'Eurypterid' Community, Armorican Massif (Silurian of France)

Also known as 'Eurypterid' Community, La Lande Muree Fm., Armorican Massif

Where: France (48.3° N, 2.1° W: paleocoordinates 66.9° S, 48.4° E)

• coordinate based on political unit

• local area-level geographic resolution

When: Monoclimacis griestonensis graptolite zone, La Lande Muree Formation, Telychian (438.5 - 433.4 Ma)

• formation-level stratigraphic resolution

Environment/lithology: marine; micaceous, black mudstone

• General statement of Central Armorican trough during Llandovery through Lochkovian: "depositional patterns typical of a platform environment...Silurian is mainly an alternating succession of unfossiliferous sandstones and locally fossiliferous black shales...The arenaceous deposits are probably related to the eustatic regression and corresponding high sedimentation rate during the Pridolian and Lochkovian...Outside the A. Massif the Pridoli-Lochkovian succesion in Artois (boreholes) is characterized by shallow marine shales and limestones overlain by areanceous deposits that correspond to the Early Devonian transgression."

•For this Community: "Eurypterids are preserved chiefly as cuticle debris, but locally both complete and nearly complete specimens have been found...[lithology suggests] a quiet, poorly oxygenated environment. The relative scarcity of spores and sporomorphs as contrsted with abundant acritarchs and chitinozoans indicates an offshore, fully marine environment in agreement with Kjelleswig-Waering's Biofacies 1. The exceptionally rich, diverse graptolie faunas indicate BA 3-5 [relatively large distance and depth from shoreline]."

• General statement: "In Brittany there are two kinds of black shale and limestone deposits during the Llandovery to lowermost Devonian interval: (1) black shales (commonly described as sapropelites) are widespread in space and time and (2) black, micritic limestones or argillaceous limestones are restricted to two localities in the eastern part of the Armorican Massif. The black shales are very rich in organic matter and locally contain detrital mica, pyrite, and nodules..."

•For this community: "In the Armorican Mssif it occurs in black shale of the La Lande Muree Fm...a mudstone very rich in organic matter, with detrital mica flakes..."

Size class: macrofossils

Primary reference: P. R. Racheboeuf. 1999. Lower Silurian to Lower Devonian communities from the Armorican Massif (western France) and Artois (northern France). In A. J. Boucot, J. D. Lawson (eds.), Paleocommunities--a case study from the Silurian and Lower Devonian 260-270 [M. Foote/M. Foote/P. Wagner]more details

Purpose of describing collection: paleoecologic analysis

PaleoDB collection 26111: authorized by Michael Foote, entered by Michael Foote on 04.10.2002

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names
Euchelicerata
 Eurypterida - Megalograptidae
Megalograptidae indet.
Megalograptidae indet. Caster and Kjellesvig-Waering 1955 eurypterid
Pterygotid eurypterids of this family, determined by Stoermer.
Pterobranchia
 Graptoloidea -
Graptoloidea indet.
Graptoloidea indet. Lapworth 1875 graptolite
other biserial forms
 Graptoloidea - Climacograptidae
Pseudoclimacograptus sp.
 Graptoloidea - Retiolitidae
"Petalograptus sp." = Petalolithus, Retiolites sp.
"Petalograptus sp." = Petalolithus graptolite
Retiolites sp. graptolite
 Graptoloidea - Monograptidae
"Monograptus spiralis" = Oktavites spiralis, Monograptus proetus, Monograptus marri, Monograptus discus, Monograptus priodon, Monoclimacis griestonensis, Pristiograptus nudus
"Monograptus spiralis" = Oktavites spiralis Geinitz 1842 graptolite
Monograptus marri graptolite
Monograptus discus graptolite
Monograptus priodon Bronn 1835 graptolite