The Beacon Limestone Formation, historically known as the Junction Bed, is a formation of the early Jurassic age (PliensbachianToarcian). It lies above the Dyrham Formation and below the Bridport Sand Formation. It forms part of the Lias Group. It is found within the Wessex Basin and parts of Somerset, in England. It is well known for the Strawberry Bank Lagerstätte, which contains the 3-dimensionally preserved remains of vertebrates, including marine crocodyliformes, ichthyosaurs and fish, as well as insect compression fossils.

Fossil content

Among others, the following fossils have been reported from the formation:

Vertebrates

Vertebrates of the Beacon Limestone
GenusSpeciesLocationStratigraphic positionAbundanceNotesImages
HauffiopteryxH. typicusStrawberry BankFalciferum zoneLectotype: GPIT 1491/4, referred: BRLSI M1399, BRLSI M1400, BRLSI M1401, BRLSI M1403, BRLSI M1404 and BRLSI M1406 partial skeletonsIchthyosaur subsequently suggested to belong to Leptonectes
StenopterygiusS. triscissusHolotype: GPIT 12/0224-2 referred: BRLSI M1405, BRLSI M1407, BRLSI M1408 and BRLSI M1409 partial skeletonsIchthyosaur
PelagosaurusP. typus"four isolated skulls and associated postcranial skeletal elements along with two articulated specimens, one of which is a small juvenile"Thalattosuchian
PachycormusP. macropterusBRLSI M1297, BRLSI M1299, BRLSI M1320, BRLSI M1332, BRLSI M1359, BRLSI M1389, BRLSI M1395, BRLSI M1341, BRLSI M1351, BRLSI M1366, BRLSI M1393Pachycormiform fish
LeptolepisIndeterminateBRLSI M1259 complete specimen.4–8 cm (1.6–3.1 in) in length
LepidotesIndeterminate40–45 cm (16–18 in) in length
CaturusIndeterminate"two specimens, including an isolated neurocranium (BRLSI M1288)"Amiiform fish

Invertebrates

Invertebrates of the Beacon Limestone
GenusSpeciesLocationStratigraphic positionAbundanceNotesImages
TrivenapteronT. mooreiStrawberry BankFalciferum zoneDermapterid earwig
FulgoridulumIndeterminateFulgoridiid planthopper
NecrotauliusN. parvulusNecrotauliid Trichopteran
LiassogomphidaeIndeterminateOdonata
ElcanidaeOrthoptera
ArchegocimicidaeHemiptera