages from the bone beds have not been described. Here, we present new observations on the two bone beds and find major faunal differences: the classic basal bone bed at Blue Anchor Bay contains an assemblage dominated by osteichthyan teeth, unexpected because elsewhere the ichthyofauna is usually dominated by chondrichthyans. The upper bone bed at Blue Anchor Bay is indeed more typical, being dominated by teeth of hybodont chondrichthyans. We report two unusual finds, first five teeth of the rare shark Parasycylloides turnerae, only the fifth such record in the UK. Further, we report here for the first time a tooth of the pycnodontiform Eomesodon, the first report of this taxon from the Triassic of the UK or Europe. The two bone beds are distinguished not only by different assemblages, but also by evidence of different degrees of anoxia and water depth: the upper bone bed contains abundant pyrite and marcasite, indicating highly anoxic conditions, and perhaps deposition in deeper water than the basal bone bed.
Rhaetian seas in the latest Triassic transgressed from west to east over the southwest of the UK, reaching parts of South Wales and the North Somerset coast first. Evidence comes from marine conditions in the pre-Rhaetian Williton Member, a unit not seen further east. Here, we confirm this hypothesis with reports of diverse, Rhaetian-style fish faunas in the Williton Member, as well as evidence that the Westbury Formation bone beds are from deeper waters than most others in the region. Our study focuses on the classic coastal section at Lilstock, which shows the entire Penarth Group and the Triassic-Jurassic boundary. The Williton Member fossil beds yield Rhaetian-type chondrichthyans (Lissodus, denticles), osteichthyan teeth (Gyrolepis, Sargodon, Saurichthys), and bivalves. The basal and higher bone beds of the Westbury Formation are dominated by osteichthyans (86.8%, 84.7%), with chondrichthyans relatively rare (13.2%, 15.3%), the opposite of what is seen at other locations in the southwest of the UK (16–59% osteichthyans; 41–84% chondrichthyans). The similarity of the faunal composition in the basal and higher Rhaetian bone beds is also unusual, and the dominance by bony fishes can be interpreted as evidence for deeper water than further to the east.
