Ponderous Ark (fragment)
Phylum: Mollusca, Class: Bivalvia, Order: Arcida, Family: Noetiidae, Genus: Noetia, Species: N. ponderosa · Noetiidae (Noetid Arks) · Bivalve (fragment); fan-shaped/triangular section
Species
Noetia ponderosa
Shell Type
Bivalve (fragment); fan-shaped/triangular section
Family
Noetiidae (Noetid Arks)
Size
Estimated 1 inch fragment. Whole adults are typically 2 to 2.5 inches in length.
Color & Pattern
Cream to pale tan base with distinctive reddish-brown to orange-brown concentric banding. The vertical ribs show a 'beaded' or 'dotted' pattern where they intersect with growth lines.
Rarity
Very Common; these fragments are ubiquitous on South Carolina beaches like Myrtle Beach.
Habitat
Marine; shallow subtidal waters, usually found buried in sandy or muddy substrates away from the direct surf zone.
Geographic Range
Western Atlantic, ranging from Virginia down through the Gulf of Mexico to the Caribbean.
Description
A thick, heavy bivalve fragment characterized by prominent radial ribs. The surface shows a cross-hatched texture caused by vertical ribs intersecting with horizontal growth increments. The shell is notably sturdy and 'ponderous' (heavy) for its size.
Key Features
Distinguishing features include the square-cut radial ribs that are often split by a fine central groove (though worn here) and the heavy, thick calcareous structure.
Collector Value
Minimal; while a whole, fresh specimen with a black periostracum is a nice cabinet addition, beach-worn fragments have purely sentimental value for beachcombers.
Condition Notes
Poor; this is a beach-worn fragment (a 'shards') missing the hinge, umbo, and most of its margin. The natural black periostracum is completely eroded away. Collectibility: Low.
Interesting Facts
Unlike many mollusks with clear blood, Arks are unusual because they possess hemoglobin, giving their live tissues a red appearance, earning them the nickname 'Bloody Clams'.
Ecological Role
Suspension feeder that filters plankton from the water column; serves as a sturdy substrate for encrusting organisms like sponges and barnacles once the animal dies.
Similar Species
Blood Ark (Anadara ovalis) which has a rounder shape and ribs that lack the fine central groove, and the Incongruous Ark (Anadara brasiliana).
Beach Finding Tips
Best found after storms or high tides at Myrtle Beach. Look in the 'shell hash' piles at the tide line for thick, ribbed pieces that feel heavier than typical clam fragments.
Notes
Myrtle Beach SC