Pink Sea Urchin Test (Sea Biscuit / Alfonso Urchin)
Phylum: Echinodermata > Class: Echinoidea > Order: Camarodonta > Family: Toxopneustidae > Genus: Echinometra or similar · Toxopneustidae / Echinidae (Sea Urchin family) · Echinoderm exoskeleton (Test). Shape: Globular / hemispherical test with five-fold (pentamerous) radial symmetry.
Species
Echinometra mathaei / Strongylocentrotus purpuratus (or related Toxopneustidae / Echinidae urchin species)
Shell Type
Echinoderm exoskeleton (Test). Shape: Globular / hemispherical test with five-fold (pentamerous) radial symmetry.
Family
Toxopneustidae / Echinidae (Sea Urchin family)
Size
Approximately 3.5 to 4.5 inches (9-11 cm) in diameter. Standard adult range for large regular sea urchin tests is 2.5 to 5 inches.
Color & Pattern
Base color is a delicate dusty rose to pinkish-tan tone, covered uniformly with raised white raised tubercles (spine attachment nodes). Five distinct radial ambulacral columns converge towards the apical system opening at the apex.
Rarity
Common to Very Common. Frequently collected as beach drift or sold commercially for home decor and marine specimen display.
Habitat
Subtidal ocean floor, shallow reefs, rocky subtidal zones, and seagrass beds in warm temperate to tropical marine waters.
Geographic Range
Indo-Pacific and Atlantic coastal waters depending on precise species; widely distributed across warm marine regions.
Description
A classic, dome-shaped sea urchin test featuring beautiful 5-fold radial symmetry. The delicate skeleton displays intricate vertical rows of small white knobby tubercles set against a warm dusty-pink shell surface. At the top apex is the circular apical opening where the anal system (periproct) resided, while the interior remains hollow.
Key Features
Pentamerous radial symmetry, thousands of small rounded white primary and secondary tubercles, distinct porous ambulacral lines, and a circular apical opening at the crown.
Collector Value
Modest collector value, typically ranging from $5 to $20 USD. Highly popular as decorative marine displays and natural history study pieces.
Condition Notes
Good to Very Fine collector condition. Completely cleaned and free of spines or organic matter. Free of major cracks or missing plates, with clear, unbleached pink hues and crisp tubercle definition.
Interesting Facts
Though often called 'shells', sea urchin tests are internal skeletons composed of interlocking calcium carbonate plates called ossicles. In life, these tiny bump-like tubercles each served as a ball-and-socket joint for a movable spine and tube feet.
Ecological Role
Living sea urchins are vital marine herbivores that graze on kelp, algae, and bio-fouling organisms, keeping coral reefs and rocky substrate clean and healthy.
Similar Species
Green Sea Urchin (Strongylocentrotus droebachiensis), Alfonso Urchin (Phyllacanthus imperialis), and White Sea Urchin (Tripneustes ventricosus). Distinguishable by its rosy-pink background color and uniform dense white node coverage.
Beach Finding Tips
Look along beach drift lines after storms or strong tides near rocky reefs or coral environments, often washed ashore once spines have detached naturally.