Keyhole Sand Dollar (also known as the Five-Hole Sand Dollar)
Phylum: Echinodermata > Class: Echinoidea > Order: Clypeasteroida > Family: Mellitidae > Genus: Mellita > Species: M. quinquiesperforata · Mellitidae (Sand Dollar family) · Echinoid Test (Echinoderm skeleton, not a true molluscan shell). Shape: Flattened, disc-like circular shape.
Species
Mellita quinquiesperforata (Confidence: 98%)
Shell Type
Echinoid Test (Echinoderm skeleton, not a true molluscan shell). Shape: Flattened, disc-like circular shape.
Family
Mellitidae (Sand Dollar family)
Size
Approximately 2 to 2.5 inches in diameter, held in palm. This is an average juvenile/small adult size; full adults typically range from 3 to 4 inches.
Color & Pattern
Off-white to sun-bleached cream beige coloration. Exterior features a distinctive five-petaled flower design (petaloid ambuclacra) on the aboral surface, formed by tiny respiratory pores.
Rarity
Common to Very Common. Whole, undamaged specimens are frequently found along beaches like Oak Island, NC, especially after storms or low tides.
Habitat
Shallow sublittoral to intertidal coastal zones, preferring soft substrates like sandy bottoms, sandbars, and shallow tide pools in marine environments.
Geographic Range
Western Atlantic Coast, ranging from Massachusetts south along the US East Coast (including North Carolina) down to Florida, the Gulf of Mexico, and Brazil.
Description
A classic, sun-bleached sand dollar test featuring a flattened circular form with five narrow slit-like openings called lunules. The center displays a prominent, delicate petal pattern on its top surface where respiratory tube feet once extended. The surface is smooth to slightly granular, stripped of its living velvety spines.
Key Features
Five distinct open slits (lunules) perforating the test, a defined 5-petal flower pattern in the center, pentamerous (five-fold) radial symmetry, and a flattened disc shape.
Collector Value
Low monetary value ($1 - $5) due to high abundance, but very popular and cherished among casual beachcombers and shell collectors. Completely intact, unbleached, or extra-large specimens hold higher decorative interest.
Condition Notes
Fair to Good condition. The test is intact with complete margins and intact lunules, though showing natural sun-bleaching and minor surface erosion. Collectibility Grade: Fine.
Interesting Facts
When alive, sand dollars are covered in tiny fuzzy brown/purple spines and microscopic hairs (cilia) that move sand grains and food particles to their mouth underneath. They use heavy iron particles (magnetite) stored in their digestive tracts to stay anchored during heavy currents.
Ecological Role
Benthic burrowers that feed on microscopic algae and organic debris in sand, helping aerate substrate. Prey for sea stars, crabs, and bottom-feeding fish. Governed by local beachcombing laws—ensure specimens are white/dead before keeping (it is illegal in many states to take live, dark-spined sand dollars).
Similar Species
Six-hole Sand Dollar (Leodia sexiesperforata - features six lunules instead of five); Sea Biscuit (Clypeaster rosaceus - thicker, inflated dome shape); Encope michelini (Arrowhead Sand Dollar - has distinct notches instead of all enclosed slits).
Beach Finding Tips
Look along Oak Island, NC at extreme low tide or right after a winter storm near sandbars. Scan the tide line where foam settles, or gently wade in knee-deep water near sand ripples.
Notes
Oak Island NC