Microvertebrates from multiple bone beds in the Rhaetian of the M4–M5 motorway junction, South Gloucestershire, U.K.

Tiffany S. Slater, Christopher J Duffin, Claudia Hildebrandt, Thomas G. Davies, Michael J. Benton*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

8 Citations (Scopus)
289 Downloads (Pure)


The Rhaetian (latest Triassic) is best known for its basal bone bed, but there are numerous other bone-rich horizons in the succession. Boreholes taken around the M4–M5 motorway junction in SW England provide measured sections with multiple Rhaetian bone beds. The microvertebrate samples in the various bone beds differ through time in their composition and in average specimen size. The onset of the Rhaetian transgression accumulated organic debris to form a fossiliferous layer high in biodiversity at the base of the Westbury Formation. The bone bed at the top of the Westbury Formation represents a community with lower biodiversity. The bone beds differ in their faunas: chondrichthyan teeth are dominant in the basal bone bed, but actinopterygians dominate the higher bone bed. These differences could be taphonomic, but are more likely evidence for ecological-evolutionary changes. Further, a change from larger to smaller specimen sizes up-sequence allows rejection of an earlier idea that the successive bone beds represented multiple reworkings of older bone beds.
Original languageEnglish
Pages (from-to)464-477
Number of pages14
JournalProceedings of the Geologists' Association
Issue number4
Early online date3 Aug 2016
Publication statusPublished - Aug 2016


  • Actinopterygii
  • Bony fishes
  • Bristol
  • Chondrichthyes
  • Late Triassic
  • Rhaetian
  • Rhaetic bone bed
  • Sharks
  • Systematics
  • Westbury Mudstone Formation

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