Thornback Ray
Platyrhinoidis triseriata

Physical Description 

    • Large rounded body disks, long thick tails
    • Two large dorsal (back) fins and a caudal (tail) fin
    • Three rows of spines on back and tail. Spines are not venomous
    • Brown, gray-brown, or olive-brown on back; white or cream on belly
    • Maximum length is 36 inches long


    • From Monterey Bay, California to Baja California, Mexico and Gulf of California
    • Most common in southern California, sometimes seen in central California


    • Common in sandy beach areas, especially sand below kelp forests
    • Prefer sandy, muddy habitats
    • Normally in shallow water (less than 25 feet), but have been seen in waters up to 450 feet deep


    • Males become sexually mature at 14.5 inches long and females at about 19 inches long
    • Thornback rays breed in late summer and eggs hatch the following summer
    • Eggs are deposited in the sand (usually 1-15 at a time)
    • Eggs are oblong capsules with stiff pointed horns at corners
    • Pups are 4-4.5 inches long when they hatch; they receive no maternal care


    • Eat food in the bottom sediment, mainly worms, clams, crabs, and shrimp
    • Eat small fish, including sculpin, sardines, anchovies, surfperch, and gobies


    • Small sharks and northern elephant seals; likely some larger fishes
    • Their dorsal spines likely protect them from some predators

Interesting Facts

    • Not to be confused with the Thornback Ray ( Raja clavata ) native to the British Isles. The two species do not swim in the same waters or look the same.
    • The Thornback Ray is also called a shovelnose shark, a pinback ray, a prickleback shark, a banjo shark, a round skate, a thornback guitarfish, and, to local fishers, a “throw-em-back”!

Sources: The Wildlife Trusts;; Aquarium of the Pacific 

Photo: Ashley Brock

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