Tricuspid Cavoline (Alternate names: Sea Butterfly, Pteropod)
Kingdom: Animalia, Phylum: Mollusca, Class: Gastropoda, Order: Thecosomata, Family: Cavoliniidae, Genus: Cavolinia, Species: Cavolinia tridentata · Cavoliniidae (The Sea Butterfly or Pteropod family) · Gastropod (Thecosome Pteropod); Whole shell; Bilaterally symmetrical, winged/triangular shape
Species
Cavolinia tridentata (90% confidence based on morphology)
Shell Type
Gastropod (Thecosome Pteropod); Whole shell; Bilaterally symmetrical, winged/triangular shape
Family
Cavoliniidae (The Sea Butterfly or Pteropod family)
Size
Approximately 5-10mm in width. This is a small specimen; adults are typically between 10-20mm.
Color & Pattern
Transparent to translucent white or light cream when fresh. This specimen appears slightly bleached or opaque due to drying, showing a matte off-white finish. No banding patterns are visible.
Rarity
Uncommon as a beach find. While biologically abundant in the open ocean, the fragile shells rarely survive the surf to wash up intact on beaches.
Habitat
Pelagic (open ocean). These are holoplanktonic mollusks that spend their entire lives drifting in the water column of tropical and subtropical seas, typically in the upper 200 meters.
Geographic Range
Circumglobal in warm temperate and tropical waters; common in the Atlantic Ocean, Mediterranean Sea, and Indo-Pacific.
Description
A highly specialized pelagic shell featuring a distinct three-pronged or trident-like posterior. The dorsal and ventral sides are fused into a globose, winged capsule with a smooth, glossy surface and a slit-like aperture from which the swimming parapodia (wings) would emerge in life.
Key Features
Triangular/tridentate shape, sharp lateral spines, a curved posterior spine, and a wide, slit-like anterior aperture. Unique bilateral symmetry for a gastropod.
Collector Value
Modest ($5 - $15 USD). Its value lies in its biological uniqueness rather than market price. It is highly desirable for specialists and those focused on deep-sea or pelagic life.
Condition Notes
Good. The core structure and lateral spines are intact, which is rare for such a delicate shell found on land. It shows minor calcification or sun-bleaching from being out of water.
Interesting Facts
Unlike most snails that crawl, Sea Butterflies 'fly' through the water using two wing-like flaps of their foot. They secrete large mucus nets (up to 2 meters wide) to trap plankton for food.
Ecological Role
Major component of the marine food web, eaten by fish, whales, and seabirds. They are vital to the carbon cycle but are highly sensitive to ocean acidification which dissolves their thin shells.
Similar Species
Cavolinia uncinata (more rounded lateral spines) and Cavolinia inflexa (more elongated and curved downward). Diacria trispinosa is also similar but has a more elongated, needle-like posterior spine.
Beach Finding Tips
Look in the 'wrack line' (seaweed debris) after strong onshore winds or storms. They are most commonly found on tropical islands or beaches facing deep water currents.