Lilstock Formation

Lilstock Formation
Lilstock Formation
Stratigraphic range: Rhaetian; ~205–202 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Unit of	Penarth Group
Sub-units	Cotham Member, Langport Member
Underlies	Blue Lias Formation, Scunthorpe Mudstone Redcar Mudstone Formation
Overlies	Westbury Formation
Thickness	1–10 m (3.3–32.8 ft)
Lithology
Primary	Shale, siltstone, limestone, mudstone
Location
Coordinates	51°12′N 3°18′W / 51.2°N 3.3°W
Approximate paleocoordinates	35°30′N 0°30′E / 35.5°N 0.5°E
Region	England
Country	United Kingdom
Type section
Named for	Lilstock
	Lilstock Formation (the United Kingdom) Lilstock Formation (England)

The Lilstock Formation is a geologic formation in England. It preserves bivalve, insect and other invertebrate fossils, as well as fossil fish of Agkistracanthus mitgelensis and the basal theropod dinosaur Newtonsaurus cambrensis dating back to the Rhaetian of the Triassic period.^[1]^[2]

White Lias

The White lias is a rare, fine-grained form of limestone from the late Triassic period, occurring only in certain parts of Somerset and infrequently in Warwickshire.^[3] It gets the name ‘lias’ from the quarrymen's dialect for ‘layers’, referring to its natural state when quarried.

White lias is part of the Langport Member of the Lilstock Formation,^[4] a multi-layered bed of stone formed from shale and limestone. At its base is a bone-bed yielding ancient marine, reptilian and ammonite fossils.^[3]

White lias varies in colour from white-cream to pale grey and is traditionally used for building and flooring.^[3] Evidence of its use can be seen in manor houses, churches and cathedrals all over the UK. It is most prevalent in the Somerset towns of Midsomer Norton, Radstock, Langport and Wincanton.^[3] Bowdens quarry in Langport is the only supplier of white lias, and of the more commonly found blue lias and grey varieties.

Fossil content

Color key

Taxon	Reclassified taxon	Taxon falsely reported as present	Dubious taxon or junior synonym	Ichnotaxon	Ootaxon	Morphotaxon

Notes
Uncertain or tentative taxa are in small text; ~~crossed out~~ taxa are discredited.

Dinosaurs

Theropods

Theropods of the Lilstock Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Newtonsaurus^[5]	N. cambrensis				A coelophysoid theropod

Fish

Cartilaginous Fish

Cartilaginous Fish of the Lilstock Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Image
Agkistracanthus	A. mitgelensis				A myriacanthid chimaeriform

References

↑ Lilstock Formation at Fossilworks.org
↑ Galton PM. Bones of large dinosaurs (Prosauropoda and Stegosauria) from the Rhaetic Bone Bed (Upper Triassic) of Aust Cliff, southwest England. Revue de Paléobiologie, Genève. 2005; 24:51–74.
1 2 3 4 "Lias Stone Suppliers | Somerset Lias Quarry | Lovell Stone Group".
↑ Swift, Andrew (1995). "A review of the nature and outcrop of the 'White Lias' facies of the Langport Member (Penarth Group: Upper Triassic) in Britain". Proceedings of the Geologists' Association. 106 (4): 247–258. Bibcode:1995PrGA..106..247S. doi:10.1016/S0016-7878(08)80236-2.
↑ Evans, Owain; Howells, Cindy; Wintle, Nathan; Benton, Michael J. (11 September 2025). "Re-assessment of a large archosaur dentary from the Late Triassic of South Wales, United Kingdom". Proceedings of the Geologists' Association. 136 (6) 101142. Bibcode:2025PrGA..13601142E. doi:10.1016/j.pgeola.2025.101142. hdl:1983/8affce5d-a313-4b23-92d1-ef3f4d383816. ISSN 0016-7878.