Petit bloc à céphalopode orthocône probable

Scientific identification

Common name: Orthoconic nautiloid cephalopod
Author: Denis Arcand

Specimen interpreted as a small orthoconic cephalopod preserved in matrix, likely represented by part of a straight conical shell or internal mold. The fossil appears to correspond to a single main cephalopod specimen rather than an assemblage. Supported by: The filename encodes CEP (cephalopod) and the keyword 'Cephanopod', interpreted here as a spelling variant of 'Cephalopod'. In Ordovician material from southern Quebec, straight-shelled nautiloid cephalopods are a reasonable conservative interpretation for such catalog wording. Species-level confirmation requires: Species-level identification would require clearer shell characters such as siphuncle position, chamber spacing, shell section, ornamentation, and better-preserved diagnostic views. Certainty: The filename and overall morphology support identification as a cephalopod with a straight orthoconic shell. The misspelling 'Cephanopod' in the filename is interpreted as 'Cephalopod'. Taxonomic placement is conservative: secure at class level, probable as an orthoconic nautiloid, but genus and species remain undetermined from the available information alone.

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 filename identifies the specimen as an Ordovician fossil from site code RTHQ. The nomenclature document indicates that RTHQ is a shale locality in the Richelieu / Chambly corridor, but no confirmed formation or group value was available in the uploaded dropdown data.

Observed lithology

Description: Dark gray fine-grained shale to shaly mudstone forming a compact fossil-bearing block. Interpretation: Fine marine siliciclastic sediment deposited in a low-energy offshore setting. Certainty: High confidence

Physical description

Assemblage description: Small matrix-supported block preserving one probable orthoconic cephalopod element. The specimen appears to represent a single principal fossil on a compact shale block. Associated fossils: No additional associated macrofossils can be confirmed from the available record.

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 5.7 × L 7 × T 2.8 cm (centimeters) Approximate volume: 111.7 cm (centimeters)³ Weight: 220 Gramme Note: The specimen is treated as a single cephalopod-bearing block rather than a multi-element debris concentration. Additional note: Dimensions converted from the filename code 2.25×2.75 inches. Support code BLK is interpreted as a compact three-dimensional block rather than a flat plate.

Taphonomy

Summary: Probable orthoconic cephalopod preserved on a small shale block from an Ordovician marine setting. Evaluator: Paleontologist Transport origin: Indeterminate Occurrence position: Indeterminate Articulation: Moderate Fragmentation: Moderate Abrasion: Low Compression: Low Observed processes: A single probable orthoconic cephalopod element is preserved on a compact shale block, with limited evidence for strong transport or concentration of multiple skeletal elements. Interpretation: The specimen likely represents an isolated orthoconic cephalopod remain preserved in fine-grained marine sediment with limited evidence for significant transport. Taphonomic quality: B — Reasonably informative preservation of a single identifiable fossil specimen Justification: The specimen is more informative than a fragmentary debris concentration because it preserves a single probable cephalopod individual, but taxonomic resolution remains limited. Evaluation date: 2026-04-03T00:00:00

Palaeoecological interpretation

Interpretation: Marine nektonic cephalopod remain preserved in offshore muddy sediment. Hypothesis: The fossil likely represents part of a straight-shelled nautiloid that lived as a mobile marine predator or scavenger above the seafloor in an Ordovician shelf environment. Certainty: Moderate; cephalopod interpretation is supported by the filename and expected morphology, but detailed ecological inference is limited by the incomplete preservation. Note: This specimen is chiefly informative as evidence of Ordovician cephalopods in the collection rather than as a fully diagnostic taxonomic reference.

Conservation state

General state: Fair Integrity: Fragmentary Alterations: Matrix friability / Crumbling at touch (High) Stability: Monitor closely Scientific readability: Poor Note: Compact but relatively small shale block; edges and fossil surface should still be handled carefully.

Museum exhibition value

Provenance: General locality known only Systematic collections: Systematic value not assessed Note: Good educational value as a small straight-shelled cephalopod block, though less visually striking than larger display plates.

Scientific value

Rarity / locality: Representative of typical fauna at locality Completeness / preservation: Moderately preserved but identifiable Taxonomic novelty: Typical morphology of known species Note: Useful collection specimen documenting an Ordovician orthoconic cephalopod from a shale locality in southern Quebec.

Public exhibit text

This small block preserves a probable straight-shelled cephalopod, one of the marine predators that lived in Ordovician seas. Its cone-shaped shell belongs to the group of ancient nautiloid cephalopods.