Grammysia armorica Community, Pridoli, Armorican Massif (Silurian of France)

Where: France (48.0° N, 2.0° W: paleocoordinates 55.6° S, 41.3° E)

• coordinate based on political unit

• local area-level geographic resolution

When: Pridoli (423.0 - 419.2 Ma)

Environment/lithology: marine; bioturbated, calcareous sandstone

• 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: "...probably represents the lowest intertidal zone, and a low BA 1 position is reasonable."

• 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: "The calcareous, sandy nature of the deposit, which is commonly very bioturbated, and the wave crossbedding suggest a rough water environment above wave base."

Collection methods: Text lists genera present, in some cases with multiple species. Table 18.5 gives abundances for collection in type area, with multiple species within a genus combined. It is not clear whether all species are present at all localities; for that reason I am listing taxa to genus level only.

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 26114: 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
Trilobita
 Phacopida - Acastidae
Acastella sp.
Acastella sp. Reed 1925 trilobite
 Phacopida - Homalonotidae
Homalonotidae indet.
Homalonotidae indet. Chapman 1890 trilobite
Rhynchonellata
 Rhynchonellida - Camarotoechiidae
"Camarotoechia" thebaulti
 Lophophorata -
Tentaculitida indet.
Tentaculitida indet. Ljaschenko 1955
Bivalvia
 Ostreida - Pterineidae
"Leiopteria sp." = Leptodesma (Leiopteria)
"Leiopteria sp." = Leptodesma (Leiopteria) Hall 1883 oyster
 Cardiidia - Grammysiidae
Grammysia sp., Fuchsella sp.
Grammysia sp. de Verneuil 1847 clam
Fuchsella sp. Dahmer 1942 clam
 Nuculanida - Cucullellidae
Nuculites ellipticus
Cephalopoda
 Orthoceratoidea -
Orthocerida indet.
Gastropoda
 Bellerophontida - Tropidodiscidae
Tropidodiscus sp.
Tropidodiscus sp. Meek and Worthen 1866 snail
 Bellerophontida - Plectonotidae
"Plectonotus" sp.
"Plectonotus" sp. Clarke 1899 snail
Crinoidea
  -
Crinoidea indet.
Crinoidea indet. Miller 1821 Sea lily