Plate with Sowerbyella (5 specimens)

Scientific identification

Genus: Sowerbyella
Family: Sowerbyellidae
Common name: Strophomenide brachiopod
Author: Denis Arcand

The specimen corresponds to a small plate bearing several flattened brachiopods attributed to the genus Sowerbyella. The assemblage appears dominated by strophomenide valves of subcircular to subtransverse outline, preserved on a dark shaly matrix. Supported by: The filename codes BRA as the principal phylum and Sowerbyella as the first taxonomic keyword, which in the nomenclature corresponds to the principal fossil. The expected appearance is compatible with an Ordovician strophomenide brachiopod preserved in low relief on a thin plate. Species-level confirmation requires: A species-level attribution would require close examination of growth lines, valve convexity, hinge width, and diagnostic internal or external characters. Certainty: The filename clearly indicates Sowerbyella as the principal taxon. Attribution to the genus is plausible; the species is not forced without more detailed morphological examination.

Geology and provenance

Formation: Nicolet River Formation
Group: Lorraine Group
Locality: Écluse de Chambly
Region: Richelieu Valley
Province: Quebec
Country: Canada

Lithostratigraphy

Locality: CEDC- Chambly Écluse de Chambly Region: Richelieu Valley Formation: Nicolet River Formation Group: Lorraine Group Depositional environment: Soft muddy seafloor Note: The RTHQ site code is indicated as a shale site in the nomenclature, but the precise formation and group are not confirmed in the provided files; they are therefore left unknown.

Observed lithology

Description: Dark gray to bluish-gray shale, fine-grained, bearing several flattened visible brachiopods on a small plate. Interpretation: Fine marine sediment deposited in a calm environment, favorable to the preservation of compressed brachiopods. Certainty: High confidence

Physical description

Assemblage description: Fossiliferous shale plate bearing five brachiopods attributed to Sowerbyella. The individuals appear to be preserved in low relief on the same fossiliferous surface. Associated fossils: No associated fossils are explicitly indicated in the filename; other small bioclasts may be present but are not retained here as principal taxa.

Matrix description

Fossil assemblage: Sparse shelly assemblage Fossil density: Low Species composition: Mixed / uncertain Plate surface: Weathered Relief: High relief Ornamentation: Fine growth lines Rock type: Calcareous Shale Color: Brown / Dark gray - Mottled - Medium-dark Shape: Sub-rounded block Dimensions: W 5.08 × L 10.16 × T 1.2 cm (centimeters) Approximate volume: 0.1 cm (centimeters)³ Weight: 0.12 Gramme Note: Surface dominated by a single principal taxon (Sowerbyella) according to the specimen nomenclature. Additional note: Dimensions derived from the 2x4 code in the filename, expressed in inches in the nomenclature.

Taphonomy

Summary: Several probable strophomenide brachiopods preserved in low relief on a small Ordovician shale plate. Evaluator: Paleontologist Transport origin: Indeterminate Occurrence position: Reworked Articulation: Moderate Fragmentation: High Abrasion: Low Compression: Low Observed processes: Concentration of a few flattened valves or individuals of brachiopods on the same fossiliferous surface, with preservation dominated by compression and external imprint. Interpretation: The specimen most likely represents a small concentration of brachiopods preserved on a quiet muddy surface, with diagenetic compaction typical of Ordovician shales. Taphonomic quality: B — Useful preservation of a small identifiable assemblage Justification: The generic identification seems plausible and several specimens are visible, but the small size and compression limit fine details. Evaluation date: 2026-03-09T00:00:00

Palaeoecological interpretation

Interpretation: Epifaunal benthic brachiopods living on or near a muddy outer-shelf seafloor in a low-energy setting. Hypothesis: The assemblage reflects a small local concentration of Ordovician brachiopods preserved on a shaly surface from a quiet marine environment. Certainty: Moderate; the general muddy Ordovician context is solid, but the precise stratigraphy of the RTHQ site remains to be confirmed. Note: The specimen is mainly useful for documenting the presence of strophomenide brachiopods in an Ordovician shale site.

Conservation state

General state: Fair Integrity: Fragmentary Alterations: Matrix friability / Crumbling at touch (High) Stability: Monitor closely Scientific readability: Poor Note: Specimen remains interpretable and displayable, but matrix friability requires cautious handling.

Museum exhibition value

Provenance: Type or figured specimen provenance documented Aesthetic appeal: High aesthetic and educational value Systematic collections: Systematic value not assessed Note: Good educational interest for illustrating Ordovician brachiopods on shale, but detailed provenance is not disclosed.

Scientific value

Rarity / locality: Very common fossil taxon Completeness / preservation: Poor preservation with limited diagnostic features Taxonomic novelty: Not evaluated for taxonomic novelty Note: Interesting specimen as a small plate of brachiopods attributed to Sowerbyella from an Ordovician shale site; the value lies mainly in the generic identification and regional context.

Public exhibit text

This small plate preserves several brachiopods attributed to the genus Sowerbyella. These marine animals lived on the floor of an ancient sea and are preserved here compressed in fine mud that later became shale.