Plate with numerous echinoderm ossicles

Scientific identification

Common name: Crinoid ossicles
Author: Denis Arcand

The specimen consists of numerous isolated echinoderm ossicles preserved on a shale plate. Most visible elements are compatible with crinoid columnals or related skeletal debris, but no articulated crown, calyx, arms, or other diagnostic parts are visible. Supported by: Abundant discoidal to subpolygonal calcareous ossicles with echinoderm appearance, consistent with disarticulated crinoid skeletal debris. Species-level confirmation requires: Articulated or more diagnostic skeletal material such as calyx plates, pluricolumnals, brachials, or associated crowns. Certainty: Identification is secure at phylum level and probable at class level; isolated ossicles do not permit a more precise taxonomic assignment.

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: RPMF site code from the filename; the exact formation and group are not confirmed in the provided source files, but the lithology is consistent with an Ordovician shale setting.

Observed lithology

Description: Dark gray to black fossiliferous shale preserving numerous isolated echinoderm ossicles on bedding surfaces. Interpretation: Fine-grained offshore siliciclastic sediment consistent with low-energy marine deposition. Certainty: High confidence

Physical description

Assemblage description: Plate bearing a dense concentration of small echinoderm ossicles, visually dominated by crinoid-like skeletal debris scattered across a dark shale surface. Associated fossils: No other associated macrofossils confidently identified on the exposed surface.

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 8.9 × L 11.4 × T 1.5 cm (centimeters) Approximate volume: 50.7 cm (centimeters)³ Weight: 0.3 Gramme Note: The assemblage is visually dominated by echinoderm ossicles, most likely crinoid debris, but monospecificity cannot be confirmed from isolated skeletal elements. Additional note: Dimensions derived from the filename code 3.5x4.5 (inches) and converted to centimeters.

Taphonomy

Summary: Dense concentration of disarticulated echinoderm ossicles preserved on a fine-grained shale plate. Evaluator: Paleontologist Transport origin: Indeterminate Occurrence position: Reworked Articulation: Moderate Fragmentation: High Abrasion: Low Compression: Low Observed processes: Numerous isolated ossicles accumulated on a single plate; the elements are disarticulated and likely represent concentrated skeletal debris. Interpretation: The specimen likely records skeletal debris from echinoderms, probably crinoids, accumulated and buried in a low-energy muddy marine setting. Taphonomic quality: C — Moderately informative preservation of disarticulated fossil debris Justification: The specimen is useful as a taphonomic and sedimentological example of concentrated echinoderm debris, but diagnostic taxonomic information is limited. Evaluation date: 2026-03-09T00:00:00

Palaeoecological interpretation

Interpretation: Disarticulated echinoderm skeletal debris preserved on a muddy marine substrate. Hypothesis: The plate likely records local accumulation of crinoid-derived ossicles in a quiet offshore setting. Certainty: Moderate. Note: This specimen is primarily informative for preservation style, taphonomic concentration, and echinoderm presence.

Conservation state

General state: Fair Integrity: Fragmentary Alterations: Matrix friability / Crumbling at touch (High) Stability: Monitor closely Scientific readability: Poor Note: The 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: Moderate educational value as an example of concentrated echinoderm ossicles preserved on shale.

Scientific value

Rarity / locality: Very common fossil taxon Completeness / preservation: Poor preservation with limited diagnostic features Taxonomic novelty: Not evaluated for taxonomic novelty Note: Useful as an Ordovician echinoderm debris plate and for documenting concentrated ossicle preservation in shale.

Public exhibit text

This plate shows an accumulation of small echinoderm skeletal elements, probably from crinoids. After the skeleton disarticulated, the calcareous pieces accumulated and were later buried in calm marine mud.