A marine vertebrate fauna from the Late Triassic of Somerset, and a review of British placodonts

The Rhaetian (Late Triassic) vertebrates of Hampstead Farm Quarry, Gloucestershire, UK

“…The Rhaetian bone beds sample only two sauropterygian clades, the plesiosaurs and placodonts (Nordén et al, 2015), but not their typical Middle and Late Triassic relatives, the pachypleurosaurs and nothosaurs. Plesiosauria diversified rapidly in the earliest Jurassic (Benson et al, 2012), and the Rhaetian specimens presumably represent some of the earliest, as yet poorly documented, members of the clade.…”

The first discovery of crinoids and cephalopod hooklets in the British Triassic

“…Swift and Martill, 1999;Allard et al, 2015;Korneisel et al, 2015;Nordén et al, 2015;Lakin et al, 2016), but elements of the accompanying invertebrate fauna are less well known. In particular, as Swift (1999, p. 180) noted, 'Cephalopods are almost unknown from the Penarth Group'.…”

The Rhaetian vertebrates of Chipping Sodbury, South Gloucestershire, UK, a comparative study

“…As much as half of the unidentified material in his collection has now been identified, based on published works (Swift and Martill, 1999;Allard et al, 2015;Nordén et al, 2015), as well as comparisons with collections from other sites.…”

“…4). An annotated, collected vast quantities of fossil material from Bristol and the surrounding area, and is hailed as a highly reliable source of information owing to his methodical collecting, identification and labelling (Nordén et al, 2015). Curtis kept meticulous records of his collecting, and wrote detailed summaries of his observations.…”

“…However, one constant throughout all occurrences is that there is generally a basal bone bed that yields abundant bones and microfossils of bony fishes, sharks, and reptiles. A number of British Rhaetian bone bed sites have been described (Swift and Martill, 1999;Allard et al, 2015;Korneisel et al, 2015;Nordén et al, 2015) and many of them share the key elements of their faunas in common; however, there has never been a numerical comparison of the faunal lists, key taxa and relative abundances between different sites. Are they constant, representing unbiased preservation of a common fauna, or are there differences in diversity and relative abundance, perhaps reflecting palaeoenvironmental or taphonomic differences ?…”